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Vineyard pruning is a potential lignocellulosic feedstock for bioethanol production from agricultural woody residues, due to its high sugar content and ready availability in whole Europe. Ethanol production from lignocellulosic biomass requires a pretreatment step and then enzymatic hydrolysis process to release sugars for fermentation to ethanol. In this work, alkaline pretreatment with NaOH on vineyard residues was investigated on laboratory scale. The raw material was firstly characterized in order to determine cellulose, hemicellulose and lignin content, using the standard laboratory analytical procedures for biomass analysis provided by the National Renewable Energy Laboratory (NREL). Then, based on Response Surface Methodology tool (RSM), a Box-Behnken model was chosen to define a design of experiments (DoE) in terms of the three independent variables that influence the process: the NaOH concentration, the reaction time and the temperature of the pretreatment process. According to the design, 15 samples of raw material were submitted to alkaline pretreatment and subsequent enzymatic hydrolysis and the glucose yield from whole process was calculated. The statistical optimization was carried out with Minitab 17 software, in order to determine the best operative pretreatment condition by maximizing the glucose yield from enzymatic hydrolysis. Results show that the best glucose yield was obtained at the highest sodium hydroxide concentration and temperature of the reaction; this condition allowed to achieve very significant glucose yield thanks to lignin removal performed with the pretreatment. [ABSTRACT FROM AUTHOR]

The bagasse of two sugar crops i.e. sugarcane (variety CoJ 83) and sweet sorghum (variety RSSV 9) were evaluated for their potential for the production of bioethanol. Different chemical pretreatments were carried out with 2 % HO, 1 % NaOH and 2 % HO + 1 % NaOH solutions each with pH 11.5 and 13 for 24, 48 and 72 h followed by saccharification of pretreated bagasse with sulfuric acid (0.8 and 1 M) for 50 min. Bagasse hydrolysates were then fermented with Saccharomyces cerevisiae var ellipsoideus for ethanol production. The amounts of cellulose, hemicellulose and lignin were 47.1, 29.2, 11.2 % in sugarcane and 45.8, 28.1, 14.0 % in sweet sorghum respectively. Loss of weight in alkaline pretreatment was found more in sugarcane (45.4 %) than in sweet sorghum (43.1 %). The maximum amounts of reducing sugars 528.8 and 504.8 mg/g were obtained by saccharification of pretreated bagasse of sugarcane and sweet sorghum respectively, after saccharification with 0.8 M HSO. Bioethanol production was found maximum 30.5 and 26.2 ml/100 g pretreated bagasse in sugarcane and sweet sorghum with pretreatment conditions of (2 % HO + 1 % NaOH; pH 11.5, 72 h) and (2 % HO + 1 % NaOH; pH 13, 72 h) respectively, followed by saccharification with 0.8 M HSO, and fermentation for 72 h. But when estimated ethanol production on unit weight basis of crops, it was found higher in sweet sorghum (25.4 L/ton stalks) crop than in sugarcane (21.4 L/ton stalks). [ABSTRACT FROM AUTHOR]

High energy consumption has been one of bottlenecks for bioconversion of lignocellulose into biofuels and biochemicals. A self-designed pilot-scale device with recycling of black liquor (BL) and waste washing water (WWW) was constructed to conduct low-temperature pretreatment and high-solid enzymatic hydrolysis of sugarcane bagasse (SCB) at ordinary atmospheric pressure. Results showed that enzymatic hydrolysis of WWW-washed BL-WWW-NaOH-treated SCB at 30% solid concentration for 72 h achieved 91.59 g/L glucose with glucan conversion of 70.94%. The pretreatment unit shared only 19.68%–22.43% of total energy consumption and 8.32%–8.81% of total cost. The non-sterile enzymatic hydrolysate could be directly fermented by BL-adapted yeasts to maximally produce 44.82 g/L ethanol at 48 h, while the sterile hydrolysate could not be fermented. 2,3-dihydro-3,5-dihydroxy-6-methyl-4H-pyran-4-one, furancarboxaldehyde and 5-hydroxymethylfurfural might be the dominant inhibitors in the sterile enzymatic hydrolysate for ethanol production. Finally, a low-emission strategy for cellulosic ethanol production with low energy consumption was proposed. [Display omitted] • A waste liquid recycling device for saccharifying lignocellulose was constructed. • Pretreatment step only shared 8.32%–8.81% of total cost. • Around 70% glucan conversion at 30% solid concentration was achieved in the device. • Adapted strains can ferment non-sterile rather than sterile hydrolysate. • A low-emission strategy for cellulosic ethanol production was proposed. [ABSTRACT FROM AUTHOR]

Medium-chain-length polyhydroxyalkanoates (mcl-PHAs), polyesters produced by bacterial fermentation of sugars and/or lipids, are potential bioplastic alternatives to petroleum-derived plastics. Lignocellulose is an abundant renewable source of sugars for bacterial fermentation. However, chemical or enzymatic release of the sugars requires a pretreatment step to dispel the rigid structure of the lignocellulose and enhance sugar access. Most pretreatments of lignocellulose involve high temperature and/or pressure, which increases processing and production costs and discourages commercialization. Here we demonstrate a chemical-biological pathway for mcl-PHAs production from rice straw and hemp hurd. We combined ambient alkaline pretreatment, enzymatic hydrolysis, and bacterial fermentation. The alkaline pretreatment reduced the particle size of pretreated solids and partially fractionated hemicellulose and lignin; these effects increased cellulose accessibility to enzymes and enabled a high sugar release (78–83% glucose yield) at a high solid loading (9 wt%). Therefore, we obtained 47 wt% and 69 wt% mcl-PHAs (with respect to gram of dry cell weight) from pretreated rice straw and hemp hurd, respectively. These findings constitute an energy-efficient pretreatment process that can be extended to other sources of lignocellulose, such as woody biomass and dedicated bioenergy crops. Moreover, mcl-PHAs from lignocellulose provide revenue to the agricultural sector, mitigate global warming from fossil fuel processing, and potentially reduce plastic pollution. [Display omitted] • Upcycling lignocellulose to mcl-PHAs promotes bioeconomy. • Ambient alkaline pretreatment retains sugars in the pretreated solids. • This treatment enhances cellulose accessibility to enzymes. • Hydrolysis of treated solids results in 78–83% glucose at a 9 wt% solid loading. • Bacterial fermentation of resulting sugars yields 0.6 g mcl-PHAs/L. [ABSTRACT FROM AUTHOR]

