Hydrolytic Exoenzymes Produced by Bacteria Isolated and Identified From the Gastrointestinal Tract of Bombay Duck.

Tanim J Hossain,Nabila Rahman,Ferdausi Ali,Sumaiya I Chowdhury,Sujan Dey,Mohammad N A Chowdhury,Halima A Mozumder

doi:10.3389/fmicb.2020.02097

Abstract

Bacteria producing hydrolytic exoenzymes are of great importance considering their contribution to the host metabolism as well as for their various applications in industrial bioprocesses. In this work hydrolytic capacity of bacteria isolated from the gastrointestinal tract of Bombay duck (Harpadon nehereus) was analyzed and the enzyme-producing bacteria were genetically characterized. A total of twenty gut-associated bacteria, classified into seventeen different species, were isolated and screened for the production of protease, lipase, pectinase, cellulase and amylase enzymes. It was found that thirteen of the isolates could produce at least one of these hydrolytic enzymes among which protease was the most common enzyme detected in ten isolates; lipase in nine, pectinase in four, and cellulase and amylase in one isolate each. This enzymatic array strongly correlated to the previously reported eating behavior of Bombay duck. 16S rRNA gene sequence-based taxonomic classification of the enzyme-producing isolates revealed that the thirteen isolates were grouped into three different classes of bacteria consisting of eight different genera. Staphylococcus, representing ∼46% of the isolates, was the most dominant genus. Measurement of enzyme-production via agar diffusion technique revealed that one of the isolates which belonged to the genus Exiguobacterium, secreted the highest amount of lipolytic and pectinolytic enzymes, whereas a Staphylococcus species produced highest proteolytic activity. The Exiguobacterium sp. expressing a maximum of four hydrolases, appeared to be the most promising isolate of all.

Highlights

The gastrointestinal (GI) tract of fishes, like those of other vertebrate-hosts, harbors a complex community of bacteria that significantly influence host’s physiology via metabolic interactions (Sommer and Bäckhed, 2013; Romero et al, 2014; Krishnan et al, 2015; Wang et al, 2018)
The GI bacteria of marine fishes are of particular interest in this regard because microbial enzymes from marine environment are renowned for their extraordinary chemical and metabolic abilities (Debashish et al, 2005; Sarkar et al, 2010; Zhang and Kim, 2010)
The objective of the present work was to investigate the production of extracellular hydrolytic enzymes by bacteria associated with the GI tract of Bombay duck

Summary

Introduction

The gastrointestinal (GI) tract of fishes, like those of other vertebrate-hosts, harbors a complex community of bacteria that significantly influence host’s physiology via metabolic interactions (Sommer and Bäckhed, 2013; Romero et al, 2014; Krishnan et al, 2015; Wang et al, 2018). Being the largest ecosystem on earth, the marine environment constitutes one of the richest reserves of bacteria, majority of which remain entirely unexplored and unexploited (Das et al, 2006; Penesyan et al, 2010; Finore et al, 2014) This massive bacterial population is considered as a potent source of novel enzymes and many other bioactive compounds (Newman and Hill, 2006; Lee et al, 2010; Rao et al, 2017; Romano et al, 2017; Sivaperumal et al, 2017). Studying GI bacteria of marine fishes is of great importance for the discovery of beneficial strains as a promising source of novel biocatalysts

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