ISOLATION, CHARACTERIZATION AND PERFORMANCE OF EXTRACELLULAR POLYSACCHARIDES PRODUCING BACTERIA IN OUTDOOR BIOFLOC CULTURE PONDS OF CHITRALADA STRAIN OF NILE TILAPIA

The present study aimed to isolate and characterize the Extracellular polymeric substance (EPS) producing bacteria from biofloc reared Chitralada strain of Nile Tilapia  in outdoor 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, 7 isolates were found to produce EPS. Based on 16s rRNA sequence analysis the isolates were identified as Bacillus subtilis, B. megaterium, B. infantis, B.cereus, Pseudomonas balearica, P.mendocina and P. alcaligenes. The highest production of EPS was recorded in B.cereus (1.25g/L).  EPS extracted from Bacillus cereus was reported to have higher protein (89µg/ml) and B. subtilis possessed higher carbohydrate (753.75µg/ml). Maximum flocculating ability of 40.18% in B. cereus and higher emulsifying activity of 63.53% was observed in B. megaterium. The EPS extracted from B.infantis showed lower sludge volume index on its treatment with aquaculture sludge (15.38 ml/g). Absorption band in the range of 4000Cm^-1 to 450Cm^-1 using FTIR analysis confirmed the presence of characteristic functional bands arising from polysaccharides, nucleic acids and proteins. The results indicated the presence of EPS producing bacteria in biofloc based Nile Tilapia aquaculture systems.