米根霉菌落形态优化对乳酸积累的影响

Optimization of lactic acid production based on the fungal morphology by rhizopus oryzae

本文研究了培养温度、前培养培养基组成包括葡萄糖浓度、大豆蛋白胨、无机离子等对米根霉菌丝形态及菌体直径的影响。其中,无机离子抑制菌丝形成颗粒状,而大豆蛋白胨促进菌丝形成颗粒状;前培养基中初始葡萄糖、大豆蛋白胨浓度直接影响颗粒直径和菌体干重,在一定范围内,颗粒直径随底物浓度升高而降低,超过此范围,颗粒直径随底物浓度升高而升高;菌体干重随底物浓度变化的趋势与此相反。因此,前培养过程中能到获得颗粒直径小、菌体干重大的情形。基于米根霉形态优化,摇瓶水平乳酸积累量达到78.89g/L,同比提高61.76%;发酵罐水平乳酸积累量达到56.87g/L,同比提高54.41%。

The effects of temperature, agitation rate and medium composition, including concentrations of glucose, soybean peptone, and inorganic ions, on pellet formation and pellet diameter of Rhizopus oryzae NRRL1526 during pre -culture were studied. Inorganic ions and soybean peptone had negative and positive effects on pellet formation, re- spectively. The initial glucose and soybean peptone concentrations directly affected pellet diameter. Within a certain range, pellet diameter decreased with the increase of initial substrate concentrations; however, above this range, there was an opposite trend. Thus, during pre - culture stage, small pellets with bigger dry mass of R. oryzae can be cu- litved. Furthermore, dry cell mass and yield of lactic acid increased with the decrease of pellet diameter. Based on the pellet morphology optimization, the final lactic acid concentration was improved by 46. 13% when fermented in a flask （54. 89 g/L） and 31.82% in stirred bioreactor tank fermentation （48.76 g/L）.