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In this study, a draft genome sequence of Zygosaccharomyces siamensis kiy1 isolated from unpasteurized honey in Japan was analyzed. This strain was reported to be a promising arabitol-producing strain, and this report contributes to a better understanding of arabitol production in yeasts., Competing Interests: The authors declare no conflict of interest. more...

This study explored the isolation and screening of an osmotolerant yeast, Wickerhamomyces anomalus BKK11-4, which is proficient in utilizing renewable feedstocks for sugar alcohol production. In batch fermentation with high initial glucose concentrations, W. anomalus BKK11-4 exhibited notable production of glycerol and arabitol. The results of the medium optimization experiments revealed that trace elements, such as H 3 BO 3 , CuSO 4 , FeCl 3 , MnSO 4 , KI, H 4 MoNa 2 O 4 , and ZnSO 4 , did not increase glucose consumption or sugar alcohol production but substantially increased cell biomass. Osmotic stress, which was manipulated by varying initial glucose concentrations, influenced metabolic outcomes. Elevated glucose levels promoted glycerol and arabitol production while decreasing citric acid production. Agitation rates significantly impacted the kinetics, enhancing glucose utilization and metabolite production rates, particularly for glycerol, arabitol, and citric acid. The operational pH dictated the distribution of the end metabolites, with glycerol production slightly reduced at pH 6, while arabitol production remained unaffected. Citric acid production was observed at pH 6 and 7, and acetic acid production was observed at pH 7. Metabolomic analysis using GC/MS identified 29 metabolites, emphasizing the abundance of sugar/sugar alcohols. Heatmaps were generated to depict the variations in metabolite levels under different osmotic stress conditions, highlighting the intricate metabolic dynamics occurring post-glucose uptake, affecting pathways such as the pentose phosphate pathway and glycerolipid metabolism. These insights contribute to the optimization of W. anomalus BKK11-4 as a whole-cell factory for desirable products, demonstrating its potential applicability in sustainable sugar alcohol production from renewable feedstocks., (© 2024. The Author(s) under exclusive licence to Sociedade Brasileira de Microbiologia.) more...

The circular economy is anticipated to bring a disruptive transformation in manufacturing technologies. Robust and industrial scalable microbial strains that can simultaneously assimilate and valorize multiple carbon substrates are highly desirable, as waste bioresources contain substantial amounts of renewable and fermentable carbon, which is diverse. Lignocellulosic biomass (LCB) is identified as an inexhaustible and alternative resource to reduce global dependence on oil. Glucose, xylose, and arabinose are the major monomeric sugars in LCB. However, primary research has focused on the use of glucose. On the other hand, the valorization of pentose sugars, xylose, and arabinose, has been mainly overlooked, despite possible assimilation by vast microbial communities. The present review highlights the research efforts that have explicitly proven the suitability of arabinose as the starting feedstock for producing various chemical building blocks via biological routes. It begins by analyzing the availability of various arabinose-rich biorenewable sources that can serve as potential feedstocks for biorefineries. The subsequent section outlines the current understanding of arabinose metabolism, biochemical routes prevalent in prokaryotic and eukaryotic systems, and possible products that can be derived from this sugar. Further, currently, exemplar products from arabinose, including arabitol, 2,3-butanediol, 1,2,3-butanetriol, ethanol, lactic acid, and xylitol are discussed, which have been produced by native and non-native microbial strains using metabolic engineering and genome editing tools. The final section deals with the challenges and obstacles associated with arabinose-based production, followed by concluding remarks and prospects. more...

