Dissolved-oxygen-stat fed-batch fermentation of 1,3-dihydroxyacetone from glycerol by Gluconobacter oxydans ZJB09112

Biotechnology and Bioprocess Engineering (Impact Factor: 1.22). 08/2010; 15(4):651-656. DOI: 10.1007/s12257-009-3068-2

ABSTRACT This study investigated the effects of DO concentration on DHA fermentation and of DO-stat fed-batch fermentation using a
pH control strategy, on 1,3-dihydroxyacetone (DHA) production. The results showed that DO-stat fed-batch fermentation with
pH-shift control was the optimal bioprocess for DHA production. DO-stat fed-batch fermentation was carried out at 30% air
saturation, and the culture pH was automatically maintained at pH 6.0 during the first 20 h and then shifted to pH 5.0 until
the end of the fermentation. An optimal DHA concentration of 175.9 ± 6.7 g/L, with a production yield to glycerol of 0.87
± 0.04 g/g, was obtained at 72 h of DO-stat fed-batch fermentation at 30°C in a 15 L fermenter.

Gluconobacter oxydans
-DO-stat fermentation-glycerol-fed-batch

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    ABSTRACT: 1,3-Dihydroxyacetone can be produced by biotransformation of glycerol with glycerol dehydrogenase from Gluconobacter oxydans cells. Firstly, improvement the activity of glycerol dehydrogenase was carried out by medium optimization. The optimal medium for cell cultivation was composed of 5.6g/l yeast extract, 4.7 g/l glycerol, 42.1g/l mannitol, 0.5 g/l K(2)HPO(4), 0.5 g/l KH(2)PO(4), 0.1g/l MgSO(4)·7H(2)O, and 2.0 g/l CaCO(3) with the initial pH of 4.9. Secondly, an internal loop airlift bioreactor was applied for DHA production from glycerol by resting cells of G. oxydans ZJB09113. Furthermore, the effects of pH, aeration rate and cell content on DHA production and glycerol feeding strategy were investigated. 156.3 ± 7.8 g/l of maximal DHA concentration with 89.8±2.4% of conversion rate of glycerol to DHA was achieved after 72h of biotransformation using 10g/l resting cells at 30°C, pH 5.0 and 1.5vvm of aeration rate.
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    ABSTRACT: The 1,3-dihydroxyacetone (DHA)-overproducing mutant of Gluconobacter oxydans was screened via UV mutagenesis to enhance the DHA production, and the DHA fermentation condition was optimized using the dissolved oxygen (DO) control strategy. The stable mutant G. oxydans ZJB11001 exhibits high DHA productivity and can tolerate high DHA concentrations. The optimal condition for DHA production by G. oxydans ZJB11001 in a 15-L fermentor required an initial medium containing 5 g/L yeast extract, 20 g/L glycerol, 0.5 g/L K(2)HPO(4), 0.1 g/L MgSO(4)·7H(2)O. The glycerol feeding rate was manually controlled to maintain the glycerol concentration at 5-10 g/L range. The culture pH was maintained at 6.0 within the first 20 h, and then adjusted to 5.0 until the end of the fermentation. The DO concentration increased from 20% to 30% after 24 h of fermentation, and then to 40% after 60 h of fermentation. The maximum DHA concentration of 209.6 ± 6.8 g/L was achieved after 72 h of fed-batch fermentation at 30 °C.
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