Development of Lactic Acid Fermentation Process Accompanied with Selective Product Separation

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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.