无载体固定化米根霉重复间歇发酵生产L-乳酸

Repeated Intermittent L-lactic Acid Fermentation Technology by Self-immobilized Rhizopus oryzae

通过研究影响米根霉菌丝体形态的培养基因素,初步构建了无载体固定化米根霉重复间歇发酵生产L-乳酸的工艺条件。研究结果表明,首批次发酵培养基采用120 g/L葡萄糖,3 g/L硝酸铵,K+和Na+浓度比为1:1,发酵72 h后,米根霉菌体形态为均匀的菌丝体小球,直径为1.0 mm^2.0 mm,此时L-乳酸产量可达100.8 g/L,葡萄糖转化率为84%。在此基础上,利用米根霉菌丝体小球重复间歇发酵16批次,每批次发酵24 h,此时葡萄糖转化率均高于75%,L-乳酸产量保持在60.0 g/L以上,米根霉菌丝体小球形态保持稳定。

In order to carry out the process of the repeated intermittent L-lactic acid fermentation by self-immobilized Rhizopus oryzae, we investigated the effect of medium compositions on the morphology of Rhizopus oryzae. In submerged culture, fungi can be grown as broths of freely suspended mycelia and pellets or clumps, the pellets can be immobilized by themselves. The optimum medium composition for the first patch of fermentation was： 120 g/L glucose, 3 g/L NH4NO3, 0.14 g/L KH2PO4, 0.16 g/L NaH2PO4 （the concentration ratio of K^＋ and Na^＋ was 1：1）. After 72 h fermentation, the physical form of Rhizopus oryzae was mostly uniform pellet with the diameter of 1.0-2.0 mm, the concentration of L-lactic acid was 100.8 g/L, and the conversion rate of glucose was 84%. During 16 batches of repeated fermentation, the L-lactic acid level was above 60.0 g/L and the conversion rate of glucose was 75%. The fermentation time of every batch was 24 h.