Search

The recently identified lytic polysaccharide monooxygenases (LPMOs) are important auxiliary proteins which contribute to lignocellulose biodegradation by oxidatively cleaving the glycosidic bonds in cellulose and other polysaccharides. The vast differences in terms of substrate specificity and regioselectivity within LPMOs provide us new possibilities to find promising candidates for the use in enzyme cocktails in biorefinery applications. In this study, a highly xyloglucan active family AA9 lytic polysaccharide monooxygenase Ep LPMO9A was identified from Eupenicillium parvum 4-14. Ep LPMO9A exhibited a mixed C1/C4 oxidative cleavage activity on cellulose and xyloglucan with a broad range of pH stability and good thermal stability at 40 °C. It showed a higher boosting effect on the enzymatic saccharification of complex lignocellulosic substrates associated with xyloglucan than on the lignocellulosic substrates without xyloglucan particularly in low commercial cellulase dosage cases. The oxidative cleavage of xyloglucan by Ep LPMO9A may facilitate to open up the sterical hindrance of cellulose by xyloglucan and thereby increase accessibility for cellulase to lignocellulosic substrates. The discovery of more and more hemicellulose-active LPMOs and their contribution to breaking down the barriers by oxidatively acting on hemicellulose may expand our knowledge for their functions of LPMOs in lignocellulose biodegradation. [ABSTRACT FROM AUTHOR]

Cassava starch factory residue (CSFR) is an attractive lignocellulosic material for bioethanol production because it is one of the most abundant renewable resources. The purpose of this work was to investigate the technical feasibility of converting CSFR into fermentable sugars using 12 different pretreatment methods. The yields of monosaccharides, oligosaccharides, and total sugars present in the hydrolysates obtained from the different pretreatment methods were examined by transferring the solid organic matter present to a liquid phase. We found that pretreatment with a dilute acid was superior to both alkaline and hot water pretreatment methods, while combined chemical‐enzymatic pretreatment was superior to single enzymatic pretreatment. More specifically, treatment with a dilute acid was conducive to the formation of monomeric sugars, whereas single enzyme pretreatment and high‐temperature alkaline pretreatment methods were conducive to the formation of oligomeric sugars. Pretreatment with 0.5% (w/v) HNO3 (160 °C, 10 min) gave the highest total monosaccharide concentration (i.e., 25,827 mg/L) with a yield of 30.99%, whereas hemicellulose (45 U/g CSFR) + cellulose (120 U/g CSFR) pretreatment gave the highest total oligosaccharide concentration (i.e., 22,152 mg/L) with a yield of 26.69%. Finally, pretreatment with 1% (w/v) H2SO4 (121 °C, 40 min) + hemicellulose (120 U/g CSFR) + cellulose (120 U/g CSFR) gave the highest total sugar concentration (i.e., 43,196 mg/L) with a yield of 51.84%. © 2018 American Institute of Chemical Engineers Environ Prog, 38: 624–629, 2019 [ABSTRACT FROM AUTHOR]

Abstract The efficiency of enzymatic hydrolysis is reduced by the naturally recalcitrant complex polymers comprising lignocellulose. Increasing enzymatic conversion, which the complex macromolecules converted into simpler molecules, is still had to be overcome. High hydrostatic pressure (HHP), an emerging technology, is expected to ameliorate the situation. The effects of enzymatic hydrolysis after HHP pretreatment on pumpkin lignocellulose were studied and compared with hydrothermal and alkaline pretreatment. Further investigation was performed to evaluate the effect of enzymatic hydrolysis of pumpkin combined with HHP treatment. The samples underwent HHP treatment simultaneously exhibited overall better performance in enzymatic hydrolysis than the untreated. The highest glucose yield of 91.2% and xylose yield of 84.2% was achieved when 400 MPa HHP with high enzyme loading was applied. HHP exerted positive effects on enzyme-substrate interactions during the enzymatic hydrolysis of lignocellulose, which implied that HHP technology combined with enzymatic hydrolysis could be used to pretreat pumpkin pomace. Highlights • Cellulose and hemicellulose removal significantly increased after hydrothermal and alkaline pretreatment. • The highest yields of glucose and xulose were achieved at 400 MPa with high enzyme loading. • High hydrostatic pressure exerted positive effects on enzyme-lignocellulose complex interactions. • The method of high hydrostatic pressure was established on the conversion of lignocellulose. [ABSTRACT FROM AUTHOR]

