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Research Project: Development of Management Strategies to Mitigate Pre-harvest Microbial-derived Off-flavors in Fish Grown in Aquaculture

Location: Natural Products Utilization Research

Title: Effects of pH on biomass, geosmin, and 2-methylisoborneol production and cellular activity by Streptomyces luridiscabiei isolated from a rainbow trout recirculating aquaculture system

Author
item Schrader, Kevin
item Harries, Marcuslene
item Page, Phaedra

Submitted to: Annals of Aquaculture and Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/28/2016
Publication Date: 12/6/2016
Publication URL: http://handle.nal.usda.gov/10113/5642504
Citation: Schrader, K., Harries, M.D., Page, P. 2016. Effects of pH on biomass, geosmin, and 2-methylisoborneol production and cellular activity by Streptomyces luridiscabiei isolated from a rainbow trout recirculating aquaculture system. Annals of Aquaculture and Research. 3(3):1027.

Interpretive Summary: A pH of 7.5 and 8.0 were found to produce the largest amounts of growth and earthy-musty off-flavor compounds by a type of bacteria isolated from a recirculating aquaculture system (RAS). Preliminary results indicate that pH 6.5 and 7.0 may potentially reduce the intensities of earthy and musty off-flavors in fish raised in RAS.

Technical Abstract: Rainbow trout (Oncorhynchus mykiss) grown in recirculating aquaculture systems (RAS) can acquire “earthy” and “musty” taints due to bioaccumulation of geosmin and 2-methyisoborneol (MIB), respectively, in the fish flesh. Certain species of actinomycetes which produce these compounds are attributed as the main causes of off-flavors in RAS. Among various taint-producing actinomycetes isolated from RAS, Streptomyces luridiscabiei was previously determined to produce the greatest amounts of geosmin and MIB at 15 oC, the water temperature maintained in the RAS. In this study, the effects of pH on growth, off-flavor compound production, and cellular activity by S. luridiscabiei were determined. Laboratory cultures were monitored over a 7-day period for biomass and adenosine 5'-triphosphate production in addition to geosmin and MIB concentrations. There was not a dramatic difference in growth by S. luridiscabiei at different pH (6.0 to 9.0), but cellular activity was significantly (P < 0.05) higher at pH 7.0 at 7 days. Significantly (P < 0.05) higher amounts of geosmin and MIB were produced at pH 7.5 and 8.0. Maintaining water pH in the RAS from 6.5 to 7.0 may decrease geosmin and MIB production by S. luridiscabiei and subsequently reduce the intensities of off-flavor problems while maintaining adequate nitrification.