Polyalcohols such as arabitol are among the main targets of biorefineries aiming to upcycle wastes and cheap substrates. In previous works Wickerhamomyces anomalus WC 1501 emerged as an excellent arabitol producer utilizing glycerol. Arabitol production by this strain is not growth associated, therefore, in this study, pre-grown cells were entrapped in calcium alginate beads (AB) and utilized for glycerol transformation to arabitol. Flasks experiments aimed to assess the medium composition (i.e., the concentration of inorganic and organic nitrogen sources and phosphates) and to establish the appropriate carrier-to-medium proportion. In flasks, under the best conditions of ammonium limitation and the carrier:medium ratio of 1:3 (w/v), 82.7 g/L glycerol were consumed in 168 h, yielding 31.2 g/L arabitol, with a conversion of 38% and volumetric productivity of 186 mg/mL/h. The process with immobilized cells was transferred to laboratory scale bioreactors with different configurations: stirred tank (STR), packed bed (PBR), fluidized bed (FBR), and airlift (ALR) bioreactors. The STR experienced oxygen limitation due to the need to maintain low stirring to preserve AB integrity and performed worse than flasks. Limitations in diffusion and mass transfer of oxygen and/or nutrients characterized also the PBR and the FBR and were partially relieved only in ALR, where 89.4 g/L glycerol were consumed in 168 h, yielding 38.1 g/L arabitol, with a conversion of 42% and volumetric productivity of 227 mg/mL/h. When the ALR was supplied with successive pulses of concentrated glycerol to replenish the glycerol as it was being consumed, 117 g/L arabitol were generated in 500 h, consuming a total of 285 g/L glycerol, with a 41% and 234 mg/L/h. The study strongly supports the potential of W. anomalus WC 1501 for efficient glycerol-to-arabitol conversion using immobilized cells. While the yeast shows promise by remaining viable and active for extended periods, further optimization is required, especially regarding mixing and oxygenation. Improving the stability of the immobilization process is also crucial for reusing pre-grown cells in multiple cycles, reducing dead times, biomass production costs, and enhancing the economic feasibility of the process., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The authors declared that they were an editorial board member of Frontiers, at the time of submission. This had no impact on the peer review process and the final decision., (Copyright © 2024 Ranieri, Candeliere, Sola, Leonardi, Rossi, Amaretti and Raimondi.) more...

Research Background: An innovative integrated bioprocess system for bioethanol production from raw sugar beet cossettes (SBC) and arabitol from remaining exhausted sugar beet cossettes (ESBC) was studied. This integrated three-stage bioprocess system is an example of the biorefinery concept to maximise the use of raw SBC for the production of high value-added products such as sugar alcohols and bioethanol., Experimental Approach: The first stage of the integrated bioprocess system was simultaneous sugar extraction from SBC and its alcoholic fermentation to produce bioethanol in an integrated bioreactor system (vertical column bioreactor and stirred tank bioreactor) containing a high-density suspension of yeast Saccharomyces cerevisiae (30 g/L). The second stage was the pretreatment of ESBC with dilute sulfuric acid to release fermentable sugars. The resulting liquid hydrolysate of ESBC was used in the third stage as a nutrient medium for arabitol production by non- Saccharomyces yeasts ( Spathaspora passalidarum CBS 10155 and Spathaspora arborariae CBS 11463)., Results and Conclusions: The obtained results show that the efficiency of bioethanol production increased with increasing temperature and prolonged residence time in the integrated bioreactor system. The maximum bioethanol production efficiency (87.22 %) was observed at a time of 60 min and a temperature of 36 °C. Further increase in residence time (above 60 min) did not result in the significant increase of bioethanol production efficiency. Weak acid hydrolysis was used for ESBC pretreatment and the highest sugar yield was reached at 200 °C and residence time of 1 min. The inhibitors of the weak acid pretreatment were produced below bioprocess inhibition threshold. The use of the obtained liqiud phase of ESBC hydrolysate for the production of arabitol in the stirred tank bioreactor under constant aeration clearly showed that S. passalidarum CBS 10155 with 8.48 g/L of arabitol ( Y P/S h)) is a better arabitol producer than . h)) is a better arabitol producer than Spathaspora arborariae CBS 10155., Novelty and Scientific Contribution: An innovative integrated bioprocess system for the production of bioethanol and arabitol was developed based on the biorefinery concept. This three-stage bioprocess system shows great potential for maximum use of SBC as a feedstock for bioethanol and arabitol production and it could be an example of a sustainable 'zero waste' production system., Competing Interests: CONFLICT OF INTEREST The authors declare that they have no competing interests., (Authors.) more...

