L-lactic acid was produced with uncooked rice powder fermentation by Rhizopus oryzae NRRL 395 for reducing costs. The influence of the following four antibiotics (Sodium penicillin, penicillin V potassium, streptomycin, and oxytetracycline) and other factors on the fermentation was investigated. Experimental results showed that all four kinds of antibiotics could inhibit bacterial contamination and promote the yield of L-lactic acid, in which 1.6 million units/L of sodium penicillin showed the most significant effect. Inoculation with mycelium could reach higher L-lactic acid yield than that of spores inoculation. Also , the simultaneous saccharification fermentation reduced the costs , while increasing L-lactic acid yield , which was better than the conventional method of separate hydrolysis and fermentation. Under preliminary optimized culture conditions , L-lactic acid yield was up to 67.80 g/L by fermentation of 120 g/L of rice powder , corresponding to 76.45%conversion rate. These results showed the practical feasibility and development prospect of the uncooked material fermentation by Rhizopus oryzae for production of L-lactic acid.%为降低生产成本,以大米粉为原料,采用米根霉NRRL395生料发酵生产L-乳酸.考察了青霉素钠、青霉素V钾、硫酸链霉素、土霉素等4种抗生素在生料发酵中的作用及不同接种方式等对发酵产酸的影响.实验结果表明, 4种抗生素都能起到较好的抑制杂菌、促进乳酸发酵的作用,其中以160万单位/L青霉素钠效果最为显著.采用菌丝体接种的乳酸产量高于孢子液接种, 采用同步糖化发酵法的生产成本及乳酸产量均优于常规的分步糖化发酵法.在初步优化的培养条件下,120 g/L大米粉发酵后乳酸产量最高达到67.80 g/L,相应的乳酸转化率为76.45%,展示了米根霉生料发酵技术生产乳酸的实践可行性及其广阔的发展前景.
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