Biological pretreatment with novel isolated microbial pure culture was utilised to pretreat water hyacinth to enhance its solubilisation followed by biogas production. Lignocellulose degrading bacterial strains isolated from soil ( Bordetella muralis VKVVG5 ) (UN3d2), the gut of silverfish ( Citrobacter werkmanii VKVVG4 ) (SFa2) and millipede ( Paenibacillus sp. VKVVG1 ) (BrB2) were employed to optimise the ideal bacterial strain illustrating accelerated hydrolysis of water hyacinth. Citrobacter werkmanii VKVVG4 pretreatment of water hyacinth with an optimum dosage of 10 9  CFU/mL and time of 4 days helped in achieving the highest solubilisation of 33.3%. Biochemical methane potential (BMP) test was conducted between untreated and Citrobacter werkmanii VKVVG4 pretreated water hyacinth. Biochemical methane potential (BMP) test of pretreated water hyacinth illustrated faster start up period than the untreated water hyacinth. Citrobacter werkmanii VKVVG4 (SFa2) pretreated water hyacinth illustrated a cumulative biogas production of 3737 ± 21 mL whereas untreated water hyacinth illustrated a cumulative biogas production of 3038 ± 13 mL on the 50 th day. Scaled up batch (20 L) study demonstrated a three times increase in the cumulative biogas generation of the microbial pretreated water hyacinth than the untreated water hyacinth. [ABSTRACT FROM AUTHOR]

Biomass hydrolysis constitutes a bottleneck for the biotransformation of lignocellulosic residues into bioethanol and high-value products. The efficient deconstruction of polysaccharides to fermentable sugars requires multiple enzymes acting concertedly. GH43 β-xylosidases are among the most interesting enzymes involved in hemicellulose deconstruction into xylose. In this work, the structural and functional properties of β-xylosidase EcXyl43 from Enterobacter sp. were thoroughly characterized. Molecular modeling suggested a 3D structure formed by a conserved N-terminal catalytic domain linked to an ancillary C-terminal domain. Both domains resulted essential for enzymatic activity, and the role of critical residues, from the catalytic and the ancillary modules, was confirmed by mutagenesis. EcXyl43 presented β-xylosidase activity towards natural and artificial substrates while arabinofuranosidase activity was only detected on nitrophenyl α-L-arabinofuranoside (pNPA). It hydrolyzed xylobiose and purified xylooligosaccharides (XOS), up to degree of polymerization 6, with higher activity towards longer XOS. Low levels of activity on commercial xylan were also observed, mainly on the soluble fraction. The addition of EcXyl43 to GH10 and GH11 endoxylanases increased the release of xylose from xylan and pre-treated wheat straw. Additionally, EcXyl43 exhibited high efficiency and thermal stability under its optimal conditions (40 °C, pH 6.5), with a half-life of 58 h. Therefore, this enzyme could be a suitable additive for hemicellulases in long-term hydrolysis reactions. Because of its moderate inhibition by monomeric sugars but its high inhibition by ethanol, EcXyl43 could be particularly more useful in separate hydrolysis and fermentation (SHF) than in simultaneous saccharification and co-fermentation (SSCF) or consolidated bioprocessing (CBP). [ABSTRACT FROM AUTHOR]

