Influence of inoculum selection on the utilisation of volatile fatty acid and glucose in sulfate reducing reactors

ABSTRACT

The capacity of three inocula (sewer biofilm, mangrove and estuary sediment) to utilise typical fermentation products of municipal solid waste for biological sulfate reduction was investigated. Each inoculum was used in two reactors, one fed a mixture of volatile fatty acids and another fed glucose to provide a suite of fermentation products via naturally occurring fermentation. Following 228 days of reactor operation, reactors inoculated with mangrove and estuary sediments exhibited higher sulfate reducing efficiencies (80–88%) compared to the biofilm-inoculated reactors (32–49%). Minimal use of acetate and its accumulation in the biofilm-inoculated reactors pointed to the high abundance of incomplete-oxidising sulfate reducing bacteria (SRB), Desulfovibrio and Desulfobulbus (90–96% of the sulfate reducing population). Although Desulfovibrio was also prominent in reactors inoculated with mangrove and estuary sediments, Desulfobacter, a known acetoclastic sulfate reducer, emerged from trace levels in these sediment (0.01% abundance in the estuary sediments and below detection in the mangrove sediments) to comprise 14%–70% of the sulfate reducing population at the end of reactor operation.

GRAPHICAL ABSTRACT

KEYWORDS:

• Sulfate-reducing bacteria
• inoculum
• acetate
• volatile fatty acids

Acknowledgments

This project was supported by the Australian Government Research Training Program Scholarship and the Australian Research Council Discovery Grant [DP140104572]. The authors would like to acknowledge Dr. Beatrice Keller-Lehmann and Nathan Clayton for their helpful assistance with the chemical analyses and Adam Shypanski for providing the inoculum used in this study. The authors acknowledge the support of the Australian Centre for Ecogenomics at the University of Queensland for their DNA extraction and pyrosequencing services.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This project was supported by the Australian Government Research Training Program Scholarship and the Australian Research Council Discovery Grant [DP140104572].