This study investigated the damages of microbial cell structures, as well as the relationships between these damages and the release of cellular organic matter in the pretreatment of waste activated sludge (WAS) by using alkaline pretreatment as model. In the alkaline pretreatment of WAS, the most damage of bound extracellular polymeric substances (EPS), cell walls, cell membranes, and cell nuclei occurred at pH 11.5–12.0 (46.2%), pH 11.0–11.5 (27.3%), pH 9.0–10.0 (34.2%), and pH 11.5–12.0 (44.4%), respectively. The damage percentages of these cell structures in the pH stabilization stage were low because most of the damages occurred when the pH increased. The structural integrities of sludge microorganisms were all damaged in the pH increase stage. The damages of EPS, cell walls, and cell membranes were significantly correlated with the release of cellular organic matter, and these damages were necessary to release the cellular matter in WAS. [ABSTRACT FROM AUTHOR]

A combination of briquetting wheat straw (BWS) and additives is presented in this work. Two experiments were designed: firstly the mold size of the briquetting equipment and the additive addition were evaluated as an integrated pre-treatment promoting methane (CH 4 ) yield and hydrolysis rate ( k ). Secondly, two combinations from the first experiment were used in continuous stirred tank reactors (CSTR) in co-digestion with cattle manure (CM). In this second experiment, CH 4 yield, reactor performance and residual CH 4 production were measured. The addition of alkali to BWS had a more significant effect on k than on the CH 4 promotion. The CSTR results showed that the addition of 3% KOH to BWS had a positive effect on VS degradation, CH 4 production and energy and economic balances. In addition, the potential for CH 4 emissions during the subsequent storage was reduced. [ABSTRACT FROM AUTHOR]

The objective of the work was to assess the effect of mild alkaline pretreatment on the anaerobic biodegradability of tomato processing waste (TPW). Experiments were carried out in duplicate BMP bottles using a pretreatment contact time of 4 and 24 h and a 1% and 5% NaOH dosage. The cumulative methane production during a 30 d period was recorded and modelled. The alkaline pretreatment did not significantly affect methane production in any of the treatments in comparison to the control. The average methane production for all runs was 320 NmL/gVS. Based on first order kinetic modelling, the alkaline pretreatment was found to slow down the rate of methanogenesis, mainly in the two reactors with the highest NaOH dosage. The biodegradability of the substrates ranged from 0.75 to 0.82 and from 0.66 to 0.72 based on two different approaches. [ABSTRACT FROM AUTHOR]

This study explores acid and alkaline pretreatments in order to enhance soybean straw biodegradability. The effects of sulfuric acid and sodium hydroxide for different pretreatment times at 30 °C and 121 °C on biomass dissolution and the subsequent enzymatic hydrolysis were investigated. The highest total conversion to reducing sugars of 93.9% was attained when soybean straw was pretreated with acid (4% H 2 SO 4 , 121 °C, 1 h) and subsequently subjected to the enzymatic process. However, conversion of 86.5%, were reached only with the hydrolysis of the pretreated residue using mild conditions, (0.5% NaOH, 30 °C, 48 h), involving the reduction cost of the process. In addition to this, this result was dramatically decreased when pectinase was removed from the enzyme cocktail. It has been also demonstrated that the reduction of the enzyme loading to less than half allowed obtaining about 96% of the reducing sugars attained with the highest enzyme dose. [ABSTRACT FROM AUTHOR]

Physico-chemical and gelling properties of agar extracted from Gracilaria tenuistipitata as affected by alkaline pretreatments using NaOH and KOH at various levels (3–7%, w/v) were investigated. Yield of native agar was 17.1%, whilst those of agars pretreated with NaOH and KOH ranged from 23.6% to 26.1%. Agar with alkaline pretreatment generally showed the better gelling property as evidenced by higher gel strength, gelling, melting temperatures and viscosity with coincidentally increased 3,6-anhydrogalactose (3,6-AG) content than did native agar. Additionally, native agar had a higher sulphate content with lower syneresis (P < 0.05) than those with alkaline pretreatment. Regardless of alkaline concentration, NaOH used for pretreatment rendered agar with a higher quality, compared with KOH. Agar (1.5%, w/v) pretreated with 5% NaOH exhibited the highest gel strength (482 g/cm 2 ) with high yield (25.3%). The decrease in total sulphate content and the increase in 3,6-AG content were observed in agar having 5% NaOH pretreatment as determined by FTIR spectroscopy. Finer and more compact network with smaller pores was visualised in gel from agar with 5% NaOH pretreatment. Therefore, the appropriate pretreatment by using 5% NaOH could increase yield and improve the gelling property of agar from G. tenuistipitata harvested from the lake of Songkhla, Thailand. [ABSTRACT FROM AUTHOR]

