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The toxicity of hemicellulosic hydrolysates is one of the main bottlenecks of the biotechnological production of xylitol, as inhibitors released/generated during plant cell wall deconstruction impair xylitol production. Yeast adaptation can be applied to overcome this issue through the development of tolerant strains, improving microbial performance. Herein, we evaluated Candida tropicalis FTI20037 pre-cultivation in original, concentrated, and concentrated/detoxified sugarcane bagasse and straw hemicellulosic hydrolysate (SBSHH) to reduce hydrolysate's toxicity during concentrated/detoxified SBSHH fermentations. Regarding glucose uptake, there were no differences between the evaluated conditions. In turn, lignocellulosic inhibitors negatively affected xylose uptake. The evaluated adaptive strategies did not improve xylose uptake at SBSHH fermentations. Xylitol production was also impaired by lignocellulosic inhibitors. However, pre-cultivation in concentrated/detoxified SBSHH increased xylitol yield and xylose-to-xylitol bioconversion efficiency by 13.3%, xylitol volumetric productivity by 7.1%, and xylitol specific production rate by 9.7%. A 21.5% reduction in glycerol production was also observed in this condition, indicating an increased tolerance to lignocellulosic inhibitors. Arabinose assimilation started slowly in all fermentations. Increased arabinose uptake rates were observed after xylose depletion, suggesting the existence of a carbon catabolite repression tendency between xylose and arabinose. Pre-cultivation in concentrated/detoxified SBSHH reduced this repression tendency, increasing arabinose consumption. Regarding lignocellulosic inhibitors, 5-HMF degradation was increased by pre-cultivation. No differences were observed for acetic acid and phenolic compounds consumption. The combination of SBSHH detoxification and C. tropicalis pre-cultivation was effective to improve xylitol production possibly due to the development of a more tolerant phenotype against SBSHH toxicity. [ABSTRACT FROM AUTHOR]

The mechanism underlying the production of fungal lignocellulolytic enzymes from lignocellulosic biomass remains unclear; therefore, it is imperative to investigate the interactions of microorganisms, culture components, and enzyme production. In this research, four native fungi isolated from agave bagasse: Aspergillus fumigatus (BC-1IB and BDJ-1S), Neurospora sitophila (BDJ-1I), and Rhizopus oryzae (BC-3IDA), were used to evaluate their interaction with lignocellulosic biomass as carbon source (agave or sugarcane bagasse) and pH (6.4 and 7.9) during the production of enzymatic extracts by solid-state fermentation with a packed-bed bioreactor. The evaluated enzymatic activities were pectinolytic, cellulolytic, and xylanolytic. The results demonstrate that the interaction between fungal strain, biomass, and pH during solid-state fermentation has a relevant effect on the final catalytic properties of the resulting enzymatic extract. The interaction between BDJ-1I and agave bagasse results in a pectinase extract that preserves above 99% of its activity at 70 °C for 5 h. Notably, the interaction between N. sitophila BDJ-1I with agave bagasse at pH 6.4 results in extracts with higher pectinase (96.8 IU/gdw), cellulase (39.3 IU/gdw), and xylanase (26.6 IU/gdw) activities suitable for hydrolyzing agro-industrial residues like wheat straw (30.2%), sugarcane (17.4%), and agave bagasse (28.4%). These findings highlight reusing agave and sugarcane bagasse residues for biotransformation into lignocellulosic enzyme cocktails with naturally present fungi strains toward the sustainable zero-waste management of agave and sugarcane bagasse biomass. [ABSTRACT FROM AUTHOR]

One of the limiting stages in the second-generation (2G) bioethanol production process is enzymatic hydrolysis due to the low availability of cellulase enzymes and their high cost. The enzymatic hydrolysis of pretreated sugarcane bagasse is optimized (Box-Behnken design) using an enzymatic extract of Aspergillus niger ITV02 cellulases produced in a bioreactor to obtain glucose. The maximum concentration of glucose (49 g/L) and conversion (70%) was reached using sugarcane bagasse with acid-alkaline pretreatment (SB-AAL) under optimal conditions of enzyme load (18 FPU/g), the concentration of substrate (84.35 g/L) and hydrolysis time (48 h). The enzymatic hydrolysate of A. niger ITV02 from SB-AAL was subsequently fermented by Saccharomyces cerevisiae ITV01 for bioethanol 2G production, reaching a yield (Yp/s) of 0.46 g/g, an efficiency of 90.77%, and 1.6 g/Lh productivity and reaching important values of parameters required for bioethanol 2G production to scale process. The present study shows that cellulases produced by A. niger ITV02 using an available and low-cost substrate such as sugarcane bagasse is efficient in the enzymatic hydrolysis of lignocellulosic residues for bioethanol 2G production. [ABSTRACT FROM AUTHOR]

