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Whey is a liquid by-product obtained by cheese elaboration, which is not completely used due to the large quantities produced. As a result, the whey is poured into rivers and soils and becomes a pollutant agent. The valorization of acid whey using membrane clarification was evaluated, where the effect of temperature and membrane cut-off were studied using acid whey. Permeability was three times higher at 70°C than 50°C (163.2±11.1 y 62.4±9.2 L/m2 .h, respectively) for membranes with a cut-off of 0.2 µm. Furthermore, the permeate flux for this cut-off was three, six and ten times higher compared with the cut-off of 300, 150 y 50 kDa at 70°C, respectively. The clarification stage was scaled-up with 0.2 µm membranes, achieving about 22 L of whey filtered for Batch mode until a volume reduction factor (VRF) of 5 with protein retention of 68%. In Fed-Batch mode, the retention of protein was 61%, but the filtration could be carried out for longer, reducing fouling and filtering almost the double of the quantity of whey compared with Batch mode. In all cases, the turbidity of permeates was lower than 12 NTU (reduction >99%), regardless of whey turbidity whose values might be superior to 12,000 NTU. [ABSTRACT FROM AUTHOR]

The aim of the current trial was to test whether leucine affected growth and accretion including test any effects on leucine upon stress. Quadruplicate tanks each containing 50 Atlantic salmon (Salmo salar) (mean start body weight of 524 ± 28 g) were fed diets containing 27.3, 30.0, 35.0 and 41.0 g leucine/kg diet for 74 days. Two tanks per dietary group were exposed to a stressor (5 min chasing) three days a week to test whether enriched leucine diet aid coping with chronic stress, while two tanks per dietary groups were left unstressed. The stressed fish consumed less feed and grew less than the unstressed fish, irrespective of diet. Leucine inclusion did not affect protein accretion, but leucine retention declined with increasing dietary leucine in both stressed and unstressed fish. No difference between the stressed or unstressed fish was present. Leucine did not affect relative liver size, but unstressed fish had slightly higher relative liver size compared with stressed fish (p = 0.05). Free leucine in the muscle and liver was not affected by dietary leucine, but unstressed fish had higher concentration of valine and isoleucine in the muscle compared with the stressed fish. Muscle of fish fed elevated leucine had lower mRNA expression of murf1 (p = 0.037) and higher expression of ppara (p = 0.012). Muscle of stressed fish had higher expression of the oxydative genes mnsod (p = 0.049) and catalase (p = 0.037) compared with the fish left unstressed, while in liver, there were no differences of expression of any of the genes tested. In conclusion, diets enriched in leucine had minor effects and neither protein accretion nor growth was affected in either stressed or unstressed fish. [ABSTRACT FROM AUTHOR]

A two‐phase feeding trial was conducted to estimate the dietary histidine requirement of juvenile and post‐juvenile rainbow trout for maximum growth and protein retention. Twelve isonitrogenous experimental diets were formulated where diet 1 was an 8% fishmeal basal diet having 0.5% histidine. Histidine was added to diets 2–6 to achieve levels of 0.7, 0.9, 1.1, 1.3 and 1.5% histidine respectively. Diets 7–12 were identical to diets 1–6 except for pellet size. In trial 1, fish (4 g) were fed test diets 1–6, and in trial 2, fish (40 g) were fed diets 7–12, to four replicate tanks per diet for 12 weeks. A nutrient digestibility trial was also conducted with trout from trial 2. Growth performance and feed utilization were not significantly influenced by dietary histidine supplementation above the basal diet level in either rainbow trout juveniles or post‐juveniles. Supplementation of histidine significantly increased protein and histidine digestibility, and it was lowest in the basal diet group. The highest histidine retention was in the lowest dietary histidine treatment group, and histidine retention progressively decreased at each increase in dietary histidine. In post‐juvenile trout, the same pattern was observed except that for the two lowest histidine levels, retention was similar and high. Finally, considering the overall growth and nutrient retention performances, the dietary histidine requirement is relatively higher in post‐juvenile trout (>0.6%) rather than juvenile trout (0.6%) under the present experimental conditions. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the effects of lysine and histidine supplementation on growth performance, gene expression, blood parameters and quality of the fillet in Nile tilapia, Oreochromis niloticus (n = 192; 136.14 ± 2.32 g). Fish were distributed into four groups and fed a control diet without lysine and histidine supplementation (CON), supplemented with lysine (LYS), histidine (HIS) or lysine and histidine (LYS + HIS) and fed until apparent satiety for 90 days. Growth performance increased significantly in fish fed diet LYS + HIS (p <.05). The fillet body weight gain and fillet yield increased by 26.61% and 2.74% unit, respectively, compared to fish fed CON diet (p <.001). Compared to the control group, fish fed diets showed decreased whole‐body lipid and plasmatic triglycerides coupled to increased mRNA levels of MyoD and myogenin in the skeletal muscle and higher texture attributes of fillets (p <.05). There was a substantial negative correlation between body lipids and hardness of fillets. Overall, the combined supplementation of lysine and histidine optimizes growth performance, expression of muscle growth‐related genes and flesh quality attributes in grow‐out Nile tilapia. [ABSTRACT FROM AUTHOR]

Current parenteral containers used for the storage and delivery of protein-based drugs, contain silicone oil which may seep into the protein solution and can result in adsorption, aggregation and denaturation of the protein. Tightly adherent surface coatings prepared by radio frequency glow-discharge (RFGD) plasma polymerization are described in this paper. Using this robust technique, methacrylic acid (MA) (hydrophilic), hexamethyldisiloxane (HMDSO) (hydrophobic), tetraglyme (TG) (hydrophilic) were plasma polymerized onto glass. In addition, HMDSO and MA were copolymerized to create a plasma polymerized HMDSO-MA (hydrophobic) surface. Untreated glass and glass dip-coated in PDMS were used as controls. TG and MA plasma coatings adsorbed the least amount of protein in all pH conditions. Interestingly HMDSO-MA retained significantly lesser protein compared to HMDSO and dip-coated PDMS samples. In the presence of Polysorbate 80 (PS80) all plasma polymerized coatings adsorbed and retained negligible amounts of protein, compared to controls. Furthermore, the peak glide force of plasma coated syringes did not significantly increase compared to syringes without plasma coating. Due to the versatility of RFGD plasma, this process is scalable and could potentially be used for the treatment of hypodermic syringes used for the storage and delivery of protein-based therapeutics. [ABSTRACT FROM AUTHOR]

The efficiency of SID Lys utilization (kSID Lys) in gilts and sows during early (days 48 to 52), mid (days 75 to 79), and late gestation (days 103 to 107) was investigated using 88 pregnant females (PIC 1050; 27 gilts, 27 parity 1 sows, 34 parity 2+ sows; 192.96 ± 22.84 kg at days 42 ±1 of gestation) and whole body nitrogen (N) retention balance studies. Females were assigned to 1 of 4 SID Lys levels ranging from 40% to 70% of the daily SID Lys requirements above maintenance for a parity 1 sow according to the NRC (2012) gestating sow model in each gestation period. Experimental diets were isocaloric (3,335 kcal ME/kg) and isoproteic (11.75 % CP) and dietary indispensable AA were set to meet or exceed 100% of AA:Lys ratios. The slope of the linear response to graded SID Lys intake was defined as kSID Lys. With the aim of increasing the accuracy of kSID Lys estimates, gilt data from the current study was combined with gilt data from a previous study conducted at the same facility using 4 SID Lys levels ranging from 60% to 90% of the daily SID Lys requirements above maintenance for gilts according to the NRC (2012) gestating sow model. Whole body Lys retention of the combined gilt data set was assessed with different broken-line and nonlinear models. The kSID Lys was 0.65, 0.38, and 0.52 for early-, mid-, and late-gestation, respectively, in gilts. A linear response to graded SID Lys intake was found in late gestation only in parity 1 and 2+ sows; kSID Lys was determined as 0.44 and 0.52 in late gestation for parity 1 and parity 2+ sows, respectively. There were no differences in kSID Lys in late gestation between parities. For the combined gilt data, the model of best performance (reduced error and greater goodness of fit) was the Hoerl model. Maximum kSID Lys (i.e., g SID Lys retention/g SID Lys intake) in gilts was 0.67, 0.54, and 0.53 in early, mid, and late gestation predicted at 7.2, 9.1, and 13.5 g of SID Lys intake/d, respectively, based on the Hoerl model. Maximum SID Lys retention in gilts was similarly predicted at 8.5, 10.5, and 20.9 g of SID Lys intake per day in early, mid, and late gestation and resultant kSID Lys of 0.61, 0.51, and 0.44, respectively. The findings of this study demonstrate that kSID Lys varies by stage of gestation and SID Lys intake level and that, at least in gilts, a dynamic kSID adjusted for daily intake more adequately reflects biological response and hence allows more precise feeding of pregnant females. [ABSTRACT FROM AUTHOR]

