基于PEG/DEX双水相体系的餐厨垃圾乳酸发酵

利用聚乙二醇(PEG)/葡聚糖(DEX)双水相体系分离餐厨垃圾发酵产物乳酸,分析了聚合物浓度和分子量的影响,以及餐厨垃圾多批次连续发酵时乳酸产率。实验结果表明,PEG/DEX双水相体系对乳酸菌生长影响不大,PEG和DEX浓度变化对乳酸产率、相体积比无显著影响;当DEX分子量由20 000升至40 000,乳酸生成速率由0.631 g/(L.h)降至0.518 g/(L.h),乳酸浓度由33 g/L降至22 g/L。多批次餐厨垃圾连续发酵可极大缩短发酵时间,在不投加缓冲剂的情况下,单批次乳酸产率仍大于0.30 g/g,累积产率大于0.45 g/g。

Lactic acid extraction from kitchen wastes fermentation using aqueous two-phase systems

Polyethylene glycol (PEG)/dextran (DEX) aqueous two-phase systems were used to extract lactic acid from kitchen wastes fermentation. Results showed that PEG/DEX system had insignificant effect on the growth of lactic acid bacteria. The variation of PEG and DEX concentrations influenced cells growth and lactic acid biosynthesis indistinctively. Volume ratio kept stable throughout the processes, despite the changes of raw material and product concentrations. Different from little influence of PEG molecular weight on fermentation, the increase of DEX molecular weight from 20 000 to 40 000 led to declines of lactate conversion rate from 0.631 g/(L·h) to 0.518 g/(L·h) and lactic acid concentration from 33 g/L To 22 g/L. A repeated extractive fermentation was carried out with four top-phase replacements. Results presented that when cell density reached the stationary phase in the first extractive fermentation, the lactate yield was maintained above 0.30 g/g per batch and 0.45 g/g in the total process.