Evolutionary engineering of Lactobacillus pentosus improves lactic acid productivity from xylose-rich media at low pH

• Published in: Bioresource technology 2019-09, Vol.288, p.121540-121540, Article 121540
• Main Authors: Cubas-Cano, Enrique, González-Fernández, Cristina, Tomás-Pejó, Elia
• Format: Article
• Language: English
• Subjects: Adaptive laboratory evolution; Lactic acid; Lactobacillus pentosus; Low-pH tolerance; Xylose
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/j.biortech.2019.121540

[Display omitted] •A new Lactobacillus pentosus strain was obtained by adaptive evolution.•Lactic acid yield from xylose at initial pH 7, 6 and 5 was enhanced by 2-fold.•Increase in xylose consumption rate was also shown when pH was set at 7.•Lactic acid productivity from wheat straw hydrolysate was increased by 1.4-fold. Since xylose is the second most abundant sugar in lignocellulose, using microorganisms able to metabolize it into bio-based chemicals like lactic acid is an attractive approach. In this study, Lactobacillus pentosus CECT4023T was evolved to improve its xylose fermentation capacity even at acid pH by adaptive laboratory evolution in repeated anaerobic batch cultures at increasing xylose concentration. The resulting strain (named MAX2) presented between 1.5 and 2-fold more xylose consumption and lactic acid production than the parental strain in 20 g L−1 xylose defined media independently of the initial pH value. When the pH was controlled in bioreactor, lactic acid productivity at 16 h increased 1.4-fold when MAX2 was grown both in xylose defined media and in wheat straw hydrolysate. These results demonstrated the potential of this new strain to produce lactic acid from hemicellulosic substrates at low pH, reducing the need of using neutralizing agents in the process.