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Biological control of hog waste odor through stimulated microbial Fe(III) reduction.

ABSTRACT: Odor control and disposal of swine waste have inhibited expansion of swine production facilities throughout the United States. Swine waste odor is associated primarily with high concentrations of volatile fatty acids (VFAs). Here, we demonstrate that stimulated Fe(III) reduction in hog manure can rapidly remove the malodorous compounds and enhance methane production by 200%. As part of these studies, we enumerated the indigenous Fe(III)-reducing population in swine waste and identified members of the family Geobacteraceae as the dominant species. These organisms were present at concentrations as high as 2 x 10(5) cells g(-1). Several pure cultures of Fe(III) reducers, including Geobacter metallireducens, Geobacter humireducens, Geobacter sulfurreducens, Geobacter grbiciae, Geothrix fermentans, and Geovibrio ferrireducens, readily degraded some or all of the malodorous VFAs found in swine manure. In contrast, Shewanella algae did not degrade any of these compounds. We isolated an Fe(III) reducer, Geobacter strain NU, from materials collected from primary swine waste lagoons. This organism degraded all of the malodorous VFAs tested and readily grew in swine waste amended with Fe(III). When raw waste amended with Fe(III) was inoculated with strain NU, the VFA content rapidly decreased, corresponding with an almost complete removal of the odor. In contrast, the raw waste without Fe(III) or strain NU showed a marked increase in VFA content and a rapid pH drop. This study showed that Fe(III) supplementation combined with appropriate bioaugmentation provides a simple, cost-effective approach to deodorize and treat swine waste, removing a significant impediment to the expansion of pork production facilities.

SUBMITTER: Coates JD

PROVIDER: S-EPMC1183269 | biostudies-literature | 2005 Aug

REPOSITORIES: biostudies-literature

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Biological control of hog waste odor through stimulated microbial Fe(III) reduction.

Coates John D JD Cole Kimberly A KA Michaelidou Urania U Patrick Jennifer J McInerney Michael J MJ Achenbach Laurie A LA

Applied and environmental microbiology 20050801 8

Odor control and disposal of swine waste have inhibited expansion of swine production facilities throughout the United States. Swine waste odor is associated primarily with high concentrations of volatile fatty acids (VFAs). Here, we demonstrate that stimulated Fe(III) reduction in hog manure can rapidly remove the malodorous compounds and enhance methane production by 200%. As part of these studies, we enumerated the indigenous Fe(III)-reducing population in swine waste and identified members o ...[more]

PMID: 16085869

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Project description:To evaluate the microbial populations involved in the reduction of Fe(III) in an acidic, iron-rich sediment, the anaerobic flow of supplemental carbon and reductant was evaluated in sediment microcosms at the in situ temperature of 12 degrees C. Supplemental glucose and cellobiose stimulated the formation of Fe(II); 42 and 21% of the reducing equivalents that were theoretically obtained from glucose and cellobiose, respectively, were recovered in Fe(II). Likewise, supplemental H(2) was consumed by acidic sediments and yielded additional amounts of Fe(II) in a ratio of approximately 1:2. In contrast, supplemental lactate did not stimulate the formation of Fe(II). Supplemental acetate was not consumed and inhibited the formation of Fe(II). Most-probable-number estimates demonstrated that glucose-utilizing acidophilic Fe(III)-reducing bacteria approximated to 1% of the total direct counts of 4', 6-diamidino-2-phenylindole-stained bacteria. From the highest growth-positive dilution of the most-probable-number series at pH 2. 3 supplemented with glucose, an isolate, JF-5, that could dissimilate Fe(III) was obtained. JF-5 was an acidophilic, gram-negative, facultative anaerobe that completely oxidized the following substrates via the dissimilation of Fe(III): glucose, fructose, xylose, ethanol, glycerol, malate, glutamate, fumarate, citrate, succinate, and H(2). Growth and the reduction of Fe(III) did not occur in the presence of acetate. Cells of JF-5 grown under Fe(III)-reducing conditions formed blebs, i.e., protrusions that were still in contact with the cytoplasmic membrane. Analysis of the 16S rRNA gene sequence of JF-5 demonstrated that it was closely related to an Australian isolate of Acidiphilium cryptum (99.6% sequence similarity), an organism not previously shown to couple the complete oxidation of sugars to the reduction of Fe(III). These collective results indicate that the in situ reduction of Fe(III) in acidic sediments can be mediated by heterotrophic Acidiphilium species that are capable of coupling the reduction of Fe(III) to the complete oxidation of a large variety of substrates including glucose and H(2).

Project description:The ability of Geobacter species to readily donate electrons to extracellular electron acceptors makes the study of their physiology not only important for the understanding of environmental processes, but also for industrial applications such as bioelectronics and electrosynthesis. Studies in G. sulfurreducens have shown that outer surface components, such as c-type cytochromes and conductive type IV pili play an important role in direct electron transfer to extracellular electron acceptors such as Fe(III) oxides and electrodes. However, many of these thoroughly studied outer surface components, including c-type cytochromes, are not well conserved among Geobacter species. In order to better understand which components are involved in extracellular electron transfer in Geobacter species other than G. sulfurreducens, studies were conducted with its close relative G. metallireducens. Whole-genome microarray analysis revealed that 23 of the 91 putative c-type cytochromes encoded in the G. metallireducens genome were upregulated at least 2-fold in cells grown with Fe(III) oxide compared to cells in which Fe(III) citrate was provided as the terminal electron acceptor. Protein identification with liquid-chromatography/mass spectrometry detected 6 c-type cytochromes that were more abundant in the outer surface cell fraction of cells that were grown with Fe(III) oxide as the terminal electron acceptor compared to cells grown on Fe(III) citrate. 22 genes encoding c-type cytochromes were chosen for gene deletion. Deletion of 6 genes encoding for c-type cytochromes, a gene encoding for a lipopolysaccharide biosynthesis-associated protein, and a gene encoding for a NHL- repeat containing protein inhibited growth when Fe(III) oxide was provided as the electron acceptor. This study suggests that there are different roads for extracellular electron transfer in Geobacteraceae since homologous c-type cytochromes have different functions from one species to the other, and novel components not previously found to be essential for extracellular electron transfer were identified.

Dataset Information

Biological control of hog waste odor through stimulated microbial Fe(III) reduction.

Publications

Biological control of hog waste odor through stimulated microbial Fe(III) reduction.

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