Co-fermentation using Recombinant Saccharomyces cerevisiae Yeast Strains Hyper-secreting Different Cellulases for the Production of Cellulosic Bioethanol

Abstract

To realize the economical production of ethanol and other bio-based chemicals from lignocellulosic biomass by consolidated bioprocessing (CBP), various cellulases from different sources were tested to improve the level of cellulase secretion in the yeast Saccharomyces cerevisiae by screening an optimal translational fusion partner (TFP) as both a secretion signal and fusion partner. Among them, four indispensable cellulases for cellulose hydrolysis, including Chaetomium thermophilum cellobiohydrolase (CtCBH1), Chrysosporium lucknowense cellobiohydrolase (ClCBH2), Trichoderma reesei endoglucanase (TrEGL2), and Saccharomycopsis fibuligera β-glucosidase (SfBGL1), were identified to be highly secreted in active form in yeast. Despite variability in the enzyme levels produced, each recombinant yeast could secrete approximately 0.6–2.0 g/L of cellulases into the fermentation broth. The synergistic effect of the mixed culture of the four strains expressing the essential cellulases with the insoluble substrate Avicel and several types of cellulosic biomass was demonstrated to be effective. Co-fermentation of these yeast strains produced approximately 14 g/L ethanol from the pre-treated rice straw containing 35 g/L glucan with 3-fold higher productivity than that of wild type yeast using a reduced amount of commercial cellulases. This process will contribute to the cost-effective production of bioenergy such as bioethanol and biochemicals from cellulosic biomass.

Chemical and Enzymatic Treatment of Hemp Biomass for Bioethanol Production

“…The decomposition of cellulose to simple sugars requires synergistic action of three types of cellulases: endoglucanases, cellobiohydrolases and ß-glucosidase. The action of enzymes involves the attack on the cellulose by bonding with cellulose fibres in amorphous places, the cleavage of cellulosic chains, cutting off their considerable fragments, and then degrading them until the glucose polymer is obtained [13].…”

Bioethanol production using vegetable peels medium and the effective role of cellulolytic bacterial (Bacillus subtilis) pre-treatment

“…Significant elevation of ethanol production rate was observed in the co-fermentation process where cellulosic media were inoculated with cellulolytic bacteria previously. Overall, the method proves the efficiency of the co-fermentation 26 – 28 . The economic advantage of using vegetable peels media over molasses is the recycling process of abundant garbage.…”

Solid-state fermentation of corn by-products mixture feed with Saccharomyces cerevisiae , Lactobacillus plantarum and protease for improving protein quality and nutrient utilization

“…Furthermore, the lignocellulosic components and amylose is poorly digested in the upper gut of monogastric animals [30]. CF, ADF and amylose are effectively degraded after fermentation in this study, which might due to the cellulase and amylase secreted by S. cerevisiae WFSC and L. plantarum CWLP [31,32].…”