Construction of industrial Saccharomyces cerevisiae strains for the efficient consolidated bioprocessing of raw starch
Date
2019-08-20
Journal Title
Journal ISSN
Volume Title
Publisher
BMC (part of Springer Nature)
Abstract
Background: Consolidated bioprocessing (CBP) combines enzyme production, saccharification and fermentation
into a one-step process. This strategy represents a promising alternative for economic ethanol production from
starchy biomass with the use of amylolytic industrial yeast strains.
Results: Recombinant Saccharomyces cerevisiae Y294 laboratory strains simultaneously expressing an α-amylase and
glucoamylase gene were screened to identify the best enzyme combination for raw starch hydrolysis. The codon optimised
Talaromyces emersonii glucoamylase encoding gene (temG_Opt) and the native T. emersonii α-amylase encoding
gene (temA) were selected for expression in two industrial S. cerevisiae yeast strains, namely Ethanol Red™ (hereafter
referred to as the ER) and M2n. Two δ-integration gene cassettes were constructed to allow for the simultaneous
multiple integrations of the temG_Opt and temA genes into the yeasts’ genomes. During the fermentation of 200 g l−1
raw corn starch, the amylolytic industrial strains were able to ferment raw corn starch to ethanol in a single step with
high ethanol yields. After 192 h at 30 °C, the S. cerevisiae ER T12 and M2n T1 strains (containing integrated temA and
temG_Opt gene cassettes) produced 89.35 and 98.13 g l−1 ethanol, respectively, corresponding to estimated carbon
conversions of 87 and 94%, respectively. The addition of a commercial granular starch enzyme cocktail in combination
with the amylolytic yeast allowed for a 90% reduction in exogenous enzyme dosage, compared to the conventional
simultaneous saccharification and fermentation (SSF) control experiment with the parental industrial host strains.
Conclusions: A novel amylolytic enzyme combination has been produced by two industrial S. cerevisiae strains.
These recombinant strains represent potential drop-in CBP yeast substitutes for the existing conventional and raw
starch fermentation processes.
Description
CITATION: Cripwell, R. A., et al. 2019. Construction of industrial Saccharomyces cerevisiae strains for the efficient consolidated bioprocessing of raw starch. Biotechnology for Biofuels, 12:201, doi:10.1186/s13068-019-1541-5.
Keywords
Bioethanol production, Ethanol production from starchy biomass, Saccharomyces cerevisiae strains, Conversion of starch to ethanol, Consolidated bioprocessing (CBP)
Citation
Cripwell, R. A., et al. 2019. Construction of industrial Saccharomyces cerevisiae strains for the efficient consolidated bioprocessing of raw starch. Biotechnology for Biofuels, 12:201, doi:10.1186/s13068-019-1541-5