Bariatric surgery may induce protein malabsorption, although data are scarce. This study aims at evaluating dietary protein bioavailability after different bariatric surgeries in rats. Diet-induced obese Wistar rats were operated for vertical sleeve gastrectomy (VSG) or Roux-en-Y gastric bypass (RYGB). The control group was composed of pair-fed, sham-operated rats (Sham). Two weeks after surgery, rats were fed a 15N protein meal. Protein bioavailability was assessed by determination of 15N recovery in the gastrointestinal tract and organs 6 h after the meal. Fractional protein synthesis rate (FSR) was assessed using a flooding dose of 13C valine. Weight loss was the highest in RYGB rats and the lowest in Sham rats. Surprisingly, RYGB (95.6 ± 0.7%) improved protein digestibility (P = 0.045) compared with Sham (93.5 ± 0.5%) and VSG (93.8 ± 0.6%). In contrast, 15N retained in the liver (P = 0.001) and plasma protein (P = 0.037) was lower than in Sham, with a similar trend in muscle (P = 0.052). FSR was little altered by bariatric surgery, except for a decrease in the kidney of RYGB (P = 0.02). The 15N distribution along the small intestinal tissue suggests that dietary nitrogen was considerably retained in the remodeled mucosa of RYGB compared with Sham. This study revealed that in contrast to VSG, RYGB slightly improved protein digestibility but altered peripheral protein bioavailability. This effect may be ascribed to a higher uptake of dietary amino acids by the remodeled intestine. [ABSTRACT FROM AUTHOR]

Two experiments were conducted to determine the efficiency of utilizing SID Lys and Thr for whole-body protein retention (kSIDLys and kSIDThr) in pregnant gilts. In Exp. 1, 45 gilts (158.0 ± 8.0 kg at day 39.4 ± 1 of gestation) in 2 groups were used in a 3-period nitrogen (N)-balance study. Gilts were assigned to 1 of 4 diets set to provide 60, 70, 80, and 90% of predicted daily SID Lys requirement for protein retention (NRC, 2012) in each of early (day 41 to 52, 10.44 g/d), mid- (day 68 to 79, 9.60 g/d), and late gestation (day 96 to 107, 16.04 g/d). Diets contained 3,300 kcal ME/kg and 11.6% CP; given at a rate of 2.13 kg/d in early and mid-gestation and at 2.53 kg/d during late gestation. The 12-d balance period (7-d adaptation; 5-d urine and fecal collection) was based on total urine collection using urinary catheters and determination of fecal N digestibility using indigestible marker. The SID Lys required for whole-body protein retention was estimated using the NRC (2012) model and the predicted Lys content of each gestation pool. Lysine efficiency at each diet Lys level was calculated as the ratio of daily Lys retention and SID Lys intake. The linear and quadratic response in whole-body N and Lys retention and Lys efficiency for each balance period was determined. The kSIDLys was determined from the slope generated by regressing whole-body Lys retention vs. SID Lys intake, with y -intercept set to 0. In Exp. 2, 45 gilts (165.7 ± 13.6 kg at day 39.1 ± 2 of gestation) were assigned to 1 of 4 diets set to provide 60, 70, 80, and 90% of the predicted daily SID Thr requirement for protein retention in each of early (6.46 g/d), mid- (6.05 g/d), and late gestation (9.75 g/d). Animal management, N-balance procedure, data collection and calculation, and statistical analyses were patterned from Exp. 1. In early and mid-gestation, whole-body N retention, as well as Lys and Thr retention, was not affected by the dietary SID Lys and Thr. In late gestation, there was a linear increase (P < 0.001) in whole-body N, Lys and Thr retention. The kSIDLys and kSIDThr in late gestation were determined to be 0.54. The lack of response in whole-body protein retention in early and mid-gestation may in partly reflect excess Lys and Thr intake. Lysine and Thr efficiency calculated at the lowest dietary Lys and Thr was 0.49 and 0.32 in early gestation and 0.61 and 0.52 in mid-gestation, respectively. Based on the available evidence, kSIDLys and kSIDThr do not appear to be constant throughout gestation. [ABSTRACT FROM AUTHOR]

Abstract To further optimize practical diets with respect to IAA requirements, this study was conducted to confirm and refine the tryptophan requirement, which is a potentially limiting AA in our matrix of ingredients. In order to ensure the best information on Trp requirement, our study used wide range of Trp levels and quality of fit of the models for calculating requirement estimates. Twelve iso‑nitrogenous and isoenergetic diets (practical defined ingredients) containing 30% protein and 8% lipid were formulated to meet the nutritional requirement of juvenile Nile tilapia (Oreochromis niloticus) with the exception of tryptophan. A basal diet deficient in tryptophan was assigned to meet all other known nutrient requirements of the Nile tilapia. L-tryptophan was then added to the basal diet at 0.04% increments to produce tryptophan levels ranging from 0.21 to 0.61% of the diet. The diet which supported the best performance of Nile tilapia in previous work, was used as a reference diet. Each diet was fed to three replicate groups of juvenile Nile tilapia (7.9 ± 0.1 g) in a recirculation system for eight weeks. Saturation kinetic model, broken line models with linear or quadratic ascending portions, were used to evaluate dose-response relationships of thermal-unit growth coefficient, apparent net protein retention, tryptophan retention against dietary tryptophan. Akaike weights were calculated and used for model selection in addition to the model's overall R 2. The tryptophan requirement of juvenile Nile tilapia was estimated at 0.31% (0.25–0.37%), 0.33% (0.26–0.39%), 0.25% (0.24–0.25%), 0.27% (0.25–0.31%) of the diet for optimum growth, tryptophan deposition, feed efficiency, and apparent net protein deposition (95% of maximum value), respectively. Highlights • The study was conducted using Nile tilapia to confirm and refine the tryptophan requirement, which is a potentially limiting AA in our matrix of ingredients. • Saturation kinetic model, broken line models with linear or quadratic ascending portions, were used to evaluate dose-response relationships of thermal-unit growth coefficient, apparent net protein retention, tryptophan retention against dietary tryptophan. Akaike weights were calculated and used for model selection in addition to the model's overall R 2. • The tryptophan requirement of juvenile Nile tilapia was estimated at 0.31% (0.25–0.37%), 0.33% (0.26–0.39%), 0.25% (0.24–0.25%), 0.27% (0.25–0.31%) of the diet for optimum growth, tryptophan deposition, feed efficiency and apparent net protein deposition (95% of maximum value), respectively. [ABSTRACT FROM AUTHOR]

Two trials were conducted to determine net protein requirements and the use of metabolizable protein (MP) for growing ram lambs when fed diets with different concentrate levels and roughage quality. In a comparative slaughter trial, eighty-four ½ Dorper × ½ Santa Inês ram lambs (18.0 ± 3.3 kg of BW) were individually penned and divided into 2 diet groups differing in roughage source: low-quality (sugarcane bagasse) roughage (LQR) or medium-quality (coastcross hay) roughage (MQR). In each group, 7 lambs were randomly selected and slaughtered after a 10 days adaptation period (baseline). Other 21 lambs from each diet group were fed ad libitum and slaughtered at 25, 35, or 45 kg of BW, and the remaining 28 lambs (14 from each diet group) were submitted to 1 of 2 levels of feed restriction (70 or 50% of the ad libitum intake). Body N content and retention were determined. In the second trial, 6 ram lambs (44.3 ± 5.6 kg of BW) were kept in metabolic cages and used in a 6 × 6 Latin square experiment designed to determine N digestibility and microbial N synthesis, and to compute MP supply by the 2 diets and 3 levels of intake. Nitrogen intake and microbial N synthesis were greater for the animals fed the MQR diet than for those fed the LQR diet ( P  < 0.05). Neither the endogenous and metabolic N losses, nor the net protein requirements for growth differed between diets ( P  > 0.05). However, the proportion of MP used for both maintenance and growth was lower for the animals fed the MQR diet ( P <  0.05), likely because of an excess of MP reaching duodenum of these animals. We concluded that a reduction of the concentrate level in diets for growing ram lambs, achieved by improving the quality of the diet roughage, allows a greater supply of MP and may contribute to reduce diet protein concentration. [ABSTRACT FROM AUTHOR]

