Effects of oxygen on invertase expression in continuous culture of recombinant Saccharomyces cerevisiae containing the SUC2 gene |
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Authors: | Y R Pyun J S Jo J W Park H H Shin |
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Institution: | (1) Department of Biotechnology, Yonsei University, Seoul 120-749, Korea. e-mail: yrpyun@bubble.yonsei.ac.kr Tel.: +82-2-361-2883 Fax: +82-2-312-6821, KR |
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Abstract: | The yeast SUC2 gene, cloned on a multicopy plasmid pRB58, was used to study the effect of oxygen on the invertase expression of the recombinant
Saccharomyces cerevisiae. Glucose repression was not the only factor affecting the invertase expression. The results obtained from the single-stage
continuous cultures under microaerobic conditions showed that invertase expression was also strongly dependent on oxygen availability,
and moving from anaerobic to aerobic conditions led to a five-fold increase in specific invertase activity. However, the cell
yields under anaerobic conditions were quite low compared to those under aerobic conditions. These opposite effects of oxygen
on cell growth and gene expression offer a strategy for maximizing invertase productivity by a two-stage continuous culture.
The first stage was operated at a low level of glucose, around 100 mg/l, under aerobic conditions in order to obtain a high
yield of yeast biomass, and the second stage maintained anaerobic conditions with residual glucose levels of 50 mg/l to derepress
and fully induce invertase expression. The two-stage continuous culture resulted in a 2.5-fold increase in invertase productivity
over that of a single-stage continuous culture.
Received: 28 July 1998 / Received revision: 22 September 1998 / Accepted: 7 November 1998 |
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