l‐Lactate oxidase‐mediated removal of l‐lactic acid derived from fermentation medium for the production of optically pure D‐lactic acid

Abstract

Background: There has been an increasing demand for optically pure D-lactic and Llactic acid for the production of stereocomplex-type polylactic acid. The D-lactic acid production from lignocellulosic biomass is important owing to its great abundance in nature. Corn steep liquor (CSL) is a cheap nitrogen source used for industrial fermentation, though it contains a significant amount of L-lactic acid, which decreases the optical purity of D-lactic acid produced. Method and results:To remove L-lactic acid derived from the CSL-based medium, Llactate oxidase (LoxL) from Enterococcus sp. NBRC 3427 was expressed in an engineered Lactiplantibacillus plantarum (formally called Lactobacillus plantarum) strain KOLP7, which exclusively produces D-lactic acid from both hexose and pentose sugars.When the resulting strain was applied for D-lactic acid fermentation from the mixed sugars consisting of the major constituent sugars of lignocellulose (35 g L -1 glucose, 10 g L -1 xylose, and 5 g L -1 arabinose) using the medium containing 10 g L -1 CSL, it completely removed L-lactic acid derived from CSL (0.52 g L -1 ) and produced 41.7 g L -1 of Dlactic acid. The L-lactic acid concentration was below the detection limit, and improvement in the optical purity of D-lactic acid was observed (from 98.2% to > 99.99%) by the overexpression of LoxL. Conclusion and implications:The LoxL-mediated consumption of L-lactic acid would enable the production of optically pure D-lactic acid in any medium contaminated by L-lactic acid.

Global trends and future prospects of lactic acid production from lignocellulosic biomass

“…37,86 The engineered L. plantarum (with a deficient l -lactate dehydrogenase gene or expressing l -lactate oxidase gene) has been extensively utilized for the production of d -LA, exhibiting excellent utilization capabilities for pentoses and hexoses, as well as high d -LA yields. 37,87,88 Research related to Bacillus strains did not appear until 1993, and it reached a maximum of 23 articles per year, accumulating a total of 167 articles on the topic. B. coagulans has the capability to grow and ferment both hexoses and pentoses present in LCB, yielding high-purity l -LA under non-sterilized conditions.…”

Optimization of an Industrial Medium and Culture Conditions for Probiotic Weissella cibaria JW15 Biomass Using the Plackett-Burman Design and Response Surface Methodology

“…LAB produce various organic acids by metabolizing diverse carbohydrates. Among the organic acids, lactic acid is a major metabolite and a crucial parameter in estimating the growth of LAB [ 24 ]. The lactic and acetic acid formation of JW15 was examined during fermentation.…”

“…Following glucose depletion, LAB will convert lactic acid into acetic acid under aerobic condition. Accordingly, long-term fermentation of LAB results in the accumulation of acetic acid as a substitute for lactic acid and subsequently induces cell pH homeostasis [ 20 , 24 ]. Overall, OM better improved the growth of JW15 than CM.…”

Unraveling the potential and constraints associated with corn steep liquor as a nutrient source for industrial fermentations

“…As lactate is the most abundant carbohydrate in CSL, 46,47 E. coli was grown on a CSL-lactate medium to further investigate the bacterium's respiratory and metabolic activity. As shown in Figure 1a, growth of E. coli on the CSL-lactate medium resulted in a maximum OTR of 28 mmol/L/h, higher than observed for the CSL-glucose medium (19.5 mmol/L/h).…”