Deoxyhexose Metabolism in Lactobacillaceae
Lactobacillaceae have a long history in food fermentation as biopreservatives. Recently, Loigolactobacillus coryniformis was shown to metabolize the deoxyhexose L-rhamnose to the antifungal compound propionate with 1,2-propanediol (1,2-PD) as an intermediate. This study aimed to investigate whether deoxyhexose metabolism to propionate is more widespread among food-related Lactobacillaceae. We tested nine strains of Lactobacillaceae species for their ability to produce propionate, combining genome analysis with anaerobic cultivation studies. Consecutive bioreactor runs were performed with Liquorilactobacillus ghanensis for 72 h at 30°C and pH 6.5 under aerobic and anaerobic conditions. Substrate utilization, including 13C-labelled L-rhamnose, and fermentation metabolites were determined via liquid chromatography with refractive index or mass spectroscopy detection. We monitored expression of key genes involved in deoxyhexose metabolism by quantitative PCR. Based on genome analysis, seven of nine strains harbored L-rhamnose metabolism-related genes. In addition, L. fuchuensis possessed the pdu operon encoding glycerol/diol dehydratase for 1,2-PD utilization, while L. ghanensis possesses a glycyl radical enzyme (gre). In agreement, L. fuchuensis, L. nagelii, Lactobacillus sp., L. bifermentans, L. satsumensis, L. ghanensis, and L. sucicola grew on L-rhamnose and produced 1,2-PD, but only L. fuchuensis and L. ghanensis produced propionate. Under anaerobic conditions, gre was upregulated, and L. ghanensis produced up to 6.4 mM of propionate. This study uncovered a new pathway for deoxyhexose utilization in Lactobacillaceae, and 13C-stable isotope probing demonstrated that propionate and lactate were the main products derived from L-rhamnose metabolism. Using propionate-producing Lactobacillaceae could provide an effective and clean-label solution for natural food biopreservation.
Lactobacillaceae have a long history in food fermentation as biopreservatives. Recently, Loigolactobacillus coryniformis was shown to metabolize the deoxyhexose L-rhamnose to the antifungal compound propionate with 1,2-propanediol (1,2-PD) as an intermediate. This study aimed to investigate whether deoxyhexose metabolism to propionate is more widespread among food-related Lactobacillaceae. We tested nine strains of Lactobacillaceae species for their ability to produce propionate, combining genome analysis with anaerobic cultivation studies. Consecutive bioreactor runs were performed with Liquorilactobacillus ghanensis for 72 h at 30°C and pH 6.5 under aerobic and anaerobic conditions. Substrate utilization, including 13C-labelled L-rhamnose, and fermentation metabolites were determined via liquid chromatography with refractive index or mass spectroscopy detection. We monitored expression of key genes involved in deoxyhexose metabolism by quantitative PCR. Based on genome analysis, seven of nine strains harbored L-rhamnose metabolism-related genes. In addition, L. fuchuensis possessed the pdu operon encoding glycerol/diol dehydratase for 1,2-PD utilization, while L. ghanensis possesses a glycyl radical enzyme (gre). In agreement, L. fuchuensis, L. nagelii, Lactobacillus sp., L. bifermentans, L. satsumensis, L. ghanensis, and L. sucicola grew on L-rhamnose and produced 1,2-PD, but only L. fuchuensis and L. ghanensis produced propionate. Under anaerobic conditions, gre was upregulated, and L. ghanensis produced up to 6.4 mM of propionate. This study uncovered a new pathway for deoxyhexose utilization in Lactobacillaceae, and 13C-stable isotope probing demonstrated that propionate and lactate were the main products derived from L-rhamnose metabolism. Using propionate-producing Lactobacillaceae could provide an effective and clean-label solution for natural food biopreservation.
AARHUS UNIVERSITY, DENMARK