Consolidated Bioprocessing for Bioethanol Production Using Saccharomyces cerevisiae

Abstract

Consolidated bioprocessing (CBP) of lignocellulose to bioethanol refers to the combining of the four biological events required for this conversion process (production of saccharolytic enzymes, hydrolysis of the polysaccharides present in pretreated biomass, fermentation of hexose sugars, and fermentation of pentose sugars) in one reactor. CBP is gaining increasing recognition as a potential breakthrough for low-cost biomass processing. Although no natural microorganism exhibits all the features desired for CBP, a number of microorganisms, both bacteria and fungi, possess some of the desirable properties. This review focuses on progress made toward the development of baker's yeast (Saccharomyces cerevisiae) for CBP. The current status of saccharolytic enzyme (cellulases and hemicellulases) expression in S. cerevisiae to complement its natural fermentative ability is highlighted. Attention is also devoted to the challenges ahead to integrate all required enzymatic activities in an industrial S. cerevisiae strain(s) and the need for molecular and selection strategies pursuant to developing a yeast capable of CBP.

Next-generation cellulosic ethanol technologies and their contribution to a sustainable Africa

“…While several micro-organisms can be found in nature with the ability to produce the required enzymes to hydrolyse all the polysaccharides found in Lignocellulose conversion to bioethanol in a single bioreactor by a CBP micro-organism is graphically illustrated (adapted from [8]). The enzymatic hydrolysis of the cellulose and hemicellulose fractions to fermentable hexoses and pentoses requires the production of both glycosyl hydrolases (cellulases and hemicellulases), and the subsequent conversion of the hexoses and pentoses to ethanol requires the introduction of pentose-fermenting pathways.…”

“…Laboratory and industrial S. cerevisiae strains were also engineered to co-ferment the pentose sugars D-xylose and L-arabinose [31]. There have been many reports detailing the expression of one or more cellulase-encoding genes in S. cerevisiae [8]. Strains of S. cerevisiae were created that could grow on and ferment cellobiose, the main product of the action of cellobiohydrolases on cellulosic substrates, at approximately the same rate as on glucose in anaerobic conditions [33].…”

Promotion of Extracellular Activity of Cellobiohydrolase I from Trichoderma reesei by Protein Glycosylation Engineering in Saccharomyces cerevisiae

“…They found that the degree of N-glycosylation plays an important role in heterologous cellulase activity and both over-and under-glycosylation may alter the enzyme activity of cellulases in S. cerevisiae. Expression of cellulases in the traditional ethanol production strain S. cerevisiae is one research aspect of the ethanol production from lignocelluloses using the consolidated bioprocessing (CBP) strategy [7,8]. Among the cellulase system in Trichoderma reesei, cellobiohydrolase I (Tr-Cel7A) is recognized as one of the effective enzymes for lignocellulose degradation.…”

Consolidated Bioprocessing Ethanol Production by Using a Mushroom

“…One of the major problems in producing ethanol from lignocellulosic biomass is the expensive production cost. Consolidated bioprocessing (CBP) is gaining recognition as a potential breakthrough for low-cost biomass processing (Lynd, 1996;Lynd et al, 2002;Lynd et al, 2005;Van Zyl et al, 2007;Xu et al 2009). CBP of lignocellulose to bioethanol refers to the combination of the 4 biological events required for this conversion process (production of lignocellulose-degrading enzymes, hydrolysis of polysaccharides present in pre-treated biomass and fermentation of hexose and pentose sugars) in one reactor.…”

“…Traditionally, proponents of CBP processes have identified two primary developmental pathways capable of producing industrially viable CBP microbial strains. These are category I, engineering a cellulase producer, such as Clostridium thermocellum, to be ethanologenic; and category II, engineering an ethanologen, such as Saccharomyces cerevisiae or Zymomonas mobilis, to be cellulolytic (Lynd, 1996;Lynd et al, 2002;Lynd et al, 2005;Van Zyl et al, 2007;Xu et al, 2009). However, the both categories have advantages and disadvantages.…”