To maintain our society’s sustainability with respect to people, prosperity, and the planet, we must produce liquid transportation fuels such as bioethanol on the renewable basis at a competitive price to petroleum-based fuels. The major challenges to commercialize cellulosic biofuels are low fermentation efficiency, low ethanol titer, and lack of technology to fully utilize the byproduct from bioconversion process such as lignin which has been underutilized. To overcome these technical barriers, we have proposed a novel design to fully utilize each component of lignocellulosic biomass for biofuels and bio-chemicals production, which involves green technologies such as hydrothermal and organosolv pretreatments to produce a cellulose-rich solid with good recovery of clean lignin after solvent recycling for improvement of plant protein-based adhesives as well as xylose remained in the aqueous phase for furfural upgradation. The focus of this study, as a part of the whole biorefinery concept, is to develop modified simultaneous saccharification and fermentation (mSSF) to enhance ethanol titers and yields, which combines the advantages of both separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF) via unique decantation process. The mSSF achieved higher ethanol concentration of 58.5 g/L and ethanol yield of 83.5% as compared to the traditional SSF process (49.9 g/L and 71.1%) at the biomass loadings of 20% (w/v). The mSSF also enabled higher ethanol titers of 72.3 g/L at higher loadings of 30% (w/v) with yields of 70.0%. As compared to published high-gravity fermentation, ethanol concentration of 72.3 g/L achieved in this study was the highest one in the lab-scale process, which proved that the proposed mSSF was an effective process to increase ethanol titers without sacrificing ethanol yields. The improved ethanol titers and yields would significantly lower the distillation cost and accelerate the commercialization of cellulosic biofuel production. [ABSTRACT FROM AUTHOR]

Biochemical conversion of lignocellulosic feedstock to biofuels and other valuable chemicals through sugar-platform process involves a pretreatment step that facilitates the conversion of polysaccharides to simple sugars. A major drawback of pretreatment process is the formation of lignocellulose-derived by-products, such as furfural and 5-hydroxy-2-methylfurfural (HMF), which inhibit the downstream enzymatic hydrolysis and microbial growth during fermentation. Hence, an efficient and environment friendly technique for removal of these inhibitors is essential. The present study reports isolation of a bacterium from soil that exhibited capability to degrade furfural and HMF present in lignocellulosic hydrolysate liquor. The isolated bacterium, Bordetella sp. BTIITR, was able to degrade 100% of furfural and 80% of HMF from simulated hydrolysate liquor in 16 h of incubation period. For the actual sugarcane bagasse hydrolysate liquor, it was able to remove 100% of furfural, 94% of HMF and 82% of acetic acid in 16 h of incubation period. It was also intriguing to observe that the bacterium selectively consumed furfural and HMF initially without significantly affecting the fermentable sugars. Once furfural and HMF were degraded to a lower concentration, consumption of sugars accelerated. This substrate priority of Bordetella sp. BTIITR for furfural and HMF over sugars renders it as a potential candidate for biodetoxification of inhibitory compounds present in the lignocellulosic hydrolysate liquor. [ABSTRACT FROM AUTHOR]

Some zwitterionic surfactants exhibit upper critical solution temperature (UCST) in aqueous solutions. For the zwitterionic surfactant solution mixed with cellulase, when its temperature is below UCST, the cellulase can be recovered by coprecipitation with zwitterionic surfactant. In this work, 3-(Hexadecyldimethylammonio) propanesulfonate (SB3-16) was selected to enhance the enzymatic hydrolysis of lignocelluloses and recover the cellulase. After adding 2 mmol/L of SB3-16, the enzymatic digestibility of eucalyptus pretreated by dilute acid (Eu-DA) and by sulfite (Eu-SPORL) increased from 27.9% and 35.1% to 72.6% and 89.7%, respectively. The results showed that SB3-16 could reduce the non-productive adsorption of cellulase on hydrophobic interface, while it did not significantly inhibit the activity of cellulase. For the solution contained 1 wt% SB3-16 and 200 mg protein/L CTec2 cellulase, 55.2% of protein could be recovered by cooling. The filter paper activity of the recovered cellulase was 1.93 FPU/mg protein, which was 95.8% of its initial activity. [ABSTRACT FROM AUTHOR]

Many species of Penicillium have exhibited great potential for lignocellulose hydrolysis. The filamentous fungus Talaromyces piceus 9-3 ( anamorph: Penicillium piceum), which was isolated from compost wastes in China, was sequenced in this study. Compared with the cellulase producer T. reesei, T. piceus 9-3 processes a lignocellulolytic enzyme system comprising more diverse enzymatic components, especially hemicellulases. This report will facilitate the use of this strain for biomass degradation. [ABSTRACT FROM AUTHOR]

