Investigation of the potential of Ulva rigida with enzyme and yeast as a functional feed additive

Aquaculture of aquatic products continues to grow faster than other major food production sectors. The increase in growth in aquaculture is primarily attributed to advancements in high-quality feeds. Functional feed additives are derived from various sources and are organic and environmentally friendly for both fish and the environment. Among these functional feed additives are prebiotics, probiotics, seaweeds, fungi, microalgae, enzymes, organic acids, mycotoxin binders, photogenic or photobiotic compounds, and yeasts. In this study, Ulva rigida, was subjected to ultrasound hydrolysis, enzymatic treatment, and yeast fermentation aiming to produce feed additive. The obtained products were compared with unfermented algae meal in terms of their properties like: chemical composition, total antioxidant content, total oxidant content, total phenolics, radical scavenging activity of antioxidants (DPPH) , antioxidant power (FRAP), Minimum inhibitory concentrations (MIC). Ulva rigida was collected from the Marmara Sea, dried and algae meal was obtained and considered as control group Ulva-Ham. Experimental groups were: Ulva-B group: Ulva rigida treated with bromelain enzyme at 50°C for 3 hours. Ulva-M group: Ulva rigida fermented with %1 Saccharomyces cerevisiae at 30°C for 24 hours. Ulva-B+M group: bromelain enzymatic treatment followed by Saccharomyces cerevisiae fermentation. At the end of the enzymatic treatment and fermentation process, the mixture in the experimental groups was dried in the drying cabinet at 40 °C, and then ground into "algae added fermented feed additive". Together with the unfermented control group, 4 different products were obtained and analyzed. According to the results, the best protein content was in Ulva-B+M group (10.13%) compared with other groups, fat content increased inUlva-M group (1.3%) among groups, Ulva-B group had less cellulose content (1.11%) of all groups, oxidative stress OSI , DPPH, FRAP , Fenolik values of the Ulva-Ham group were found to be higher than values of the other groups. MIC (Minimum Inhibition Concentration) against positive and negative bacteria showed the best results in the Ulva-B group ( 625, 312.5, 1250)μg/mL.