In this work, an alkaline delignification was investigated for several industrially relevant hardwoods to understand the kinetics of xylan solubilization and degradation and the role of residual lignin content in setting cell wall recalcitrance to enzymatic hydrolysis. Between 34 and 50 % of the xylan was solubilized during the heat-up stage of the pretreatment and undergoes degradation, depolymerization, as well as substantial disappearance of the glucuronic acid substitutions on the xylan during the bulk delignification phase. An important finding is that substantial xylan is still present in the liquor without degradation. Cellulose hydrolysis yields in the range of 80 to 90 % were achievable within 24-48 h for the diverse hardwoods subjected to delignification by alkali at modest enzyme loadings. It was found that substantial delignification was not necessary to achieve these high hydrolysis yields and that hybrid poplar subjected to pretreatment removing only 46 % of the lignin was capable of reaching yields comparable to hybrid poplar pretreated to 67 or 86 % lignin removal. Decreasing the lignin content was found to increase the initial rate of cellulose hydrolysis to glucose while lignin contents under approximately 70 mg/g original biomass were found to slightly decrease the maximum extent of hydrolysis, presumably due to drying-induced cellulose aggregation and pore collapse. Pretreatments were performed on woodchips, which necessitated a 'disintegration' step following pretreatment. This allowed the effect of comminution method to be investigated for the three hardwoods subjected to the highest level of delignification. It was found that additional knife-milling following distintegration did not impact either the rate or extent of glucan and xylan hydrolysis. [ABSTRACT FROM AUTHOR]

Various alkaline pretreatments were applied to Scots pine (Pinus sylvestris) and silver/white birch (Betula pendula/pubescens) wood chips and the characterization of sulfur-free lignin dissolved was performed. The behavior of lignin during these pretreatments (alkali charge 1–8% NaOH, time 30–120 minutes, and temperature 130–150°C) was studied mainly in terms of lignin removal efficiency and molar mass distribution of dissolved lignin. The amount of lignin in pretreatment liquors increased along with an increase in the alkali charge of 0.8–4.4% and 0.6–3.4% of o.d. pine and birch wood, respectively. The most significant parameter affecting the molar mass of the dissolved lignin was shown to be the alkali charge, since an increase in this parameter clearly increased the-values of dissolved lignin, varying from 2,260 g/mol to 7,050 g/mol and from 2,200 g/mol to 5,550 g/mol for pine and birch lignin, respectively. [ABSTRACT FROM PUBLISHER]

Alkaline pretreatment using NaOH, KOH, or NaOCl has been applied to various types of waste biomass to enhance enzymatic digestibility. Pretreatment (2% NaOH, 121 °C, 30 min) of rice paddy straw (PS) resulted in a maximum yield of 703 mg of reducing sugar per gram of PS with 84.19% hydrolysis yield after a two-step enzymatic hydrolysis process. Ralstonia eutropha ATCC 17699 was tested for its ability to synthesize poly-3-hydroxybutyrate (PHB) using PS hydrolysates as its sole carbon source. It is noteworthy that dry cell weight, polyhydroxyalkanoate (PHA) accumulation and PHB yield with the use of laboratory-grade sugars were similar to those achieved with PS-derived sugars. Under optimized conditions, we observed maximal PHA accumulation (75.45%) and PHB production (11.42 g/L) within 48 h of fermentation. After PHB recovery, the physicochemical properties of PHB were determined by various analytical techniques, showed the results were consistent with the characteristics of a standard polymer of PHB. Thus, the PS hydrolysate proved to be an excellent cheap carbon substrate for PHB production. [ABSTRACT FROM AUTHOR]

A step of pretreatment prior to anaerobic digestion has been widely studied to enhance biogas production from lingocellulosic biomass. In this study, alkaline pretreatment and mechanical pretreatment by size reduction were tested on the two phase olive mill waste (TPOMW) in order to facilitate the degradation of lignocellulosic organic matter and thereafter the subsequent bioconversion to methane. For alkaline pretreatment, NaOH and CaO with concentrations in the range of 2.4 % to 30 % were tested. Following pretreatment, anaerobic digestion was conducted in batch mode for 26 days. Mechanical pretreatment did not increase the soluble compounds, measured as soluble chemical oxygen demand (sCOD), nor improved methane production. On the other hand, both CaO and NaOH were able to degrade part of the lignocellulosic organic matter to more easily degradable organic compounds. Especially NaOH was strong enough to solubilize part of the lignocellulosic organic matter; sCOD was increased to 265 ± 49.5 g O2/kg after pretreatment with 30% NaOH compared with 74.1 g O2/kg for the untreated TPOMW. However, inhibition because of high initial alkalinity or high sodium ion concentration was recognized for high NaOH dosage. Six percent NaOH increased methane production by 20.3% and 11.2% compared with the untreated and the CaO pretreated TPOMW respectively. Although NaOH concentration of 6% was found to be reasonable for improving methane production without pH neutralization, considering a full scale reactor system receiving food waste as a main substrate and the NaOH-treated TPOMW as a co-substrate, the NaOH concentration of 20% might be optimum regarding the soluble COD concentration. [ABSTRACT FROM AUTHOR]

