Hydrolysis Of Sugarcane Bagasse Research Articles

Metabolic Engineering of Candida glycerinogenes for Sustainable Production of Geraniol.

Geraniol is a class of natural products that are widely used in the aroma industry due to their unique aroma. Here, to achieve the synthesis of geraniol and alleviate the intense competition from the yeast ergosterol pathway, a transcription factor-mediated ergosterol feedback system was developed in this study to autonomously regulate ergosterol metabolism and redirect carbon flux to geraniol synthesis. In addition, the modification of ergosterol-responsive promoters, the optimization of transcription factor expression intensity, and stepwise metabolic engineering resulted in a geraniol titer of 531.7 mg L-1. For sustainable production of geraniol, we constructed a xylose assimilation pathway in Candida glycerinogenes (C. glycerinogenes). Then, the xylose metabolic capacity was ameliorated and the growth of the engineered strain was rescued by activating the pentose phosphate (PP) pathway. Finally, we obtained 1091.6, 862.4, and 921.8 mg L-1 of geraniol in a 5 L bioreactor by using pure glucose, simulated wheat straw hydrolysates, and simulated sugarcane bagasse hydrolysates, with yields of 47.5, 57.9, and 59.1 mg g-1 DCW, respectively. Our study demonstrated that C. glycerinogenes has the potential to produce geraniol from lignocellulosic biomass, providing a powerful tool for the sustainable synthesis of other valuable monoterpenes.

Semi-Simultaneous Saccharification and Fermentation Improved by Lignin and Extractives Removal from Sugarcane Bagasse

Lignocellulosic biomass and agro-industrial residues are a source of fermentable sugars; however, pretreatments are needed to overcome biomass recalcitrance. This study evaluated the effect of sugarcane bagasse hydrolysis and fermentation in response to dilute acid pretreatment. In natura bagasse, extractive-free bagasse, partially delignified bagasse, and bagasse with added butylated hydroxytoluene antioxidant were pretreated with diluted acid and investigated in semi-simultaneous saccharification and fermentation (S-SSF). The effect of butylated hydroxytoluene (BHT) resulted in lower yields of inhibitors in the liquid fraction of the acid pretreatment (0.01 g L−1 of furfural, 0.01 g L−1 of 5-hydroxymethylfurfural, and 0.68 g L−1 of acetic acid). Partially delignified material and material with BHT resulted in biomass with low hemicellulose and lignin contents, indicating that BHT influenced lignin removal. Extractives removal showed benefits for the acid pretreatment, decreasing the dioxane-soluble material, and a higher yield of glucose and ethanol via S-SSF for the partially delignified material. Enzymatic saccharification of partially delignified material showed 87% of cellulose conversion (24 h with 15 FPU/g), and after 48 h of S-SSF (25 FPU/g), residual 7.06 g L−1 of glucose and production of 15.17 g L−1 of ethanol were observed. The low content of extractives, lignin, and dioxane soluble material resulted in better cellulose accessibility and ethanol yield. Chemical compounds can help remove lignin from biomass favoring ethanol production by S-SSF.

Enhancement of Enzymatic Hydrolysis of Sugarcane Bagasse by the Combination of Delignification Pretreatment and Polysorbate 80

Delignification pretreatment with alkali under various conditions (25–160 °C for 1–12 h) or sodium chlorite at 75 °C for 4 h was applied to improve the enzymatic digestibility of sugarcane bagasse by removing hemicellulose and lignin. Compared with the elimination of hemicellulose, delignification contributed more in achieving a higher glucose yield. In addition, the characterization of untreated and pretreated sugarcane bagasse was conducted to determine the influence of hemicellulose and lignin degradation on subsequent enzymatic digestibility. Furthermore, Polysorbate 80 was added to reduce the enzyme loading, shorten the hydrolysis time, and enhance the efficiency of enzymatic hydrolysis, suggesting that the glucose yield of 92.2% was obtained with enzyme loading of 5 FPU/g substrate. However, the increased yield of glucose with Polysorbate 80 occurred with an increased lignin content and a reduction of enzyme loading, and the yield decreased sharply as the hydrolysis time was prolonged from 6 h to 24 h.

