Abstract

Lactic acid has a privileged position in the family of carboxylic substances due to its several applications, including the production of biodegradable polymers such as polylactic acid in recent years. Thus, it has been considered one of the top 10 biorefinery chemicals by the United States Department of Energy. Lactic acid can be obtained by chemical synthesis and fermentation. However, only the fermentative process allows the formation of a pure enantiomer, which is crucial in biopolymer production. In this context and considering a possible second-generation production of lactic acid, the aim of the study was to evaluate the enantiomer produced by 4 lactic acid bacteria and their capacity of production in MRS medium containing xylose. There was no observed xylose consumption or catabolite repression. Lactobacillus helveticus produced a racemic mixture of D(–) and L(+) lactic acid and Lactobacillus delbrueckii lactis produced mostly D(–) lactic acid. In comparison, Lactobacillus coryniformis strains presented the most expressive results, with an exclusive production of D(–) lactic acid (optical purity >99%) and high resistance to pH variation, achieving production from 18.5 to 21.0 g/L with yield of 0.95 g/g of glucose. These strains could be indicated for the second-generation D(–) lactic acid production.

中文翻译：

---

在有限溶解氧条件下，在戊糖馏分存在的情况下，通过乳杆菌菌株生产乳酸对映体

摘要

乳酸在羧酸类物质家族中具有特殊地位，因为它有多种应用，包括近年来可生物降解的聚合物（如聚乳酸）的生产。因此，它被美国能源部视为十大生物精炼化学品之一。乳酸可通过化学合成和发酵获得。然而，只有发酵过程才能形成纯对映异构体，这在生物聚合物生产中至关重要。在此背景下，并考虑到可能的第二代乳酸生产，该研究的目的是评估 4 种乳酸菌产生的对映异构体及其在含有木糖的 MRS 培养基中的生产能力。没有观察到木糖消耗或分解代谢物抑制。瑞士乳杆菌产生 D(-) 和 L(+) 乳酸的外消旋混合物，而德氏乳杆菌主要产生 D(-) 乳酸。相比之下，棒状乳杆菌菌株表现出最丰富的结果，独家生产 D(–) 乳酸（光学纯度 >99%）和对 pH 变化的高抗性，产量从 18.5 到 21.0 g/L，产量为 0.95克/克葡萄糖。这些菌株可用于第二代 D(-) 乳酸生产。