Ribitol (C 5 H 12 O 5 ) is an acyclic sugar alcohol that was recently identified in O -mannose glycan on mammalian α-dystroglycan. The conformation and dynamics of acyclic sugar alcohols such as ribitol are dependent on the stereochemistry of the hydroxyl groups; however, the dynamics are not fully understood. To gain insights into the conformation and dynamics of sugar alcohols, we carried out comparative analyses of ribitol, d-arabitol and xylitol by a crystal structure database search, solution NMR analysis and molecular dynamics (MD) simulations. The crystal structures of the sugar alcohols showed a limited number of conformations, suggesting that only certain stable conformations are prevalent among all possible conformations. The three-bond scholar coupling constants and exchange rates of hydroxyl protons were measured to obtain information on the backbone torsion angle and possible hydrogen bonding of each hydroxyl group. The 100 ns MD simulations indicate that the ribitol backbone has frequent conformational transitions with torsion angles between 180∘ and ±60∘, while d-arabitol and xylitol showed fewer conformational transitions. Taking our experimental and computational data together, it can be concluded that ribitol is more flexible than d-arabitol or xylitol, and the flexibility is at least in part defined by the configuration of the OH groups, which may form intramolecular hydrogen bonds. more...

Hydrated ions have essential applications in biochemical processes. The objective of the present work is to study the behaviour of kosmotropic and chaotropic ions in aqueous solutions of polyhydroxy compounds in terms of sweetness response, volumetric and acoustic parameters such as apparent molar volume (∅ v ), apparent specific volume (ASV), compressibility (∅ k 0 values of arabitol showed more kosmotropic nature for Na v ion developing more stabilize structure of arabitol with water through strong hydrogen bonding, while the presence of K + ion developing more stabilize structure of arabitol with water through strong hydrogen bonding, while the presence of K + form weak hydrogen bonding with water termed as chaotropic ions. The ASV values showed that arabitol remained sweet in the presence of electrolytes. The negative results of ∅ - for arabitol in aqueous electrolytic solutions give valuable information about interactions occurring among solute, electrolytic ions, and water molecules. The structure-making/breaking behaviour has been observed by Hepler's constant (∂ k 0 for arabitol in aqueous electrolytic solutions give valuable information about interactions occurring among solute, electrolytic ions, and water molecules. The structure-making/breaking behaviour has been observed by Hepler's constant (∂ 2 ∅ v o /∂T 2 )p., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.) more...

Arabitol is gaining attention in the food industry as an alternative sweetener owing to its low-caloric and non-cariogenic characteristics. The yeast strain kiy1 was newly isolated from unpasteurized honey for arabitol production. Based on internal transcribed spacer sequence analysis, the isolated strain was identified as Zygosaccharomyces siamensis. In this study, the effects of different substrates and sugar concentrations on arabitol production were investigated. When three types of carbon sources (glycerol, fructose, and glucose) were used, glucose was the most suitable substrate for arabitol production (68.7 g/L). Maximum arabitol production (101.4 g/L) was observed at a glucose concentration of 30%, and the highest arabitol production yield was 0.34 g/g of initial glucose. In the time-course production of sugar alcohols by strain kiy1, glucose was completely consumed for 8 days. The concentration of arabitol exceeded that of glycerol after 3 days, and the final arabitol concentration reached 83.6 g/L after 10 days. The maximum production rate was 16.7 g/L/day. The yeast produced glycerol as an intracellular sugar alcohol in the early stage of culture and switched its metabolism to arabitol production after the middle stage. Z. siamensis kiy1 possessed an NADP + -dependent arabitol dehydrogenase, which indicated that it probably produces arabitol via ribulose from glucose. These results suggest that the novel yeast strain, Z. siamensis kiy1, is promising for arabitol production. The proposed arabitol production approach can contribute toward its production at the industrial scale., (© 2023. The Author(s).) more...