Cellulosic ethanol production relies on the biochemical (enzymatic) conversion of lignocellulose to fermentable sugars and ultimately to bioethanol. However, the cost of lignocellulolytic enzymes is a limiting factor in the commercialisation of this technology. This therefore necessitates the optimisation of lignocellulolytic enzyme cocktails through the elucidation of synergistic interactions between enzymes so as to improve lignocellulose hydrolysis and also lower protein loadings in these reactions. However, many factors affect the synergism that occurs between these lignocellulolytic enzymes, such as enzyme ratios, substrate characteristics, substrate loadings, enzyme loadings and time. This review examines the effect of time on the synergistic dynamics between lignocellulolytic enzymes during the hydrolysis of both complex (true) lignocellulosic substrates and model substrates. The effect of sequential and simultaneous application of the lignocellulolytic enzymes on the synergistic dynamics during the hydrolysis of these substrates is also explored in this review. Finally, approaches are further proposed for efficient and synergistic hydrolysis of both complex lignocellulosic substrates and model substrates. With respect to the synergistic enzymatic hydrolysis of lignocellulosic biomass, this review exposed knowledge gaps that should be covered in future work in order to fully understand how enzyme synergism works: e.g. elucidating protein to protein interactions that exist between these enzymes in establishing synergy; and the effect of lignocellulose degradation products of one enzyme on the behaviour of the other enzyme and ultimately their synergistic relationship. [ABSTRACT FROM AUTHOR]

In enzymatic hydrolysis, high lignocellulose loadings are required to obtain high sugar titers. However, the high solids loadings limit enzymatic hydrolysis. In this study, to overcome this limitation, the promoting and synergistic effects of the accessory agents of hemicellulase (i.e., Cellic HTec2) and polyethylene glycol (PEG) 8000 were investigated in the enzymatic hydrolysis of hydrothermally pretreated empty fruit bunches (EFBs). After the optimal addition of Cellic HTec2 and PEG, high enzymatic digestion of the pretreated EFBs was achieved owing to their synergistic effects, even at high solids loadings. For example, the enzymatic digestibility of pretreated EFBs at a 21.7% (w/v) solids loading with 10 FPU of Cellic CTec2/g glucan reached 72.5% when 2.7 mg of Cellic HTec2/g glucan and 62.5 mg of PEG/g glucan were used as the accessory agents. These results suggested that the optimal addition of accessory agents is effective for the enhanced hydrolysis of lignocellulose using even a commercial cellulase preparation. [ABSTRACT FROM AUTHOR]

Background: Filamentous fungi are among the most powerful cellulolytic organisms in terrestrial ecosystems. To perform the degradation of lignocellulosic substrates, these microorganisms employ both hydrolytic and oxidative mechanisms that involve the secretion and synergism of a wide variety of enzymes. Interactions between these enzymes occur on the level of saccharification, i.e., the release of neutral and oxidized products, but sometimes also reflected in the substrate liquefaction. Although the synergism regarding the yield of neutral sugars has been extensively studied, further studies should focus on the oxidized sugars, as well as the effect of enzyme combinations on the viscosity properties of the substrates. Results: In the present study, the heterologous expression of an endoglucanase (EG) and its combined activity together with a lytic polysaccharide monooxygenase (LPMO), both from the thermophilic fungus Myceliophthora thermophila, are described. The EG gene, belonging to the glycoside hydrolase family 5, was functionally expressed in the methylotrophic yeast Pichia pastoris. The produced MtEG5A (75 kDa) featured remarkable thermal stability and showed high specific activity on microcrystalline cellulose compared to CMC, which is indicative of its processivity properties. The enzyme was capable of releasing high amounts of cellobiose from wheat straw, birch, and spruce biomass. Addition of MtLPMO9 together with MtEG5A showed enhanced enzymatic hydrolysis yields against regenerated amorphous cellulose (PASC) by improving the release not only of the neutral but also of the oxidized sugars. Assessment of activity of MtEG5A on the reduction of viscosity of PASC and pretreated wheat straw using dynamic viscosity measurements revealed that the enzyme is able to perform liquefaction of the model substrate and the natural lignocellulosic material, while when added together with MtLPMO9, no further synergistic effect was observed. Conclusions: The endoglucanase MtEG5A from the thermophilic fungus M. thermophila exhibited excellent properties that render it a suitable candidate for use in biotechnological applications. Its strong synergism with LPMO was reflected in sugars release, but not in substrate viscosity reduction. Based on the level of oxidative sugar formation, this is the first indication of synergy between LPMO and EG reported. [ABSTRACT FROM AUTHOR]