Integration of first- and second-generation ethanol production is a strategy to strengthen the economic viability of individual processes and the overall viability of biorefineries. The sharing of storage, fermentation, distillation, and energy infrastructure is an important advantage of process integration. Furthermore, integration contributes to the utilization and valorization of all products and by-products, which is key to the success of a biorefinery. Selenium-enriched yeasts have aroused great interest as mineral sources for their high bioavailability and low toxicity. This study aimed to evaluate the effect of selenium on yeast cell growth and production of ethanol and xylitol from hydrolyzed hemicellulosic biomass and sugarcane molasses. For this, cultures were enriched with sodium selenite at concentrations ranging from 1 to 20 mg/L. A miniaturization protocol was used to simulate biorefinery production of first-generation ethanol. The yeasts Spathaspora passalidarum and Kluyveromyces marxianus were able to grow under all tested conditions. The maximum specific growth rate, lag time, and biomass production were influenced by selenium concentration. S. passalidarum provided the best fermentation results, with 77.9% ethanol fermentation efficiency, 24.7% xylitol fermentation efficiency, 0.25 g/g glycerol yield, and 3.3 g cell biomass production. K. marxianus accumulated 122.92 mg selenium/kg biomass, whereas S. passalidarum had a maximum accumulation of 37.40 mg selenium/kg biomass. Yeasts also accumulated other minerals. Therefore, S. passalidarum has great potential as a biological platform and the results of this work could be useful for supporting the development of integrated processes to produce ethanol-, xylitol-, glycerol-, and selenium-enriched yeast products. [ABSTRACT FROM AUTHOR]

In the present work, a new alternative of hydrodynamic cavitation–assisted pretreatment associated with an advanced oxidative process was proposed, together with a new approach to obtain bioproducts in sequential fermentations. Enzymatic hydrolysate of sugarcane bagasse (SCB) was fermented to ethanol by Saccharomyces cerevisiae. After distillation of this alcohol, the obtained vinasse was used to produce xylitol by Candida tropicalis. Influent variables in pretreatment were evaluated by performing experiments according to a statistical design, and, at optimum conditions (ozone flowrate of 10 mg/min, and H2O2 concentration of 0.61%), about 84% and 78% of glucan and xylan hydrolysis yields were obtained in enzymatic hydrolysis, respectively. In the sequential fermentations for ethanol and xylitol production, yield values of 0.41 g/g and 0.55 g/g, respectively, were obtained, with corresponding volumetric productivities of 8.33 g/Lh and 0.64 g/Lh, respectively. The proposed strategy was shown as a promising approach for biorefineries, considering the mild conditions of pretreatment and the possibility of high ethanol production using S. cerevisiae in a fermentation process similar to that one already available in sucro-alcoholic sector, followed by xylitol production in vinasse-based medium. [ABSTRACT FROM AUTHOR]

Acid and alkali pretreatment are the most commonly employed strategy in a lignocellulosic biorefinery. The main objective of the study was to evaluate the chemical implications of acid and alkali on the lignin structure and subsequently on the adhesive performance. The study also aimed to investigate the effect of complete replacement of phenol and formaldehyde in the commercial wood adhesive with phenolic lignin and glyoxal, respectively. The phenolic lignin was derived from the two differentially pretreated sugarcane bagasse, i.e., acid and alkali. The isolated lignin was characterized and utilized for the synthesis of lignin-based glyoxal resin. The resins were comparatively evaluated for their mechanical properties as wood adhesives. Adhesives derived from acid pretreated sugarcane bagasse were found to be superior to lignin derived from alkali pretreated sugarcane bagasse in terms of mechanical properties and shear strength. [ABSTRACT FROM AUTHOR]