Ability of converting sugarcane bagasse hydrolysate into polyhydroxybutyrate (PHB) by bacteria isolated from stressed environmental soils

We isolated 109 potential polyhydroxybutyrate (PHB)-producing bacteria from various soil sources. Using Sudan Black B staining, lipid granules were observed in 65 isolates. UV spectrophotometry-based quantification revealed that 14 isolates effectively produced PHB, and all isolates carried the phaC gene encoding polyhydroxyalkanoate synthase required for PHB polymerization. After cultivation at 30 °C for 72 h in E2 medium containing 3.5% (w/v) glucose as the carbon source and 0.354% (w/v) NH4Y as the nitrogen source, the highest PHB content (%-CDW) and yield (g-PHB/g-glucose) with values of 20.4% and 0.28 and 19.7% and 0.07 were obtained for Priestia megaterium KKR5 and Burkholderia cepacia ASL22, respectively. TEM analysis revealed PHB granules with diameters of 0.2–0.7 μm inside KKR5 and ASL22 cells. We achieved the bioconversion of sugarcane bagasse hydrolysate (BGH) into PHB by these strains via separate hydrolysis and fermentation. H3PO4 steam-pretreated BGH generated reducing sugars containing glucose and xylose without toxic chemicals. Using the reducing sugars of BGH as the carbon source, ASL22 exhibited a higher PHB yield (0.22 g-PHB/g-reducing sugar) than KKR5 (0.12 g-PHB/g-reducing sugar). PHB from KKR5 and ASL22 had FTIR and NMR spectra that were similar to those of standard PHB. A GC/MS analysis confirmed the molecular structure of PHB as methyl hydroxybutyrate with a mass value of 43–103. By DSC analysis, the melting temperatures of PHB from KKR5 and ASL22 and standard PHB were 167.8, 168.5, and 176.6 °C, respectively. Thus, PHB-producing bacteria isolated from stressed soils successfully utilize a low-cost BGH substrate for PHB accumulation.

Fed-batch enzymatic hydrolysis of steam-exploded sugarcane bagasse

Statistical design and mathematical modeling were used to investigate the fed-batch enzymatic hydrolysis of steam-exploded sugarcane bagasse (195 °C, 7.5 min). First, a Box-Behnken experimental design was used to evaluate the effect of enzyme loading (8, 24, and 40 FPU g-1 glucans of Cellic CTec3®), stirring speed (100, 150, and 200 rpm), and substrate total solids (5, 12.5, and 20 wt%) on the release of glucose equivalents (GlcEq, mostly glucose) after hydrolysis for 48 h in batch mode. A simplified kinetic model was used to fit the experimental data, in which specific activities in Cellic CTec3 were not differentiated, enzyme adsorption was ignored, and end-product inhibition was only attributed to glucose accumulation. The adjusted kinetic model was used to predict the effects of substrate and enzyme intermittent feedings in fed-batch hydrolysis experiments. Compared with batch experiments at 20 wt%, the proposed fed-batch procedure was able to increase GlcEq productivity by nearly 68% using the same enzyme loading, producing substrate hydrolysates containing 91.8 g L-1 GlcEq.

Removal of Fermentation Inhibitors from Sugarcane Bagasse Hydrolysate via Post-cross-linked Hydrophilic-Hydrophobic Interpenetrating Polymer Networks.

