Abstract
The effects of pH values on cell growth and glutathione (GSH) production were studied in batch cultivation of Candida utilis. According to the fact that lower pH value favors cells growth but retards GSH production and higher pH value promotes GSH production while inhibits cells growth, a pH-shift strategy, optimized via simulating Gauss function, was developed. By applying two-stage pH-shift strategy of controlling pH at 5.0 for first 7.5 h and switching to 6.0 afterwards, final GSH yield and productivity reached 279 and 12.7 mg/l/h after 22 h cultivation, increased by 30 and 42%, respectively, compared to constant pH 5.5 operation. Moreover, by feeding glucose instead of sulphuric acid (H2SO4) solution to control pH, maximal GSH yield of 315 mg/l was achieved, suggesting application of pH-shift strategy for GSH overproduction as being feasible. Key words: Batch fermentation, Candida utilis, glutathione (GSH), gauss function, pH-shift strategy.
Highlights
Glutathione (GSH), as the most abundant non-protein thiol compound, is widely distributed in living organisms (Meister and Anderson, 1983)
It was demonstrated that GSH could be synthesized by chemical method (Harington and Mead, 1935)
Effects of broth pH values on cells growth and GSH formation in batch culture of C. utilis were investigated in this paper
Summary
Glutathione (GSH), as the most abundant non-protein thiol compound, is widely distributed in living organisms (Meister and Anderson, 1983). For batch GSH production, the optimal conditions for cell growth and GSH formation may be quite different (Li et al, 2004). To obtain high GSH yield and productivity, it is vital to optimize conditions for cells growth and GSH formation during batch fermentation. Based on the fact that the optimal temperature for cells growth and GSH formation differed, a temperature-shift strategy was developed to enhance GSH production in batch culture of C. utilis (Wei et al, 2003). Effects of broth pH values on cells growth and GSH formation in batch culture of C. utilis were investigated in this paper. Based on the results that the optimal pH values for cells growth and GSH formation differed, a novel two-stage pH-shift strategy, optimized by simulating Gauss function, was developed to enhance. By feeding glucose replacing H2SO4 for controlling pH, a maximal GSH production was achieved
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