In this study, production of cellulosic ethanol from two cotton processing residues was investigated after pretreatment with dilute sodium hydroxide. Pretreatment performance was investigated using a 2 2 factorial design and the highest glucan conversion was achieved at the most severe alkaline conditions (0.4 g NaOH g −1 of dry biomass and 120 °C), reaching 51.6% and 38.8% for cotton gin waste (CGW) and cotton gin dust (CGD), respectively. The susceptibility of pretreated substrates to enzymatic hydrolysis was also investigated and the best condition was achieved at the lowest total solids (5 wt%) and the highest enzyme loading (85 mg of Cellic CTec2 g −1 of dry substrate). However, the highest concentration of fermentable sugars – 47.8 and 42.5 g L −1 for CGD and CGW, respectively – was obtained at 15 wt% total solids using this same enzyme loading. Substrate hydrolysates had no inhibitory effects on the fermenting microorganism. [ABSTRACT FROM AUTHOR]

Fermentation of lignocellulosic biomass requires auxiliary materials such as nutrients for fermentation. Because of the low prices of fermentation products such as bioethanol, the costs of nutrients are not negligible. We have developed the concept of using substances natively present in lignocellulosic biomass as nutrients for the downstream fermentation. The leaves and stalks of young dent corn plants were used as biomass and the nutrients were recovered by soaking them in water before alkaline pretreatment, followed by enzymatic saccharification and fermentation. Performing thermophilic l -lactic acid fermentation using these recovered nutrients support their use as commercially feasible alternatives. A level of recovered nutrients of 40% was sufficient to support the fermentation of recovered sugars derived from the same corn biomass. However, the amount of recovered nutrients required for fermentation was almost double that when using yeast extract based on the amounts of nitrogen and/or phosphorus added. The nitrogen and phosphorus balances in the process indicated that adding nutrients was crucial for promoting fermentation based on the amounts of nitrogen and phosphorus. The nutrients proposed were considered to be effective for fermenting biomass pretreated by alkaline, dilute acid, and hydrothermal methods. [ABSTRACT FROM AUTHOR]

A simple hydrodynamic cavitation (HC) system was newly employed as a pretreatment method for H 2 production from cheese whey. This system offered not only the sonication effect but also an increase in the temperature of the solution. With HC pretreatment for 15 min, a higher H 2 production yield (1.89 mol H 2 /mol lactose) was obtained than with other conventional pretreatment methods such as heating and sonication. HC pretreatment efficiency was synergistically increased when combined with alkaline conditions. In this way, the amount of solubilized nutrient was greatly increased and methanogens were completely removed, leading to H 2 gas of higher purity (48%) and a yield of 3.30 mol H 2 /mol lactose. HC pretreatment under alkaline conditions can be used to efficiently pretreat organic-rich wastewater, including cheese whey, without any scale-up problem, and is an excellent pretreatment option for H 2 production. [ABSTRACT FROM AUTHOR]

Rice husk as a widely available lignocellulosic material was subjected to an alkaline pretreatment process. The alkaline pretreatment was carried out under various conditions. The influence of process parameters, such as pretreatment time, solid loading, and NaOH concentration, on the glucose and xylose yields were investigated by means of appropriate models. The maximum glucose and xylose yields obtained under optimum pretreatment condition were 68.82% and 53.77%, respectively. Response surface methodology (RSM) and artificial neural network were used to model the pretreatment processes. Both modeling methodologies were statistically compared by means of the coefficient of determination and relative mean square error. It was concluded that the artificial neural network shows a somewhat better performance compared to RSM. [ABSTRACT FROM PUBLISHER]

As a biggest palm oil producer in the world, Indonesia also produces a huge amount of oil palm waste, like oil palm empty fruit bunch (EFB) and oil palm fronds (OPF). Oil palm EFB and OPF contain cellulose that can be converted to bioethanol through pretreatment, saccharification, and fermentation processes. The pretreatment is required to liberate the cellulose from lignocellulosic matrix. One of pretreatment method is chemical pretreatment process using alkaline solution at high pressure and temperature. This paper reports the influence of alkaline pretreatment to chemical composition, cellulose crystallinity index, and morphology of oil palm EFB and OPF. The results show that increasing of alkaline concentration causes decreasing of lignin content from 25.83% to 13.61% for oil palm EFB and from 30.92% to 19.23% for OPF at 10% of NaOH solution. The lowest cellulose crystallinity index of oil palm EFB and OPF are achieved at 10% and 8% of NaOH solution, respectively. The result also indicates the changing of oil palm EFB and OPF morphology. After alkaline pretreatment, the surface of oil palm EFB and OPF look rougher than the raw material, some holes are formed on them. [ABSTRACT FROM AUTHOR]

This study investigated the effects of alkaline pretreatments and acid extraction conditions on the production of acid-soluble collagen (ASC) from grass carp skin. For alkaline pretreatment, 0.05 and 0.1 M NaOH removed non-collagenous proteins without significant loss of ASC at 4, 10, 15 and 20 °C; while 0.2 and 0.5 M NaOH caused significant loss of ASC, and 0.5 M NaOH caused structural modification of ASC at 15 and 20 °C. For acid extraction at 4, 10, 15 and 20 °C, ASC was partly extracted by 0.1 and 0.2 M acetic acid, while 0.5 and 1.0 M acetic acid resulted in almost complete extraction. The processing conditions involving 0.05–0.1 M NaOH for pretreatment, 0.5 M acetic acid for extraction and 4–20 °C for both pretreatment and extraction, produced ASC with the structural integrity being well maintained and hence were recommended to prepare ASC from grass carp skin in practical application. [ABSTRACT FROM AUTHOR]