Abstract: In this study, two different dietary protein levels were tested (500 and 600 g/kg) in meagre juveniles of approximately 2 g, to determine whether a higher body protein diet would favour muscle growth. Results showed that meagre survival and growth were not affected by different levels of dietary protein. However, a higher content of protein was observed in the body composition of meagre fed the P60 diet (656 g/kg versus 624 g/kg). When fish were 82 days after hatched (DAH), protein retention efficiency was significantly higher in fish that were fed the P50 diet (37.1% versus 32.5%). Muscle cellularity changed considerably from the beginning to the end of the trial. The contribution of fibre hyperplasia to muscle growth was reduced although still accounted for 30% in 96 DAH meagre. Several differences were found in the frequency of fibres with areas between 1,000 μm2 and 2,200 μm2 between younger and older meagre, but no effect was found associated with dietary protein. This study suggests that neither growth nor muscle cellularity of fast‐growing juvenile meagre is positively affected by an increased dietary protein levels. [ABSTRACT FROM AUTHOR]

Methionine-choline-deficient ( MCD) mammals are known to accumulate liver TAG probably due to phosphatidylcholine ( PC) deficiency and thus assembly of VLDL and transport of lipids from liver to peripheral organs. To assess whether supplementation of choline could spare methionine and secure a healthy liver metabolism, by reducing the endogenous PC synthesis without interfering with lipid transport and distribution, Atlantic salmon with initial BW of 700 g were fed adequate (1.9 g Met/16 gN) or surplus methionine (2.5 g Met/16 gN) diets of which were supplemented with choline or not for a period of 19 weeks. Fish fed the low-methionine diets had reduced growth ( p = .013) due to reduced protein gain ( p = .007), while lipid gain slightly improved in fish fed the choline-supplemented diets ( p = .047). Also, feed conversion improved when fed surplus methionine ( p < .001), while choline supplementation had no impact on feed conversion. No interaction between choline and methionine on growth performance or retention existed. Phospholipid status in liver and muscle was not affected by treatments, and no liver TAG accumulation occurred at the methionine levels used. Gene expression of ApoB100 necessary for assembling VLDL or pemt necessary for endogenous PC synthesis was unaffected by treatments. Capacity of methylation ( MAT, BHMT) within the liver was not affected by treatment nor was the gene expression of enzymes in liver transsulfuration ( CBS or CDO). Methionine status within liver was unaffected by treatments, while free methionine reduced in those fish fed the low-methionine diets in muscle and plasma. Cystathionine and taurine were elevated when fed surplus methionine. Choline supplementation had no impact on sulphur amino acid metabolites in either tissue. Neither did choline supplementation improve TAG mobilization from liver to muscle. To conclude, choline does not improve endogenous phospholipid synthesis or transport of TAG from liver to muscle depot when added to diets containing 1.9 g Met/16 gN, while surplus methionine improved growth and protein retention, indicating that 1.9 g Met/16 gN is enough to support a healthy liver metabolism, but too low to support muscle protein deposition in adult salmon fed high plant protein diets for longer periods of time. [ABSTRACT FROM AUTHOR]

The purpose of this work was to evaluate the effect of the temperature (50 and 60 °C) of a NaOH cleaning solution during the diafiltration of a binary mixture of bovine serum albumin and β-lactoglobulin, through a 300 kDa tubular ceramic membrane along repeated operational cycles. To this aim, final permeate volume, membrane and fouling resistances and individual protein concentration were analyzed. At the end of each individual study, the membranes were characterized by liquid-liquid displacement porosimetry. As a result, 50 °C was found to be the most appropriated temperature due to its higher capability to restore the initial membrane resistance and the higher efficiency achieved in terms of protein separation. Both conditions fulfilled without altering the structural properties of the membrane as given by porosimetric analysis. In contrast, a great fouling resistance involving null protein transmission occurred when cleaning was performed at 60 °C. [ABSTRACT FROM AUTHOR]

Proper nutrient management is essential for the environmental sustainability of aquaculture. While increasing daily rations generally may lead to improved growth rates, this does not necessarily mean that nutrients are utilized more efficiently. To investigate how ration size affects partitioning of dietary nutrient intake, the effects of meal size on growth and metabolism were examined in triplicate groups of adult Nile tilapia ( Oreochromis niloticus ) receiving daily rations corresponding to 1, 2, 3, or 4% of their biomass. While biomass gain and specific growth rates were positively correlated with ration size, feed conversion and protein retention were most efficient at ration sizes of 3%. Although the magnitude of the SDA response following feeding also increased with ration size, this was not proportionate to meal size. Therefore the metabolic cost of meal processing (SDA coefficient) was found to be lowest in the 3% ration group. The lowest rates of nitrogen excretion as well as the lowest SDA coefficients were also observed for fish receiving meal sizes corresponding to 3% of their body mass. In contrast, fish fed ration sizes of 1% displayed a reduction in apparent digestibility of protein, nitrogen free extract and dry matter, in addition to excreting a disproportionate amount of ingested nitrogen as ammonia and urea. [ABSTRACT FROM AUTHOR]

The study was conducted using channel catfish and tilapia to evaluate the production performance of these fish to increasing levels of lysine from crystalline and intact lysine supplemented in practical diets. A practical lysine deficient basal diet was developed using corn protein concentrate (Empyreal® 75) as a primary protein source. To this diet either graded levels of crystalline lysine or similar levels from a high lysine corn protein concentrate (Lysto™) were added. In the channel catfish trial, the first five diets were designed to contain increasing levels of crystalline lysine (1.21%, 1.34%, 1.45%, 1.56%, and 1.72%) with an additional four diets using intact protein from a high lysine corn protein concentrate (1.40%, 1.57%, 1.77%, and 1.91% lysine). In the tilapia trial, lysine from two sources was added to 11 diets to produce analyzed lysine levels of 0.92%, 1.11%, 1.23%, 1.34%, 1.54% 1.65% in the first six diets using crystalline lysine and 1.13%, 1.38%, 1.61%, 1.81%, 2.02% in the last five diets using intact lysine. Results indicated that channel catfish and tilapia have positive performance with increasing lysine supplementation up to the requirement. Fish fed with the higher levels of lysine had the highest weight gain and lowest feed conversion ratio. The regression analysis on the increased level of inclusion of crystalline lysine and intact lysine showed no significant difference in slope. Based on the growth, feed conversion ratio and apparent net protein retention data obtained from this study, it can be concluded that the effectiveness of using intact lysine via high lysine corn protein concentrate as a lysine supplement is not significantly different from crystalline lysine. Thus, the high lysine corn protein concentrate is a feasible ingredient for aquaculture feeds, which can be used to balance the amino acid composition of the diet without addition of crystalline lysine. Statement of relevance Present study shows that high lysine corn protein concentrate is a feasible ingredient for aquaculture feeds, which can be used to balance the amino acid composition of the diet without addition of crystalline lysine. [ABSTRACT FROM AUTHOR]

Four diets were formulated to evaluate the partial to total substitution of fishmeal with poultry by-product meal ( PBM) (0, 33, 67 and 100 PBM) in diets for totoaba juveniles ( Totoaba macdonaldi). Amino acid profiles from diets and fatty acid content in diets and muscle tissue were used to assess the fish performance using PBM as fishmeal replacement. Stable isotopes of nitrogen (δ15N) were measured in muscle and liver tissue to quantify the retention of each protein source. At the end of the experimental period, the fish fed the 67 PBM diet had a significantly higher growth gain increase compared to the other treatments (almost 2000% over an 86 days period; TGC of 1.06). The total replacement of fishmeal with PBM led to low growth gain increase (ca. 220% over 72 days; TGC of 0.52) and increased mortality. Both fish performance and tissues' fatty acid composition suggest that the 100 PBM diet was deficient in essential fatty acids. An isotope-mixing model applied to isotope ratios of muscle and liver tissues of fish fed the 67 PBM tissues indicated that PBM was retained into muscle and liver tissue in a higher proportion than its level of inclusion in the diet. We conclude that PBM is a good source of nutrients for totoaba juveniles when used in up to 67% fishmeal replacement level in diets containing 52% protein leading to adequate growth rate and survival. [ABSTRACT FROM AUTHOR]

