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Research Project: Management of Off-flavors and Undesirable Bacteria in Aquaculture

Location: Natural Products Utilization Research

2010 Annual Report

1a. Objectives (from AD-416)
1)Discover and develop management strategies for mitigating pre-harvest microbial-derived off-flavors in fish cultured in re-circulating aquaculture systems (RAS) to help reduce off-flavor delayed harvest. 2)Discover and conduct primary development of novel natural and natural-based compounds for controlling disease causing microorganisms in pond-based production systems.

1b. Approach (from AD-416)
Isolate and identify the microorganisms responsible for the most common environmental off-flavors in finfish cultured in recirculating aquaculture systems (RAS). Perform laboratory physiology studies on the off-flavor microorganisms to determine the environmental and nutritional conditions that favor growth and production of the off-flavor compounds. Conduct depuration studies to identify factors such as adipose content of the fish flesh and fish size that may affect depuration rates. Perform efficacy studies to determine if activated carbon filtration can be utilized to reduce levels of the off-flavor compounds in the RAS water and subsequently in fish flesh. Determine the efficacy of antifouling coatings to reduce biofilm formation on RAS culture tank walls and subsequently reduce levels of microbial off-flavor compounds in RAS-cultured fish. Conduct bacterial bioassays to identify natural or natural-product based compounds as potential leads for use in managing diseases in catfish aquaculture. Perform primary development of promising natural compounds identified from bacterial bioassays for use as therapeutic drugs to manage common catfish diseases and improve catfish health.

3. Progress Report
In 2009-2010, several species of odorous bacteria were isolated from organic matter obtained at different locations within a series of recirculating aquaculture systems (RAS) at the research facility located at The Conservation Fund Freshwater Institute, Shepherdstown, West Virginia. These novel isolates of odor-producing bacteria were determined to be contributors to the earthy-musty off-flavor in the RAS-cultured rainbow trout. The identification of the microbial sources of earth-musty taints in RAS-cultured fish is the first step in the development of methods to mitigate the earthy-musty off-flavor problems that may occur in RAS-cultured finfish. In collaboration with the University of Naples Federico II, Portici, Italy, two compounds produced by certain plants were discovered to inhibit the growth of disease-causing bacteria in pond-raised channel catfish. These natural compounds may eventually be useful as therapeutants and alternatives to current management approaches (e.g., medicated feed containing antibiotics) to manage and prevent common bacterial diseases in cultured channel catfish.

4. Accomplishments

Review Publications
Bialonska, D., Kasimsetty, S.G., Schrader, K., Ferreira, D. 2009. The Effect of Pomegranate (Punica granatum L.) Byproducts and Ellagitannins on the Growth of Human Gut Bacteria. Journal of Agricultural and Food Chemistry. 57:8344-8349.

Schrader, K. 2010. Plant Natural Compounds with Antibacterial Activity Towards Common Pathogens of Pond-Cultured Channel Catfish (Ictalurus punctatus). Toxins. 2:1676-1689.