Bacterial cellulose (BC) exhibits beneficial properties for use in biomedical applications but is limited by its lack of tunable transparency capabilities. To overcome this deficiency, a novel method to synthesize transparent BC materials using an alternative carbon source, namely arabitol, was developed. Characterization of the BC pellicles was performed for yield, transparency, surface morphology, and molecular assembly. Transparent BC was produced using mixtures of glucose and arabitol. Zero percent arabitol pellicles exhibited 25% light transmittance, which increased with increasing arabitol concentration through to 75% light transmittance. While transparency increased, overall BC yield was maintained indicating that the altered transparency may be induced on a micro-scale rather than a macro-scale. Significant differences in fiber diameter and the presence of aromatic signatures were observed. Overall, this research outlines methods for producing BC with tunable optical transparency, while also bringing new insight to insoluble components of exopolymers produced by Komagataeibacter hansenii., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Jeannine M. Coburn, Elizabeth M. van Zyl, and Eric M. Young have the patent Transparent Cellulose-Based Materials and Methods of Making the Same pending to Worcester Polytechnic Institute., (Copyright © 2023 Elsevier B.V. All rights reserved.) more...

Background: D-Arabitol, a five-carbon sugar alcohol, represents a main target of microbial biorefineries aiming to valorize cheap substrates. The yeast Wickerhamomyces anomalus WC 1501 is known to produce arabitol in a glycerol-based nitrogen-limited medium and preliminary fed-batch processes with this yeast were reported to yield 18.0 g/L arabitol., Results: Fed-batch fermentations with W. anomalus WC 1501 were optimized using central composite design (CCD). Dissolved oxygen had not a significant effect, while optimum values were found for glycerol concentration (114.5 g/L), pH (5.9), and temperature (32.5 °C), yielding 29 g/L D-arabitol in 160 h, a conversion yield of 0.25 g of arabitol per g of consumed glycerol, and a volumetric productivity of 0.18 g/L/h. CCD optimal conditions were the basis for further improvement, consisting in increasing the cellular density (3✕), applying a constant feeding of glycerol, and increasing temperature during production. The best performing fed-batch fermentations achieved 265 g/L D-arabitol after 325 h, a conversion yield of 0.74 g/g, and a volumetric productivity of 0.82 g/L/h., Conclusion: W. anomalus WC 1501 confirmed as an excellent producer of D-arabitol, exhibiting a remarkable capability of transforming pure glycerol. The study reports among the highest values ever reported for microbial transformation of glycerol into D-arabitol, in terms of arabitol titer, conversion yield, and productivity., (© 2022. The Author(s).) more...

Evolutionary adaptation of living organisms is commonly thought to be the result of processes that have taken place over long periods of time. By contrast, we found that the filamentous rice blast fungus Magnaporthe oryzae rapidly suppresses the osmosensitive "loss of function" (lof) phenotype in knockout mutants of the high-osmolarity glycerol (HOG) pathway. That suppression occurs highly reproducibly after 4 weeks of continuous growth upon salt stress. Stable mutants reestablished in osmoregulation arise independently out of individual osmosensitive lof mutants of the HOG pathway. The major compatible solute produced upon salt stress by these suppressor strains was found to be glycerol, whereas it is arabitol in the wildtype strain. We aim to address the molecular or biochemical mechanisms behind this rapid suppression and characterize the associated factors and signaling pathways which enable or prevent suppression. Therefore, we present a protocol to generate these suppressor mutants in M. oryzae easily to study the molecular basis of evolutionary processes or even epigenetic modulation. This protocol may be applicable to many other fungi and will open a door for researchers worldwide since the HOG pathway is worked on intensively in many different model organisms. more...

Xylitol is a widely marketed sweetener with good functionality and health-promoting properties. It can be synthetized by many yeast species in a one-step reduction of xylose. Arabinose is a common contaminant found in xylose and there is ongoing interest in finding biocatalysts that selectively produce xyltiol. From a screen of 99 yeasts, Barnettozyma populi Y-12728 was found to selectively produce xylitol from both mixed sugars and corn stover hemicellulosic hydrolysate. Here, fermentation conditions for xylitol production from xylose by B. populi were optimized. The medium for xylitol production was optimized through response surface methodology. The yeast produced 31.2 ± 0.4 g xylitol from xylose (50 g L -1 ) in 62 h using the optimized medium. The optimal pH for xylitol production was 6.0. Glucose (10 g L -1 ), acetic acid (6.0 g L -1 ), HMF (4 mM) and ethanol (2.0 g L -1 ) inhibited the xylitol production. The glucose inhibition was entirely mitigated by using a 2-stage aeration strategy, indicating that the yeast was inhibited by ethanol produced from glucose under low aeration. This culture strategy will greatly benefit xylitol production from hemicellulosic hydrolysates, which often contain glucose. This is the first report on optimization of xylitol production by a Barnettozyma species. more...

