Use of starch and potato peel waste for perchlorate bioreduction in water

Abstract

The cost of carbon substrates for microbial reduction of perchlorate (ClO 4 −) is central to the success and competitiveness of a sustainable bioremediation strategy for ClO 4 −. This study explored the potential application of starch in combination with an amylolytic bacterial consortia and potato peel waste for ClO 4 − bioreduction. We obtained a potent amylolytic bacterial consortium that consisted of a Citrobacter sp . S4, Streptomyces sp. S2, Flavobacterium sp. S6, Pseudoxanthomonas sp. S5, Streptomyces sp. S7, and an Aeromonas sp. S8 identified by 16S rDNA sequencing. ClO 4 − concentration substantially decreased in purified starch medium inoculated with the amylolytic bacterial consortium and Dechlorosoma sp. perclace. Potato peel waste supported ClO 4 − reduction by perclace with the rate of ClO 4 − reduction being dependent on the amount of potato peels. Over 90% ClO 4 − removal was achieved in 4 days in a single time point experiment with 2% (w/v) potato peels waste. ClO 4 − reduction in a non-sterile 0.5% potato peel media inoculated with perclace occurred with an initial concentration of 10.14±0.04 mg L −1 to 2.87±0.4 mg L −1 (71.7% reduction) within 5 days. ClO 4 − was not detected in the cultures in 6 days. In a non-sterile 0.5% potato media without perclace, ClO 4 − depletion occurred slowly from an initial value of 9.99±0.15 mg L −1 to 6.33±0.43 mg L −1 (36.63% reduction) in 5 days. Thereafter, ClO 4 − was rapidly degraded achieving 77.1% reduction in 7 days and not detected in 9 days. No susbstantial reduction of ClO 4 − was observed in the sterile potato peel media without perclace in 7 days. Redox potential of the potato peel cultures was favorable for ClO 4 − reduction, decreasing to as low as −294 mV in 24 h. Sugar levels remained very low in cultures effectively reducing ClO 4 − and was substantially higher in sterilized controls. Our results indicate that potato peel waste in combination with amylolytic microorganisms and Dechlorosoma sp. perclace can be economically used to achieve complete ClO 4 − removal from water.