Colonization of enzymatic bacterial flora in biofloc grown shrimp Penaeus vannamei and evaluation of their beneficial effect

Experiments were conducted to explore the colonization of beneficial bacteria in shrimp Penaeus vannamei grown in different sources of biofloc and clear water. Beneficial effect in terms of extracellular enzyme production and antibiofilm activity of the isolated strains was determined. Heterotrophic bacterial population were isolated by using different agar plates and resulted in isolation of 94 isolates in total. Extracellular enzyme production such as amylase, protease, lipase, cellulase, xylanase, and pectinase were screened. Antibiofilm activity of culture supernatants of enzymatic strains against pathogenic Vibrio was also determined. Out of 94 strains screened, 36 strains were found to produce amylase enzyme, 20 strains protease, 27 strains lipase, 6 strains cellulase, and 8 strains xylanase. Totally, 21 isolates selected for further identification and different species of Cobetia, Exiguobacterium, Bacillus, Marinilactibacillus, Staphyllococcus, and Novosphingobium genera from biofloc treatments were identified. In control group animals, strains of Bacillus and Exiguobacterium were isolated and identified. The genus Exiguobacterium was found common in all the different treatments and control. The result showed that shrimp grown on biofloc system allows colonizing more beneficial bacteria in gut than control. Few promising strains under Bacillus genus were found to produce all the extracellular enzymes along with antibiofilm activity.