Enzymatic breakdown of lignocellulose is a major limiting step in second generation biorefineries. Assembly of the necessary activities into designer cellulosomes increases the productivity of this step by enhancing enzyme synergy through the proximity effect. However, most cellulosomal components are obtained from mesophilic microorganisms, limiting the applications to temperatures up to 50 °C. We hypothesized that a scaffoldin, comprising modular components of mainly mesophilic origin, can function at higher temperatures when combined with thermophilic enzymes, and the resulting designer cellulosomes could be employed in higher temperature reactions. For this purpose, we used a tetravalent scaffoldin constituted of three cohesins of mesophilic origin as well as a cohesin and cellulose-binding module derived from the thermophilic bacterium Clostridium thermocellum. The scaffoldin was combined with four thermophilic enzymes from Geobacillus and Caldicellulosiruptor species, each fused with a dockerin whose specificity matched one of the cohesins. We initially verified that the biochemical properties and thermal stability of the resulting chimeric enzymes were not affected by the presence of the mesophilic dockerins. Then we examined the stability of the individual single-enzyme-scaffoldin complexes and the full tetravalent cellulosome showing that all complexes are stable and functional for at least 6 h at 60 °C. Finally, within this time frame and conditions, the full complex appeared over 50 % more efficient in the hydrolysis of corn stover compared to the free enzymes. Overall, the results support the utilization of scaffoldin components of mesophilic origin at relatively high temperatures and provide a framework for the production of designer cellulosomes suitable for high temperature biorefinery applications. [ABSTRACT FROM AUTHOR]

Pretreatment is a critical step in the enzymatic conversion of lignocellulosic substrate to sugars. A unique pretreatment sequence involving thermochemical treatment (steam explosion) followed by biological treatment (fungal exposure) was evaluated for Pinus radiata as a biofuel substrate. The effect of biological treatment using the white rot Trametes versicolor was investigated on control (sapwood blocks) and steam-exploded wood (SEW) for changes in the profile of fungal enzyme activity and lignocellulose composition. The results indicated that compared to blocks, Trametes versicolor expressed more lignocellulose-degrading enzymes when grown on SEW for 6 and 12 weeks. After fungal exposure, the biomass was mixed with a commercial enzyme cocktail for enzymatic hydrolysis. The maximum conversion of biomass to sugars was obtained for Trametes versicolor-treated SEW, with a yield of 4.80 g of glucose l, which is greater compared to that obtained from non-fungal-treated SEW (3.80 g of glucose l) and Trametes versicolor-treated sapwood blocks (0.80 g of glucose l). Examination by microscopy suggests relative increase in the porosity of SEW after fungal treatment, and compositional analysis indicates reduction in lignin content. Both these factors are likely to contribute to the improved hydrolysis of SEW. [ABSTRACT FROM AUTHOR]

