Source: SEAMEO BIOTROP's Research Grant | 2013
Abstract:In superintensive fish farming system, the accumulation of toxic compounds (Nitrogen wastes) such as ammonia and nitrite, often cause the degradation of water quality. The heterotrophic microbes are capable of removing the accumulated N wastes and coverting it into their cells biomass; by addition of organic C sources. This study aimed to obtain local strain heterotrophic microbes with the potential to be applied in bioflocs-based superintensive fish farming.
In this study, screening of the potential heterotrophic microbes was carried out through some steps of experiments, including physiological and genetic characterizations, the in-vitro antagonistic test against pathogenic type, biosafety/non pathogenicity test, determination of capability of heterotrophic microbes to improve the nutrient values, as well as biomass production and viability monitoring using commercial and non-commercial media.
L1k was selected as a potential candidate of heterotrophic isolate. Based on the characterization of the physiological, biochemical and molecular of the 16S rRNA gene; L1k was identified as a Gram-positive, Staphylococcus lentus. This isolate was sensitive to the antibiotics Kanamycin, Streptomycin, Penicillin G , and Rifampisin (50 ug.ml-1). L1k showed its capability to inhibit pathogenic type of S. agalactiae and reduced up to 75% of pathogenic cells density compared to control. This isolate also showed its non-pathogenic fature, since the final survival rate of injected fish was 100%. Proximate analysis of fermented fish feed by L1k cells improved the nutrient levels, especially showed by the protein values after 48 hrs. of fermentation. The biomass production of L1k cells performed in a commercial medium of TSB generated logarithmic phase in the first 6th hour after cell inoculation. During this duration the number of cells increased 1000 times from the initial concentration of 105.5 to 108.5 cfu ml-1. Whereas L1k cells grown in a non-commercial medium containing organic carbon source (molasses) and organic proteins (fish feed containing 30 % protein) showed the fastest growth of L1k occurred after cells inoculation until the 36th hour, where the cells density increased 100 times from 102.6 to 104.6 cfu ml-1. Although the cell growth of heterotrophic isolates L1k in this medium is slower, however it is far more economical, applicable for farmers, easy to find the source of materials and is similar to the condition for bioflocs-based superintensive fish farming.
Keywords: heterotrophic, bioflocs, L1k, superintensive, fish farming, N waste
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