果糖及葡萄糖混合物为底物的丙酮丁醇发酵

Acetone-butanol fermentation from the mixture of fructose and glucose

旨在以果糖和葡萄糖混合物模拟能源作物菊芋块茎水解液发酵生产丁醇。在培养基初始pH 5.5,发酵过程不控制pH的混合糖发酵中,出现了发酵提前终止现象,终点残糖浓度达23.26 g/L,而丁醇产量仅5.51 g/L。进一步对比混合糖及葡萄糖、果糖不控制pH的发酵结果表明,导致这一现象的原因可能是有机酸毒性太大和pH太低。全程控制pH的混合糖发酵结果表明,高pH条件有利于提高糖利用率,但产酸多,丁醇产量较低;而低pH条件下发酵残糖较多,但丁醇产量相对较高。基于此,文中采用阶段性pH调控策略,即将发酵初期的pH控制在5.5,待菌体OD620上升到1.0后,解除pH控制,发酵终点残糖浓度下降到2.05 g/L,丁醇产量也相应提高到10.48 g/L。

A mixture of fructose and glucose was developed to simulate the hydrolysate of Jerusalem artichoke tubers,the fructose-based feedstock suitable for butanol production.With the initial pH of 5.5 without regulation during mixed-sugar fermentation,as high as 23.26 g/L sugars were remained unconverted,and butanol production of 5.51 g/L were obtained.Compared with either glucose or fructose fermentation,the early termination of mixed-sugar fermentation might be caused by toxic organic acids and the low pH.When the pH of the fermentation system was controlled at higher levels,it was found that sugars utilization was facilitated,but less butanol was produced due to the over-accumulation of organic acids.On the other hand,when the pH was controlled at lower levels,more sugars were remained unconverted,although butanol production was improved.Based on these experimental results,a stage-wise pH regulation strategy,e.g.,controlling the pH of the fermentation system at 5.5 untill the OD620 reached 1.0,and then the pH control was removed,was developed,which significantly improved the fermentation performance of the system,with only 2.05 g/L sugars unconverted and 10.48 g/L butanol produced.