Background: The lignocellulose biorefinery based on the sugar platform usually focuses on polysaccharide bioconversion, while lignin is only burned for energy recovery. Pyrolysis can provide a novel route for the efficient utilization of residual lignin obtained from the enzymatic hydrolysis of lignocellulose. The pyrolysis characteristics of residual lignin are usually significantly affected by the pretreatment process because of structural alteration of lignin during pretreatment. In recent years, biological pretreatment using white-rot fungi has attracted extensive attention, but there are only few reports on thermal conversion of lignin derived from enzymatic hydrolysis residue (EHRL) of the bio-pretreated lignocellulose. Therefore, the study investigated the pyrolysis characteristics and kinetics of EHRL obtained from bamboo pretreated with Echinodontium taxodii in order to evaluate the potential of thermal conversion processes of EHRL. Results: Fourier transform infrared spectroscopy spectra showed that EHRL of bamboo treated with E. taxodii had the typical lignin structure, but aromatic skeletal carbon and side chain of lignin were partially altered by the fungus. Thermogravimetric analysis indicated that EHRL pyrolysis at different heating rates could be divided into two depolymerization stages and covered a wide temperature range from 500 to 900 K. The thermal decomposition reaction can be well described by two third-order reactions. The kinetics study indicated that the EHRL of bamboo treated with white-rot fungus had lower apparent activation energies, lower peak temperatures of pyrolysis reaction, and higher char residue than the EHRL of raw bamboo. Pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS) was applied to characterize the fast pyrolysis products of EHRL at 600 °C. The ratios of guaiacyl-type to syringyl-type derivatives yield (G/S) and guaiacyl-type to p-hydroxy-phenylpropane-type derivatives yield (G/H) for the treated sample were increased by 33.18 and 25.30 % in comparison with the raw bamboo, respectively. Conclusions: The structural alterations of lignin during pretreatment can decrease the thermal stability of EHRL from the bio-treated bamboo and concentrate the guaiacyl-type derivatives in the fast pyrolysis products. Thus, the pyrolysis can be a promising route for effective utilization of the enzymatic hydrolysis residue from bio-pretreated lignocellulose. [ABSTRACT FROM AUTHOR]

Degradation of lignocellulosic fibers such as untreated jute fibers and those treated with an alkaline solution of neem oil and phenolic resin are studied by monitoring enzyme activities during burial of fibers within a compost of organic soil and animal refuse. Results indicate that biodegradation of fibers is dominated initially by enzymatic hydrolysis of hemicellulose and amorphous cellulose and subsequently by crystalline cellulose degradation. For neem oil and phenolic resin treated fibers, the degradation of hemicelluloses and cellulose were found to proceed at a remarkably slower rate compared to untreated fibers due to relative nonavailability of degradable matter. [ABSTRACT FROM PUBLISHER]

Biofuel derived from lignocellulosic biomass has attracted considerable attention as a renewable energy source. Nevertheless, the conversion of lignocellulose into fermentable sugars is inherently difficult because of the complex structures of lignocelluloses. Accessory proteins, like expansins, have a non-hydrolytic disruptive effect on crystalline cellulose and can synergistically cooperate with cellulase to improve hydrolysis efficiency. This review summarizes recent studies on expansins and expansin-like proteins, in terms of their expression and purification, synergism in lignocellulose hydrolysis, structure-function studies and binding characteristics. Future research prospects are also presented. This review provides a discussion of expansins in the context of lignocellulose hydrolysis. [ABSTRACT FROM AUTHOR]

The development of an immobilized enzyme for efficient biocatalysis and catalyst recycling is of great importance in cost-effective and green chemical synthesis, with the hydrolysis of cellulose to glucose for the utilization of lignocellulosic biomass as a prominent and challenging example. We developed a novel concept of engineering temperature-responsive nanobiocatalysts with an upper critical solution temperature (UCST) for efficient catalysis as a soluble catalyst at a temperature ＞UCST and for easy catalyst separation as an insoluble catalyst at a temperature ＜UCST. The first polymeric nanoparticles showing an UCST were fabricated in high yield, and the immobilization of cellulase and cellobiase onto the particles afforded the first UCST-biocatalysts, with high specific enzyme loading and enzyme loading efficiency, an UCST of 13–14 °C, and high retention of the initial hydrolysis activity of the free enzyme at 50 °C (＞UCST). The hydrolysis of insoluble cellulose, such as filter paper and pre-treated oil palm Empty Fruit Bunch (EFB, a waste biomass), with a mixture of the UCST-nanobiocatalysts containing cellulase and cellobiase at 50 °C reached the same catalytic performance as the free enzymes and gave 97% and 93% glucose yield at 2 wt% of cellulase loading, respectively. These catalytic performances are much better than any other known immobilized cellulases, due to the use of soluble catalysts. The catalysts were easily recovered at 4 °C and recycled to retain 71% and 73% productivity in the 8th and 6th reaction cycles for hydrolyzing filter paper and pre-treated EFB, respectively. The engineered UCST-nanobiocatalysts are potentially useful for the practical green hydrolysis of cellulose to glucose. [ABSTRACT FROM AUTHOR]

