Development of Lactic Acid Fermentation Process Accompanied with Selective Product Separation

采用鼠李糖乳杆菌和米根霉发酵生产L-乳酸并作为生物降解聚合物的原料，在发酵和产物分离方面取得了以下结果：1）在鼠李糖乳杆菌的提取发酵中，可以通过使用填充有阳离子交换的清洗柱完全除去溶解的对微生物有毒的萃取剂，树脂在100 g/L的初始葡萄糖浓度下，发酵过程中的产物抑制现象得到了抑制，发酵得以顺利进行。2）在鼠李糖乳杆菌的电渗析发酵中，发现了一种利用水渗透的连续发酵方法，可以长期稳定地生产乳酸。通过在发酵罐中使用葡萄糖传感器，可以将葡萄糖浓度保持在低水平并提高乳酸产量。3）在根霉发酵中，向发酵液中添加活性炭在提高生产率和产量以及获得简化下游处理的清洁发酵液方面非常有效。对本项目研究的乳酸生产系统进行了评价。由此得出结论，与鼠李糖乳杆菌的提取发酵是适合于小规模的分批操作，而与相同的细菌的电渗析发酵是一个小规模的连续操作。根霉适合于大规模发酵。

The fermentative production process of L-lactic and as a raw material of biodegradable polymer was developed by employing Lactobacillus rhamnosus and Rhizopus oryzae and the following results were obtained concerning the fermentation and products separation.1) In the extractive fermentation with Lactobacillus rhamnosus, it became possible to remove completely the dissolved extractant which is toxic for microbes by using a cleaning column packed with cation exchange resin. The product inhibition, which severely retarded the fermentation under the initial glucose concentration of 100g/L, was suppressed with the present extractive fermentation system and fermentation proceeded satisfactorily.2) In the electrodialysis fermentation with Lactobacillus rhamnosus, a continuous fermentation method utilizing the permeation of water was found to give a stable production of lactic acid for long term. By using a glucose sensor in a fermentor, it was possible to keep the concentration of glucose at low level and to increase the yield of lactic acid.3) In the fermentation with Rhizopus oryzae, the addition of activated carbon to the fermentation broth was very effective in increasing the productivity and yield and obtaining clean broth which simplified the downstream processing.4) The lactic acid production systems investigated in this project were evaluated. It was concluded that an extractive fermentation with Lactobacillus rhamnosus was suitable for a small-scale batch operation whereas an electrodialysis fermentation with the same bacteria was for a small-scale continuous operation. Rhizopus oryzae was suitable for a large-scale fermentation.