Production and use of microbial biomass helping sustainability in tilapia production chain
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In this study, the cultivation of Rubrivivax gelatinosus in fish industry effluent was carried out to cause the depollution of the by-product and generate a protein–carotenoid-rich biomass suitable to be used in tilapia feed. The bacterium was grown in the effluent (inoculum 1% v/v, 30 ± 5 °C, 2000 ± 500 lx, 7 days) and recovered as a biomass (microfiltration + centrifugation + lyophilization), resulting in a decrease of ca. 80% in the chemical oxygen demand of the industry by-product and so putting it within the required limits for wastewater discard in Brazil. The biomass was characterized as a nontoxic product (behavior and physiology data) provided of nutritional and technological properties due to its composition—46% protein, 17% lipid, 5% minerals and 0.3% red oxycarotenoids. When cultured tilapias were fed the biomass (0, 175, 350, 700 or 1400 mg/kg, 80 days), their fillets got redder and had increased protein and carotenoid contents. Feeding the tilapias with the biomass also delayed fillet rancidity up to 80 days of storage under freezing. Therefore, the biotechnological application of R. gelatinosus was demonstrated, providing a useful product and a service for the environment.