This study compares growth, intake and retention efficiencies of nutrients and energy between common sole ( Solea solea L.) fed ragworm ( Nereis virens, Sars), blue mussel ( Mytilus edulis L.) and an artificial (commercial) feed. Food types were fed to common sole (mean initial body weight: 44.9 ± 2.3 g) in excess three times a day over a 54-day-period. The growth rate in common sole fed the natural prey (8.5 g kg−0.8 d−1) was significantly higher compared to the growth rate in fish fed the artificial feed (5.1 g kg−0.8 d−1). Nutrient and energy intake was significantly lower in common sole fed the artificial feed than in fish fed natural prey. The only exception was fat intake which was higher in common sole fed the artificial feed in contrast to fish fed the natural prey. Nutrient and energy retention efficiencies were significantly lower in common sole fed the artificial feed than in fish fed the natural prey. In conclusion, the low growth in common sole fed the artificial feed was related to lower nutrient and energy intake as well as lower nutrient and energy retention efficiencies. It is suggested that reduced intake of the artificial feed might be related to the high dietary fat content of the artificial feed. [ABSTRACT FROM AUTHOR]

To enhance the biocompatibility or extend the biomedical application of poly(caprolactone) (PCL), protein retention on PCL surface is often required. In this study, poly(acrylamide) (PAAm) brushes were grown from PCL surface via surface-initiated atom transfer radical polymerization (SI-ATRP) and served as a protein-capturing platform. Grafted PAAm was densely packed on surface and exhibited superior protein retention ability. Captured protein was found to be resistant to washing under detergent environment. Furthermore, protein structure after being captured was investigated by circular dichroism (CD) spectroscopy, and the CD spectra verified that secondary structure of captured proteins was maintained, indicating no denaturation of protein happened for retention process. [ABSTRACT FROM AUTHOR]

The suitability of land animal by-products (ABPs) in feed for Atlantic salmon postsmolts (initial weight 372 g) in sea water was studied in a feeding experiment, using poultry by-product meal (PBM) and porcine blood meal (BM) as protein sources and poultry oil as fat source. Four extruded feeds were tested in a 2 * 2 factorial model, with or without ABP protein sources and with or without poultry oil. The control feed contained a mix of marine and plant ingredients. Initial feed intake was highest in the ABP protein-based diets, whereas poultry oil had a weak opposite effect. No differences were seen in growth rate or body weight. Addition of PBM and BM led to increased FCR, and lower retention of crude protein and energy. This could be explained by lower digestibility of amino acids and crude protein, and a slightly lower energy level in these diets. Reduced igf1 mRNA levels in liver and muscle were seen in fish fed dietary ABP protein and oil. Despite lower protein digestibility of ABP protein, this study confirms the suitability of ABP protein and lipid in combination with plant ingredients in feed for Atlantic salmon growers. [ABSTRACT FROM AUTHOR]

A factorial experiment was conducted with black tiger shrimp ( Penaeus monodon ) juveniles to determine the effects of varying protein inclusion in the diet and also varying inclusion of a microbial biomass on growth, feed and nutrient utilization when fed in indoor laboratory conditions. The growth performance of the shrimp improved with increasing diet protein level. However, in the absence of the added microbial biomass, this growth performance plateaued at the 480 g/kg protein level. The addition of the microbial biomass improved growth at each inclusion level of both protein and microbial biomass. No plateau in growth was observed with the addition of the microbial biomass. Improvements in feed conversion were seen with increasing dietary protein levels and also the inclusion of the microbial biomass. Examination of the feed intake of each treatment supports that there was a combined effect of an increase in feed intake and improvements in feed conversion that contributed to the improvements in growth performance with the use of the microbial biomass, but the increases in dietary protein level largely influenced growth through improvements in feed conversion. [ABSTRACT FROM AUTHOR]

The present study evaluates the effect of dietary glutamate and glutamine supplementation on growth performance, body composition and expression of key enzymes involved in the hepatic metabolism of juvenile gilthead seabream ( Sparus aurata ). Fish were fed for 52 days with four diets, which were identical in composition except for a 4% supplementation with glutamate (GLU diet), glutamine (GLN diet), carbohydrate (CHO diet) or bovine serum albumin (BSA diet). Glutamate and glutamine supplementation improved feed conversion ratio and protein retention compared to carbohydrate supplementation, and, in the case of glutamate, protein retention was improved over that of fish fed the protein supplemented diet. Feeding CHO and GLU diets resulted in up-regulation of glucokinase and lipogenic enzymes compared to fish fed GLN and BSA diets. Consistently, fish fed CHO or GLU diets showed higher triglyceride levels in serum and liver, and feeding the GLU diet resulted in higher body fat content than in fish fed GLN or BSA diets. The liver of fish fed GLN or BSA diets showed increased glutamate dehydrogenase activity in the direction of the glutamate oxidation. In contrast to fish fed the BSA diet, increased glutamate oxidation did not reduce free glutamine and glutamate levels in the liver of fish fed the GLN diet, suggesting that glutamine intake exceeded liver's energy requirements. In conclusion, glutamate supplementation improved hepatic glucose metabolism, whereas supplemented glutamine seems to be preferentially oxidized over amino acids derived from dietary protein, thus promoting higher protein retention in both cases. Our findings indicate that glutamate and glutamine could partly replace dietary protein and that glutamate supplementation could also facilitate protein replacement by carbohydrates in fish feeds. [ABSTRACT FROM AUTHOR]

Fish appear to have a limited capacity for digesting complex proteins during the early life stages. A better understanding of fish larvae protein digestive capacity and subsequent metabolic utilisation (amino acid (AA) catabolism and retention), depending on dietary protein molecular weight (MW) and larval development stages, is essential for developing formulated microdiets suited to larval requirements throughout ontogeny. The aim of this work was to develop a method enabling the in vivo production of radiolabelled polypeptides and protein fractions of different MW using Artemia metanauplii , and apply this new tool to assess protein digestive capacity and evaluate protein metabolic utilisation (catabolism and retention) throughout ontogeny of Senegalese sole larvae. Characterisation of MW distribution of Artemia protein content by size exclusion chromatography at different time points after hatching showed that from hatching to 24 h post-hatching (hph), the profile is dominated by polypeptides and proteins having a MW in the ranges 0.5–1.9 kDa, 2.8–7.0 kDa and above 476 kDa. At 36 hph a shift from high MW proteins to lower MW polypeptides was observed in the elution patterns. Fractions of radiolabelled polypeptides and proteins of various MW were produced through in vivo labelling of A. metanauplii , by incubation in a [U– 14 C] free AA mixture, and subsequent separation of Artemia proteins according to their MW by size exclusion chromatography. Digestibility and metabolic utilisation of some of the radiolabelled polypeptide fractions obtained (fractions of 1.0 kDa and 6.8 kDa) were assessed throughout Senegalese sole larval development (12, 21 and 34 days after hatching (DAH)) fed on live feed, through the controlled tube-feeding methodology combined with metabolic chambers. The results showed that the polypeptide fraction of 1.0 kDa was highly digestible and similarly retained in larval body at all developmental stages assayed. Conversely, the 6.8 kDa polypeptide fraction was poorly absorbed by young larval stages (12 DAH) but absorption improved throughout larval development (from 12 to 34 DAH). Body retention efficiency of the 6.8 kDa polypeptide fraction tended also to increase (and catabolism rate tended to decrease) throughout ontogeny, displaying a positive correlation (Spearman's correlation) with larval age. The method we report here is novel and may constitute a useful tool to assist in defining the most suitable MW range of proteins to incorporate into larval diets, for different developmental stages of Senegalese sole and other teleost larvae. [ABSTRACT FROM AUTHOR]

