Volatile Sulfur Production by Pig Cecal Bacteria in Batch Culture and Screening Inhibitors of Sulfate Reducing Bacteria

Abstract

We studied the effects of specific inhibitors of methanogenesis (2-bromo-ethane sulfonate, BES) and sulfate reduction (sodium molybdate) on volatile sulfur production in batch cultures of pig cecal bacteria. The volatile sulfur concentration in head-space gas was determined by flame-photometric detector gas chromatography. BES stimulated production of hydrogen sulfide (H₂S) and methanethiol, and sodium molybdate completely inhibited the production of these volatile sulfur compounds. The results indicated that dissimilate sulfate reduction is mainly responsible for volatile sulfur production in the hindgut. Therefore the extracts of herbs, food colors, and aroma chemicals were tested for their inhibitory effects on H₂S production by a dissimilatory sulfate-reducing bacteria, Desulfovibrio desulfuricans DSM642. H₂S was measured by the chromatography of the headspace gas, using a flame photometric detector. Of 306 herbal extracts tested, 69 extracts from 38 herbs inhibited H₂S production at 1.0mg/mL. Sisymbrium officinale (hedge mustard) was the most potent inhibitor. Six pigments inhibited H₂S release. Erythrosine and rose Bengal showed inhibitory effects at 0.01mg/mL. Peppermint oil and 96 aroma chemicals were assayed for their effects on H₂S release. Thirty-two aroma chemicals suppressed H₂S production at 0.1mg/mL, and camphene, l-decanol, and 2-nonanone were effective at 0.01mg/mL.