Isolation of cellulolytic bacteria from the gastro-intestinal tract of Achatina fulica (Gastropoda: Pulmonata) and their evaluation for cellulose biodegradation

Abstract

Gastrointestinal tract of Giant African snail, Achatina fulica was investigated as a source for isolation of cellulose degrading bacteria. The cellulose degrading bacteria from different gastrointestinal tract regions such as esophagus, crop, stomach, intestine and rectum were enriched in carboxymethyl cellulose and identified. Thirty two cellulose degrading bacteria belonging to two major phyla namely Proteobacteria and Firmicutes were enriched, isolated and identified by 16S rDNA amplification and sequencing. Based on plate based assay, 18 of these isolates displayed cellulase activity and were identified as the members of Bacillus, Achromobacter, Ochrobactrum and Klebsiella. Among the 18 isolates, 5 isolates with high activity were further studied for various enzyme activities such as endoglucanase, exoglucanase and xylanase on different lignocellulosic substrates. Isolate identified as Ochrobactrum sp. K38 exhibited the highest CMCase activity (501.75 IU/ml extract) after 14 days of incubation. The highest avicelase activity (3116.92 IU/ml extract) was shown by Bacillus subtilis Cf60 on Filter paper as substrate after 10 days of incubation whereas all other isolates showed a low xylanase activity on all tested substrates except filter paper. The present study demonstrates the utility of snail gut as a rich source for isolation of cellulose degrading bacteria that can have many industrial applications.