The objectives of this study were to further optimize balance of dietary amino acids (AA) offered to Nile tilapia by investigating the role of dispensable AA (DAA) across the range of indispensable AA (IAA) intakes. The possible limitation of IAA intake in fish consuming diets with high inclusion of crystalline AA (CAA) supplemented to the diets was also confirmed. The basal diet was formulated to contain 22.2% intact protein in which IAA were adjusted to reach 100%, 110% and 120% of NRC requirements with or without DAA supplementation. Glycine and glutamic acid were used as DAA sources at 1:1 and 2:2 ratio to assign 2 levels of DAA at 2% and 4% of the diet. Fish were hand sorted to a uniform size then randomly stocked into 44 aquaria with 15 fish per/tank. Fish were fed 4 times a day to near satiation over a 10-week period. To evaluate feeding regimes on CAA utilization diets with 100% IAA without DAA supplements and 110% IAA with 4% DAA supplements were paired and fed to fish using 2 and 4 feedings per day. Results confirmed that DAA contribute to meeting the nitrogen requirement of fish in which fish fed diets with DAA supplementation had significantly higher growth rates (thermal-unit growth coefficient, TGC) and lower FCR compared to fish fed diets without DAA supplementation. Growth of fish fed diets without DAA supplementation was not comparable to fish fed diets supplemented with DAA irrespective of IAA supplements up to 120% NRC requirement. Fish fed diets with DAA supplements at 4% exhibited superior growth compared to fish fed diets with 0% and 2% DAA supplements. The supplementation of IAA at 110% NRC requirement helped the fish have better growth compared to fish fed diets formulated to 100% NRC. However, no further benefit was observed on growth performance of fish fed diets with IAA supplements up to 120%. Fish fed diets with IAA supplements at 110% NRC and 4% DAA supplements exhibited the best response. The results of this study indicated that although DAA provided benefits in balancing AA profiles of feed, limitation of IAA intake at 100% NRC might cause impaired growth of Nile tilapia. In addition to this, no influence of feeding frequency was obtained on growth performance of fish feed, suggesting that fish can be fed successfully two times per day regardless of high inclusion levels of CAA. • The important role of DAA in meeting the nitrogen requirement of Nile tilapia is confirmed in which DAA inclusion rate of 4% of the diet offering the best performance of fish. • The result of this study also indicates the inferior growth of fish fed diet with IAA supplements at 100% NRC requirements which might result from limitation of daily IAA intake. • Fish can be fed successfully two times per day regardless of high inclusion levels of crystalline amino acid. [ABSTRACT FROM AUTHOR]

A 9-week feeding trial was carried out to evaluate dietary arginine requirement of juvenile red sea bream. Six isonitrogenous and isocaloric diets (50% crude protein and 17.7 kJ g − 1 gross energy) were formulated to contain graded levels of arginine including 1.42, 1.88, 2.22, 2.54, 3.08 and 3.43% of diet (2.84–6.86% of dietary protein), and fed triplicate groups of fish (13.3 ± 0.2 g) to apparent satiation twice daily. At the end of the feeding trial, fish fed ≥ 2.22% arginine showed significantly ( P < 0.05) higher growth than those fed 1.42% arginine. Significant improvement in protein productive value was found at dietary arginine level of 2.54% compared to the fish fed 1.42% arginine. Significant reductions in whole-body and muscle lipid contents were found by increment of arginine level and whole-body protein increased significantly in fish fed 2.22–2.54% arginine compared to those fed 1.42% arginine. Plasma total protein level significantly was increased in fish fed 2.54–3.08% arginine, and alanine aminotransferase activity and glucose level were significantly decreased in fish fed 2.22–2.54% and ≥ 1.88% arginine, respectively, compared to the group fed 1.42% arginine. Significant improvements in lysozyme and myeloperoxidase activities and total immunoglobulin level were obtained by dietary arginine increment. Also, significantly higher total nitric oxide synthase activity was recorded at 3.08% arginine level in comparison to 1.42% arginine. A broken-line regression analysis on weight gain showed that the optimum dietary arginine level is 2.37% of diet (4.74% of dietary protein). [ABSTRACT FROM AUTHOR]

Amino acids are vital for all living organisms including fish and histidine is an essential amino acid for fish. In view of this, dietary histidine requirement of fry Heteropneustes fossilis was determined by feeding casein-gelatin-based isonitrogenous (430 g kg−1 CP) and isocaloric (17.9 MJ kg−1 GE; 15.5 MJ kg−1 DE) amino acid test diets (10 to 20 g histidine kg−1 dry diet) to quadruplicate groups of randomly assigned fish to apparent satiety for 12 weeks. Maximum absolute weight gain (AWG; 44 g fish−1), protein retention efficiency (PRE; 20%), protein efficiency ratio (PER; 1.04), haemoglobin (Hb; 11.24 g dL−1), haematocrit (Hct; 35.11%), red blood count (RBCs; 2.98 × 109 mL−1) and lowest erythrocyte sedimentation rate (ESR; 1.92 mm h−1) were obtained at 16 g histidine kg−1 dry diet. The 95% maximum quadratic response of above data exhibited the requirement to be at 15.2, 15.1, 15.6 and 15.5 g histidine kg−1 diet. As histidine is found in higher concentration in haemoglobin, requirement obtained for Hct% and Hb is 4% greater than that required for maximizing weight gain and protein retention. Based on these results, dietary histidine requirement of H. fossilis fry is recommended between 15.1 and 15.6 g kg−1, corresponding to 35.1-36.3 g kg−1 protein. [ABSTRACT FROM AUTHOR]

The lack of specific compound diets for cephalopods is limiting the industrial development of some species. In this study, four agglutinated moist diets were tested in individually reared Octopus vulgaris (979 ± 151 g) for 8 weeks. All diets were based on bogue Boops boops, accidentally reared in fish farms (aquaculture by-product), and agglutinated with alginate and calcium. One diet was based exclusively on bogue fillets, two on bogue fillets complemented with meat from two crab species ( Portunus pelagicus, Grapsus grapsus) and the last one on bogue and G. grapsus meals. As a control diet, bogue and P. pelagicus were supplied fresh on alternate days. All diets induced similar feed intake (2.1-2.6% day−1). However, the meal-based diet induced negative growth in comparison with the control and the other agglutinated diets (0.80-0.85% day−1). Higher lipid content in agglutinated diets (28-30% dw) in comparison with the control diet (16% dw) led to higher protein retention in muscle. These results underline the inadequacy of traditional meals in diets for cephalopods and that the inclusion of crab meat did not increase feeding rates and growth in O. vulgaris. The dietary fatty acid, with high levels of oleic and linoleic acid and low levels of ARA, clearly reflected in digestive gland, while only decreasing ARA and increasing EPA levels were observed in muscle, with no apparent negative effect on growth. [ABSTRACT FROM AUTHOR]

Two slaughter experiments were carried out to evaluate the growth, content and deposition of tissues and the protein and energy retention in the meat of the carcass in growing broiler fed with canola meal (CANM) in substitution of soybean meal (SOYM). In Exp 1, six male broilers, 43 d of age, were slaughtered at the beginning and 36 broilers were assigned to three diets with increasing amounts of CANM (0, 10 and 20 %) combined with two levels of digestible lysine (DL: 0.85 y 0.95 %). In Exp 2, six female and six male broilers, 28 d of age, were slaughtered at the beginning and 72 broilers were assigned, within sex, to two diets (SOYM or CANM as unique protein source) combined with three energy levels (3.0, 3.1 and 3.2 Mcal of ME/kg of feed). Each experiment lasted two weeks and at the end all birds were sacrificed. In Exp 1, there were not statistical differences in the productivity or the protein and energy retention in the carcass among CANM levels (P>0.05). In Exp 2, the feed, protein and energy intake and the fat deposition were greater (P<0.05) with SOYM, but the weight gain, feed efficiency and the protein and energy retention in the carcass were similar among diets. The results indicate that is feasible to partial- or totally substitute the soybean meal by canola meal in the diets of grower broiler chickens. [ABSTRACT FROM AUTHOR]

