Effects of pH and oxygen supply on production of 2,3-butanediol from biodiesel-derived glycerol by Bacillus amyloliquefaciens

Abstract:

Bacillus amyloliquefaciens B10-127 was used to produce 2,3-butanediol (2,3-BD) from residual glycerol obtained from biodiesel synthesis. Important variables for 2,3-BD fermentation, pH and dissolved oxygen, were studied. When pH was maintained constant, the yield of 2,3-BD was inhibited. The highest 2,3-BD yields were achieved by fermentation without any pH control with an optimized initial pH 6.5. Batch fermentative production of 2,3-BD by B. amyloliquefaciens was investigated using various oxygen supply methods by changing agitation speed. Based on the analysis of three kinetic parameters including specific cell growth rate (μ), specific glucose consumption rate (qs) and specific 2,3-BD formation rate (qp), a three-stage agitation speed control strategy was proposed, aimed at achieving high concentration, high yield and high productivity of 2,3-BD. Maximum concentration of 2,3-BD reached 38.1 g/L, with the productivity of 1.06 g/(L·h), which were 14.8% and 63.1% over the best results from constant agitation speeds. In a pulse fed-batch fermentation, 2,3-BD concentration and productivity were significantly improved to 71.2 g/L and 0.99 g/(L·h), respectively. To our knowledge, these results were the highest for 2,3-BD production from biodiesel-derived glycerol.

Key words:Bacillus amyloliquefaciens, biodiesel-derived glycerol, pH, three-stage control strategy, fed-batch, 2.3-butanediol