Recently, research on the catalytic production of glucose, the first platform chemical in biorefinery, has become attractive in catalysis studies and the chemical/fuel industry owing to its broad applications. It opens up a new route for achieving sustainable chemical production and energy supply. From this viewpoint, this contribution attempts to overview the recent advances in the catalytic routes for the synthesis of glucose from lignocellulosic biomass over various homogeneous and heterogeneous catalysts. [ABSTRACT FROM AUTHOR]

In the present study, we developed a novel ligninolytic enzymes based pre-treatment method for lignocellulosic wheat straw to depolymerize lignin and expose the cellulose polymers to produce bio-ethanol. Wheat straw was pre-treated with ligninolytic enzymes extract produced from Ganoderma lucidum under optimum solid state fermentation conditions. The pre-treated biomass was further subjected to the enzymatic hydrolysis by the crude unprocessed cellulases (β-1,4 endoglucanase, 53.5 ± 1.24 U/mL; (β-1,4 exoglucanase, 41.3 ± 1.31 U/mL; (β-1,4 glucosidase, 46.8 ± 1.43 U/mL; and xylanase 39 ± 2.2 U/mL) produced by Trichoderma harzaianum. Under optimal conditions for enzymatic saccharification, 10% (w/v) of pre-treated biomass was hydrolyzed completely and converted to 72.5 and 2.4 g/L of glucose and xylose, respectively. Initial time screening Sequential Saccharification and Fermentation (SSF) of the concentrated enzymatic hydrolyzate (10%, w/v) by Saccharomyces cereuisiae produced 22.6 g/L ethanol in a fermented medium after 72 h of temperature controlled incubation at 37 °C. For maximum ethanol production, different physical and nutritional parameters like pH, temperature, substrate level and inoculum sizes were optimized. Under optimal conditions ethanol production of 33.5 g/L was obtained from ligninolytic treated residual (wheat straw) biomass. [ABSTRACT FROM AUTHOR]

Three white rot fungi (Lenzites betulinus, Trametes orientalis, and Trametes velutina) as well as their respective paired cultures were used to pretreat Populus tomentosa for enhanced lignocellulosic degradation and enzymatic hydrolysis. Hemicellulose and cellulose were slightly degraded, while a maximum lignin degradation of 58% was caused by T. velutina during the 12-week cultivation. After the pretreated samples were subjected to enzymatic hydrolysis for 96 h, the reducing sugar released by T. orientalis at week 12 was as high as 41%, which was in line with the lignin loss at 2.2 times the control sample. Overall, the monocultures of white-rot fungi exhibited better degradation and saccharification of woody biomass than their co-culture. This can be attributed to the partial removal of lignin and hemicellulose, with an associated increase of cellulose accessibility to enzymes. [ABSTRACT FROM AUTHOR]

The presented results of research on the effectiveness of enzymatic hydrolysis of lignocellulosic waste, depending on their initial depolymerisation in alkaline medium were considered in the context of the possibility of their further use in the fermentation media focused on the recovery of energy in the form of molecular hydrogen. The aim of this study was to determine the appropriate dose and concentration of a chemical reagent, whose efficiency would be high enough to cause decomposition of the complex, but without an excessive production of by-products which could adversely affect the progress and effectiveness of the enzymatic hydrolysis and fermentation. The effect of treatment on physical-chemical changes of homogenates' properties such as pH, COD, the concentration of monosaccharide and total sugars and the concentration of total suspended solids and volatile suspended solids was determined. The enzymatic decomposition of lignocellulosic complex was repeatedly more efficient if the sample homogenates were subjected to an initial exposure to NaOH. The degree of conversion of complex sugars into simple sugars during enzymatic hydrolysis of homogenates pre-alkalized to pH 11.5 and 12.0 was 83.3 and 84.2% respectively, which should be sufficient for efficient hydrogen fermentation process. [ABSTRACT FROM AUTHOR]

