Cost-effective cellulase production, improvement strategies, and future challenges

Ionic liquid (IL) pretreatment of lignocellulose is an efficient method for the enhancement of enzymatic saccharification. However, the remaining residues of ILs deactivate cellulase, therefore making intensive biomass washing after pretreatment necessary. This study aimed to develop the one-pot process combining IL pretreatment and enzymatic saccharification by using low-toxic choline acetate ([Ch][OAc]) and IL-tolerant bacterial cellulases. Crude cellulases produced from saline soil inhabited Bacillus sp. CBD2 and Brevibacillus sp. CBD3 were tested under the influence of 0.5–2.0 M [Ch][OAc], which showed that their activities retained at more than 95%. However, [Ch][OAc] had toxicity to CBD2 and CBD3 cultures, in which only 32.85% and 12.88% were alive at 0.5 M [Ch][OAc]. Based on the specific enzyme activities, the sugar amounts produced from one-pot processes using 1 mg of CBD2 and CBD3 were higher than that of Celluclast 1.5 L by 2.0 and 4.5 times, respectively, suggesting their potential for further application in the biorefining process of value-added products.

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One-Pot Ionic Liquid-Mediated Bioprocess for Pretreatment and Enzymatic Hydrolysis of Rice Straw with Ionic Liquid-Tolerance Bacterial Cellulase

Second-generation biofuels produced from lignocellulose biomass (LCB) have the potential to compete with fossil fuels, provided that appropriate cost-effective and efficient technologies are used in the production process. As agriculture is practiced all over the world and millions of tons of biomass are produced every year, the production of biofuel from such wastes could be an environmentally friendly approach to meet the increasing energy demand. Biofuel production is quite a challenging process involving several technologies and methods that need to be employed for maximum conversion of complex lignocellulose into functional biofuel. This review provides insight into the various strategies, including upstream and downstream, involved in the production of biofuels from agriculturally produced LCB. For decades, numerous researches have been conducted worldwide to find the best strategies for biofuel production. This has led to several recent advances that help to achieve maximum biofuel production in an environmentally friendly and cost-effective system. To complete the overview, the analysis of the impact of biofuel production has also been discussed in this review. • Cost effective and environment friendly strategies important for biofuel generation. • Agriculture based lignocellulose biomass may be used as cheap biofuel substrate. • Choosing correct pretreatment strategies may influence biofuel production. • Proper pretreatment and production system combination influence biofuel production. 

Strategies involved in biofuel production from agro-based lignocellulose biomass

Enzymes are the complex protein moieties, catalyze the rate of chemical reactions by transforming various substrates to specific products and play an integral part in multiple biochemical cycles. Advancement in enzyme research and its integration with industries have reformed the biotech industries. It provides a superior monetary and ecological exchange to traditional material measures in an efficient and environmentally sustainable manner. The cost-effective production of pure and highly active enzymes is still a challenge for the biocatalyst industries. The use of high purity substrates further raises the cost of a typical biocatalyst. The use of low-cost plant-based biomasses as an enticing and sustainable substrate for enzyme production is the most cost-effective approach to these problems. Given the relevance of biomass as a substrate for enzyme development, this review article focuses on the key source, composition and major enzyme generated using various biomass residues. Furthermore, the difficulties associated with the use of biomass as a substrate and technical developments in this area, are also addressed. The use of waste biomass as a substrate lowers the ultimate cost for the production of biocatalysts while simultaneously reduces the waste burden from the environment.

Cost-effective production of biocatalysts using inexpensive plant biomass: a review

Cellulolytic enzymes have gained considerable importance as potential candidates for the efficient bioconversion of agricultural biomass into second-generation biofuel. This study aimed to improve cellulase production from a bacterial strain isolated from cow dung. The biochemical and molecular identification was performed, and the capacity of the isolated bacterium to hydrolyze sugarcane bagasse was also determined. Response surface methodology (RSM) and one-variable-at-a-time (OVAT) designs were employed to maximize the cellulase production. The bacterium identified as Bacillus subtilis gave the highest cellulase yield at temperature of 45 °C, pH-7.0, and 72 h of incubation time. Optimization by the Plackett–Burman design consisting of 12 experimental runs at two levels of nine independent variables displayed the significant contribution of galactose (22%) and sodium nitrate (16%) in cellulase production. The responses in the form of contour and 3D plots (generated by Box-Behnken design) predicted maximum cellulase production with an activity of 0.8 U/mL/min in a medium containing 3.0 g/L carboxymethyl cellulose, 3.0 g/L galactose, 0.5 g/L sodium nitrate, 0.75 g/L KH2PO4, and 0.375 g/L MgSO4·7H2O. The experimentally deduced activity value was 0.698 U/mL/min, showing 90% validity of the predicted value and gave a threefold increase in cellulase production. The process adequately represented by the quadratic model (p < 0.0343) for all the responses was significant. Results obtained show that optimization of fermentation medium favored the increased production of cellulase by the bacterium. The bacterial isolate B. subtilis CD001 was found to be a potential candidate to hydrolyze the lignocellulosic feedstock, sugarcane bagasse.

Bioprocess Optimization for Enhanced Production of Bacterial Cellulase and Hydrolysis of Sugarcane Bagasse

Lignocellulosic wastes, rice straw, sugarcane bagasse, rice bran and sawdust, and pure commercial carboxymethyl cellulose (CMC) and xylan were used as substrates to cultivate cellulolytic fungus, Aspergillus flavus KUB2, in submerged fermentation at 30°C Of all the substrates, sugarcane bagasse was a good source for the production of cellulolytic and also hemicellulolytic enzymes The maximum activities of endoglucanase (CMCase), total cellulase (FPase) and xylanase using sugarcane bagasse as substrate were 8%, 75% and 165%, respectively, higher than those of the commercial substrates The time course determination of enzyme production revealed that the highest CMCase (127 U/ml), FPase (072 U/ml) and xylanase (37681 U/ml) activities were observed at 14 days of fermentation Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) analyses confirmed the efficient structural alteration of sugarcane bagasse caused by enzymatic actions during A flavus KUB2 cultivation Based on the results of the hydrolytic enzyme activities, FTIR and SEM, A flavus KUB2 is suggested as an efficient hydrolytic enzymes producer and an effective lignocellulose degrader, while sugarcane bagasse can be applied as a low-cost carbon source for the economical production of lignocellulose hydrolytic enzymes by A flavus KUB2

https://www.tandfonline.com/doi/pdf/10.1080/21501203.2020.1806938

Nattida Namnuch

Papers

Lignocellulose hydrolytic enzymes production by Aspergillus flavus KUB2 using submerged fermentation of sugarcane bagasse waste.