Anaerobic degradation of glycerol by Desulfovibrio fructosovorans and D. carbinolicus and evidence for glycerol-dependent utilization of 1,2-propanediol

The degradation of glycerol by #Desulfovibrio carbinolicus$ and #Desulfovibrio fructosovorans$ was tested in pure culture with sulfate and in coculture with #Methanospirillum hungatei$. #Desulfovibrio carbinolicus$ degraded glycerol into 3-hydroxypropionate with the formation of sulfide in pure culture and methane in the coculture. The maximum growth rates were 0.063/h in pure culture and 0.014/h in coculture (corresponding growth yields : 8.9 and 6.0 g dry weight/mol glycerol). With #D. fructosovorans$, the pathway of glycerol degradation depended upon the terminal electron acceptor. Acetate and sulfide were produced in the presence of sulfate, while 3-hydroxypropionate and methane were formed by the syntrophic association with #M. hungatei$. The maximum growth rates were 0.057/h in pure culture and 0.020/h in coculture (corresponding growth yields : 8.9 and 6.0 g dry weight/mol glycerol). In a medium containing both glycerol and 1,2-propanediol but no sulfate, #D. carbinolicus$ and #D. fructosovorans$ degraded both substrates. A drop in the concentration of 1,3-propanediol was observed, and propionate and n-propanol production was recorded. Putative biochemical pathways of 1,2-propanediol degradation by #D. carbinolicus$ and #D. fructosovorans$ indicated that the enzymes involved in this metabolism are present only when the strains are grown on a mixture of 1,2-propanediol and glycerol without sulfate. (Résumé d'auteur