Enhancement of erythritol production by Trichosporonoides oedocephalis ATCC 16958 through regulating key enzyme activity and the NADPH/NADP ratio with metal ion supplementation.

Erythritol, a well-known natural sweetener, is mainly produced by microbial fermentation. Various metal ions (Al, Cu, Mn, and Ni) were added to the culture medium of Trichosporonoides oedocephalis ATCC 16958 at 30 mg/L in shake flask cultures. Compared with controls, Cu increased the erythritol content by 86% and decreased the glycerol by-product by 31%. After 48 hr of shake flask culture, sodium dodecyl sulfate polyacrylamide gel electrophoresis showed that expression levels of erythrose reductase (ER) in the presence of 30 mg/L CuSO · 5HO were higher than those obtained after treatment with other examined metal ions. Furthermore, after 108 hr of batch culture in a 5-L bioreactor, supplementation with 30 mg/L of CuSO · 5HO increased the specific erythritol content by 27%. Further studies demonstrated that ER activity under 30 mg/L CuSO · 5HO supplementation in a fermentor was overtly increased compared with the control after 60 hr, while glycerol-3-phosphate dehydrogenase activity was clearly reduced in most of the fermentation process. Furthermore, the NADPH/NADP ratio was slightly lower in T. oedocephalis cells treated with Cu compared with control cells. These results provide further insights into Cu effects on erythritol biosynthesis in T. oedocephalis and should improve the industrial production of erythritol by biological processes.