Anaerobic degradation of sorbic acid by sulfate-reducing and fermenting bacteria: pentanone-2 and isopentanone-2 as byproducts.

Strictly anaerobic bacteria were enriched and isolated from freshwater sediment sources in the presence and absence of sulfate with sorbic acid as sole source of carbon and energy. Strain WoSo1, a Gram-negative vibrioid sulfate-reducing bacterium which was assigned to the species Desulfoarculus (formerly Desulfovibrio) baarsii oxidized sorbic acid completely to CO2 with concomitant stoichiometric reduction of sulfate to sulfide. This strain also oxidized a wide variety of fatty acids and other organic compounds. A Gram-negative rod-shaped fermenting bacterium, strain AmSo1, fermented sorbic acid stoichiometrically to about equal amounts of acetate and butyrate. At concentrations higher than 10 mM, sorbic acid fermentation led to the production of pentanone-2 and isopentanone-2 (3-methyl-2-butanone) as byproducts. Strain AmSo1 fermented also crotonate and 3-hydroxybutyrate to acetate and butyrate, and hexoses to acetate, ethanol, hydrogen, and formate. The guanine-plus-cytosine content of the DNA was 41.8 +/- 1.0 mol%. Sorbic acid at concentrations higher than 5 mM inhibited growth of this strain while strain WoSo1 tolerated sorbic acid up to 10 mM concentration.