The efficient and economical removal of fermentation inhibitors from the complex system of biomass hydrolysate was one of the basics and keys in bio-chemical transformation. In this work, post-cross-linked hydrophilic-hydrophobic interpenetrating polymer networks (PMA/PS_pc IPNs and PAM/PS_pc IPNs) were proposed to remove fermentation inhibitors from sugarcane bagasse hydrolysate for the first time. PMA/PS_pc and PAM/PS_pc IPNs can obviously enhance the adsorption performance towards fermentation inhibitors due to their higher surface area and hydrophilic-hydrophobic synergetic surface properties, especially PMA/PS_pc IPNs has higher selectivity coefficients of 4.57, 4.63, 4.85, 16.0, 49.43, and 22.69, and higher adsorption capacity of 24.7 mg/g, 39.2 mg/g, 52.4 mg/g, 9.1 mg/g, 13.2 mg/g, and 144.9 mg/g towards formic acid, acetic acid, levulinic acid (LA), 5-hydroxymethylfurfural (HMF), furfural, and acid-soluble lignin (ASL), respectively, in a lower total sugar loss of 2.03%. The adsorption kinetics and isotherm of PMA/PS_pc IPNs were studied to elucidate its adsorption behavior towards fermentation inhibitors. In addition, the cyclic utilization property of PMA/PS_pc IPNs was stable. Synthesizing PMA/PS_pc IPNs is a new strategy to provide an efficient adsorbent for the removal of fermentation inhibitors from lignocellulosic hydrolysate.

Monomethyl branched-chain fatty acids enriched bacterial oil production by furan aldehydes tolerant halophile Lentibacillus salarius strain BPIITR using non-detoxified sugarcane bagasse

The structural diversity of monomethyl branched-chain fatty acids (mBCFAs) expanded their application in biolubricants, biofuels for enhancing cold flow and thermo-oxidative properties. Current study focuses on mBCFAs production from sugarcane bagasse hydrolysate in biorefinery approach with halophilic Lentibacillus salarius BPIITR. Halophilic bacterium exhibited tolerance towards furan aldehydes up to 150 mM in minimal medium and produced 3.40 ± 0.13 and 2.47 ± 0.15 gL−1 lipid rich in mBCFAs, in xylose and glucose rich non-detoxified hydrolysate, respectively at bench-scale bioreactor. In addition, 2,5-furandicarboxylic acid and 2-furancarboxylic acids were co-produced as value-added products up to 41.34 ± 4.73 and 59.84 ± 5.17 mM, respectively. The biosynthesized bacterial oil exhibited onset oxidation temperature of 319.5 °C and low temperature viscosity ratio of 2.92. The accumulated lipid was rich in triacylglycerol content more than 67 % with 12-methyl tetradecanoic acid as major fatty acid.

Evaluation of Xylose-Utilising Yeasts for Xylitol Production from Second-Generation Ethanol Vinasse and Effect of Agitation Intensity in Flask-Scale Xylitol Production

This study aimed to select a yeast strain that effectively utilises xylose to produce xylitol from the vinasse of ethanol broth obtained from the fermentation of sugarcane bagasse hydrolysate. Eleven strains of xylose-fermenting yeasts were evaluated for their abilities to utilise xylose and produce xylitol. Two strains that showed outstanding performance in the semi-defined xylose medium were selected for further testing with a vinasse medium. Candida guilliermondii TISTR 5068 showed a superior xylitol production of 7.03 ± 0.08 g/L with the xylitol yield of 0.70 g/gxylose when cultured in bagasse-based ethanol vinasse. The strain was further tested for its xylitol production performance when cultured at four different agitation intensities. Excessive agitation resulted in a rapid xylitol production rate but caused xylitol consumption once the xylose was depleted. Moderate agitation resulted in the highest xylitol yield of 0.79 g/gxylose. The results of this study have provided important information for the development of the xylitol production process using waste streams from cellulosic ethanol production.

Enhanced cellulosic ethanol production via fed-batch simultaneous saccharification and fermentation of sequential dilute acid-alkali pretreated sugarcane bagasse

This study reports high gravity fed-batch simultaneous saccharification and fermentation (FB-SSF) of sequentially pretreated sugarcane bagasse (SCB) for enhanced bioethanol by employing multiple inhibitor tolerant Kluyveromyces marxianusJKH5 C60. FB-SSF with intermittent feeding of SCB (total 20 % solid loading) and enzyme (total dose of 20 FPU/g) at 6 and 12 h resulted in superior bioethanol production at42 °C. Under optimizedlab-scaleFB-SSF, the maximum ethanoltiter, efficiency and productivities were73.4 ± 1.2 g/L,78 % and 3.0 g/L/h, respectively, after 72 h in presence of inhibitors (acetic acid, furfural, and vanillin at 3, 1, and 1 g/L, respectively). Furthermore, pentose rich dilute acid hydrolysate of SCB was subjected to fermentation by Pichia stipitis NCIM 3499, resulting in ethanol titer of 6.8 g/L. Overall ethanol yield during the developed process was 260.1 g/kg native SCB, which proves industrial potential of the developed bioethanol conversion process.

