Lactic acid extraction from kitchen wastes fermentation using aqueous two-phase systems
基于PEG/DEX双水相体系的餐厨垃圾乳酸发酵

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.