Strategies for production of butanol and butyl-butyrate through lipase-catalyzed esterification

• Butyl butyrate is produced by Clostridium sp. strain BOH3 in ABE fermentation.
• Indigenous lipases can be efficiently induced by olive oil or Bio-OSR.
• 6.3 g/L of butyl butyrate is obtained from an emulsified solution.
• Additional lipases and butyric acid increase the yield of butyl-butyrate.
• Up to 22.4 g/L of butyl butyrate can be obtained from fermentation with in situ product extraction.

In this study, a fermentation process for production of butanol and butyl-butyrate by using Clostridium sp. strain BOH3 is developed. This strain is able to produce butyric acid and butanol when it ferments 60 g/L xylose. Meanwhile, it also excreted indigenous lipases (induced by olive oil) which naturally convert butyric acid and butanol into 1.2 g/L of butyl-butyrate. When Bio-OSR was used as both an inducer for lipase and extractant for butyl-butyrate, the butyl-butyrate concentration can reach 6.3 g/L. To further increase the yield, additional lipases and butyric acid are added to the fermentation system. Moreover, kerosene was used as an extractant to remove butyl-butyrate in situ. When all strategies are combined, 22.4 g/L butyl-butyrate can be produced in a fed-batch reactor spiked with 70 g/L xylose and 7.9 g/L butyric acid, which is 4.5-fold of that in a similar system (5 g/L) with hexadecane as the extractant.