Deoxyhexose metabolism of food-related Lactobacillaceae and identification of a distinctive 1,2-propanediol utilization pathway in Liquorilactobacillus ghanensis DSM 18630

Lactobacillaceae have a long history as natural or starter cultures in food and produce antimicrobial short-chain carboxylic acids (SCCA) during fermentation. Recently, Loigolactobacillus coryniformis was shown to metabolize the deoxyhexose L-rhamnose to the antifungal SCCA propionate with 1,2-propanediol (1,2-PD) as an intermediate. This study aimed to investigate whether deoxyhexose metabolism is more widespread among food-related Lactobacillaceae . We tested nine Lactobacillaceae species (one strain each) for their ability to produce propionate combining genome analysis with anaerobic cultivation in Hungate tubes. Substrate utilization included 13 C-labelled L-rhamnose. Bioreactor runs were performed for 72 h at 30°C and pH 6.5 under aerobic and anaerobic conditions and expression of key genes was monitored. Seven out of nine strains including four Liquorilactobacillus species harbored deoxyhexose metabolism-related genes and produced 1,2-PD. In addition, Latilactobacillus fuchuensis that possessed the pdu operon encoding glycerol/diol dehydratase, and Liquorilactobacillus ghanensis with a gene encoding a glycyl radical enzyme (GRE) formed propionate, which was confirmed by 13 C-stable isotope probing. In bioreactors , L. ghanensis gre expression and propionate formation were regulated by the presence of oxygen. This study identified new strains that were able to use deoxyhexoses and uncovered a new deoxyhexose utilization pathway in L. ghanensis . Propionate-producing Lactobacillaceae have potential to produce antifungal fermentates for food biopreservation. • Lactobacillaceae shared the potential to metabolize deoxyhexoses • L. ghanensis utilized an alternative pathway to metabolize 1,2-PD to propionate • Propionate and lactate were the two main metabolites from L-rhamnose metabolism • Oxygen affected gene expression regulation and propionate formation by L. ghanensis