ENHANCED PRODUCTION OF LACTIC-ACID THROUGH THE USE OF A NOVEL AQUEOUS2-PHASE SYSTEM AS AN EXTRACTIVE FERMENTATION SYSTEM

In order to enhance the productivity of lactic acid and reduce the end -product inhibition of fermentation, the partitioning and growth of fo ur different strains of lactic acid bacteria in three different aqueou s two-phase systems were studied. Polyethyleneglycol/dextran, polyethy leneglycol/hydroxypropyl starch polymer (HPS), and a random copolymer of ethylene oxide and propylene oxide (EO-PO)/HPS were used as polymer systems. One strain each of Lactococcus lactis subsp. lactis and of L actobacillus delbrueckii subsp. delbrueckii partitioned completely to the interface and bottom phase in two-phase systems with low polymer c oncentrations of EO-PO/HPS100 and EO-PO/HPS200. The growth and product ion of lactic acid by two of three L. lactis strains in a two-phase sy stem with 5.5% (w/w) EO-PO and 12.0% (w/w) HPS100 were reduced by less than 10% compared with a reference fermentation in a normal growth me dium. The viability of L. lactis subsp. lactis ATCC 19435 was maintain ed for at least 50 h and with four top-phase replacements during extra ctive fermentation in the EO-PO/HPS100 system. Moreover, when cell den sity reached the stationary phase in the first extractive fermentation , the lactate production in this aqueous two-phase system was maintain ed.