Jang Byeong-Kwan, Ju Yebin, Jeong Deokyeol, Jung Sung-Keun, Kim Chang-Kil, Chung Yong-Suk, Kim Soo-Rin
Major in Food Application Technology, School of Food Science and Biotechnology, Kyungpook National University, Daegu 41566, Korea.
Department of Horticulture, Kyungpook National University, Daegu 41566, Korea.
J Fungi (Basel). 2021 Oct 31;7(11):928. doi: 10.3390/jof7110928.
Lactic acid is mainly used to produce bio-based, bio-degradable polylactic acid. For industrial production of lactic acid, engineered can be used. To avoid cellular toxicity caused by lactic acid accumulation, pH-neutralizing agents are used, leading to increased production costs. In this study, lactic acid-producing BK01 was developed with improved lactic acid tolerance through adaptive laboratory evolution (ALE) on 8% lactic acid. The genetic basis of BK01 could not be determined, suggesting complex mechanisms associated with lactic acid tolerance. However, BK01 had distinctive metabolomic traits clearly separated from the parental strain, and lactic acid production was improved by 17% (from 102 g/L to 119 g/L). To the best of our knowledge, this is the highest lactic acid titer produced by engineered without the use of pH neutralizers. Moreover, cellulosic lactic acid production by BK01 was demonstrated using acetate-rich buckwheat husk hydrolysates. Particularly, BK01 revealed improved tolerance against acetic acid of the hydrolysates, a major fermentation inhibitor of lignocellulosic biomass. In short, ALE with a high concentration of lactic acid improved lactic acid production as well as acetic acid tolerance of BK01, suggesting a potential for economically viable cellulosic lactic acid production.
乳酸主要用于生产生物基、可生物降解的聚乳酸。对于乳酸的工业生产，可以使用工程菌。为避免乳酸积累导致的细胞毒性，需使用pH中和剂，这会增加生产成本。在本研究中，通过在8%乳酸上进行适应性实验室进化（ALE），开发出了具有提高的乳酸耐受性的产乳酸工程菌BK01。无法确定BK01的遗传基础，这表明与乳酸耐受性相关的机制很复杂。然而，BK01具有与亲本菌株明显不同的代谢组学特征，乳酸产量提高了17%（从102克/升提高到119克/升）。据我们所知，这是在不使用pH中和剂的情况下工程菌产生的最高乳酸滴度。此外，使用富含乙酸的荞麦壳水解物证明了BK01能够生产纤维素乳酸。特别是，BK01对水解物中的乙酸耐受性有所提高，乙酸是木质纤维素生物质的主要发酵抑制剂。简而言之，在高浓度乳酸条件下的ALE提高了BK01的乳酸产量以及对乙酸的耐受性，这表明其在经济可行的纤维素乳酸生产方面具有潜力。