Background: Human milk composition is altered by maternal obesity. The association between milk metabolites and infant outcomes has not been thoroughly investigated., Objectives: This study aimed to quantify maternal adiposity-related differences in the human milk metabolome and to identify metabolites associated with infant adiposity during the first 6 mo postpartum using untargeted metabolomics., Method: Maternal anthropometrics were assessed ≤14 weeks of gestation. Human milk samples were collected at 0.5 mo (n = 159), 2 mo (n = 131), and 6 mo (n = 94) postpartum from normal weight (NW, BMI = 18.5-24.9 kg/m2) and obese (OB, BMI >30 kg/m2) mothers. GC-time-of-flight-MS was used to identify metabolic signatures that discriminate NW and OB women. Partial least squared (PLS)-discriminant analysis, and PLS-regression models were assessed to examine relations between metabolites and maternal BMI and fat mass. Metabolites altered by maternal obesity were used in linear mixed effect models to predict infant adiposity., Results: Multivariate modeling identified 23, 17, and 10 metabolites that described maternal adiposity indices at 0.5 mo, 2 mo, and 6 mo postpartum, respectively. Monosaccharides and sugar alcohols were the most representative annotated metabolite classes that were increased in milk from OB women and included: mannose, ribose, lyxose, lyxitol (0.5 mo); mannose, ribitol, glycerol, isothreonic acid, lyxitol (2 mo); lyxitol and isothreonic acid (6 mo). Other discriminant metabolites included: 1-monostearin, xylonolactone, shikimic acid, pseudo uridine, and dodecanol (0.5 mo); N-acetyl-D-hexosamine and fumaric acid (2 mo); uric acid and tyrosine (6 mo). Mannose, lyxitol, and shikimic acid predicted higher infant adiposity over the first 6 mo of life., Conclusions: This study reports on 1 of the largest cohorts to date examining the metabolic profiles in human milk comparing NW and OB women. Maternal adiposity was associated with increased amounts of milk nonglucose monosaccharides. Human milk metabolomics may be useful in predicting infant adiposity. These trials were registered at www.clinicaltrials.gov as NCT01131117 and NCT02125149., (Copyright © The Author(s) on behalf of the American Society for Nutrition 2020.) more...

Lactic acid is the monomeric unit of polylactide (PLA), a bioplastic widely used in the packaging, automotive, food, and pharmaceutical industries. Previously, the yeast Komagataella phaffii was genetically modified for the production of lactate from glycerol. For this, the bovine L-lactate dehydrogenase- (LDH)-encoding gene was inserted and the gene encoding the pyruvate decarboxylase (PDC) was disrupted, resulting in the GLp strain. This showed a yield of 67% L-lactic acid and 20% arabitol as a by-product in batches with oxygen limitation. Following up on these results, the present work endeavored to perform a detailed study of the metabolism of this yeast, as well as perturbing arabitol synthesis in an attempt to increase lactic acid titers. The GLp strain was cultivated in a glycerol-limited chemostat at different dilution rates, confirming that the production of both lactic acid and arabitol is dependent on the specific growth rate (and consequently on the concentration of the limiting carbon source) as well as on the oxygen level. Moreover, disruption of the gene encoding arabitol dehydrogenase (ArDH) was carried out, resulting in an increase of 20% in lactic acid and a 50% reduction in arabitol. This study clarifies the underlying metabolic reasons for arabitol formation in K. phaffii and points to ways for improving production of lactic acid using K. phaffii as a biocatalyst., Competing Interests: The authors declare no conflict of interest. more...

