Extracellular Enzymes and Antimicrobial Activities of Celluloytic Bacteria from the Gut of Black Surgeonfish (Acanthurus gahhm)

Abstract

The diverse microflora of the gastrointestinal tracts of fish is a promising frontier for the discovery of beneficial bacteria and further microbiological investigations. Isolation, characterization, and determination of the enzymatic and antibacterial activities of the culturable cellulolytic bacteria from the gut of Acanthurus gahhm (black surgeonfish) were investigated. The bacterial strains were isolated from the three gut regions (anterior, mid and hind) using minimum medium. The isolates were characterized morphologically, biochemically and physiologically using standard methods. The isolates were qualitatively tested for activities of extracellular enzymes such as in amylase, protease and lipase. Results showed that the cellulolytic bacteria were Grampositive bacilli, coccobacilli and cocci exhibiting varied biochemical activities most notably fermentative abilities. Physiological tests revealed that the bacteria were able to tolerate high salt concentration.The strains exhibited varying levels of activities for protease and lipase but not on amylase. The isolates were further tested for their antibacterial activity and only one isolate, AG 5H showed signs of efficacy through a zone of inhibition against S. aureus but not for E. coli. The isolate AG5H is interesting because of its high level of enzymatic activities and antibacterial action, which can be exploited for further study for fish health and nutrition and other industrial applications.