Bagasse liquefaction (BL) in water, tetralin, and water/tetralin mixed solvents (WTMS) was investigated, and effects of tetralin content in WTMS, temperature, and alkaline pretreatment of bagasse on liquefaction efficiency were studied. At 300 °C, bagasse conversion in WTMS with tetralin content higher than 50 wt% was 86–87 wt%, whereas bagasse conversion in water or tetralin was 67 wt% or 84 wt%, respectively. Because the solid conversion from liquefaction in WTMS with tetralin content higher than 50 wt% was always higher than that in water or tetralin at temperatures between 250 and 300 °C, a synergic effect between water and tetralin is suggested. Alkaline pretreatment of bagasse resulted in significantly higher conversion and heavy oil yield from BL in water or WTMS. The effect of deoxygenation by the present liquefaction method is demonstrated by lower oxygen contents (16.01–19.59 wt%) and higher heating values (31.9–34.8 MJ/kg) in the produced oils. [ABSTRACT FROM AUTHOR]

This study compares the efficacy of a soaking pretreatment with an alkaline solution for banana pseudostem prior to enzymatic hydrolysis. Banana pseudostem was pretreated by soaking in sodium hydroxide solutions at various concentrations and durations. The pretreatment more than doubled delignification but retained 82.09% of the holocellulose content and 73.74% of the cellulose content. The enzymatic (Trichoderma reesei) digestibility of pretreated banana pseudostem was found to have been enhanced by 44.41% as compared to initial biomass. This was evidenced by higher enzymatic activities (endoglucanase, exoglucanase, and ß-glucosidase) on the treated sample. Meanwhile, glucose yield showed a proportional relationship with incubation time and enzyme loading throughout the hydrolysis process. [ABSTRACT FROM AUTHOR]

This study was conducted to analyse structural changes through scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) after alkaline pretreatment of wheat straw for optimum steaming period. During the study, 2 mm size of substrate was soaked in 2.5% NaOH for 1 h at room temperature and then autoclaved at 121°C for various steaming time (30, 60, 90 and 120 min). Results revealed that residence time of 90 min at 121°C has strong effect on substrate, achieving a maximum cellulose content of 83%, delignification of 81% and hemicellulose content of 10.5%. Further SEM and FTIR spectroscopy confirmed structural modification caused by alkaline pretreatment in substrate. Maximum saccharification yield of 52.93% was achieved with 0.5% enzyme concentration using 2.5% substrate concentration for 8 h of incubation at 50°C. This result indicates that the above-mentioned pretreatment conditions create accessible areas for enzymatic hydrolysis. [ABSTRACT FROM PUBLISHER]

Whole parts of castor plant, as a non-edible energy crop, were used for multiple biofuels production. Extracted castor oil was used for biodiesel production by transesterification, whereas the castor plant residues, i.e., stem, seed cake, and leaves, were employed for ethanol and biogas production. Effects of operating conditions, including methanol to oil ratio, temperature, and reaction time on biodiesel production yield were investigated. The optimum biodiesel yield was 88.2%, obtained at 0.4:1 methanol to oil mass ratio at 40 °C for 90 min. This yield corresponded to 155 g biodiesel per kg castor plant. In addition, pretreatment using 8% w/v NaOH at 0 and 100 °C for 30 and 60 min was applied to improve ethanol and biogas yields. The best results for both enzymatic hydrolysis and ethanol production by simultaneous saccharification and fermentation (SSF) were obtained after alkali pretreatment at 100 °C for 60 min for all plant residues. The highest ethanol production yield achieved from pretreated castor stem was as high as 82.2%, corresponding to 63 g ethanol per kg castor plant. In the case of biogas production, alkali pretreatment enhanced the methane production yield from castor stem; however, it could not improve the production yield of castor seed cake and leaves. Furthermore, untreated castor seed cake had the highest methane production yield of 252.1 ml/g VS, equal to 68.2 L per kg of castor plant. [ABSTRACT FROM AUTHOR]

Biofuel is a renewable and sustainable energy as an substitute of fossil fuel. In China, the key challenge to develop biofuels is how to balance the competition of food and bioenergy and supply a sustainable feedstock. Sweet sorghum is highlighted as a multiple platform plant which can supply grain, sugar, cellulose and feed. In addition, sweet sorghum has so good tolerance of drought and sterilize that it can grow on marginal land. However, the loose stalk pith of sweet sorghum results in the infeasibility of liquid fermentation technology due to the considerably high energy consumption. In present research, an integrated process combined advanced solid-state fermentation technology (ASSF) and alkaline pretreatment was presented in this work. Soluble sugars in sweet sorghum stalks were firstly converted into ethanol by ASSF using crushed stalks directly. Then, the operation combining ethanol distillation and alkaline pretreatment was performed in one distillation-reactor simultaneously. The process was optimized according to the yield of sugar-ethanol and amounts of monosaccharide released from SSB. In our novel process, energy consumption of mechanically squeeze and pretreatment of SSB was avoided. Meanwhile, the recalcitrance of lignocellulose was destructed and the biodegradation of lignocellulose into chemical products is feasible to achieve. Cellulosic ethanol as a model product was studied by using this novel integrated process. The mass balance of the overall process was calculated, and 91.9 kg was achieved from one tonne of fresh sweet sorghum stalk. Energy consumption for raw materials preparation and pretreatment were reduced or avoided in our process. To produce 1 tonne of ethanol, the energy input in this process was 12,481.2 MJ/tonne, while the energy input in other cellulosic ethanol processes is from 17,430 to 33,330 MJ/tonne. Based on this technology, the recalcitrance of lignocellulose was destructed via a cost-efficient process and structural carbohydrates in sweet sorghum stalks were hydrolysed into fermentable sugars. Bioconversion of fermentable sugars released from sweet sorghum bagasse into different products except ethanol, such as butanol, biogas, and chemicals was feasible to operate under low energy-consumption conditions. So it is considered as a promising process to produce biofuels at commercial scale. [ABSTRACT FROM AUTHOR]

