ARS | Publication request: Inhibitory Effects of Condensed Tannins on Sulfate-Reducing Bacteria Populations and Hydrogen Sulfide Production from Swine Manure

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: August 27, 2010
Publication Date: N/A

Technical Abstract: Odorous compounds and emissions associated with consolidated storage of swine manure are produced as a result of anaerobic microbial digestion of materials present in the manure. Hydrogen sulfide (H2S) is one such offensive and toxic odorant that can reach hazardous levels during manure storage and handling. Production of H2S involves sulfate reduction largely by anaerobic sulfate-reducing bacteria (SRB). The objective of this study was to test the effects of applying condensed tannins to swine manure in an effort to reduce odors and emissions and target bacterial groups responsible for odor production. Fresh swine manure was diluted in anaerobic buffer to a 10% final solution, then treated with condensed tannins ranging in concentration from 0.1-1% w/v and incubated anaerobically at room temperature. H2S production was measured and aliquots of manure were removed periodically for enumeration of the bacterial populations. Treatment of swine manure with tannins resulted in a decrease in H2S production, with the highest treatment dose of 1% w/v tannins inhibiting 99% of H2S production, compared to the control. A quantitative polymerase chain reaction (qPCR) approach was used to target and quantify the SRB population in manure, in response to treatment with tannins. This assay targeted the conserved dsrA gene of SRB, which encodes a key enzyme involved in sulfate respiration and production of H2S. Addition of tannins reduced the SRB population in stored swine manure by 95% after 7 days of treatment, and this reduction was maintained throughout the course of the study. Specific SRB groups were targeted for enumeration and data suggest that Desulfobulbus-like SRB were most significantly affected by condensed tannin treatment. Total bacteria, as quantified by 16S rDNA-targetted qPCR, were also significantly reduced by tannin treatment. This study demonstrates that condensed tannins are effective at reducing both H2S production and bacterial populations in the manure.