Development of novel extractive fermentation process of lactic acid with solvent-tolerant bacteria

乳酸主要作为添加剂用于传统食品工业，最近作为生产可生物降解聚乳酸的原料引起了人们的关注。随着对环境友好材料的需求的增加，通过发酵方法生产乳酸已经引起了人们的兴趣。然而，该方法的经济性取决于开发从发酵液中回收乳酸的有效方法，因为分离和纯化步骤占生产成本的50%。溶剂萃取已被提出作为一种有前途的回收技术，作为替代传统的沉淀过程。最近，从抑制终产物（乳酸）抑制和提高反应器效率的角度来看，其中在发酵液中生产乳酸的过程中通过溶剂萃取同时回收乳酸的原位萃取发酵方法被认为是有吸引力的。本研究以嗜醇的食果乳杆菌（Lactobacillus fruclivorans）NRIC 0224（hiochibacterium）为原料，采用原位萃取发酵的新工艺，以抑制萃取剂和有机溶剂的毒性。正癸醇中的三正辛胺（TOA）对乳酸的萃取率最高。发现发酵液中的酵母膏和蛋白胨对乳酸的提取有抑制作用。测试了TOA对食果乳杆菌NRIC 0224的毒性。在TOA和CaCO_3存在下，该菌能生长、消耗葡萄糖并产生乳酸，在此基础上，我们考察了含有该菌和CaCO_3的海藻酸胶囊填充柱在乳酸提取发酵中的适用性。从细胞生长和减少终产物抑制的角度来看，乳酸的提取发酵是成功的。

Lactic acid is mainly used in the traditional food industry as an additive, and has recently drawn attention as the raw material for the production of biodegradable polylactic acid. With an increase in demand for environmentally friendly materials, lactic acid production by fermentation methods has gained interest. The economics of the process, however, depend on the development of an effective recovery method for lactic acid from the broth, because the separation and purification steps account for up to 50% of the production costs. Solvent extraction has been proposed as a promising recovery technique as an alternative to the conventional precipitation process. Recently, in situ extractive fermentation processes, in which lactic acid is simultaneously recovered by solvent extraction during the production of lactic acid in the fermentation broth, have been deemed attractive from the perspectives of suppression of the end-product (lactic acid) inhibition and enhanced reactor efficiency. In the present study, in order to repress the toxicity of the extractant and organic solvent we developed the new process for in situ extractive fermentation by using Lactobacillus fruclivorans NRIC0224 (hiochibacterium), which was alcoholophilic and could grow in the presence of 1-deanol. Tri-n-octylamine (TOA) in decanol gave the highest extractability of lactic acid. It was found that yeast extract and peptone in fermentation broth inhibited to extract lactic acid. The toxicity of TOA to Lb.fructivorans NRIC0224 was tested. In the presence of TOA and calcium carbonate (CaCO_3), the bacterium could grow, consume glucose, and produce lactic acid.Based on these results, we examined the applicability of a column packed with alginate capsules containing the cells and calcium carbonate to the extractive fermentation of lactic acid. The extractive fermentation of lactic acid was successful from the points of view of cell growth and reduction of the end-product inhibition.