This study aimed to understand the pretreatment-aided anaerobic digestion of lignocellulosic residues and to assess the substrate solubilization capacity of pretreatment processes. We evaluated the feasibility of biogas production using chemically pretreated Areca catechu L. (Arecanut husk, AH). AH was pretreated for 24h at two different temperatures—25 °C and 90 °C with four different chemicals viz. H 2 SO 4 (acidic), NaOH (alkaline), H 2 O 2 (oxidative), and ethanol in 1% H 2 SO 4 (organosolv) under each temperature. AH solubilization assessment included analyses of parameters such as volatile solids to total solids (VS:TS) ratio, soluble chemical oxygen demand, total phenolic content, and biomass composition. Alkaline pretreatment of AH at 90 °C resulted in the maximum biogas yield of 683.89mL/gVS, which was 2.3 times more than that obtained using raw AH without pretreatment. Methane content of biogas produced using AH pretreated with 2–10% of NaOH was found to be between 71.53% and 75.06%; methane content of biogas using raw AH was 62.31%. In order to describe the AH degradation patterns, biogas production potential from pretreated AH was evaluated using bacterial kinetic growth models (First-order exponential, logistic, transference, and modified Gompertz models). The modified Gompertz and logistic models (correlation coefficient >0.99) were found to have the best fit of all kinetic models for the cumulative experimental biogas curve. We formulated a multiple linear regression equation depicting the biodegradability index (BI) as a technical tool to determine biomethane production; BI is represented as a function of biomass composition (cellulose, hemicellulose, and lignin), with a high correlation (>0.95). Based on our analyses of AH pretreatment and substrate utilization for biogas production, we propose that the biochemical composition of lignocellulosic residues should be carefully considered to ensure their biodegradability when subjected to anaerobic digestion. [Display omitted] • Alkaline pretreatment at 90 °C improved the lignin fractionation of Arecanut husk. • 4% alkaline dosage at 90 °C yielded 2.3 times more biogas than raw Arecanut husk. • Logistics and Modified Gompertz model fits the experimental biogas curve. • Deviation between actual and predicted data of both models is −1.65% to +4.39%. • Representation of BI as a function of biomass compositions (R2 value of 0.95). [ABSTRACT FROM AUTHOR]

Although sulfomethylation (SM) and carboxymethylation (CM) have been used in the pretreatments of lignocelluloses, their effects on lignin structure of biomass and the interaction between lignin and cellulase remain unclear. In this work, alkaline pretreatment firstly removed 52.5% of lignin in sugarcane bagasse (SCB). The sequential SM and CM further increased the delignification capacities by 43.1% and 34.3%, respectively. Results of nuclear magnetic resonance, Fourier transform infrared spectroscopy and adsorption experiments show that the unites of ferulic acid and p -coumaric acid in residual lignin in alkaline-pretreated SCB (AP-SCB) were dissociated, and the -SO 3 - and carboxyl groups were introduced into the residual lignin in AP-SCB by SM and CM. The structural modification of residual lignin by SM and CM decreased the adsorption capacity of cellulase toward residual lignin in AP-SCB by 25.6% and 21.7%, resulting in the increase of glucose yield of AP-SCB from 52.2% to 83.8% and 73.6%, respectively. This work provides an efficient strategy to enhance sugars yields of alkaline-pretreated SCB through the mitigated nonproductive adsorption of residual lignin by SM and CM. • Sulfomethylation (SM) and carboxymethylation (CM) were used to pretreat bagasse. • The -SO 3 - and -COOH groups were introduced into lignin in bagasse by SM and CM. • SM and CM reduced the nonproductive adsorption of cellulase by lignin in bagasse. • Glucose yields of alkaline-pretreated bagasse were largely increased by SM and CM. [ABSTRACT FROM AUTHOR]

To date, the introduction of biodegradable plastics such as PLA in anaerobic digestion systems has been limited by a very low rate of biodegradation. To overcome these limitations, pretreatment technologies can be applied. In this study, the impact of pretreatments (mechanical, thermal, thermo-acid, and thermo-alkaline) was investigated. Mechanical pretreatment of PLA improved its biodegradation rate but did not affect the ultimate methane potential (430–461 NL CH 4 kg−1 VS). In parallel, thermal and thermo-acid pretreatments exhibited a similar trend for PLA solubilization. Both of these pretreatments only achieved substantial solubilization (>60%) at higher temperatures (120 and 150 °C). At lower temperatures (70 and 90 °C), negligible solubilization (between 1 and 6%) occurred after 48 h. By contrast, coupling of thermal and alkaline pretreatment significantly increased solubilization at the lower temperatures (70 and 90 °C). In terms of biodegradation, thermo-alkaline pretreatment (with 5% w/v Ca(OH) 2) of PLA resulted in a similar methane potential (from 325 to 390 NL CH 4 kg−1 VS) for 1 h at 150 °C, 6 h at 120 °C, 24 h at 90 °C, and 48 h at 70 °C. Reduction of the Ca(OH) 2 concentration (from 5% to 0.5% w/v) highlighted that a concentration of 2.5% w/v was sufficient to achieve a substantial level of biodegradation. Pretreatment at 70 and 90 °C using 2.5% w/v Ca(OH) 2 for 48 h resulted in biodegradation yields of 73% and 68%, respectively. Finally, a good correlation (R2 = 0.90) was found between the PLA solubilization and its biodegradation. [Display omitted] • PLA has very low biodegradation rate under mesophilic anaerobic digestion. • Mechanical pretreatment only slightly improved the biodegradation kinetic of PLA. • Thermal pretreatment (120 or 150 °C) resulted in substantial improvement of biodegradation. • Addition of Ca(OH) 2 allowed to find similar biodegradation at lower temperature. • 70 °C with 2.5% w/v Ca(OH) 2 for 48 h allows 73% biodegradation of PLA in 30 days. [ABSTRACT FROM AUTHOR]

