Productivity enhancement in L-sorbose fermentation using oxygen vector

Sorbose, an intermediate of Vitamin-C is produced by biological oxidation of sorbitol by Acetobacter suboxydans. The utility of oxygen vector (N-hexadecane) in enhancing the sorbose accumulation and its productivity was examined for sorbitol to sorbose bioconversion process. Shake flask fermentations were conducted using 1% to 6% (v/v) N-hexadecane. Higher sorbose production was observed in shake flask containing 1-4% N-hexadecane as compared to shake flasks without N-hexadecane. A maximum of 82.12 kgm(-3) sorbose accumulated in 24 h by the addition of 4% N-hexadecane as against 64.83 kgm(-3) sorbose without the addition of N-hexadecane. However, the concentration of sorbose produced in the same time decreased when 5% and 6% N-hexadecane were used. Batch sorbose fermentation conducted using 4% N-hexadecane demonstrated decrease in the process time from 14 h to 12 h. The productivity increased from 14.3 kgm(-3) h(-1) to 16.7 kgm(-3) h(-1) when 4% N-hexadecane was used. Fed-batch fermentation using 4% N-hexadecane was over in 20 h with a productivity of 15.9 kgm(-3) h(-1), and a sorbose accumulation of 311.68 kgm(-3) was obtained. The same fed-batch fermentation finished in 25 h when no N-hexadecane was used. A productivity of 12.6 kgm(-3) h(-1) and a final sorbose accumulation of 316 kgm(-3) were obtained. The increase in productivity and lower process time were achieved by the addition of N-hexadecane to the fermentation medium. (C) 2000 Elsevier Science Inc. All rights reserved.