Utilization of cellobiose by recombinant β-glucosidase-expressing strains of Saccharomyces cerevisiae: Characterization and evaluation of the sufficiency of expression
Enzyme and Microbial Technology
Chem. and Biochem. Eng. Program, Thayer School of Engineering, Dartmouth College, Hanover, NH 03755, United States; Department of Microbiology, University of Stellenbosch, Stellenbosch, South Africa
Two recombinant strains of Saccharomyces cerevisiae expressing the BGL1 (β-glucosidase) gene originating from Saccharomycopsis fibuligera were characterized with respect to gene expression and growth on cellobiose under air and nitrogen gas phases. The laboratory strain Y294[ySF1], with β-glucosidase expression from a multi-copy plasmid, grew at comparable rates on cellobiose and glucose under both air and nitrogen gas phases. By contrast, strain N96[ySF1] grew at a much slower rate on cellobiose than on glucose under both gas phases. For the various strain and substrate combinations tested, cell-specific enzyme activity was significantly higher under a nitrogen gas phase as compared to an air gas phase. The ability of these strains to grow on cellobiose, a non-native substrate, was evaluated in terms of a dimensionless 'sufficiency' parameter, S, consisting of the ratio of the maximum cell-specific rate of glucose production from cellobiose to the maximum cell-specific rate of glucose consumption. At sufficiency values substantially less than one, specific growth rates were found to be limited by heterologous enzyme expression, whereas for values of sufficiency near and greater to one, specific growth rates on cellobiose approached their values on glucose. The concept of sufficiency appears to have general utility for work aimed at growth enablement on non-native substrates by virtue of heterologous enzyme expression. © 2005 Elsevier Inc. All rights reserved.
Cell culture; Genes; Glucose; Microorganisms; Strain; Substrates; Cellobiose; Gas phase; Gene expression; Saccharomycel cerevisiae; Enzymes; beta glucosidase; cellobiose; nitrogen; air; article; controlled study; culture medium; fungal metabolism; fungal strain; fungus growth; gene expression; glucose metabolism; growth rate; nonhuman; protein expression; Saccharomyces cerevisiae; Saccharomyces cerevisiae; Saccharomycopsis fibuligera