Production, Physicochemical and Structural Characterization of a Bioemulsifier Produced in a Culture Medium Composed of Sugarcane Bagasse Hemicellulosic Hydrolysate and Soybean Oil in the Context of Biorefineries

Biosurfactants are amphipathic molecules, biodegradable, with reduced toxicity. They can be synthesized by fermentative processes from oleaginous compounds and agro-industrial by-products. In this context, the present study describes the production and the physical, chemical, and structural characterization of the bioemulsifier secreted by the yeast Scheffersomyces shehatae 16-BR6-2AI in a medium containing hemicellulosic sugarcane bagasse hydrolysate combined with soybean oil. The bioemulsifier was produced in Erlenmeyer flasks and isolated; then, the physicochemical and structural characterization of the formed molecule was carried out. The following fermentation parameters were obtained: YX/S = 0.45, YP/S = 0.083, and productivity of 0.076 g/L/h. The bioemulsifier was found to be a polymer containing 53% of carbohydrates, 40.92% of proteins, and 6.08% of lipids, respectively. The FTIR spectrum confirmed the presence of functional groups such as amides, amines, and carbonyls. The bioemulsifier was stable over a range of temperature (−20 °C to 120 °C), salinity (1–15%), and pH (2–12). It was observed that the biomolecule has a better emulsifying action in organic solvents with a non-polar character. Therefore, this biomolecule is a potential substitute for synthetic surfactants and can be used in different applications.

Sorbitol production from a mixture of sugarcane bagasse and cassava pulp hydrolysates using thermotolerant Zymomonas mobilis TISTR548

The sorbitol production capability of different thermotolerant strains of Zymomonas mobilis and the optimization conditions for sorbitol production using sugarcane bagasse hydrolysate (SBH) and cassava pulp hydrolysate (CPH) as feedstocks were investigated. Among the different bacterial strains and combinations of SBH and CPH, the thermotolerant Z. mobilis TISTR548 and a mixture of SBH and CPH at a ratio of 0.50:0.50 provided the highest sorbitol concentration at 37 °C. A screening of the environmental factors influencing sorbitol production by Z. mobilis TISTR548 using the Plackett-Burman design (PBD) revealed three significant independent variables, i.e., CaCl 2 , NaCl, and pH, which positively affected sorbitol production using a mixture of SBH and CPH as substrate. The response surface methodology (RSM) based on the central composite design (CCD) resulted in the optimum CaCl 2 concentration of 2.47 g/L, a NaCl concentration of 0.08 g/L, and a pH of 6.49, yielding the maximum sorbitol concentration of 5.89 g/L, which was approximately 2.0-fold higher than that of the non-optimal conditions. This finding suggested that the bioconversion of lignocellulosic biomasses into sorbitol through microbial fermentation is another platform for sustainable industrial high-value bioproducts . • Sorbitol production from a mixture of sugarcane bagasse and cassava pulp hydrolysates. • High-temperature sorbitol fermentation using thermotolerant Zymomonas mobilis. • Optimization conditions for sorbitol production using a statistical experimental model.

