ISOLATION AND CHARACTERIZATION OF SULPHUR OXIDISING BACTERIA IN THE GROWOUT CULTURE OF GENETICALLY IMPROVED FARM TILAPIA (GIFT) USING BIOFLOC TECHNOLOGY

The present study aimed to isolate and characterize the Sulphur oxidizing bacteria from biofloc reared GIFT Tilapia ponds. Distillery spent wash was used as a carbon source to maintain the C: N ratio at 10:1 in the fish culture ponds and screening of bacteria were done fortnightly in 180 days culture. Out of 40 bacterial isolates, 11 isolates were found to reduce the colour of the bromocresol purple as an initial screening of sulphur oxidizing bacteria (Dye reduction test).  Based on 16s rRNA sequence analysis the isolates were identified as Bacillus subtilis, B. megaterium, B. infantis, B.cereus, Pseudomonas balearica, P.mendocina, P. alcaligenes, Klebsiella pneumonia, Atlantibacter hermanii Exiguobacterium profundum and Staphylococcus gallinrum. The highest sulphate prodution was recorded in Pseudomonas balearica (1.6mM) followed by B. infantis (1.56 mM). The sulphide reduction ability was checked for the 11 isolates by inoculating in the broth supplemented with 5ppm of sodium sulphide. The sulphide reduction was checked once in 24, 48, 72 and 96hrs for all the 11 isolates. B. infantis showed the highest reduction percentage of 43.08%. The study proved the presence of sulphur oxidizing bacteria in the biofloc culture ponds of GIFT Tilapia and are identified as sulphide reducers as a mode of bioremediation of excess hydrogen sulphide in the culture ponds.