To produce lignocellulosic biofuels economically, the complete release of monomers from the plant cell wall components, cellulose, hemicellulose, and lignin, through pre-treatment and hydrolysis (both enzymatic and chemical), and the efficient utilization of these monomers as carbon sources, is crucial. In addition, the identification and development of robust microbial biofuel production strains that can tolerate the toxic compounds generated during pre-treatment and hydrolysis is also essential. In this work, Cupriavidus necator was selected due to its capabilities for utilizing lignin monomers and producing polyhydroxylbutyrate (PHB), a bioplastic as well as an advanced biofuel intermediate. We characterized the growth kinetics of C. necator in pre-treated corn stover slurry as well as individually in the pre-sence of 11 potentially toxic compounds in the saccharified slurry. We found that C. necator was sensitive to the saccharified slurry produced from dilute acid pre-treated corn stover. Five out of 11 compounds within the slurry were characterized as toxic to C. necator, namely ammonium acetate, furfural, hydroxymethylfurfural (HMF), benzoic acid, and p-coumaric acid. Aldehydes (e.g., furfural and HMF) were more toxic than the acetate and the lignin degradation products benzoic acid and p-coumaric acid; furfural was identified as the most toxic compound. Although toxic to C. necator at high concentration, ammonium acetate, benzoic acid, and p-coumaric acid could be utilized by C. necator with a stimulating effect on C. necator growth. Consequently, the lignin degradation pathway of C. necator was reconstructed based on genomic information and literature. The efficient conversion of intermediate catechol to downstream products of cis,cis-muconate or 2-hydroxymuconate-6-semialdehyde may help improve the robustness of C. necator to benzoic acid and p-coumaric acid as well as improve PHB productivity. [ABSTRACT FROM AUTHOR]

Levulinic acid is a feasible platform chemical derived from acid-catalyzed hydrolysis of lignocellulose. The conversion of this substrate to ( S)-γ-valerolactone (( S)-GVL) was investigated in a chemo-enzymatic reaction sequence that benefits from mild reaction conditions and excellent enantiomeric excess of the desired ( S)-GVL. For that purpose, levulinic acid was chemically esterified over the ion exchange resin Amberlyst 15 to yield ethyl levulinate (LaOEt). The keto ester was successfully reduced by ( S)-specific carbonyl reductase from Candida parapsilosis (CPCR2) in a substrate-coupled cofactor regeneration system utilizing isopropanol as cosubstrate. In classical batch experiments, a maximum conversion of 95 % was achieved using a 20-fold excess of isopropanol. Continuous reduction of LaOEt was carried out for 24 h, and a productivity of more than 5 mg ( S)-ethyl-4-hydroxypentanoate (4HPOEt) per μg CPCR2 was achieved. Afterwards ( S)-4HPOEt (>99% ee) was substituted to lipase-catalyzed lactonization using immobilized lipase B from Candida antarctica to yield ( S)-GVL in 90 % overall yield and >99% ee. [ABSTRACT FROM AUTHOR]

Abstract: Winery wastes were composted in the laboratory during five months in order to study the composting process of lignocellulosic wastes. In a first experiment, spent grape marc was composted alone, and in a second one, hydrolyzed grape marc, which is the residue generated after the acid hydrolysis of spent grape marc for biotechnological purposes, was composted together with vinification lees. During the composting of spent grape marc, total organic matter did not change, and as total N increased only slightly (from 1.7% to 1.9%), the reduction in the C/N ratio was very low (from 31 to 28). The mixture of hydrolyzed grape marc and lees showed bigger changes, reaching a C/N ratio around 20 from the third month on. Water-soluble organic matter followed the usual trend during composting, showing a progressive decrease in both experiments. Although the mixture of hydrolyzed grape marc and lees presented the highest initial water-soluble carbon concentrations, the final values for both experiments were similar (8.1 g kg−1 for the spent grape marc, and 9.1 g kg−1 for the mixture). The analysis of the humification parameters did not allow an adequate description of the composting process, maybe as a consequence of the inherent problems existing with alkaline extractions. The total humic substances, which usually increase during composting as a consequence of the humification process, followed no trend, and they were even reduced with respect to the initial values. Notwithstanding, the fractionation of organic matter into cellulose, hemicellulose and lignin enabled a better monitoring of the waste decomposition. Cellulose and hemicellulose were degraded mainly during the first three months of composting, and the progressive reduction of the cellulose/lignin ratio proved that the main evolution of these wastes took place during the first three months of composting. [Copyright &y& Elsevier]