【作者】 卫强；

【导师】 韩振为；

【作者基本信息】 天津大学 ， 生物化工， 2004， 硕士

【摘要】 本文开展了乳酸细菌BME5-18M 利用葡萄糖发酵产L-乳酸的研究，在间歇发酵的基础上研究了温度、pH、碳源种类及其浓度对发酵过程菌体生长及产酸的影响，确定了发酵的最适温度、碳源及pH。以5L B.Braun发酵罐间歇发酵实验数据为基础，进行了乳酸细菌BME5-18M间歇发酵动力学分析。结果表明菌体生长适合于Logistic方程，L-乳酸生成符合Luedeking-Piret方程，葡萄糖消耗可用简化的基质消耗方程描述。所用模型可较好地描述L-乳酸的间歇发酵过程。在间歇发酵实验及动力学分析的基础上，进行了基质恒速流加发酵实验，确定了基质流加的最佳速率。对流加发酵和间歇发酵进行了比较，结果表明，流加发酵实现了菌体的高密度培养，提高了L-乳酸的产量和得率，是一种高效的发酵操作方式。本文还进行了分子蒸馏技术应用于L-乳酸精制的研究，考察了分子蒸馏装置的刮膜器转子转速、进料速率和蒸馏温度对乳酸纯度和收率的影响，并考察了乳酸进料温度对乳酸收率的影响。结果表明，分子蒸馏是制备高纯L-乳酸的一种有效方法，产品纯度高于95%。采用钙盐法提取工艺从发酵液中提取L-乳酸，发酵液经处理后不结晶而直接酸解，并进一步省去脱色与离子交换等步骤，得到的粗乳酸经脱水后用分子蒸馏精制，同样可以得到高纯乳酸，在合适的条件下甚至得到了L-乳酸晶体。但所采用的提取工艺操作步骤明显减少，产品收率也有了较大的提高。更多还原

【Abstract】 The fermentation of glucose to L-lactic acid was conducted using Lactobacillus delbrueckii BME5-18M. The effects of temperature, pH, carbon resources and its concentration on cell growth and L-lactate production were investigated during the batch fermentation. The results showed that the optimal carbon resource was glucose, and the optimal operation parameters were 37℃ and pH 6.5.The batch fermentation process was studied in a 5 L system under the optimal conditions. A kinetic model was proposed based on the Logistic equation, Luedeking-Piret equation and simplified substrate consumption equation for cell growth, L-lactate production and glucose consumption. With the evaluated model parameters, the model appears to provide a reasonable description for the L-lactic acid fermentation process.Based on the experiment and kinetics of batch fermentation, the effects of different glucose constant feeding rate were investigated during the fed-batch fermentation. The results indicated that 25mL/h was the optimal strategy for fed-batch fermentation. It was found that fed-batch fermentation was very useful for highly efficient accumulation of biomass and L-lactic acid and the productivity of fermentation was greatly improved in comparison with batch fermentation.Purification of L-lactic acid by molecular evaporator was studied, the effects of wiper agitation speed, feeding flow speed and evaporating temperature on purity and yield of L-lactic acid were investigated, and the effect of feed temperature of L-lactic acid on yield was also investigated. The results showed that molecular distillation was an efficient method for purification of L-lactic acid. The purity of production was higher than 95%.The feasibility was investigated to the application of simplified calcium salt recovery method with molecular distillation technique for the preparation of high purity L-lactic acid at laboratory scale. Fermentation broth was directly taken into sulfuric acid hydrolysis without crystallization, and the conventional active carbon for decolorization and ion exchange were omitted. The crude L-lactic acid produced was concentrated directly by rotary evaporator, and the enriched material was purified in molecular evaporator. The results showed that we still can get high <WP=5>purity L-lactic acid, and we even can get L-lactic acid crystal under the proper condition. The operation units of the calcium salt recovery method were greatly decreased, and the yield of production was increased.更多还原