Two experiments were done to evaluate the effects of poultry meal (PM), meat meal (MM) or solvent-extracted soybean meal (SBM) inclusion on the performance of Australian snapper Pagrus auratus. In each experiment, test feeds were formulated with similar contents of digestible protein (DP) and digestible energy (DE) using previously determined digestibility coefficients for this species. In experiment 1, groups of snapper (initial weight 14 g) were fed 4 feeds containing 360, 480, 610 or 730 g kg PM; 3 feeds containing 345, 320 or 500 g kg MM; 3 feeds containing 420, 600 or 780 g kg SBM. In experiment 2, groups of snapper (initial weight 87 g) were fed 3 extruded test feeds that contained combinations of PM, MM, SBM or blood meal (BM) which replaced all but 600, 250 or 160 g kg of fishmeal in respective diet formulations. Both experiments included a proprietary extruded aquafeed (COM) to benchmark fish performance. In experiment 1, weight gain was highest in snapper fed feeds containing 360, 345 or 420 g kg of PM, MM or SBM, respectively, and was similar ( P > 0.05) to snapper fed the COM feed. Nonetheless, weight gain and protein retention efficiency tended to decrease as the amount of each test ingredient was increased. Relative feed intake was not affected by the inclusion level of PM, MM or BM, but declined significantly in snapper fed diets containing 600 or 780 g kg SBM. Feeding behaviour indicated fish found these feeds unpalatable. In experiment 2, the harvest weight of snapper fed the 3 extruded test feeds was similar ( P > 0.05), but lower than snapper fed the COM feed (i.e. 234 vs. 256 g). Feed conversion ratio (FCR) was best in snapper fed the COM feed (FCR = 1.53); however, the FCR of snapper fed feeds containing 160 (FCR = 1.66), 250 (FCR = 1.70) or 600 g kg fishmeal (FCR = 1.60) was not different ( P > 0.05). Australian snapper will readily accept feeds containing high levels of PM, MM or SBM and feeds containing these ingredients will support rapid weight and protein gain with little affect on whole body composition. In combination, these feed ingredients were able to replace all but 160 g kg of fishmeal in an extruded test feed. As such, they serve as valuable alternatives to fishmeal and extend the manufacturing options available to aquafeed producers. [ABSTRACT FROM AUTHOR]

Twelve 4-week-old male Wistar rats weighing 100 g were fed diets semi-ad libitum for 22 d containing either 1.5% conjugated linoleic acid (CLA-diet) or high oleic sunflower oil (Control-diet). The CLA was structured triacylglycerol with predominantly cis-9, trans-11 and trans-10, cis-12 fatty acid isomers in the inner position and oleic acid in the other positions of the glycerol molecule. The rats were kept individually in metabolic cages. From days 8-16 energy, nitrogen (N) and carbon (C) balances as well as gas exchange measurements in open-air circuit respiration chambers were performed. CLA had no significant influence on feed intake, daily gain in weight or feed conversion efficiency, but the digestibility of nutrients and energy was significantly reduced (except for fat). CLA did not affect N-balance, but reduced the level of daily retained fat (RQ-method: 0.107 vs. 0.417 g/d, p < 0.01) and consequently energy retention in fat. This was explained by increased heat production (HP, RQ-method: 224.6 vs. 214.6 kJ/d, p < 0.001) caused by a higher fat oxidation (28.9% vs. 22.3%, p < 0.001) at the expense of oxidation of carbohydrates (65.6% vs. 71.4%, p < 0.001), while there was no significant effect on the oxidation of protein (5.5% vs. 6.3%). Consequently, the non-protein respiratory quotient (RQnp) was lower in the rats fed the CLA-diet than in the rats fed the Control-diet (0.907 vs. 0.928, p < 0.001). Plasma total lipids of the CLA-fed rats had higher concentrations of the cis-9, trans-11 than the trans-10, cis-12 CLA-isomer. This study shows that young male Wistar rats respond to CLA fed as structured triacylglycerol. [ABSTRACT FROM AUTHOR]

Abstract: A comparison of membrane fouling caused by filtration of a protein (BSA) through two macroporous membranes, one polymeric (polysulfone) and other ceramic (ZrO2/Al2O3), is carried out. Clean and fouled membranes were characterized by SEM micrographs, water permeability, streaming/zeta potential and impedance spectroscopy measurements. SEM micrographs show BSA on the polymeric and ceramic membranes surfaces but only the polymeric membrane is completely covered, while trans-membrane (or through membrane) zeta potential results indicate protein deposition on the pore walls of both membranes; moreover, differences in time evolution of permeate flow, protein rejection and water permeability for both membranes were also obtained. According to these results, two different main fouling mechanisms can be assumed: a cake layer on the surface of the polysulfone membrane and pore narrowing for the ceramic sample. Impedance spectroscopy measurements allow the estimation of membrane electrical resistance and a reduction in membrane porosity associated to protein deposition was estimated considering a simple system of non-conducting cylindrical capillaries filled by the (conducting) electrolyte solution. [Copyright &y& Elsevier]

Accurate measurement of apparent digestibility (AD) is essential to characterise the nutritive value of ingredients in aquaculture. For crustaceans, current methods rely on collection of excreted faeces by settlement. Excreted faeces lose soluble nutrients through leaching, leading to an over-estimation of AD. An alternative approach is to remove faeces by dissecting them from the hindgut prior to evacuation. In this study, we compared estimates of nutrient AD of ingredients in Penaeus monodon from three faecal collection methods: faeces obtained by dissection, faeces collection onto a screen (FS) and faeces collection into a bucket which is then centrifuged in freshwater and decanted (FB). Furthermore, we dissected faeces from three gastro-intestinal tract regions: foregut, proximal hindgut and distal hindgut, to test the validity of the hypothesis that digestion and absorption do not occur beyond the hepatopancreas of P. monodon. Protein and amino acid AD of protein-rich ingredients were significantly different between methods. On average, estimates of protein AD of ingredients obtained using dissection were 15.2% and 27.0% lower compared to the FS and FB methods respectively (AD values of 60.6% vs. 71.5% and 83.0% respectively). Similar trends were observed regarding amino acid (AA) AD of ingredients, where values of AD by dissection were consistently lower than the other two methods. The range of protein and AA AD values observed for different ingredients was greater when using dissection than the other methods. Potentially, dissection allows for greater sensitivity in detecting differences in digestibility of protein ingredients. In contrast, AD estimates of dry matter, starch and lipid were not affected by sampling method. These results suggest that AD of protein and AA is significantly over-estimated using traditional faecal collection methods and that the standard practices for evaluating digestible protein of protein-rich ingredients in shrimp needs to be reconsidered. • Overestimates of protein AD occurred when excreted faeces were collected from water. • Dissection of faeces led to lower measures of protein and amino acids AD compared to methods using excreted faeces. • Dissection provides a rapid and cost effective method to determine ingredient AD. • All methods of collection resulted in similar starch and lipid AD. [ABSTRACT FROM AUTHOR]

This study was undertaken to investigate: (1) the effects of both deficiencies and excesses in essential amino acids (EAAs) from an estimated optimum dietary EAA pattern on nitrogen (N) utilization and excretion of rainbow trout Oncorhynchus mykiss, (2) the effects of dietary digestible protein ( PD): digestible energy ( ED) ratio ( PD: ED) on N utilization and excretion of O. mykiss and (3) the potential interaction of these two factors. A 3 × 3 factorial experiment was conducted, with the two factors EAA pattern and PD: ED ratio. The three levels of EAA pattern were: (1) optimum EAA pattern, (2) 60% deficiencies in the three amino acids arginine, histidine and lysine, and (3) 60% excesses in the three amino acids arginine, histidine and leucine. The three levels of PD: ED ratio were 18, 21 and 24 g MJ−1. Amino acid deficiencies from an optimum amino acid pattern caused reductions in mean N retention of 29 to 37%, with the greatest reduction associated with the lowest PD: ED ratio, and similar substantial increases in total N and ammonia-N excretion at all of the dietary PD: ED ratios investigated. Amino acid excesses, however, did not negatively affect N retention or excretion. Increasing PD: ED ratio was associated with decreasing N retention and increasing N excretion over the range of dietary protein and lipid levels tested. Results of this study showed that a diet with optimum dietary amino acid pattern and lowest PD: ED ratio produced the highest N retention (47% of ingested N) and the lowest total N and ammonia-N excretion of O. mykiss. [ABSTRACT FROM AUTHOR]

Formylglycine-generating enzyme (FGE) catalyzes in newly synthesized sulfatases the oxidation of a specific cysteine residue to formylglycine, which is the catalytic residue required for sulfate ester hydrolysis. This post-translational modification occurs in the endoplasmic reticulum (ER), and is an essential step in the biogenesis of this enzyme family. A paralog of FGE (pFGE) also localizes to the ER. It shares many properties with FGE, but lacks formylglycine-generating activity. There is evidence that FGE and pFGE act in concert, possibly by forming complexes with sulfatases and one another. Here we show that human pFGE, but not FGE, is retained in the ER through its C -terminal tetrapeptide PGEL, a noncanonical variant of the classic KDEL ER-retention signal. Surprisingly, PGEL, although having two nonconsensus residues (PG), confers efficient ER retention when fused to a secretory protein. Inducible coexpression of pFGE at different levels in FGE-expressing cells did not significantly influence the kinetics of FGE secretion, suggesting that pFGE is not a retention factor for FGE in vivo. PGEL is accessible at the surface of the pFGE structure. It is found in 21 mammalian species with available pFGE sequences. Other species carry either canonical signals (eight mammals and 26 nonmammals) or different noncanonical variants (six mammals and six nonmammals). Among the latter, SGEL was tested and found to also confer ER retention. Although evolutionarily conserved for mammalian pFGE, the PGEL signal is found only in one further human protein entering the ER. Its consequences for KDEL receptor-mediated ER retrieval and benefit for pFGE functionality remain to be fully resolved. [ABSTRACT FROM AUTHOR]

