THIS 2-YEAR PROJECT IS PROPOSED TO DEVELOP A COST-EFFECTIVE METHOD OF PRODUCING THE ORGANIC ACID POLY-&BETA;-HYDROXYBUTYRATE (PHB) AND APPLYING IT TO FEED TO ENHANCE IMMUNE RESPONSES AND DISEASE RESISTANCE OF HYBRID STRIPED BASS AND NILE TILAPIA TO STREPTOCOCCUS INIAE AND AEROMONAS HYDROPHILA, LEADING FISH PATHOGENS. THIS INTER-DISCIPLINARY PROJECT WILL DEVELOP PROCESSES FOR HIGH-YIELD PRODUCTION OF PHB FROM ORGANIC WASTES BY AN EFFECTIVE PHB-PRODUCING CULTURE OF ZOBELLELLA DENITRIFICANS ZD1. IN ADDITION, THE DIETARY APPLICATION OF PHB WILL BE REFINED WITH BOTH IN VITRO AND IN VIVO ASSAYS TO MAXIMIZE ITS EFFECTIVENESS IN ENHANCING IMMUNE RESPONSES AND INCREASING RESISTANCE OF HYBRID STRIPED BASS AND NILE TILAPIA TO PROMINENT BACTERIAL DISEASES, NAMELY STREPTOCOCCUS INIAE AND AEROMONAS HYDROPHILA. THE OUTCOMES OF THIS RESEARCH ARE EXPECTED TO POSITIVELY AFFECT U.S. AQUACULTURE BY PROVIDING A NOVEL MEANS OF COMBATING INFECTIOUS DISEASES WITHOUT ANTIBIOTICS OR OTHER CHEMOTHERAPEUTIC AGENTS. THE EFFICIENT PRODUCTION OF THE NATURAL IMMUNE-STIMULANT PHB FROM AQUACULTURE EFFLUENTS WILL PROVIDE THE COMPOUND WHICH BY DIETARY ADMINISTRATION WILL INCREASE IMMUNE RESPONSES AND DISEASE RESISTANCE OF HYBRID STRIPED BASS AND NILE TILAPIA. IT IS LIKELY THAT PHB ALSO WILL HAVE SIMILAR IMMUNOLOGICAL EFFECTS ON OTHER FISH SPECIES CULTURED IN THE U.S.