Aims: To assess the ability of various newly isolated or belonging in official collections yeast strains to convert biodiesel-derived glycerol (Gly) into added-value compounds., Methods and Results: Ten newly isolated yeast strains belonging to Debaryomyces sp., Naganishia uzbekistanensis, Rhodotorula sp. and Yarrowia lipolytica, isolated from fishes, metabolized Gly under nitrogen limitation. The aim of the study was to identify potential newly isolated microbial candidates that could produce single-cell oil (SCO), endopolysaccharides and polyols when these micro-organisms were grown on biodiesel-derived Gly. As controls producing SCO and endopolysaccharides were the strains Rhodotorula glutinis NRRL YB-252 and Cryptococcus curvatus NRRL Y-1511. At initial Gly (Gly 0 ) ≈40 g l -1 , most strains presented remarkable dry cell weight (DCW) production, whereas Y. lipolytica and Debaryomyces sp. produced non-negligible quantities of mannitol and arabitol (Ara). Five strains were further cultivated at increasing Gly 0 concentrations. Rhodotorula glutinis NRRL YB-252 produced 7·2 g l -1 of lipid (lipid in DCW value ≈38% w/w), whereas Debaryomyces sp. FMCC Y 69 in batch-bioreactor experiment with Gly 0 ≈80 g l -1 , produced 30-33 g l -1 of DCW and ~30 g l -1 of Ara. At shake-flasks with Gly 0 ≈125 g l -1 , Ara of ~48 g l -1 (conversion yield of polyol on Gly consumed ≈0·62 g g -1 ) was achieved. Cellular lipids of all yeasts contained in variable concentrations oleic, palmitic, stearic and linoleic acids., Conclusions: Newly isolated, food-derived and non-previously studied yeast isolates converted biodiesel-derived Gly into several added-value metabolites., Significance and Impact of the Study: Alternative ways of crude Gly valorization through yeast fermentations were provided and added-value compounds were synthesized., (© 2019 The Society for Applied Microbiology.) more...

Despite the worldwide consumption of bovine milk, dairy products from small ruminants, such as goat's and sheep's milk, are gaining a large interest especially in the Mediterranean area. The aim of this work was to study the metabolite profiles of 30 sheep's and 28 goat's milk using an untargeted metabolomics approach by a gas chromatography coupled with mass spectrometry (GC-MS) analysis. Results showed several differences in the metabolite profiles: arabitol, citric acid, α-ketoglutaric acid, glyceric acid, myo-inositol, and glycine were more abundant in sheep's milk, while goat's milk had higher levels of mannose-6-phosphate, isomaltulose, valine, pyroglutamic acid, leucine, and fucose. Associations between metabolite profile and milk compositional traits were also found. Predictive capabilities of statistical models indicated a good correlation between the metabolite profile and the protein content in sheep's milk, and with the fat content in goat's milk. This work leads to a better understanding of milk metabolites in small ruminants and their role in the evaluation of milk properties., (Copyright © 2018 Elsevier Ltd. All rights reserved.) more...

Arabitol has several applications in food and pharmaceutical industries as a natural sweetener, dental caries inhibitor, and texturing agent. Newly isolated yeast strains from seawater, sugarcane plantation soil samples, and Zygosaccharomyces rouxii 2635 from MTCC were tested for arabitol production. The yield of arabitol was found to be higher in seawater isolate (24.6 g L -1 ) compared to two soil isolates (22.5 g L -1 ) and Z. rouxii (19.4 g L -1 ). Based on ITS 26S rDNA sequence analysis, the seawater isolate was identified as Pichia manchurica. In the present study, the effect of different substrates, trace elements, nitrogen sources, pH, and temperature on arabitol production was examined. Three different carbon sources viz. glucose, arabinose, and galactose were studied. Glucose was determined to be the best substrate for arabitol production (27.6 g L -1 ) followed by arabinose (13.7 g L -1 ) and galactose (7.7 g L -1 ). Maximum production of arabitol was observed at pH 6.0 (34.7 g L -1 ). In addition, arabitol production was high (35.7 g L -1 ) at temperature of 30 °C. Among the different concentrations of ammonium sulfate tested (3, 4.5, 6, 7.5, and 9 g L -1 ) concentration of 6 g L -1 resulted in higher arabitol Individual metal ions had no effect on arabitol production by this strain as compared to control. Results obtained in this study identify ways for improved arabitol production with natural isolates using microbial processes., (© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.) more...

