earticle

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Bioethanol from cellulosic biomass has the potential to become an competitive fuel resource, but currently requires many technological improvements to be economically viable. One-pot fermentation of cellulosic biomass into bioethanol through consolidated bioprocessing (CBP) using multi-functional microbes can make a major breakthrough for low cost biomass processing. Unfortunately, however, there are no natural microbes which can do this process effectively. Brewer's yeast Saccharomyces cerevisiae is often chosen as a candidate workhorse for CBP owing to its high productivity of ethanol and resistance to ethanol, even though it has no cellulolytic activity. To develop S. cerevisiae as a CBP yeast, it is essential to make yeast produce sufficient amounts of cellulases required for the complete hydrolysis of cellulosic biomass. Hyper-secretion technology using yeast translational fusion partner (TFP) have been applied to produce several fungal cellulases and hemicellulases. Grams per liter of different cellulases could be secreted into culture supernatant during fed-batch fermentation. Reconstituted cellulase cocktails using cellulases produced separately, showed cellulolytic activities on a filter paper and pretreated biomass. Recombinant yeasts of this study will be useful for the development of a cost-effective CBP system to convert cellulosic biomasses into bioethanol.