Technoeconomic and environmental perspectives of biofuel production from sugarcane bagasse: Current status, challenges and future outlook

Sugarcane bagasse (SCB) is an attractive lignocellulose feedstock for biofuel production due to its high organic content and biomass yield, and ease of collection and storage. SCB-based biofuel production through the biochemical route is considered to be an eco-friendly option. However, the sustainability of this green technology is still questionable for some technoeconomic challenges associated with the pretreatment , detoxification, microbial tolerance to inhibitors, and conversion of SCB hydrolysates into biofuels. Researchers have attempted to overcome these issues, particularly by developing cost-effective pretreatment methods and engineered strains capable of tolerating inhibitors and converting SCB-derived components more efficiently. This review aims to present the current status and challenges in the conversion of SCB into biofuels like biohydrogen, biomethane, biomethanol, bioethanol , and biobutanol. The major economic and environmental perspectives are also discussed to assess the economics and eco-friendliness of SCB as the feedstocks for biofuel production. In addition, this paper also highlights existing knowledge gaps that might inspire the readers to fine-tune their research, innovations, and business plan for the development of cost-effective technologies for SCB-based biofuel production. • SCB as a feedstock for various biofuels has been discussed in this review. • Production of SCB-based biofuels has a high affordability of the raw material. • Pretreatment still remains a key challenge in viable SCB-based biofuel production. • Multi-product biorefinery for maximum use of SCB is of great importance.

Continuous long-term glucose biosensor in agitation condition for bioconversion processes

The use of a glucose biosensor in the bioconversion processes is challenging due to a long period of intensive stirring that is required to mix the heterogenous substants together. In this work, a glucose biosensor was developed to be accurate and robust for an extended period of measuring time in agitated conditions. The sensor probe was fabricated by electro-polymerization of polyaniline (PANI) nanostructures on a gold wire before putting in gold nanoparticles (AuNPs) and carrageenan (carr) solution to make an PANI-carr-AuNPs layer. Then the probe was soaked in PQQ-Glucose dehydrogenase (GDH) solution before coating with polyurethane (PU) to prevent the enzymes from leaching away from the sensor. The sensor probe showed a sensitivity of 0.85 μA/mg/ml of glucose with R2 of 0.9973. The storage stability of the probe was up to 4 days with stable signal. In agitated condition of 150 rpm, steady signals from the sensor were continuously obtained for 72 h. In sugarcane bagasse hydrolysis with speed at 150 rpm for 72 h, the biosensor continuously displayed signals which were not significantly different in glucose concentration to the results from the HPLC method. This biosensor displayed promising applications in bioconversion processes.

An Approach for Incorporating Glycerol as a Co-Substrate into Unconcentrated Sugarcane Bagasse Hydrolysate for Improved Lipid Production in Rhodotorula glutinis

Sugarcane bagasse is a potential raw material for microbial lipid production by oleaginous yeasts. Due to the limited sugar concentrations in bagasse hydrolysate, increasing carbon the concentration is necessary in order to improve lipid production. We aimed to increase carbon concentration by incorporating glycerol as a co-substrate into unconcentrated bagasse hydrolysate in the cultivation of Rhodotorula glutinis TISTR 5159. Cultivation in hydrolysate without nitrogen supplementation (C/N = 42) resulted in 60.31% lipid accumulation with 11.45 ± 0.75 g/L biomass. Nitrogen source supplementation increased biomass to 26.29 ± 2.05 g/L without losing lipid accumulation at a C/N of 25. Yeast extract improved lipid production in the hydrolysate due to high growth without altering the lipid content of the cells. Mixing glycerol up to 10% v/v into the unconcentrated hydrolysate improved biomass and lipid production. A further increase in glycerol concentrations drastically decreased growth and lipid accumulation by the yeast. By maintaining C/N at 27 using yeast extract as the sole nitrogen source, hydrolysate mixed with 10% v/v glycerol resulted in the highest lipid yield, at 19.57 ± 0.53 g/L with 50.55% lipid content, which was a 2.8-fold increase compared to using the hydrolysate alone. In addition, yeast extracts were superior for promoting growth and lipid production compared to inorganic nitrogen sources.

