Efficient, galactose-free production of Candida antarctica lipase B by GAL10 promoter in Δgal80 mutant of Saccharomyces cerevisiae

An efficient yeast gene expression system with GAL10 promoter that does not require galactose as an inducer was developed using Δgal80 mutant strain of Saccharomyces cerevisiae. We constructed several combinations of gal mutations (Δgal1, Δgal80, Δmig1, Δmig2, and Δgal6) of S. cerevisiae and tested for their effect on efficiency of recombinant protein production by GAL10 promoter using a lipase, Candida antarctica lipase B (CalB), as a reporter. While the use of Δgal1 mutant strain required the addition of a certain amount of galactose to the medium, Δgal80 mutant strain did not require galactose. Furthermore, it was found that the recombinant CalB could be produced more efficiently (1.6-fold at 5 L-scale fermentation) in Δgal80 mutant strain than in the Δgal1 mutant. The Δgal80 mutant strain showed glucose repressible mode of expression of GAL10 promoter. Using Δgal80 mutant strain of S. cerevisiae, CalB was efficiently produced in a glucose-only fermentation at volumes up to 500 L.