Construction of consolidated bio-saccharification biocatalyst and process optimization for highly efficient lignocellulose solubilization

Abstract

Background The industrial conversion of biomass to high-value biofuels and biochemical is mainly restricted by lignocellulose solubilization. Consolidated bio-saccharification (CBS) is considered a promising process for lignocellulose solubilization depending on whole-cell biocatalysts that simultaneously perform effective cellulase production and hydrolysis. However, it usually takes a long time to reach a high saccharification level using the current CBS biocatalyst and process. Results To promote the saccharification efficiency and reduce the cost, a Clostridium thermocellum recombinant strain ∆pyrF ::KBm was constructed as a new CBS biocatalyst in this study. The key CBS factors, including the medium, inoculum size and cultivation, and substrate load, were investigated and optimized. The saccharification process was also stimulated by adding free hemicellulases, suggesting the need to further enhance hemicellulase activity of the whole-cell catalyst. Under the optimal conditions, the CBS process was shortened by 50% with pretreated wheat straw as the substrate. The sugar yield reached 0.795 g/g and the saccharification level was 89.3%. Conclusions This work provided a new biocatalyst and an optimized process of CBS and confirmed that CBS is a feasible strategy for cost-efficient solubilization of lignocellulose, which will greatly promote the industrial utilization of lignocellulosic biomass. Electronic supplementary material The online version of this article (10.1186/s13068-019-1374-2) contains supplementary material, which is available to authorized users.

Thermophilic whole‐cell degradation of polyethylene terephthalate using engineered Clostridium thermocellum

“…C. thermocellum is considered one of the most promising species for highly efficient and low‐cost lignocellulose bioconversion (Lynd, et al , 2005), and mature genetic manipulation platforms have been constructed for this thermophile (Tripathi, et al , 2010; Olson and Lynd, 2012; Mohr, et al , 2013, Olson, et al , 2015; Zhang, et al , 2017). By using the developed tools, C. thermocellum recombinant strains have been constructed and employed as whole‐cell biocatalysts in lignocellulose saccharification and biofuel production (Argyros, et al , 2011; Lin, et al , 2015; Liu, et al , 2019). Thus, C. thermocellum has the potential to be used as the microbial chassis for the degradation of plastic waste at high temperature, e.g.…”

Bioconversion of non-food corn biomass to polyol esters of fatty acid and single-cell oils

“…CBS is a recently developed lignocellulose saccharification technology using cellulosome-producing bacterial cells as whole-cell biocatalysts [ 5 ]. By introducing heterologous secretory β-glucosidase (BGL) proteins to release the cellobiose inhibition to the cellulosome system [ 37 , 38 ], several biocatalysts have been developed with increasing saccharification efficiency [ 6 , 7 , 39 ]. It was reported that the substrate-to-sugar conversion ratio of the engineered C. thermocellum ∆ pyrF ::p2638-BGL could be over 75% with alkali-treated CCR as the substrate [ 39 ].…”

“…Therefore, compared with the PEFA and SCO production from glucose, xylose metabolism is less efficient. However, according to our previous study, the glucan-to-xylan ratio in pretreated LCB biomass was usually higher than 75%:25%, and for CBS, the glucan saccharification efficiency could be similar to or higher than that of xylan [ 6 , 39 ]. Indeed, we determined that glucan accounted for up to 79% and 92% of the polysaccharides in alkali-pretreated CS and CCR, respectively (Fig.…”

“…The LCB conversion strategies are mainly known as simultaneous saccharification and fermentation (SSF) and consolidated bioprocessing (CBP), employing cellulases from fungi or cellulosome-producing strains as the biocatalysts to produce target products via separated or one-pot reaction, respectively [ 5 ]. Consolidated bio-saccharification (CBS) is a recently developed technology based on CBP, aiming at the efficient conversion of lignocellulose to fermentable sugars using engineered Clostridium thermocellum as the whole-cell biocatalyst [ 6 , 7 ].…”

Bioreactor and Bioprocess Design Issues in Enzymatic Hydrolysis of Lignocellulosic Biomass

“…The combination of cellulase production, cellulose hydrolysis and sugar fermentation into a one-pot process is called a "consolidated bioprocess" strategy [2,11,37,[47][48][49][50]]. This strategy is made possible by a microorganism community that exhibits a cellulolytic activity that is able to hydrolyse glycosylic bonds of the cellulose and to use the lignocellulosic sugars for further fermentation into valuable products.…”