Study Of Microelement Regulation On Line In The L-lactic Acid And Solid State Fermentation

This paper screened Rhizopus oryzae which could produce lactic acid efficiently and studied the method of regulation fermentation in order to produce lactic acid with higher optical purity and production as well as lower cost. The research divided into two areas:1) The microelement plays an important role in the L-lactic acid fermention. In this study, Mg2+,K+,Zn2+ were choosed to regulate. We analyzed the affection of Rhizopus oryzae L-lactic acid fermention through the regulation of the microelement concentration on line. The results show that the concentration of Mg2+ has positive relativity to the accumulation of L-lactic acid and it is supplied in the 12th hour of fermention. Low concentration of K+ and Zn2+ have negative relativity to the accumulation of L-lactic acid and they are diluted in the 36th and 12th hour of fermention respectively. The production of L-lactic acid increased by 28.15% after the synthesis of regulation of microelement than that of no regulation. The optical purity of L-lactic acid is 100%.2) The effect of cultivation conditions on the optical purity of (+)-lactic acid produced by Rhizopus oryzae HZS6 was investigated. The (+)-lactic acid yield decreased with the dosage. Under suitable conditions, 100g/L initial glucose, 2g/L NH4NO3, 1.5 g/L supplemented (+)-lactic acid, R. oryzae HZS6 could produce 99% (+)-form lactic acid with the yield of 80% and final concentration of 81.3 g/L, at pH 6.0 and temperature 34°C. The isomeric composition of lactic acid was influenced by the supplementation of L(+)-lactic acid to fermentation medium. L(+)-Isomer increased with the dosage, no D(-)-lactic acid was observed when the concentration of supplemented L(+)-lactic acid in matrix was≥1.5 g/L. However, the L(+)-lactic acid yield, biomass and glucose conversion rate decreased with the dosage.