Background & Objective: Crude glycerol (Glol), used as substrate for screening eleven natural Yarrowia lipolytica strains in shake-flask experiments. Aim of this study was to assess the ability of the screened strains to produce biomass (dry cell weight; X), lipid (L), citric acid (Cit), mannitol (Man), arabitol (Ara) and erythritol (Ery), compounds presenting pharmaceutical and biotechnological interest, in glycerol-based nitrogen-limited media, in which initial glycerol concentration had been adjusted to 40 g/L., Methods: Citric acid may find use in biomedical engineering (i.e. drug delivery, tissue engineering, bioimaging, orthopedics, medical device coating, wound dressings). Polyols are considered as compounds with non-cariogenic and less calorigenic properties as also with low insulin-mediated response. Microbial lipids containing polyunsaturated fatty acids (PUFA) are medically and dietetically important (selective pharmaceutical and anticancer properties, aid fetal brain development, the sight function of the eye, hormonal balance and the cardio-vascular system, prevent reasons leading to type-2 diabetes, present healing and anti-inflammatory effects)., Results: All strains presented satisfactory microbial growth (Xmax=5.34-6.26 g/L) and almost complete substrate uptake. The principal metabolic product was citric acid (Citmax=8.5-31.7 g/L). Production of cellular lipid reached the values of 0.33-0.84 g/L. Polyols were also synthesized as strain dependent compounds (Manmax=2.8-6.1 g/L, Aramax ~2.0 g/L, Erymax= 0.5-3.8 g/L). The selected Y. lipolytica strain ACA-DC 5029 presented satisfactory growth along with synthesis of citric acid and polyols, thus, was further grown on media presenting an increased concentration of Glol~75 g/L. Biomass, lipid and citric acid production presented significant enhancement (Xmax=11.80 g/L, Lmax=1.26 g/L, Citmax=30.8 g/L), but conversion yield of citric acid produced per glycerol consumed was decreased compared to screening trials. Erythritol secretion (Erymax=15.6 g/L) was highly favored, suggesting a shift of yeast metabolism from citric acid accumulation towards erythritol production. Maximum endopolysaccharides (IPS) concentration was 4.04 g/L with yield in dry weight 34.2 % w/w., Conclusion: Y. lipolytica strain ACA-YC 5029 can be considered as a satisfactory candidate grown in high concentrations of crude glycerol to produce added-value compounds that interest pharmaceutical and biotechnology industries., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.) more...

Arabitol is used in the food industry as a low-calorie sweetener. It is produced by yeasts during the biotransformation process of l-arabinose. Genome shuffling was performed in Candida parapsilosis DSM 70125, an efficient producer of arabitol, to obtain fusants with improved arabitol production ability. Four mutants from the parental library were used for the first round of genome shuffling. The best fusants, GSI-1 and GSI-10A, were subjected to a second round of genome shuffling. Finally, two fusants, GSII-3 and GSII-16, produced concentrations of arabitol that were 50% higher than that of the wild-type strain during selection culture. Under the optimal conditions established for C. parapsilosis , the two fusants produced 11.83 and 11.75 g/L of arabitol and were approximately 15-16% more efficient than the wild-type strain. Flow cytometry analysis showed that the ploidy of the new strains did not change., Competing Interests: Compliance with ethical standardsThe authors declare no conflicts of interest. more...

Lactic acid is the monomer unit of the bioplastic poly-lactic acid (PLA). One candidate organism for lactic acid production is Pichia pastoris , a yeast widely used for heterologous protein production. Nevertheless, this yeast has a poor fermentative capability that can be modulated by controlling oxygen levels. In a previous study, lactate dehydrogenase (LDH) activity was introduced into P. pastoris, enabling this yeast to produce lactic acid. The present study aimed to increase the flow of pyruvate towards the production of lactic acid in P. pastoris . To this end, a strain designated GLp was constructed by inserting the bovine lactic acid dehydrogenase gene (LDHb) concomitantly with the interruption of the gene encoding pyruvate decarboxylase (PDC). Aerobic fermentation, followed by micro-aerophilic culture two-phase fermentations, showed that the GLp strain achieved a lactic acid yield of 0.65 g/g. The distribution of fermentation products demonstrated that the acetate titer was reduced by 20% in the GLp strain with a concomitant increase in arabitol production: arabitol increased from 0.025 g/g to 0.174 g/g when compared to the GS115 strain. Taken together, the results show a significant potential for P. pastoris in producing lactic acid. Moreover, for the first time, physiological data regarding co-product formation have indicated the redox balance limitations of this yeast., Competing Interests: The authors declare no conflict of interest. more...