Pretreatment is a prerequisite step for increasing the enzymatic digestibility of agricultural residues for conversion to fuels and chemicals in biorefineries. In this study, a sequential acid and alkaline process was developed for pretreatment of rice straw for ethanol fermentation. Effects of key parameters in acid pretreatment were studied using a full factorial design model, which showed the higher influence of time compared to acid concentration and temperature on reducing sugar yields. The combined sequential process involved an initial hemicellulose solubilization by dilute acid using 1% (w/v) H2SO4 at 125 °C for 10 min, followed by alkaline delignification using 1.25% NaOH at 90 °C for 10 min. Under these conditions, a glucose recovery yield of 70.9% from saccharification of the cellulose enriched fraction was obtained with 2- to 4-fold savings in chemical usage as compared with single-step processes. Scanning electron microscopy revealed modification of biomass micro-structure and increases in reactive surface area. Simultaneous saccharification and fermentation of the solid residues by Saccharomyces cerevisiae, using 25 FPU/g Accellerase® 1500, led to a final ethanol concentration of 21.0 g/L with the productivity of 0.27 g/L/h, equivalent to 84.6% theoretical yield. The results indicate the potential of the sequential process for increasing pretreatment efficiency and allowing stepwise separation of lignocellulose components for multi-product biorefineries. [ABSTRACT FROM AUTHOR]

The fungal arabinofuranosidase from Pleurotus ostreatus PoAbf recombinantly expressed in Pichia pastoris rPoAbf and its evolved variant rPoAbf F435Y/Y446F were tested for their effectiveness to enhance the enzymatic saccharification of three lignocellulosic biomasses, namely Arundo donax , corn cobs and brewer’s spent grains (BSG), after chemical or chemical–physical pretreatment. All the raw materials were subjected to an alkaline pretreatment by soaking in aqueous ammonia solution whilst the biomass from A. donax was also pretreated by steam explosion. The capability of the wild-type and mutant rPoAbf to increase the fermentable sugars recovery was assessed by using these enzymes in combination with different (hemi)cellulolytic activities. These enzymatic mixtures were either entirely of commercial origin or contained the cellulase from Streptomyces sp. G12 CelStrep recombinantly expressed in Escherichia coli in substitution to the commercial counterparts. The addition of the arabinofuranosidases from P. ostreatus improved the hydrolytic efficiency of the commercial enzymatic cocktails on all the pretreated biomasses. The best results were obtained using the rPoAbf evolved variant and are represented by increases of the xylose recovery up to 56.4%. These data clearly highlight the important role of the accessory hemicellulolytic activities to optimize the xylan bioconversion yields. [ABSTRACT FROM AUTHOR]

In this work, corn stover was refined by a pulp refining instrument (PFI refiner) after NaOH pretreatment under varied conditions. The quantitative characterization of the influence of PFI refining on enzymatic hydrolysis was studied, and it was proved that the enhancement of enzymatic saccharification by PFI refining of the pretreated corn stover was largely due to the significant increment of porosity of substrates and the reduction of cellulose crystallinity. Furthermore, a linear relationship between beating degree and final total sugar yields was found, and a simple way to predict the final total sugar yields by easily testing the beating degree of PFI refined corn stover was established. Therefore, this paper provided the possibility and feasibility for easily monitoring the fermentable sugar production by the simple test of beating degree, and this will be of significant importance for the monitoring and controlling of industrial production in the future. [ABSTRACT FROM AUTHOR]

Alkaline pretreatment was studied to analyze the influence on waste activated sludge (WAS) reduction, methane production and microbial community structure during anaerobic digestion. Methane production from alkaline pretreated sludge (A-WAS) (pH = 12) increased from 251.2 mL/L d to 362.2 mL/L d with the methane content of 68.7% compared to raw sludge (R-WAS). Sludge reduction had been improved, and volatile suspended solids (VSS) removal rate and protein reduction had increased by ∼10% and ∼35%, respectively. The bacterial and methanogenic communities were analyzed using 454 pyrosequencing and clone libraries of 16S rRNA gene. Remarkable shifts were observed in microbial community structures after alkaline pretreatment, especially for Archaea . The dominant methanogenic population changed from Methanosaeta for R-WAS to Methanosarcina for A-WAS. In addition to the enhancement of solubilization and hydrolysis of anaerobic digestion of WAS, alkaline pretreatment showed significant impacts on the enrichment and syntrophic interactions between microbial communities. [ABSTRACT FROM AUTHOR]

The majority of textiles typically contain a biodegradable part that is cellulose and a non-biodegradable part which is a polyester. In this study, alkali pretreatment was evaluated for improvement of ethanol production from the cellulose part of a polyester-cotton textile and recovery of the polyester. The pretreatment was conducted by different alkali solutions of NaOH (12 wt%), NaOH/urea (7/12 wt%), NaOH/thiourea (9.5/4.5 wt%) and NaOH/urea/thiourea (8/8/6.4 wt%) at -20, 0, 23, and 100 °C for 1 h. All of the pretreatments resulted in improvement of enzymatic hydrolysis yield to over 88%, while it was only 46.3% for the untreated textile. The best hydrolysis results were observed by the pretreatments at the reduced temperatures (-20 and 0 °C). The maximum yield of ethanol production from the textile by simultaneous saccharification and fermentation was 70%, obtained after the pretreatment with NaOH/urea at -20 °C whereas it was only 36% for the untreated textile. The polyester part of the textile was recovered after the hydrolysis of the cellulosic part and its properties were studied by FTIR, Differential Scanning Calorimetry (DSC), and viscosity measurements and compared with the untreated polyester used in the textile. The results showed that the alkaline pretreatment followed by hydrolysis resulted in recovery of 98% of the polyester without significant change in its properties. [ABSTRACT FROM AUTHOR]

