Metabolically engineered Lactobacillus gasseri JCM 1131 as a novel producer of optically pure L- and D-lactate

• Published in: World journal of microbiology & biotechnology 2020-07, Vol.36 (8), p.111, Article 111
• Main Authors: Žunar, Bojan, Trontel, Antonija, Svetec Miklenić, Marina, Prah, Juliana Lana, Štafa, Anamarija, Marđetko, Nenad, Novak, Mario, Šantek, Božidar, Svetec, Ivan Krešimir
• Format: Article
• Language: English
• Subjects: Applied Microbiology; Bacillus megaterium - genetics; Bacillus megaterium - metabolism; Biochemistry; Biomedical and Life Sciences; Bioplastics; Biorefineries; Biotechnology; Culture Media - chemistry; Deactivation; Dehydrogenases; Environmental Engineering/Biotechnology; Fermentation; Fermented food; Gene disruption; Genes; Glucose - metabolism; Growth conditions; Hydrolysis; Inactivation; L-Lactate Dehydrogenase - genetics; L-Lactate Dehydrogenase - metabolism; Lactic acid; Lactic Acid - metabolism; Lactobacilli; Lactobacillus gasseri; Lactobacillus gasseri - genetics; Lactobacillus gasseri - metabolism; Life Sciences; Lignin - metabolism; Lignocellulose; Metabolic Engineering; Microbiology; Microorganisms, Genetically-Modified - genetics; Original Paper; Plasmids; Plasmids - genetics; Stereoisomers; Straw; Sugar; Wheat; Wheat straw
• ISSN: 0959-3993; 1573-0972
• DOI: 10.1007/s11274-020-02887-2

High-quality environmentally-friendly bioplastics can be produced by mixing poly-L-lactate with poly-D-lactate. On an industrial scale, this process simultaneously consumes large amounts of both optically pure lactate stereoisomers. However, because optimal growth conditions of L-lactate producers often differ from those of D-lactate producers, each stereoisomer is produced in a specialised facility, which raises cost and lowers sustainability. To address this challenge, we metabolically engineered Lactobacillus gasseri JCM 1131 T , a bioprocess-friendly and genetically malleable strain of homofermentative lactic acid bacterium, to efficiently produce either pure L- or pure D-lactate under the same bioprocess conditions. Transformation of L. gasseri with plasmids carrying additional genes for L- or D-lactate dehydrogenases failed to affect the ratio of produced stereoisomers, but inactivation of the endogenous genes created strains which yielded 0.96 g of either L- or D-lactate per gram of glucose. In this study, the plasmid pHBintE, routinely used for gene disruption in Bacillus megaterium , was used for the first time to inactivate genes in lactobacilli. Strains with inactivated genes for endogenous lactate dehydrogenases efficiently fermented sugars released by enzymatic hydrolysis of alkali pre-treated wheat straw, an abundant lignocellulose-containing raw material, producing 0.37–0.42 g of lactate per gram of solid part of alkali-treated wheat straw. Thus, the constructed strains are primed to serve as producers of both optically pure L-lactate and D-lactate in the next-generation biorefineries. Graphic abstract