Optimization of growth characteristics for the potential probiotics to be used in fish aquaculturing

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Tezin Türü: Yüksek Lisans

Tezin Yürütüldüğü Kurum: Orta Doğu Teknik Üniversitesi, Mühendislik Fakültesi, Gıda Mühendisliği Bölümü, Türkiye

Tezin Onay Tarihi: 2013

Öğrenci: NİHAL DESTAN AYTEKİN

Danışman: HALUK HAMAMCI

Özet:

The aquaculturing of marine and fresh water fish is continually increasing in the world and in Turkey. Of the three fish species; sea bass (Dicentrarchus labrax), seabream (Sparus aurata) and trout (Oncorhynchus mykiss), the latter has the highest share in Turkey, with a current production rate of 170000 tons per annum. The use of antibiotics in true feed is being phased out in the world. Probiotics have emerged one way of making up for the lack of antibiotics in the feed. In order to increase the probiotics usage, optimization of the strains’ growth conditions, development of sustainable and economic manufacturing process are required. While there are commercial probiotics for the farm animals, there is none so far produced for the aquaculture, in Turkey. Enterococcus faecium is one of the widely used probiotic in farm animals sector. Due to the characteristics of E. faecium to tolerate acid and bile salts in the gastrointestinal tract, to produce inhibitory compounds and show antagonistic effects towards target fish pathogens, to stimulate immune system and better growth, the microorganism may be evaluated as a strong potential probiotic for aquaculturing. Aim of this study was to optimize the culture conditions in order to maximize the biomass concentration and the biomass yield of E. faecium. In the first part of this study, several growth media, temperature and pH values were tested. In the second part, the microorganism was grown using different fermentation modes in bioreactor. In the last part, a membrane filtration system was incorporated to the fermentor in order to recycle biomass. Results showed that temperature 37 °C and pH 6.5 yielded higher amount of biomass compared to others. The biomass concentration was 6.3 g/L at pH 6.5, 37 °C, 350 rpm when the fresh medium was added continuously and biomass was recycled back to the fermentor using the membrane filter.