Abstract: A two-step methodology has been developed for the prediction of protein retention time in linear-gradient HIC systems. Isocratic retention parameters were determined from ln(k′)-salt concentration plots for a number of commercially available proteins with a range of properties. Quantitative structure property relationship (QSPR) models based on a support vector machine (SVM) approach were generated for predicting isocratic retention parameters for proteins not included in the model generation. The predicted parameters were then used to calculate protein gradient retention times and the results indicate that this approach is well suited for predicting experimental gradient retention data. The approach presented in this paper may have implications for HIC methods development at both the bench and process scales. [Copyright &y& Elsevier]

Abstract: The retention of proteins in hydrophobic interaction chromatographic (HIC) systems was investigated using the preferential interaction theory in concert with quantitative structure property relationship (QSPR) modeling. The numbers of water molecules and salt ions released upon protein binding were determined from ln(k′) vs. salt concentration plots for a large number of proteins with a range of properties. The effect of salt type on protein binding was also studied by comparing the number of water molecules released in the presence of different salts. Quantitative structure property relationship (QSPR) models based on a support vector machine (SVM) approach were successfully generated for predicting the water molecules released values. These models employed protein crystal structure and primary sequence information as well as a set of hydrophobicity descriptors based on the solvent accessible surface area of the proteins. In addition to successfully predicting the water release values, the selected descriptors provide insights into the protein physicochemical properties which influence protein affinity in HIC system. [Copyright &y& Elsevier]

Abstract: The effects of feed intake level on energy and nitrogen partitioning were studied in juvenile Atlantic cod (250 g) fed two fish meal based diets differing in protein and lipid content (54:31 and 65:16) at 10 °C. Replicate groups of cod were feed deprived for 32 days or fed one of the two diets at 25, 50, 75 or 100% of group satiation for 60 days. Feed intake and oxygen consumption were measured daily and weights and chemical composition of carcass, liver, viscera and whole body were measured at start and end. Diet digestibilities were assessed in a separate experiment. The whole body and carcass growth rates at a given feed intake did not differ between dietary groups, but the liver grew faster in the fish fed the low protein diet, resulting in higher hepatosomatic indices at the end of the experiment in the groups fed this diet. The efficiency of utilisation of digestible nitrogen for growth (k DNg) was higher for the low protein diet (0.73±0.02) than for the high protein diet (0.53±0.05), resulting in higher nitrogen retention at a given nitrogen intake. No difference in percentage nitrogen retention was seen in full-fed fish however (31.2±2.5 and 28.4±1.6% for the low protein and high protein diets, respectively). This can be explained by higher nitrogen intake in the fish fed the high protein diet, resulting in a smaller proportion of the intake being used for maintenance. There was no difference in energy utilisation between dietary groups. The digestible energy requirement for maintenance (DEmaint) was 53.8±0.9 kJ kg−1 d−1 (42.3±0.7 kJ kg−0.8 d−1) and the utilisation efficiency for growth (k DEg) was 0.80±0.02. The energy retention in full-fed fish was 31.3±3.5 and 31.7±1.0% for the low protein and high protein diets, respectively. The deposited energy was distributed in approximately equal proportions in the liver and carcass, whereas viscera accounted for a minor proportion. At a given energy intake, the fish fed the high protein diet deposited more energy in the carcass and less in the liver than did those fed the low protein diet. [Copyright &y& Elsevier]

A study was conducted to evaluate fish meal-free practical diets, with and without amino acid supplementation, for the rearing of first feeding Nile tilapia, Oreochromis niloticus. A basal diet was formulated that appeared marginally deficient in lysine, methionine and threonine; thus, experimental diets were supplemented with all possible combinations of those three essential amino acids. Diets contained 45% crude protein and 12% lipid. Diets were fed to apparent satiation four times daily (0800, 1100, 1400, and 1700 hours) for a period of 30 days. No significant differences (P < 0.05) in specific growth rate, weight gain, apparent consumption, food conversion ratio or survival were observed. A significant difference (P < 0.01) in protein retention was observed between fish fed the positive control diet (51.84%) and experimental treatments (22.80-35.17%). This initial evaluation of fish meal-free practical diets for first feeding Nile tilapia demonstrates the potential for eliminating fish meal in diets for larval tilapia, but additional research appears needed to enhance retention of amino acids. doi:10.1300/J028v19n03_06 [ABSTRACT FROM PUBLISHER]

Exit of soluble secretory proteins from the endoplasmic reticulum (ER) can occur by receptor-mediated export as exemplified by blood coagulation factors V and VIII. Their efficient secretion requires the membrane lectin ER Golgi intermediate compartment protein-53 (ERGIC-53) and its soluble luminal interaction partner multiple coagulation factor deficiency protein 2 (MCFD2), which form a cargo receptor complex in the early secretory pathway. ERGIC-53 also interacts with the two lysosomal glycoproteins cathepsin Z and cathepsin C. Here, we tested the subunit interdependence and cargo selectivity of ERGIC-53 and MCFD2 by short interference RNA-based knockdown. In the absence of ERGIC-53, MCFD2 was secreted, whereas knocking down MCFD2 had no effect on the localization of ERGIC-53. Cargo binding properties of the ERGIC-53/MCFD2 complex were analyzed in vivo using yellow fluorescent protein fragment complementation. We found that MCFD2 is dispensable for the binding of cathepsin Z and cathepsin C to ERGIC-53. The results indicate that ERGIC-53 can bind cargo glycoproteins in an MCFD2-independent fashion and suggest that MCFD2 is a recruitment factor for blood coagulation factors V and VIII. [ABSTRACT FROM AUTHOR]

Stability of protein-encapsulating DRV (dried-rehydrated vesicle) liposomes is evaluated after freeze-drying vesicles in presence (or not) of trehalose. Two proteins, bovine serum albumin (BSA) and tissue-type plasminogen activator (t-PA), are used, and protein-encapsulating liposomes with different lipid compositions are prepared by DRV technique. Encapsulation efficiencies are calculated, after measuring BSA with a fluorescence technique and t-PA's amidolytic activity toward a chromogenic substrate.Experimental results show that encapsulation of BSA in vesicles ranges between 35 and 53% of the protein and is only slightly affected by lipid composition. For t-PA, entrapment efficiencies are lower, ranging between 2 and 16%, while lipid composition has substantial effect on entrapment (cholesterol inclusion is very important). After freeze-drying, some lipid compositions remain stable, retaining most of initially entrapped proteins, while others do not, but they may be stabilized by trehalose. In the case of BSA, liposome behavior cannot be explained based on lipid membrane rigidity (more rigid = more stable). This may be connected with previously demonstrated interactions of BSA with membranes. Oppositely, t-PA behavior is more predictable, meaning that the lipid composition selected for the specific therapeutic application determines the need for cryoprotectant addition before freeze-drying t-PA containing DRV liposomes, perhaps due to the fact that under conditions applying minimum or no interactions between t-PA and lipid membranes occur.Thereby, interactions between proteins and membranes determine not only the encapsulation efficiency but also the need for cryopreservation of liposomal protein formulations. [ABSTRACT FROM AUTHOR]

Abstract: A novel set of protein descriptors has been developed to increase the understanding of protein behavior on chromatographic media. The protein descriptors are pH-dependent and based on electrostatic and hydrophobic properties of mainly the surface of the proteins as revealed by their three-dimensional structure. Interpretable and predictive quantitative structure property relationship (QSPR) models were then obtained for protein retention in ion exchange chromatography at different pH values. In most cases the calculated average surface potential could be directly related to retention times. Moreover, the high retention of human lactoferrin observed in cation exchange even at high pH values could be modeled by adding descriptors of the charge asymmetry. [Copyright &y& Elsevier]

