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Novel and sustainable pretreatment approaches are desired to improve the techno-commercial feasibility of biorefineries in the future. In this study, 10 renewable deep eutectic solvents (DESs) were evaluated for their pretreatment efficiency at facile conditions with sugar cane bagasse as substrate and compared with conventional pretreatment approaches (dilute alkali, dilute acid, and ionic liquid (IL)) for lignin removal, saccharification yield, cellulose accessibility, crystallinity, and physiochemical properties. Although, the highest delignification was obtained with dilute alkali (59.7%) and choline chloride:lactic acid or ChCl:LA (50.6%), the maximum enzymatic conversion of 98.0% and 90.4% was observed with IL (1-butyl-3-methylimidazolium acetate) and ChCl:LA, respectively. uclear magnetic resonance analysis of ChCl:LA-derived lignin showed selective removal of guaiacyl lignin without condensation structure formation observed. Interestingly, unlike IL, the lignin was substantially depolymerized afte...

b-glucosidases are very important in the improvement of cellulose degradation rates by diminishing the inhibition of end products. Although, cellulase cost has reduced significantly in last decade but still the high costs of biomass saccharification is one of the main challenges for the commercialization of ethanol from LC biomass. In this work, -glucosidase immobilization in calcium alginate was optimized using response surface methodology. 89% immobilization efficiency was achieved under optimum conditions (i.e., calcium alginate 4.19% (w/v), calcium chloride 0.14 M and -glucosidase 4.42% (v/v) or 57.46 U/mL of reaction mixture). pH and temperature optima of both free and immobilized -glucosidase was found to be 5 and 50 C, respectively. Enzyme kinetics of free and immobilized -glucosidase was done to evaluate Michaelis constant (Km) and Vmax values, using pnitrophenyl- -D-glucopyranoside (pNPG) as the substrate and glucose as inhibitor. Increase in Km value (0.995 mM) for immobilized -glucosidase as compared to the free -glucosidase (0.617 mM) was observed. A decrease in Vmax from (1191.74 mol min-1 for free -glucosidase) to (736.65 mol min-1 immobilized -glucosidase) was observed after immobilization. Glucose was found to inhibit -glucosidase by competitive mode of inhibition (Ki= 3.01 mM). Studies were carried out in a batch reactor using 2% cellobiose, 0.1 M sodium acetate buffer, 5 pH and 50 C. 84% cellobiose to glucose conversion was found in first cycle which was about 67% in fifth cycle. This study suggests that enzyme immobilization improved enzyme stability, substrate inhibition and permits enzyme reusability.

In this study, commercial surfactants have been investigated at economically viable dosage to enhance the enzymatic saccharification of pretreated wheat straw at high solid loadings. Twenty one surfactants were evaluated with pilot scale pretreated wheat straw and mechanism of surfactant action has been elucidated. One surfactant has improved the saccharification of dilute acid wheat straw (DAWS) by 26.4% after 24 h and 23.1% after 48 h while, steam exploded wheat straw (SEWS) saccharification was increased by 51.2% after 24 h and 36.4% after 48 h at 10% solid loading. At 20% solid loading, about 31% increase in yield was obtained on DAWS and about 55% on SEWS after 48 h. Further, lignin was isolated from pretreated wheat straws and characterized which revealed that SEWS derived lignin was more hydrophobic than DAWS lignin. This investigation suggests that surfactant supplementation during saccharification is an effective strategy to achieve higher saccharification yield.

Co-culture of fungal strains Penicillium janthinellum EMS-UV-8 (E), Penicillium funiculosum strain P (P) and Aspergillus sp. strain G (G) and blending of their crude cellulase were evaluated for improvements in cellulase activities as well as for enhanced hydrolysis of dilute acid pretreated wheat straw (PWS). The blending of crude enzymes of P and E enhanced the hydrolysis of PWS more effectively due to synergism in cellulolytic enzyme activities. Here, three types of blends were made on the basis of equal FPUs, equal protein content or fixed volume containing different proportions of individual enzymes, the former blend hydrolyzed 42.6% of PWS due to the 98%,62%, 64% and 34% synergistic enhancement in endo-glucanase, cellulase (FPU), β-glucosidase and xylanase activities, respectively. Hydrolysis at 10% solid loading of PWS in roller bottle reactor with this blend further enhanced hydrolysis yield to 74% within 24 h, which was much better than the corresponding hydrolysis yields of individual (38.1% by E and 61.5% by P) or the commercial enzyme (62.3%). This study proved that synergistic blends of cellulases from two Penicillium spp. are cost-effective tools for efficient wheat straw hydrolysis for on-site biofuel production.

