Coordinated β-glucosidase activity with the cellulosome is effective for enhanced lignocellulose saccharification. (October 2021)

• Record Type: Journal Article
• Authors: Qi, Kuan; Chen, Chao; Yan, Fei; Feng, Yingang; Bayer, Edward A.; Kosugi, Akihiko; Cui, Qiu; Liu, Ya-Jun
• Is Part Of: Bioresource technology. Volume 337(2021)
• Publication Date: 2021-10
• Subjects: β-glucosidase -- Cellulosome -- Clostridium thermocellum -- Lignocellulose -- Saccharification; Biomass -- Periodicals; Biomass energy -- Periodicals; Bioremediation -- Periodicals; Agricultural wastes -- Periodicals; Factory and trade waste -- Periodicals; Organic wastes -- Periodicals; Bioénergie -- Périodiques; Déchets agricoles -- Périodiques; Déchets industriels -- Périodiques; Déchets organiques -- Périodiques; Déchets (Combustible) -- Périodiques; 662.88
• DOI: 10.1016/j.biortech.2021.125441
• Languages: English
• ISSNs: 0960-8524

Abstract

Highlights: Consolidated bio-saccharification (CBS) depends on cellulosome-producing strains. β-Glucosidase (BGL) is indispensable for effective cellulose hydrolysis. CBS requires extracellular BGL expression, but overproduction should be avoided. Proper BGL-to-cellulosome ratio would stimulate cellulose saccharification. The assembly of BGL into the cellulosome could lead to reduced cellulase activity. Abstract: Consolidated bio-saccharification (CBS) technology employs cellulosome-producing bacterial cells, rather than fungal cellulases, as biocatalysts for cost-effective production of lignocellulosic sugars. Extracellular β-glucosidase (BGL) expression in the whole-cell arsenal is indispensable, due to severe cellobiose inhibition of the cellulosome. However, high-level BGL expression in Clostridium thermocellum is challenging, and the optimal BGL production level for efficient cellulose saccharification is currently unknown. Herein, we obtained new CBS biocatalysts by transforming BGL-expressing plasmids into C. thermocellum, which produced abundant BGL proteins and hydrolyzed cellulose effectively. The optimal ratio of extracellular BGL-to-cellulosome activity was determined to be in a range of 5.5 to 21.6. Despite the critical impact of BGL, both excessive BGL expression and its assembly on the cellulosome via type I cohesin-dockerin interaction led to reduced cellulosomal activity, which further confirmed the importance of coordinated BGL expression with the cellulosome. This study will further promote industrial CBS application in lignocellulose conversion.