The fermentation efficiency exhibited by Saccharomyces cerevisiae on Sugarcane bagasse hydrolysate, by analyzing the effects of pre-treatment and detoxification

In this study, the possibility of increasing fermentation efficiency of Saccharomyces cerevisiae on sugarcane bagasse (a type of lignocellulosic waste) was analyzed. Sugarcane bagasse was subjected to hydrothermal and acidic pre-treatment. Next, the enzymatic hydrolysis of raw biomass and each pre-treated biomass was performed using CellicCtec® enzymatic complex to obtain sugarcane hydrolysate, hydrothermal hydrolysate and acidic hydrolysate. Next, these were fermented by S. cerevisiae to check if the by-products of enzymatic hydrolysis, furfural and acetic acid had an inhibitory effect on fermentation efficiency. Next, each pre-treated biomass was subjected to detoxification involving activated charcoal. Each detoxified biomass was tested for fermentation efficiency. The lignocellulosic composition for sugarcane hydrolysate, hydrothermal hydrolysate and acidic hydrolysate, varied significantly, and were found to be, for cellulose 36.7%, 27.7% and 63.7% respectively; for hemicellulose 22.2%, 4.4% and 12% respectively; and for lignin 21.2%, 27.7% and 28.7% respectively. The presence of furfural and acetic acid had a strong influence on the fermentation efficiency of S. cerevisiae, and affected the consumption of sugars in each biomass by more than 90%. Further, we found that the detoxification process increased fermentation efficiency by 12.7% for the hydrothermal hydrolysate while for the acidic hydrolysate no significant difference was observed. This study showed that fermentation with greater efficiency is viable through the combined use of hydrothermal pre-treatment and detoxification. This combination of methods also causes less pollution as compared with the method involving acid pre-treatment due to the reduced number of effluents produced.

Production of Enzymatic Extract with High Cellulolytic and Oxidative Activities by Co-Culture of Trichoderma reesei and Panus lecomtei

This work aimed to produce enzymatic fungi extracts with hydrolytic and oxidative activities to hydrolyze lignocellulosic biomasses efficiently. For this, the fungi Trichoderma reesei and Panus lecomtei were co-cultured using the vegetable biomasses oil palm decanter cake, wheat bran, and cottonseed cake as substrates in submerged fermentation. T. reesei and P. lecomtei showed partially compatible positive interaction on plates. The co-cultures respond positively to variations of temperature and inoculum interval, generating extracts responsible for higher hydrolysis yield when grown at 25 °C, and P. lecomtei is inoculated 24 h after T. reesei. The enzymatic extract production of co-cultures was also improved by modifying the components of the initial media and evaluating enzymatic activities, hydrolysis of sugarcane bagasse pretreated by autohydrolysis and ethanol production as a response. Five culture media were evaluated with variations in the composition of nutritional elements, minerals and substrates. The best extract showed a maximum cellulose hydrolysis efficiency of 68.7% compared with 44.8% of the initial medium. The ethanolic fermentation of hydrolysates obtained by co-culture extracts showed higher ethanol yields than monocultures. This work demonstrates the use of fungi co-cultures to produce enzymatic extracts composed of cellulolytic, hemicellulolytic, and ligninolytic enzymes complexes, which allow hydrolyzing pretreated lignocellulosic biomass with high efficiency, generating hydrolysates that are easier fermented by yeast.

Lychee-Derived, Thermotolerant Yeasts for Second-Generation Bioethanol Production

Thermotolerant yeasts are widely considered to be alternative strains to traditional yeasts for bioethanol production at high temperatures. In this study, thirty-two yeasts isolated from lychees were screened for thermotolerance, and seven selected isolates were identified as Candida tropicalis (isolates H8, H19, and H23), Meyerozyma guilliermondii (isolates H1 and H12) and Saccharomyces cerevisiae (isolates H10 and H18). They tolerated up to 45 °C, 12% (v/v) ethanol concentration, 10 g/L acetic acid, and 5 g/L furfural, respectively, and produced 47.96 to 70.18 g/L of ethanol from 160 g/L glucose at 40 °C during 48 h of fermentation. Among the evaluated yeasts, M. guilliermondii H1 showed great potential for second-generation bioethanol fermentation with its ability to ferment xylose and arabinose. Under the optimal conditions resulting from a Plackett Burman design and a Box Behnken design, the highest ethanol concentration of 11.12 g/L was produced from 40 g/L substrate-based sugarcane bagasse hydrolysate (non-detoxified hydrolysate) at 40 °C by M. guilliermondii H1. These findings suggested that the newly isolated thermotolerant yeast M. guilliermondii H1 is a good candidate for ethanol production from agricultural wastes.

