Metabolic characterization and transformation of the non‐dairy Lactococcus lactis strain KF147, for production of ethanol from xylose

Abstract

The non-dairy lactic acid bacterium Lactococcus lactis KF147 can utilize xylose as the sole energy source. To assess whether KF147 could serve as a platform organism for converting second generation sugars into useful chemicals, the authors characterized growth and product formation for KF147 when grown on xylose. In a defined medium KF147 was found to co-metabolize xylose and arginine, resulting in bi-phasic growth. Especially at low xylose concentrations, arginine significantly improved growth rate. To facilitate further studies of the xylose metabolism, the authors eliminated arginine catabolism by deleting the arcA gene encoding the arginine deiminase. The fermentation product profile suggested two routes for xylose degradation, the phosphoketolase pathway and the pentose phosphate pathway. Inactivation of the phosphoketolase pathway redirected the entire flux through the pentose phosphate pathway whereas over-expression of phosphoketolase increased the flux through the phosphoketolase pathway. In general, significant amounts of the mixed-acid products, including lactate, formate, acetate and ethanol, were formed irrespective of xylose concentrations. To demonstrate the potential of KF147 for converting xylose into useful chemicals the authors chose to redirect metabolism towards ethanol production. A synthetic promoter library was used to drive the expression of codon-optimized versions of the Zymomonas mobilis genes encoding pyruvate decarboxylase and alcohol dehydrogenase, and the outcome was a strain producing ethanol as the sole fermentation product with a high yield corresponding to 83% of the theoretical maximum. The results clearly indicate the great potential of using the more metabolically diverse non-dairy L. lactis strains for bio-production based on xylose containing feedstocks.

Systems Biology – A Guide for Understanding and Developing Improved Strains of Lactic Acid Bacteria

“…On the other hand, we also explored the possibility to use the non-dairy L. lactis strain KF147 to produce ethanol as the only dominant product from xylose, although the final titer was low. This work demonstrated the great potential of using the more metabolically diverse non-dairy L. lactis strains for bio-production from xylose containing feedstocks (Petersen et al, 2017).…”

Screening of mixed lactic acid bacteria starter and its effects on the quality and flavor compounds of fermented Lentinus edodes

“…The types and contents of volatile flavor mixeds are important indexes affecting the quality of fermented products (Petersen et al, 2017). L. edodes was fermented with the best LAB mixed starter and technological conditions, and the types and contents of volatile flavor compounds in the fermented products were analyzed.…”

Engineering Tools for the Development of Recombinant Lactic Acid Bacteria

“…Generally, Lactobacillus strain shows tetracycline and erythromycin sensitivity. [ 82 ] Therefore, erythromycin resistance is applied routinely in many recombinant LAB for the production of biofuel, including ethanol [ 25,26 ] and butanediol [ 27,28 ] with each plasmid vectors.…”