Enhancement of erythritol production by Trichosporonoides oedocephalis ATCC 16958 through regulating key enzyme activity and the NADPH/NADP ratio with metal ion supplementation |
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Authors: | Liangzhi Li Pei Kang Xin Ju Jiajia Chen Huibin Zou Cuiying Hu |
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Institution: | 1. School of Chemistry, Biology, and Material Engineering, Suzhou University of Science and Technology, Suzhou, P. R. China;2. School of Chemical Engineering, Qingdao University of Science and Technology, Qingdao, P. R. China |
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Abstract: | Erythritol, a well-known natural sweetener, is mainly produced by microbial fermentation. Various metal ions (Al3+, Cu2+, Mn2+, and Ni2+) were added to the culture medium of Trichosporonoides oedocephalis ATCC 16958 at 30?mg/L in shake flask cultures. Compared with controls, Cu2+ 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 CuSO4?·?5H2O 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 CuSO4?·?5H2O increased the specific erythritol content by 27%. Further studies demonstrated that ER activity under 30?mg/L CuSO4?·?5H2O 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 Cu2+ compared with control cells. These results provide further insights into Cu2+ effects on erythritol biosynthesis in T. oedocephalis and should improve the industrial production of erythritol by biological processes. |
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Keywords: | Erythritol erythrose reductase glycerol-3-phosphate dehydrogenase metal ion polyol |
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