Abstract: Our group recently reported on the application of protein-doped monolithic silica columns for immobilized enzyme reactor chromatography, which allowed screening of enzyme inhibitors present in mixtures using mass spectrometry for detection. The enzyme was immobilized by entrapment within a bimodal meso/macroporous silica material prepared by a biocompatible sol–gel processing route. While such columns proved to be useful for applications such as screening of protein–ligand interactions, significant amounts of entrapped proteins leached from the columns owing to the high proportion of macropores within the materials. Herein, we describe a detailed study of factors affecting the morphology of protein-doped bioaffinity columns and demonstrate that specific pH values and concentrations of poly(ethylene glycol) can be used to prepare essentially mesoporous columns that retain over 80% of initially loaded enzyme in an active and accessible form and yet still retain sufficient porosity to allow pressure-driven flow in the low μL/min range. Using the enzyme γ-glutamyl transpeptidase (γ-GT), we further evaluated the catalytic constants of the enzyme entrapped in capillary columns with different silica morphologies as a function of flowrate and backpressure using the enzyme reactor assay mode. It was found that the apparent activity of the enzyme was highest in mesoporous columns that retained high levels of enzyme. In such columns, enzyme activity increased by ∼2-fold with increases in both flowrate (from 250 to 1000nL/min) and backpressure generated (from 500 to 2100psi) during the chromatographic activity assay owing to increases in k cat and decreases in K M, switching from diffusion controlled to reaction controlled conditions at ca. 2000psi. These results suggest that columns with minimal macropore volumes (<5%) are advantageous for the entrapment of soluble proteins for bioaffinity and bioreactor chromatography. [Copyright &y& Elsevier]

Abstract: Two size groups (60 and 800 g) of Atlantic halibut were fed four different experimental diets varying in content of protein (41–56% of dry matter) in substitution to starch (22–6%). The response to dietary treatments differed between the two sizes of fish. In 60 g halibut growth, feed efficiency and percentage energy retention were 20%, 25% and 23% greater, respectively, in the groups fed the highest protein level compared with those fed the lowest level (P &#60;0.05). In contrast, no effect of diet was seen on these variables in the 800 g fish. Further, the 60 g fish fed the diets with highest protein content became leaner than those fed the lowest protein levels, whereas no response was seen in whole body composition of 800 g fish. In the 60 g halibut, liver glycogen content increased with dietary starch level and ended more than three times higher in fish fed the diet with the highest starch level than in those fed the lowest. Liver lipid, protein and ash levels showed marked and significant trends in the opposite direction. In conclusion, 800 g halibut seem to have a lower optimal dietary protein level and to be less sensitive to dietary carbohydrates than 60 g halibut. [Copyright &y& Elsevier]

The present work was designed to study whether changes in dietary protein quality by means of partial inclusion of fish protein hydrolysate (FPH) would alter fish growth, feed utilization, protein retention and metabolism and fish health in general. FPH was produced after hydrolysing whole minced herring using the industrial enzyme Alcalase®. The dietary protein source, low-temperature-dried (LT) fishmeal nitrogen was exchanged with FPH nitrogen at six levels of inclusion ranging from 0 to 300 g kg−1. The experimental diets were fed to post-smolt (1+) Atlantic salmon ( Salmo salar), with mean initial weight of 174 g for a period of 68 days. All diets were iso-nitrogenous, iso-energetic and contained the same amount of amino acids. Fish fed medium inclusion of FPH (180–240 g kg−1) showed a tendency to have higher feed intake than fish fed lower and higher levels of FPH inclusions. Significant higher individual specific growth rates were present in fish fed diets with 180 and 240 g kg−1 FPH when compared with those fed 300 g kg−1. Feed conversion ratio increased significantly ( R2 = 0.61) and protein efficiency ratio decreased significantly ( R2 = 0.59) in fish fed increased levels of FPH. Further, apparent digestibility of crude protein and the amino acids arginine, lysine, methionine and phenylalanine increased significantly with increased dietary inclusion of FPH. Plasma free amino acids, ammonium and urea indicated that FPH amino acids was absorbed earlier and nonsynchronously, and may thus be more prone to be catabolized than in those fish fed the less solubilized protein. FPH inclusion did not have an impact on fish health, as evaluated by haematology and clinical parameters. [ABSTRACT FROM AUTHOR]

Abstract: The applicability of the stoichiometric displacement model (SDM) to description of the retention behavior of charged-fusion proteins in large ion exchange resin (∼90μm diameter) packed column was studied. Proteins were characterized by SDM for isocratic elution. The parameters were subsequently used to evaluate their suitability in predicting protein retention and peak width under gradient elution. The proteins were β-glucuronidase (GUS) and its fusions with polypeptides of 5, 10 and 15 aspartic acids at the C-terminal of the wild-type GUS. Predictions of retention time were within 10% of the experiment results. The plate number obtained at high salt concentration from isocratic elution was used as a first estimate for predictions of peak width. The results show that the SDM is sufficient to describe the binding equilibrium of fusion proteins in ion-exchange columns packed with large resin particles. In addition, the binding mechanism between fusion proteins and the ion exchanger is explored with the assistance of comparative molecular modeling. [Copyright &y& Elsevier]

The search for new materials for chromatographic separation of proteins is a major endeavor nowadays. In order to obtain better chromatographic separation media, poli(glycidyl methacrylate co-ethylen dimethacrylate) matrices were synthesized, milled, classified, functionalized with different reagents and then comparatively tested in batch experiments for protein retention. The Methacrylate/Dimethacrylate resin was treated in different sequences of experiments with Urea, Iminodiacetic acid, N-N dimethyl formamide and ammonia, in order to determine whether functionalization provides sufficient amino groups to capacitate them for protein retention. Fixed bed experiments with particulate resin were also carried out. Previous characterization confirms that the polymeric matrix is macroporous and exhibits a unimodal pore size distribution. The resin also presents a good thermal stability. [Copyright &y& Elsevier]

A 9-week feeding experiment was conducted to evaluate different dietary protein levels in juvenile Nile tilapia reared in either a biofloc (Bio-RAS) or clear water recirculating aquaculture system (CW-RAS). The fish were fed four isoenergetic (19 MJ kg−1) diets with graded levels of a fixed mixture of three protein sources (animal, plant, and microbial origin) and containing 23, 27, 31 or 35% crude protein. Triplicate groups of 20 juvenile tilapia (initial weight: 39.1 ± 2.5 g) were randomly assigned to 24 identical conical 500-L tanks equipped with feed waste traps. Twelve of the tanks were supplied with clear water purified by a mechanical and biological filter, denoted CW-RAS, and on average 15% daily replacement of water. The other 12 tanks were supplied with a biofloc suspension, maintained by a bioreactor system, denoted Bio-RAS, where the mechanical and biological filters were replaced with four serial 10 m3 open bioreactor tanks. In this later system only evaporated water was replaced. The bioreactor tanks were initially inoculated with Bacillus subtilis, and nutrients were supplied to achieve a C: N ratio of 10, supporting heterotrophic bacterial growth. Feed and protein intake, weight gain, specific growth rate, protein efficiency of fish in all treatments, and biomass of micro components in the bioreactor tanks, as well as apparent digestibility of dietary components, were determined at end of the experiment. Growth, feed intake and protein efficiency, especially if retention of the floc was included, was overall higher in the Bio-RAS than in the CW- RAS system. Feed conversion was influenced both by protein level and by the availability of biofloc, with a general lower value in the Bio-RAS and fish given higher protein containing diets. Apparent digestibility of total protein did not vary with the rearing system but was higher with higher dietary levels of crude protein. No significant effect was found for mortality or body index, except for hepato-somatic index and intestinal quotient index, with the latter being significantly higher in the fish given access to biofloc. In all fish given access to biofloc, given all other factors being equal, displayed higher and more feed efficient growth than fish kept in clear water with only access to fabricated diets. Our results tally with other studies using biofloc tank technology and reports from more commercial settings indicating that our data is valid also at a more general level. • The study introduces a new concept of Bio-RAS, exchanging a traditional mechanical and bio-filter of RAS with an external anaerobic bio-reactor, circulating the microbial community in the whole RAS system as an external biota. • Tilapia kept in Bio-RAS grew faster than fish kept in identical RAS but in clear water, and given the same diet. • Tilapia kept in Bio-RAS compensate for reduced feed protein levels compared to fish kept in clear water. [ABSTRACT FROM AUTHOR]