Disaccharides or their derivatives were analyzed for the induction of cellulases by Penicillium janthinellum EMS-UV-8 mutant. Among seven (Crocin, Gentiobiose, Cellobiose, α-D-Cellobiose octaacetat...

Study describes the production of cellulases by Penicillium janthinellum EMS-UV-8 using untreated wheat straw (WS), treated WS (acid, alkali, steam exploded, organo-solv) and pure cellulosic substrates (avicel, cellulose-II and carboxymethyl cellulose). Severely pretreated WS and cellulose-II produced more cellulolytic enzymes than untreated samples. XRD and FTIR analysis revels that the increase in the amorphous structure of pretreated WS/cellulose increases enzyme production. Enzyme samples prepared using different substrates were used for the hydrolysis of dilute acid treated wheat straw (DATWS), steam exploded wheat straw (SEWS) and avicel. The enzyme prepared using untreated WS gave more hydrolysis of DATWS and SEWS than the enzyme prepared using pretreated WS or pure cellulosic substrates. This revels that more diverse/potential enzymes were secreted by P. janthinellum EMS-UV-8 mutant using untreated WS. This study may contribute in production of efficient enzyme mixture/cocktail by single fungal strain for economic conversion of biomass to sugars.

Conversion of pretreated lignocellulosic biomass (LCB) into sugars is one of the critical steps for bioethanol production. High LCB hydrolysis could be achieved by employing robust enzymes having high inhibitor tolerance, low irreversible lignin binding, and low end-product inhibition. In this study, acid pretreatment of wheat straw was carried out at pilot scale (250 kg/day) and three commercial cellulase preparations from Advanced Enzyme (AD), Novozyme (CL), and Genencor (AC) were evaluated for inhibitor (lignin, furfural, hydroxyl methyl furfural, vanillin) tolerance. Pretreated wheat straw (PWS) hydrolysis was carried out at different enzyme concentrations (1–30 mg protein/g of PWS) under optimum pH and temperature in rolling bottle reactor. Simultaneous saccharification and fermentation was performed employing in-house thermotolerant Saccharomyces cerevisiae . Results indicated that, maximum saccharification (more than 85%) was achieved at low protein loadings (10–15 mg protein/g PWS) of CL and this enzyme was also found to be more robust in presence of inhibitors. Maximum ethanol yield (78%) was found at 20 mg protein/g of PWS using CL. This study suggests that inhibitors have significant detrimental effect on enzymes and better understanding of enzyme-inhibitor correlation with its critical moderation would help in further enhancing the LCB hydrolysis at low enzyme dosage.

Requirement of high enzyme dosage for lignocellulosic biomass hydrolysis is one of the challenges for the viability of the second generation bioethanol technology. Here, an optimal enzyme mixture was developed by partially replacing the cellulase proportion with accessory enzymes (β-glucosidase, xylanase, pectinase, laccase) and its hydrolytic performance was compared with different commercial counterparts for the saccharification of pretreated wheat straw (PWS) using a 250 kg per day continuous pilot plant. Maximum degree of synergism was observed with xylanase followed by pectinase, laccase, and β-glucosidase. The statistically optimized enzyme mixture enhanced hydrolysis by 51.23% and 40.66% in 6 h and 24 h, respectively. This study elucidates that presence of even small amount of oligomers and cellobiose pose a strong inhibition for the enzymes. Therefore, development of an optimal enzyme formulation is a sustainable approach to reduce overall enzyme loading for biomass saccharification.