Whole-cell catalytic synthesis of trehalose by Corynebacterium glutamicum displaying trehalose synthase on its cell surface

Trehalose is a disaccharide with many applications in cosmetics, refrigeration, and food. Trehalose synthase is a significant enzyme in trehalose production. Escherichia coli is usually used to express this enzyme heterologously. Since E. coli is a pathogenic strain, we chose Corynebacterium glutamicum ATCC13032 as an engineering strain in this study for food safety reasons. Because of its poor permeability, we constructed two recombinant C. glutamicum strains using two anchor proteins, PorH, and short-length NCgl1337, to anchor trehalose synthase from Streptomyces coelicolor on the cell surface and synthesize trehalose directly from maltose. Studies on enzymatic properties indicated that NCgl1337S-ScTreSK246A had better enzyme activity and thermal stability than the free enzyme. After optimizing the whole-cell transformation, the optimal transformation condition was 35 degree celsius, pH 7.0, and OD(600 )of 30. Under this condition, the conversion rate of 300 g/L maltose reached 69.5% in a 5 L fermentor. The relative conversion rate was still above 75% after repeated five times.