High Butanol Production by Clostridium saccharoperbutylacetonicum N1-4 in Fed-Batch Culture with pH-Stat Continuous Butyric Acid and Glucose Feeding Method

摘要

A pH-stat fed-batch culture by feeding butyric acid and glucose has been studied in an acetone-butanol-ethanol (ABE) fermentation using Clostridium saccharoperbutylacetonicum Nl-4.The specific butanol production rate increased from 0.10 g-butanol/g-cells/h with no feeding of butyric acid to 0.42 g-butanol/g-cells/h with 5.0 g/l butyric acid.The pH value in broth decreases with butyric acid production during acidogenesis,and then butyric acid reutilization and butanol production result in a pH increase during solventogensis.The pH-stat fed-batch culture was performed to maintain a constant pH and butyric acid concentration in the culture broth,but feeding only butyric acid could not support butyric acid utilization and butanol production.Subsequently,when a mixture of butyric acid and glucose was fed,butyric acid was utilized and butanol was produced.To investigate the effect of the feeding ratio of butyric acid to glucose (B/G ratio),several B/G ratio solutions were fed.The maximum butanol production was 16 g/l and the residual glucose concentration in broth was very low at a B/G ratio of 1.4.Moreover,yields of butanol in relation to cell mass and glucose utilization were 54% and 72% higher in pH-stat fed-batch culture with butyric acid than that of conventional batch culture,respectively.