This paper introduces a methodological framework for assessing the sustainability of solid biofuels in Mexico. The designed framework comprises 13 normalized indicators and two diagnostic studies, covering the economic, social, environmental, and institutional sustainability dimensions, and their intersections. Indicators are normalized using the concept of load capacity of a system, similarly to the planetary boundaries. Thus, the graphical representation of results facilitates their multidimensional analysis. The framework was applied to three case studies: traditional fuelwood in rural households, charcoal for restaurant grilling, and electricity cogeneration from sugarcane bagasse. This was part of an iterative process of testing and refining the framework and simultaneously demonstrating its application in the Mexican bioenergy context. This led to the conclusion that the resulting framework (a) provides a useful, quantitative, and comprehensive overview of both broad and specific sustainability aspects of the assessed system; (b) requires a balance of accessible but also scattered or sensitive data, similarly to most existing frameworks; (c) is highly flexible and applicable to both modern and traditional solid biofuels; and (d) is simple to communicate and interpret for a wide audience. Key directions for improvement of the framework are also discussed. [ABSTRACT FROM AUTHOR]

The present work investigated the techno-economic feasibility of using gasification as an alternative to direct combustion to generate steam and electric power generation in a sugarcane mill using different types of solid biofuels. Two cogeneration scenarios were analyzed: scenario 1 (S1), using a boiler and steam turbines only, while scenario 2 (S2) uses gas and steam turbines. It was found that for a solid biofuel cost of 8 US $/ton, the economic results between types of biomass are similar, but at a higher solid biofuel cost, the cost of energy production is lower in S2 when compared to S1. The cost of generated power in S1 using sugarcane bagasse (0.091 US $/kWh) is higher than the cost considered for grid electricity (0.077 US$/kWh), while in S2 is lower (0.063 US$/kWh); therefore, electricity might be exported to the grid at a competitive price in S2. In both scenarios, the greatest contribution to the total annual costs comes from the investment required by about 83%. In the case of the other biofuels, such as cladodes, oil brunches, and coffee pulp, the cost obtained is less than 0.077 US$/kWh for all cases in both scenarios, except for the tender cladodes in S1, mainly due to its higher moisture content. The systems studied in S2 using oil palm empty brunches as complementary solid biofuel in the sugar mill are recommended for year-round bioenergy production. [ABSTRACT FROM AUTHOR]

There are still bottlenecks to be overcome for the feasible industrial production of first- and second-generation ethanol (1G2G EtOH). One of them is the pretreatment stage. Washing is a candidate strategy to remove lignocellulose-derived byproducts from pretreated biomass, in order to reduce the negative effects of furaldehydes and phenolic compounds in the downstream biochemical reactions. However, the effectiveness of the removal of these inhibitors is highly influenced by the operational conditions of the washing process. Here, evaluation was made of the techno-economic impacts of including a washing operation after hydrothermally pretreating sugarcane bagasse for 2G EtOH production in an integrated 1G2G biorefinery. Different washing protocols were tested, considering their effects on the enzymatic hydrolysis and fermentation, and experimental data were used for simulation of process scale-up. The removal of inhibitors improved the glucose yield by 40%, followed by an increase of ~ 30% in EtOH productivity. These findings showed that washing is a cost-competitive option for a 1G2G biorefinery, with a net present value for the industrial unit of ~US$ 2.3E + 8, which was the highest among the 1G2G scenarios analyzed. [ABSTRACT FROM AUTHOR]

Abstact: Simplex-centroid design along with artificial neural network coupled with genetic algorithm (ANN-GA) was applied to maximize exoglucanase production by Penicillium roqueforti ATCC 10110 under solid-state fermentation (SSF), using a blend of agroindustrial wastes as substrate. The first statistical treatment determined the ideal contents of green coconut shell, corn cob, and sugarcane bagasse in the substrate, which were 0.44, 2.06, and 2.50 g, respectively. The optimum conditions by the ANN-GA were obtained as follows: 24 h, 21 °C, and 8.1 and 81.0% for the time, temperature, pH, and moisture, respectively. Moreover, the predicted and the experimental values of exoglucanase activity were 267.94 and 268.58 IU/g, respectively. The optimization process increased the enzyme activity by up to 1263% compared with the preliminary analysis using individual substrates, demonstrating the high efficiency of the algorithms on predicting and optimizing enzyme production. Biochemical characterization demonstrated good thermostability, basic pH stability, halotolerance, and increased enzyme activity in the presence of metal ions (Co2+, Ca2+, Mg2+, and Fe2), solvents (ethanol and dichloromethane), and organic compounds (EDTA, Triton-X, and lactose,). These results indicate the algorithm efficiency for enzyme production purposes. [ABSTRACT FROM AUTHOR]

