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In the current study, the inhibitory effects of condensed quebracho tannins on in vitro swine manure for reduction of microbial activity and reduced production of gaseous emissions, including the toxic odorant hydrogen sulfide produced by sulfate-reducing bacteria (SRB), was examined.
Swine manure was collected from a local swine facility, diluted in anaerobic buffer, and mixed with 1 % w/v fresh feces. This slurry was combined with quebracho tannins, and total gas and hydrogen sulfide production was monitored over time. Aliquots were removed periodically for isolation of DNA to measure the SRB populations using quantitative PCR.
Addition of tannins reduced overall gas, hydrogen sulfide, and methane production by greater than 90 % after 7 days of treatment and continued to at least 28 days. SRB population was also significantly decreased by tannin addition. qRT-PCR of 16S rDNA bacteria genes showed that the total bacterial population was also decreased in these incubations.
These results indicate that the tannins elicited a collective effect on the bacterial population and also suggest a reduction in the population of methanogenic microorganisms as demonstrated by reduced methane production in these experiments. Such a generalized effect could be extrapolated to a reduction in other odor-associated emissions during manure storage.
Terence R. Whitehead, Cheryl Spence, Michael A. Cotta. Inhibition of hydrogen sulfide, methane, and total gas production and sulfate-reducing bacteria in in vitro swine manure by tannins, with focus on condensed quebracho tannins. Applied Microbiology and Biotechnology. September 2013, Volume 97, Issue 18, pp 8403-8409. doi: 10.1007/s00253-012-4562-6
