Consolidated bioprocessing of raw starch with Saccharomyces cerevisiae strains expressing fungal alpha-amylase and glucoamylase combinations

FEMS Yeast Res. 2018 Nov 1;18(7). doi: 10.1093/femsyr/foy085.

Abstract

Cost-effective consolidated bioprocessing (CBP) of raw starch for biofuel production requires recombinant Saccharomyces cerevisiae strains expressing α-amylases and glucoamylases. Native Aureobasidium pullulans apuA, Aspergillus terreus ateA, Cryptococcus sp. S-2 cryA and Saccharomycopsis fibuligera sfiA genes encoding raw-starch α-amylases were cloned and expressed in the S. cerevisiae Y294 laboratory strain. Recombinant S. cerevisiae Y294[ApuA] and Y294[AteA] strains produced the highest extracellular α-amylase activities (2.17 U mL-1 and 2.98 U mL-1, respectively). Both the ApuA and AteA α-amylases displayed a preference for pH 4 to 5 and retained more than 75% activity after 5 days at 30°C. When ateA was co-expressed with the previously reported Aspergillus. tubingensis glucoamylase gene (glaA), the amylolytic S. cerevisiae Y294[AteA-GlaA] strain produced 45.77 g L-1 ethanol after 6 days. Ethanol production by this strain was improved with the addition of either 2.83 μL STARGEN 002 (54.54 g L-1 ethanol and 70.44% carbon conversion) or 20 μL commercial glucoamylase from Sigma-Aldrich (73.80 g L-1 ethanol and 90.19% carbon conversion). This is the first report of an engineered yeast strain that can replace up to 90% of the enzymes required for raw starch hydrolysis, and thus contributes to the realisation of a CBP yeast for starch-based biofuel production.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Biofuels
  • Ethanol / metabolism
  • Fungal Proteins / genetics
  • Fungal Proteins / metabolism*
  • Fungi / enzymology
  • Fungi / genetics
  • Glucan 1,4-alpha-Glucosidase / genetics
  • Glucan 1,4-alpha-Glucosidase / metabolism*
  • Hydrolysis
  • Industrial Microbiology
  • Metabolic Engineering
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • Saccharomyces cerevisiae / enzymology
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae / growth & development
  • Saccharomyces cerevisiae / metabolism*
  • Starch / metabolism*
  • alpha-Amylases / genetics
  • alpha-Amylases / metabolism*

Substances

  • Biofuels
  • Fungal Proteins
  • Recombinant Proteins
  • Ethanol
  • Starch
  • alpha-Amylases
  • Glucan 1,4-alpha-Glucosidase