In order to understand the relationship among enzymatic hydrolysis of lignocellulose, cellulase adsorption characteristics, and physicochemical properties of lignocellulose, a series of investigations was conducted, including composition, surface morphology, chemical bonds, functional groups, pore characteristics, cellulase accessibility, productive cellulase adsorption, cellulase adsorption isotherm, and kinetics of sodium hydroxide (NaOH) and ammonia-treated sugarcane bagasse (SCB) substrates. The results showed that the hydrolysis efficiency of NaOH-treated SCB (87.85%) was higher than that of ammonia-treated SCB (33.65%) and NaOH-treated SCB had less lignin, looser surface, and larger specific surface area and pore volume. This suggested that better accessibility of NaOH-treated SCB to cellulase resulted in higher enzymatic hydrolysis efficiency. The data on cellulase adsorption showed that NaOH-treated SCB had more productive adsorption, less non-productive adsorption, better adsorption capacity, and smaller binding strength with cellulase, which was also beneficial to the enhancement of enzymatic hydrolysis of NaOH-treated SCB. In addition, it was found that once cellulase molecules were adsorbed onto these two SCB substrates, two types of bonds as follows might be formed: one was C-OR (R means organic groups) and the other was C-OH··NH that was a type of hydrogen bond formed between the hydrogen of amino group in cellulase and the hydroxyl group in lignocellulose. This study would help further learn the link between lignocellulosic substrate characteristics and enzymatic hydrolysis or cellulase adsorption properties of lignocellulose. [ABSTRACT FROM AUTHOR]

Levulinic acid (LA) is currently one of the most promising chemicals derived from biomass. However, its large-scale production is hampered by the challenges in biomass hydrolysis and the poor selectivity due to the formation of humins (HUs). This study addresses these challenges using the biorefinery concept of biomass fractionation. A three-step process (pretreatment, delignification, and acid-catalyzed conversion) was optimized to produce LA from SCB considering the yield (YLA), efficiency (ELA), and concentration of LA (CLA) as functions of temperature, reaction time, acid concentration, and solids loading. By means of a multi-response optimization, values of YLA (20.9 ± 1.25 g/100gISF-D), ELA (37.5 ± 2.24 mol%), and CLA (25.1 ± 1.50 g/L) were obtained at 180 °C, 75 min, 7.0% w/v H2SO4, and 12.0% w/v of solids loading. Six scenarios for production of LA were analyzed in terms of yields of LA, HUs, lignin, and other sugar-derived products considering one-, two-, or three-step processes. The economic analysis indicated that the three-step scenario delivers better economic figures given that other valuable biomass fractions (hemicellulosic sugars and lignin) are better used and contribute to the overall economic performance of the process. The results also demonstrate the burden of HUs in the economics of the process because it was shown that the largest production of LA is also linked to the largest formation of HUs, which does not necessarily yield the best economic results. These findings indicate the importance of added value by-products for the profitable production of LA in biorefineries. [ABSTRACT FROM AUTHOR]

Bioethanol production from sugarcane bagasse hemicellulosic hydrolysate using immobilized Scheffersomyces shehatae on magnetic biosupports in a fluidized bed bioreactor assisted by magnetic field has been studied. Fermentations were carried out in two experimental setups operating in a magnetically stabilized bed mode with transversal and axial magnetic field lines at 8 and 12 kA/m, respectively. The best results were attained when experiments were carried out using a fermenter assisted by axial field whose ethanol/substrate yield and ethanol productivity were 0.15 ± 0.8E-3 g/g and 0.055 ± 0.3E-3 g/gh. These values were 12 and 34%, respectively, higher than those observed in fermentations with transversal field lines (Tukey's test, p < 0.05). Thus, these results are attractive and can be considered as a technological advance in the bioethanol production from biomass using this unconventional fermentation technology. [ABSTRACT FROM AUTHOR]

