Beta-Glucosidase: Key Enzyme in Determining Efficiency of Cellulase and Biomass Hydrolysis

Abstract

Overall economics of the biomass to ethanol process is largely determined by the efficiency of biomass hydrolysis. Performance of cellulase cocktails used for saccharification of cellulose in biomass is often limited by lower amounts of β-glucosidases present, which catalyse hydrolysis of cellobiose, the product of endo and exocellulases to glucose. Inappropriate ratio of these enzymes in commercial cocktails leads to accumulation of cellobiose which inhibits the activity of cellulases. Thus, this rate limiting enzyme is of crucial importance in determining the efficiency of commercial cellulases. The saprophytic fungus Trichoderma sp., exploited for production of commercial cellulases, produces very minute quantities of β-glucosidases as compared to endo and exocellulases. However, several other organisms are known to produce β-glucosidases in higher quantities, over a broader substrate range. Strategies to get optimal ratio of exocellulases, endocellulases and β-glucosidases to enhance saccharification yields are, therefore, discussed. Appropriate levels of β-glucosidase activity in commercial cocktails have been obtained by supplementing with accessory β-glucosidases, transgenic approaches and by optimizing β-glucosidase production through manipulation of culture conditions. These approaches have resulted in achieving higher β-glucosidase activity in cellulase cocktails, facilitating higher sugar yields and thereby potentially improving enzymatic saccharification of biomass and eventually ethanol production.

Process optimization of β-glucosidase production by a mutant strain, Aspergillus niger C112

“…Nevertheless, because of the insufficient presence of β-glucosidase (BGL) in T. reesei, cellulase preparations improvement should be carried out for cost-effective saccharification (Escamilla-Alvarado et al 2016). The supplementation and enhancement of BGL produced by other microbes in cellulase preparations is a promising method (Vijaya Rani et al 2014).…”

Expression of novel glucose tolerant β-glucosidase on cell surface by Rhodotorula glutinis isolate

“…The optimum temperature for enzyme activity was found to be 50°C and pH 6.0-6.5. Activity parameters from many fungi and yeasts have been summarised (Rani et al, 2015), where temperature optima was found to mostly lie between 30-60°C while pH optima lie in the range of 4.0-6.5 while certain β-glucosidases from thermophiles, show higher temperature optima (Teugjas and Valjamae, 2013). While higher temperature optima increase catalytic efficiency but for selecting β-glucosidase, its compatibility with process set up is more important consideration.…”

Tissue Composition of Agave americana L. Yields Greater Carbohydrates From Enzymatic Hydrolysis Than Advanced Bioenergy Crops

“…Both the plant tissue composition and hydrolytic degradation of A. americana are evaluated in this study and compared to three advanced biofuel feedstocks that use the C 4 photosynthetic pathway (i.e., miscanthus, switchgrass, and sorghum). Previous work to increase fermentable products from lignocellulosic biomass includes improving pretreatment methods to increase enzymatic hydrolysis (Faik, 2013;Camesasca et al, 2015;Jin et al, 2016), biochemical engineering to improve enzyme activity (Zhang et al, 2006;Raghuwanshi et al, 2014), discovering novel cellulolytic enzymes (Zhang et al, 2006;Rani et al, 2014), optimizing enzyme blends for specific feedstocks (Gao et al, 2010), and decreasing the cost of enzymes (Klein-Marcuschamer et al, 2012;Culbertson et al, 2013;Johnson, 2016). This study specifically evaluated acid hydrolysis, enzymatic hydrolysis with a commercially available enzyme mixture, and saccharification of plant tissue from each of the four feedstocks to quantify the difference in conversion efficiency with difference tissue compositions.…”