Bioconversion of chitin and concomitant production of chitinase and N-acetylglucosamine by novel Achromobacter xylosoxidans isolated from shrimp waste disposal area

Kumaran Subramanian,Anandajothi Elamaran,Guru Prasad Srinivasan,Balamurugan Sadaiappan,Wilson Aruni,Prasannabalaji Nainangu,Selvaraj Bharathi,Pugazhvendan Sampath Renuga,Mahendran Subramanian,Alagappan Kumarappan,Rajasekar Thirunavukarasu,Deivasigamani Balaraman

doi:10.1038/s41598-020-68772-y

Abstract

Marine pollution is a significant issue in recent decades, with the increase in industries and their waste harming the environment and ecosystems. Notably, the rise in shellfish industries contributes to tons of shellfish waste composed of up to 58% chitin. Chitin, the second most ample polymer next to cellulose, is insoluble and resistant to degradation. It requires chemical-based treatment or enzymatic hydrolysis to cleave the chitin polymers. The chemical-based treatment can lead to environmental pollution, so to solve this problem, enzymatic hydrolysis is the best option. Moreover, the resulting biopolymer by-products can be used to boost the fish immune system and also as drug delivery agents. Many marine microbial strains have chitinase producing ability. Nevertheless, we still lack an economical and highly stable chitinase enzyme for use in the industrial sector. So we isolate a novel marine bacterial strain Achromobacter xylosoxidans from the shrimp waste disposal site using chitin minimal medium. Placket–Burman and central composite design statistical models for culture condition optimisation predicted a 464.2 U/ml of chitinase production. The culture conditions were optimised for maximum chitinase production recording up to 467 U/ml. This chitinase from the A. xylosoxidans was 100% active at an optimum temperature of 45 °C (withstand up to 55 °C) and pH 8 with 80% stability. The HPLC analysis of chitinase degraded shellfish waste reveals a major amino acid profile composition—arginine, lysine, aspartic acid, alanine, threonine and low levels of isoleucine and methionine. These chitinase degraded products and by-products can be used as supplements in the aquaculture industry.

Highlights

IntroductionAbout 1012–1014 tons of chitin is produced as waste per year[1] and the major problem for the aquaculture industries is to dispose of this waste
Fourteen bacterial strains were isolated from the shrimp waste disposal site, among the 14 strains one bacterial strain showing maximal chitinase activity (1.8 U/ml, Fig. 1) was selected, and this strain was named as chitinase producing bacterial strain 4 (CHI4)
The 1091 bp 16S rDNA sequence and blast analysis showed that this bacterial strain was closely similar to Achromobacter xylosoxidans

Summary

Introduction

About 1012–1014 tons of chitin is produced as waste per year[1] and the major problem for the aquaculture industries is to dispose of this waste. If it is not adequately disposed of or degraded, this waste may cause potential peril to the natural environment and b iodiversity[2]. Bioconversion of the squandered chitinous waste to valuable chitooligosaccharides involves procedures such as deproteinisation, demineralisation or hydrolysis. The shrimp waste disposal site should be a potential source for identifying and isolating a suitable chitinase producing bacteria

Methods

Results

Conclusion