ANAEROBIC DEGRADATION OF GLYCEROL BY DESULFOVIBRIO FRUCTOSOVORANS ANDD-CARBINOLICUS AND EVIDENCE FOR GLYCEROL-DEPENDENT UTILIZATION OF 1,2-PROPANEDIOL

The degradation of glycerol by Desulfovibrio carbinolicus and Desulfov ibrio fructosovorans was tested in pure culture with sulfate and in co culture with Methanospirillum hungatei. Desulfovibrio carbinolicus deg raded 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(-1) in pure culture and 0.014 h(-1) in coculture (corres ponding 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 ra tes were 0.057 h(-1) in pure culture and 0.020 h(-1) in coculture (cor responding 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 a nd n-propanol production was recorded. Putative biochemical pathways o f 1,2-propanediol degradation by D. carbinolicus and D. fructosovorans indicated that the enzymes involved in this metabolism are present on ly when the strains are grown on a mixture of 1,2-propanediol and glyc erol without sulfate.