Arabitol is a low-calorie sugar alcohol with anti-cariogenic properties. Enzymatic hydrolysate of soybean flour is a new renewable biorefinery feedstock containing hexose, pentose, and organic nitrogen sources. Arabitol production by Debaryomyces hansenii using soybean flour hydrolysate was investigated. Effects of medium composition, operating conditions, and culture stage (growing or stationary phase) were studied. Production was also compared at different culture volumes to understand the effect of dissolved oxygen concentration (DO). Main factors examined for medium composition effects were the carbon to nitrogen concentration ratio (C/N), inorganic (ammonium) to organic nitrogen ratio (I/O-N), and sugar composition. Arabitol yield increased with increasing C/N ratio and a high I/O-N (0.8-1.0), suggesting higher yield at stationary phase of low pH (3.5-4.5). Catabolite repression was observed, with the following order of consumption: glucose > fructose > galactose > xylose > arabinose. Arabitol production also favored hexoses and, among hexoses, glucose. DO condition was of critical importance to arabitol production and cell metabolism. The yeast consumed pentoses (xylose and arabinose) only at more favorable DO conditions. Finally, arabitol was produced in fermentors using mixed hydrolysates of soy flour and hulls. The process gave an arabitol yield of 54%, volumetric productivity of 0.90 g/L-h, and specific productivity of 0.031 g/g-h. more...

The aim of this study was to compare arabitol with its better studied isomer xylitol for their inhibitory effects on cell growth and acid production of oral bacteria. Streptococcus mutans, Streptococcus salivarius and Streptococcus sobrinus were used as representatives of oral streptococci and Lactobacillus acidophilus and Lactobacillus fermentum were used for oral lactobacilli. Growth was followed by measuring the absorbance at 660nm, acid production by pH change. Sensitivity of these oral bacteria to arabitol and xylitol was first compared at 1% (65mM) additive concentration with glucose as sugar substrate. For all bacteria tested, the inhibitory effects of the two polyols were comparable; both were significantly stronger on streptococci (with 20-60% inhibition) than on lactobacilli (with 5-10% inhibition). Effects of arabitol and xylitol were also compared for S. mutans and S. salivarius in media with 1% of different sugar substrates: glucose (55mM), fructose (55mM), galactose (55mM) and sucrose (30mM). Inhibition occurred for all sugars: stronger on glucose and galactose (60-65%) than on fructose and sucrose (40-45%). Inhibition dependency on the arabitol/xylitol concentration from 0.01% (0.65mM) to 2% (130mM) was further determined for S. mutans and S. salivarius. Regardless of the concentration, sugar substrate and bacterial species tested, arabitol showed very similar inhibition effects to its isomer xylitol., (Copyright © 2015 Elsevier Ltd. All rights reserved.) more...

Arabitol belongs to the pentitol family and is used in the food industry as a sweetener and in the production of human therapeutics as an anticariogenic agent and an adipose tissue reducer. It can also be utilized as a substrate for chemical products such as arabinoic and xylonic acids, propylene, ethylene glycol, xylitol and others. It is included on the list of 12 building block C3-C6 compounds, designated for further biotechnological research. This polyol can be produced by yeasts in the processes of bioconversion or biotransformation of waste materials from agriculture, the forest industry (l-arabinose, glucose) and the biodiesel industry (glycerol). The present review discusses research on native yeasts from the genera Candida, Pichia, Debaryomyces and Zygosaccharomyces as well as genetically modified strains of Saccharomyces cerevisiae which are able to utilize biomass hydrolysates to effectively produce L- or D-arabitol. The metabolic pathways of these yeasts leading from sugars and glycerol to arabitol are presented. Although the number of reports concerning microbial production of arabitol is rather limited, the research on this topic has been growing for the last several years, with researchers looking for new micro-organisms, substrates and technologies., (© 2015 The Society for Applied Microbiology.) more...