The bioconversion yield of ethanol from lignocellulosic feedstocks is negatively affected by the unproductive adsorption of cellulolytic enzymes onto lignin. In this work, soybean protein was used as a lignin-blocking additive, with the aim of improving the production of ethanol from enzymatic hydrolysates of pretreated sugarcane bagasse. Investigation was made of the effects of the type of hydrothermal pretreatment process—steam explosion (SE) or liquid hot water (LHW), loadings of solids and enzymes, and bioreactor type. The addition of soybean protein led to a exceptional 76% increase of glucose released using the LHW pretreated bagasse, after 24 h of reaction, employing a high-solids loading (15%, w/v) and a low enzyme dosage (5 FPU/g dry biomass). A significant improvement was also achieved for industrial-like mixing conditions in a bench-scale stirred tank reactor, increasing the glucose released by 61 and 42% for the LHW and SE processes, respectively. Ethanol production was also positively affected by the presence of soybean protein, with increases of up to 86 and 65% for the LHW and SE hydrolysates, compared to the control experiment. Characterization of the sugarcane bagasse after the adsorption of soybean protein, using Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM), corroborated the higher affinity of the additive for the LHW bagasse. These findings suggest that soybean protein supplementation during enzymatic hydrolysis by commercially available enzymes is an effective strategy for achieving higher saccharification yields from hydrothermally pretreated biomass, hence improving ethanol production. [ABSTRACT FROM AUTHOR]

The aim of this study was to valorize the hemicellulose-rich liquid fraction (liquor) arising from hydrothermal pretreatment of sugarcane bagasse (SCB) through its utilization as an unconventional, soluble carbon source for the production of hemicellulases, namely xylanases and α-L-arabinofuranosidases (ABFases), by Aspergillus niger DCFS11. Through the use of factorial design, pretreatment conditions producing liquors optimized for either early- or late-phase enzyme production were identified. Subsequent deep characterization of liquor components using liquid chromatography and mass spectrometry was performed to identify compounds likely responsible for hemicellulase induction. SCB liquors arising from various pretreatment configurations induced up to 2- and 8.6-fold higher xylanase and ABFase production, respectively, by A. niger DCFS11 than raw SCB substrate owing to the strong inducing potential of arabinosylated xylooligosaccharides and free arabinose solubilized during pretreatment. Notably, unlike the severe pretreatment conditions required for maximum cellulose saccharification and ethanol yields during biomass conversion, low severity and low biomass loading are required if enzyme production from liquor is desired at early-phase growth with no additional detoxification steps. This suggests that for effective application in biorefineries, separate or multi-step processes would be required to optimize both hemicellulase production by A. niger DCFS11 and cellulose digestion. This work demonstrates the potential of hydrothermal pretreatment of lignocellulosic substrates as a tool to increase the production of enzymes by filamentous fungi. [ABSTRACT FROM AUTHOR]

Two general strategies have been proposed for microbial cellulose degradation: filamentous fungi and aerobic bacteria secrete uncomplexed cellulases, while some anaerobic bacteria produce a cell-associated and large extracellular multienzymatic complex called cellulosomes. By using a combination of 1D-blue native (BN)-PAGE, 2D-BN/SDS-PAGE, zymography, and LC-MS/MS methods, we demonstrate here that Streptomyces sp. I1.2, an aerobic bacterium associated with the land snail Achatina fulica, is able to degrade both crystalline cellulose and sugarcane bagasse through the production of cellulolytic multienzymatic complexes containing different combinations of cellobiohydrolases, endo-glucanases, xylanases, lytic polysaccharide monooxygenases (LPMOs), and peptidases. The assembly and subunit composition of these complexes is specifically affected by the carbon source, while the multienzymatic complexes produced after growth in crystalline cellulose are composed mainly by one cellobiohydrolase and chitinase, in which the complexes produced in response to sugarcane bagasse are more heterogeneous and contain cellobiohydrolases, endo-glucanases, pectate lyases, one LPMO, β-1,3-glucanases, and one xylanase. Our results suggest that Streptomyces sp. I1.2 displays an alternative mechanism for deconstruction of cellulose that depends upon a noncellulosomic association of catalytic subunits into high molecular weight complexes in order to achieve higher catalytic efficiencies. [ABSTRACT FROM AUTHOR]