Evaluation of Enzymatic Hydrolysis of Sugarcane Bagasse Using Combination of Enzymes or Co-Substrate to Boost Lytic Polysaccharide Monooxygenases Action

This study evaluated innovative approaches for the enzymatic hydrolysis of lignocellulosic biomass. More specifically, assays were performed to evaluate the supplementation of the commercial cellulolytic cocktail Cellic® CTec2 (CC2) with LPMO (GcLPMO9B), H2O2, or cello-oligosaccharide dehydrogenase (CelDH) FgCelDH7C in order to boost the LPMO action and improve the saccharification efficiency of biomass into monosaccharides. The enzymatic hydrolysis was carried out using sugarcane bagasse pretreated by hydrodynamic cavitation-assisted oxidative process, 10% (w/w) solid loading, and 30 FPU CC2/g dry biomass. The results were compared in terms of sugars release and revealed an important influence of the supplementations at the initial 6 h of hydrolysis. While the addition of CelDH led to a steady increase in glucose production to reach 101.1 mg of glucose/g DM, accounting for the highest value achieved after 72 h of hydrolysis, boosting the LPMOs activity by the supplementation of pure LPMOs or the LPMO co-substrate H2O2 were also effective to improve the cellulose conversion, increasing the initial reaction rate of the hydrolysis. These results revealed that LPMOs play an important role on enzymatic hydrolysis of cellulose and boosting their action can help to improve the reaction rate and increase the hydrolysis yield. LPMOs-CelDH oxidative pairs represent a novel potent combination for use in the enzymatic hydrolysis of lignocellulose biomass. Finally, the strategies presented in this study are promising approaches for application in lignocellulosic biorefineries, especially using sugarcane bagasse as a feedstock.

Wastes recycling of non-sterile cellulosic ethanol production from low-temperature pilot-scale enzymatic saccharification of alkali-treated sugarcane bagasse

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.

Hydrolysis of Mixed Sugarcane Bagasse and Rice Husk Using Cellulase Enzyme for Reducing Sugar Production

Reducing sugar can be produced from lignocellulosic raw materials. The content of polysaccharides such as cellulose, hemicellulose, and starch will be broken down into simpler carbohydrates. This study used a mixture of sugarcane bagasse and rice husks as lignocellulosic raw materials. The lignin content in the raw material must be removed through delignification or pretreatment so that enzymes can access cellulose and hemicellulose. This study used a physics-chemical pretreatment method, in which lignocellulosic material soak in 3% NaOH then heated with microwave and boiling water. The next process is enzymatic hydrolysis with variations of cellulase enzymes activity 0.434, 0.871, 2.61, and 3.49 FPU/g mixture of bagasse and rice husks. The cellulase enzyme used in this study was also derived from the fungus Trichoderma viride. Analysis of the sugar concentration resulting from hydrolysis used the DNS method with the 3.5-dinitrosalicylic acid reagent. The concentration of sugar from hydrolysis using a variety of enzymes with microwave heating pretreatment and boiling water pretreatment obtained the highest results which were the same at the addition of enzyme activity 3.49 FPU/g substrate at 24 hours, namely 4.077 g/L and 15.18 g/L. The optimum time for enzymatic hydrolysis is 12 hours and optimum enzyme activity is the addition of enzyme activity 2.61 FPU/g. The average concentration of sugar hydrolyzed by the addition of Trichoderma viride solution in pretreatment using microwave heating was 0.7611 g/L with a yield of 21.01 mg sugar/g substrate and with pretreatment in boiling water obtained 0.8679 g/L with a yield of 23.95 mg sugar/g substrate.