Greener L-lactic acid production through in situ extractive fermentation by an acid-tolerant Lactobacillus strain
Greener L-lactic acid production through in situ extractive fermentation by an acid-tolerant Lactobacillus strain
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DOI：
10.1007/s00253-018-9084-4
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发表时间：
2018-08-01
影响因子：
5
通讯作者：
Sonomoto, Kenji
中科院分区：
文献类型：
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作者：
Singhvi, Mamata;Zendo, Takeshi;Sonomoto, Kenji
乳酸（LA）发酵需要在生理上可接受的范围内使用中和剂。然而，中和剂会产生大量的石膏，这是一种环境污染物。此外，下游加工复杂且昂贵，占总成本的50-70%。我们以前开发的德氏乳杆菌FM 1，它可以产生不解离的LA没有中和剂。在这里，我们通过在pH 4.5下的适应性进化改进了FM 1，其产生的Adp FM 1显示出与FM 1相比LA产量增加了1.80倍。通过补料分批发酵生产LA，产量为36.2g/L，生产率为0.500g/L/h。然而，由于酸性pH和/或终产物抑制，细胞活力降低。因此，采用使用提取溶剂的原位LA回收方法来维持细胞活力。Adp FM 1经LA提取后的补料分批发酵产LA 49.2 g/L，是未提取前的1.4倍。Adp FM 1在96 h内的总LA生产率为0.512 g/L/h。在所有供试菌株中，Adp FM 1的H+-ATPase活性最高，其H+-ATPase基因表达量是亲本菌株的415倍。这些结果表明，原位LA提取发酵工艺将使下游加工变得容易，并且证明与本发明的发酵相比是更经济和环境友好的选择。据我们所知，这是第一个报告的生产未解离的L-LA的乳酸杆菌使用原位回收过程，具有高的LA生产水平和生产力。
Lactic acid (LA) fermentation requires a neutralizer for a physiologically acceptable range. However, a neutralizer generates a large amount of gypsum, an environmental pollutant. Furthermore, the downstream processing is complicated and expensive, comprising 50-70% of the total cost. We previously developed a Lactobacillus delbrueckii FM1, which can produce undissociated LA without neutralizer. Here, we improved FM1 by adaptive evolution at pH 4.5, which generated Adp FM1 showing an 1.80-fold increase in LA production compared to FM1. The LA production via fed-batch fermentation yielded 36.2 g/L of LA, with a productivity of 0.500 g/L/h. However, cell viability was reduced due to the acidic pH and/or end-product inhibition. Therefore, an in situ LA recovery process using an extractive solvent was employed to maintain cell viability. Adp FM1 produced 49.2 g/L of LA via in situ LA-extractive fed-batch fermentation, which was 1.4-fold higher than that without LA extraction. Adp FM1 provided a total LA productivity of 0.512 g/L/h in 96 h. Among the tested strains, Adp FM1 exhibited the highest H+-ATPase activity and a 415-fold increase in H+-ATPase gene expression compared to the parent strain. These results suggest that the in situ LA extractive fermentation process will ease downstream processing and prove to be a more economical and environmentally friendly option compared to the present fermentation. To our knowledge, this is the first report on the production of undissociated L-LA by Lactobacillus using an in situ recovery process, with high LA production levels and productivity.