To improve anaerobic digestion efficiency, combination pretreatment of alkaline and high pressure homogenization was applied to pretreat sewage sludge. Effect of alkaline dosage on anaerobic sludge digestion was investigated in detail. SCOD of sludge supernatant significantly increased with the alkaline dosage increase after the combined pretreatment because of sludge disintegration. Organics were significantly degraded after the anaerobic digestion, and the maximal SCOD, TCOD and VS removal was 73.5%, 61.3% and 43.5%, respectively. Cumulative biogas production, methane content in biogas and biogas production rate obviously increased with the alkaline dosage increase. Considering both the biogas production and alkaline dosage, the optimal alkaline dosage was selected as 0.04 mol/L. Relationships between biogas production and sludge disintegration showed that the accumulative biogas was mainly enhanced by the sludge disintegration. The methane yield linearly increased with the DD COD increase as Methane yield (ml/gVS) = 4.66 DD COD - 9.69. [ABSTRACT FROM AUTHOR]

Highlights: [•] Asparagus stem had a C/N ratio of 20.5 and could be used as the sole feedstock for methane production. [•] The hydrolysis rate was increased with the increasing NaOH dose. [•] Alkaline pretreatment significantly increased methane production from asparagus stem. [•] The highest methane production was 242.3mL/g VS for the 6.0% NaOH dose. [•] The maximal biodegradability of 55.4% was obtained for 6.0% NaOH pretreated asparagus stem. [Copyright &y& Elsevier]

Highlights: [•] Alkaline pretreatment could markedly enhance bio-oil yield. [•] Alkaline pretreatment could inhibit re-polymerization reactions. [•] Resulting solid/liquid mixture was divided into six lumps. [ABSTRACT FROM AUTHOR]

Pretreatment is a unit operation in the conversion of biomass to valuable products that utilizes various combinations of conditions, including chemicals, heat, pressure, and time, to reduce the recalcitrance of lignocellulose. Many such pretreatments have been developed over the years, as the operating conditions can be adapted so that lignocellulose is modified in ways unique to each pretreatment. By tailoring pretreatment conditions to achieve these modifications, the types of final products produced can be controlled. The purpose of this review is to provide a consolidated source of information for sodium hydroxide effects on lignocellulose. The structural characteristics of lignocellulose and the alterations that occur due to the application of sodium hydroxide are detailed. This review also includes a brief description of the chemical reaction mechanism that ensues during the pretreatment. Lastly, the results of studies that utilized sodium hydroxide pretreatment are discussed. [ABSTRACT FROM AUTHOR]

Pelletization, a form of densification, increases bulk density and improves the convenience and accessibility of biomass feedstock due to the uniform shape and size. Pretreatment of biomass enhances the breakdown and accessibility of the cross-linking lignin, which acts as a binding agent. In this study, pelletization of radio frequency-alkaline and steam explosion pretreated barley straw was performed. Three levels of temperature (70°C, 80°C, and 90°C), five levels of the mass ratio of biomass to NaOH solution (1:4, 1:5, 1:6, 1:7, and 1:8), one hour equilibration time, biomass screen size of 1.6 mm, 1% NaOH concentration, and 20 min residence time in the radio frequency chamber were used for the radio frequency-alkaline pretreatment. Three levels of steam temperature (140°C, 160°C, and 180°C), three levels of moisture content of 8%, 30%, and 50% (mass fraction of total mass), and 5 min and 10 min exposure to steam were tested for the steam explosion pretreatment. The effects of both pretreatment methods were evaluated by pelletizing the pretreated and non-pretreated barley straw samples in a single pelleting unit. The pellet density, tensile strength, durability, dimensional stability, and color of the pellets were determined. Radio frequency-alkaline pretreatment with the use of 1% NaOH solution and a ratio of biomass: NaOH solution of 1:8 has significant effect (P<0.05) on the breakdown of the lignified matrix, resulting in pellets with superior physical characteristics. The steam exploded samples pretreated at higher temperatures (180°C) and retention time of 10 min resulted into pellets with good physical qualities. [ABSTRACT FROM AUTHOR]

Hydrogen (H 2 ) production from lignocellulosic materials may be enhanced by removing lignin and increasing the porosity of the material prior to enzymatic hydrolysis. Alkaline pretreatment conditions, used to delignify disposable wooden chopsticks (DWC) waste, were investigated. The effects of NaOH concentration, temperature and retention time were examined and it was found that retention time had no effect on lignin removal or carbohydrate released in enzymatic hydrolysate. The highest percentage of lignin removal (41%) was obtained with 2% NaOH at 100°C, correlated with the highest carbohydrate released (67 mg/g pretreated DWC ) in the hydrolysate. An enriched culture from a hot spring was used as inoculum for fermentative H 2 production, and its optimum initial pH and temperature were determined to be 7.0 and 50°C, respectively. Furthermore, enzymatic hydrolysate from pretreated DWC was successfully demonstrated as a substrate for fermentative H 2 production by the enriched culture. The maximum H 2 yield and production rate were achieved at 195 mL H 2 /g total sugars consumed and 116 mL H 2 /(L·day), respectively. [ABSTRACT FROM AUTHOR]