The reuse of the solid residues generated in the production of second-generation (2G) ethanol to obtain high-value products is a potential strategy for improving the economic and environmental viability of the overall process. This study evaluated the feasibility of using the residual solids remaining after the enzymatic hydrolysis of sugarcane bagasse for the production of cellulose nanocrystals (CNC), a valuable bionanomaterial. To this end, sugarcane bagasse subjected to steam explosion (SEB) or liquid hot water (LHWB) pretreatment was hydrolysed using different loadings of a commercial cellulase cocktail. Samples of SEB and LHWB were hydrolysed enzymatically, resulting in glucose releases close to 40 g/L, which would be suitable for producing 2G ethanol by microbial fermentation. The solid residues after the enzymatic hydrolysis step presented cellulose contents of up to 54 %, indicating that a significant amount of recalcitrant crystalline cellulose remained available for subsequent use. These solid residues were purified and submitted to acid hydrolysis, resulting in the successful formation of CNC with crystallinity close to 80 %, lengths of 193-246 nm and diameters of 14-18 nm. The CNC produced presented morphology, dimensions, physical-chemical characteristics, thermal stability and crystallinity within the ranges reported for this type of material. Moreover, the enzyme loading or the type of hydrothermal pretreatment process employed here showed no significant effects on the CNC obtained, indicating that these variables could be flexibly adjusted according to specific interests. [ABSTRACT FROM AUTHOR]

A simplified kinetic model for autohydrolysis of hemicelluloses from sugarcane bagasse was evaluated in the context of a global process in a batch reactor. In this work, all sugars, oligomers, and decomposition products from hemicelluloses were taken into account in the determination of kinetic parameters. This approach has not been reported in previous kinetic studies which assume just the xylan, xylose, and furfural as compounds from hemicelluloses. Experimental results for hemicelluloses removal from residual solids and dissolved fractions in the liquor are reported at various temperatures and reaction times. Because of the decomposition of sugars in the pretreatment liquors, optimal temperatures and reaction times were maintained at 170 °C and 90 min. Under these conditions, 61.7 % of hemicelluloses were converted to oligomeric and monomeric sugars. In addition, 90 % of cellulose was preserved in the residual solid fraction. Correlation parameters between the kinetic model and experimental data validate the proposed model, although deviations from an Arrhenius-type model were observed. The reaction steps for production of oligomers, monomers, and sugar derivatives/decomposition compounds present activation energies of 143.1, 158.9, and 138.3 kJ/mol, respectively. [ABSTRACT FROM AUTHOR]

In order to examine the potential for coproduct generation, we have characterised chemical compounds released by a range of alkaline and acidic aqueous pretreatments as well as the effect of these pretreatments on the saccharification ability of the lignocellulosic material. Comparative experiments were performed using three biomass types chosen for their potential as second-generation biofuel feedstocks: maize stover, miscanthus and sugarcane bagasse. The release of lignin from the feedstock correlated with the residual biomass saccharification potential, which was consistently higher after alkaline pretreament for all three feedstock types. Alkaline pretreatment released more complex mixtures of pentose and hexose sugars into the pretreatment liquor than did acid pretreatment. In addition, complex mixtures of aromatic and aliphatic compounds were released into pretreatment liquors under alkaline conditions, in a temperature-dependent manner, but far less so under acidic conditions. We show that the three feedstocks characterised interact with the pretreatment conditions in a specific manner to generate different ranges of products, highlighting the need to tailor pretreatments to both the starting feedstock and desired outcomes. [ABSTRACT FROM AUTHOR]

A novel simplified configuration is proposed for the conversion of biomass to ethanol using whole medium enzymatic cocktails (WM) and enzymatic extracts (EE) from different filamentous fungi ( Trichoderma reesei, Aspergillus niger, and Aspergillus oryzae) cultivated under solid-state fermentation (SSF) for the hydrolysis of steam-exploded sugarcane bagasse (SESB). The hydrolyzed material derived from the saccharification of SESB using the combinations A. niger WM + T. reesei EE, A. oryzae WM + A. niger EE, and A. niger EE + T. reesei WM resulted in the best biomass conversion yields (66, 65, and 64 % of the theoretical reducing sugar yields, respectively). The best ethanol production (84 % of the theoretical yield) was obtained using the material hydrolyzed by a combination of A. oryzae WM + A. niger EE. The enzymatic conversion of SESB using on-site produced enzymes from the whole SSF cultivation medium, followed by an ethanol production step, is a potential configuration for the biomass to ethanol conversion process. This novel simplified configuration would enable the use of a single reactor system, avoiding the need for additional separation steps. [ABSTRACT FROM AUTHOR]

Sugarcane bagasse (SCB) was pretreated with liquid hot water (LHW) and aqueous ammonia (AA), with the objective of investigating the influence of hemicellulose and lignin removal on the enzymatic digestibility and sugar recovery. The experimental results show that LHW and aqueous ammonia have a good performance in terms of hemicellulose dissolution and lignin removal respectively. The biggest xylan recovery of 74.3 % was obtained for LHW pretreatment at 160 °C, 5 % w/v for 20 min with the xylan dissolution of 83.1 %. And the biggest lignin removal of 84.0 % was obtained for aqueous ammonia pretreatment at 160 °C, 10 % w/v for 60 min. Moreover, the aperture and surface area of the sample were enlarged by the liquid hot water, which improves the accessibility of the substrate to the enzyme. The lignin removal caused by aqueous ammonia pretreatment can reduce the absorption of enzyme. In addition, the correlation between the compositional change and the enzymatic digestibility indicates that the removal of hemicellulose was more effective than lignin for destruction of the hemicellulose–lignin–cellulose structure. [ABSTRACT FROM AUTHOR]

An endo-acting xylanase is isolated from the culture medium of Clostridium sp. BOH3 when xylan, glucose, xylose, or sugarcane bagasse hydrolysate (SBH) is used as a carbon source. Crude xylanase is purified by using an anionic Q-column with a yield of 39 %. The pure xylanase has a molecular weight of 35.8 kDa, and it shows optimal activity at pH 5 and 60 °C. When beechwood xylan is used as a substrate, this xylanase liberates short oligosaccharides (XOS) predominantly, ranging from xylobiose (X2) to xylopentaose (X5). However, no xylose can be detected, suggesting that this is an endo-β-1,4-xylanase. Kinetic study of this xylanase reveals that K and V are 1.36 mg/ml and 212 μmol/(min. mg protein), respectively. On the basis of amino acid sequence, this enzyme shows homology to xylanase ( xynb) from Clostridium acetobutylicum ATCC 824, but this enzyme has several distinctive characteristics. For example, its activity can be enhanced with the addition of divalent metal ions, and it produces XOS exclusively when xylan is used as a substrate. These unique characteristics suggest that this is a new enzyme. [ABSTRACT FROM AUTHOR]

The conversion of agro-industrial residues, such as sugarcane bagasse, into high-value products and renewable energy, within the biorefinery concept, is a potential alternative towards the sustainable management of these resources. This work evaluates the production of cellulolytic enzymes by a selected strain of Aspergillus niger cultivated in sugarcane bagasse under solid-state fermentation using an instrumented lab-scale bioreactor. The effects of environmental factors including the type of substrate and medium composition, as well as the operational conditions (air flow rate, inlet air relative humidity, and initial substrate moisture content) on the production of the enzymatic complex were evaluated using statistical design tools. Significant increases in FPase, endoglucanase, and xylanase activities were achieved under the optimized conditions predicted by the models, with values of 0.88, 21.77, and 143.85 IU/g of dry solid substrate, respectively, representing around ten-, four-, and twofold increases compared to the activities obtained under the initial growth conditions. This demonstrates the importance of evaluating environmental and operational criteria in order to achieve efficient enzyme production. The crude enzymatic extract obtained under optimized conditions was employed for enzymatic hydrolysis of pretreated sugarcane bagasse. Approximately 13 % of total reducing sugars, and a glucose concentration of 2.54 g/L, were obtained after 22 h of hydrolysis of steam exploded sugarcane bagasse, indicating that the enzymatic cocktail produced has good potential for use in the conversion of biomass. [ABSTRACT FROM AUTHOR]