Thermoxylanolytic and Thermosaccharolytic Potential of a Heat Adapted Bacterial Consortium Developed From Goat Rumen Contents

Khusboo Lepcha,Subham Kanoo,Prayatna Sharma,Puja Bk,Shilpi Ghosh,Arijita Basak

doi:10.3389/fenrg.2021.755779

Abstract

Thermoactive xylanases have important applications in the industrial deconstruction of lignocellulosic plant biomass, due to their sustained activity even at high temperature conditions of industrial bioreactors. We herein report the development of a thermoactive xylanolytic microbial consortium from the semi-digested contents of goat rumen and characterization of the xylanolytic enzyme cocktail produced by it. The consortium exhibited maximum endoxylanase activity at pH6 and at 60°C. Zymogram analysis revealed the production of multiple xylanases. The xylanase cocktail was stable over a pH range of 5–9 after pre-incubation for 3 h. It retained 74% activity after pre-incubation (60°C) for 50 min. It’s activity was enhanced in presence of β-mercaptoethanol, NH4+, Mg2⁺ and Ca2⁺, whereas Hg2⁺ had an inhibitory effect. The xylanolytic cocktail was further utilized for the saccharification of alkali pre-treated rice straw and mushroom spent rice straw. Saccharification was studied quantitatively using the dinitrosalicylic acid method and qualitatively using scanning electron microscopy. Results indicated the potential of the xylanolytic cocktail for the saccharification of rice straw and highlighted the significance of chemical and/or biological pre-treatment in improving the accessibility of the substrate towards the xylanase cocktail.

Highlights

With a rampant increase in agro-industrial activities, large quantities of agro residues are being generated worldwide
With the aim to develop an industrially applicable enzyme cocktail, this study focuses on the development of a thermotolerant xylanolytic consortium from goat rumen contents, characterization of it’s xylanolytic enzymes and it’s utilization in the saccharification of alkali pre-treated Rice straw (RS) and spent rice straw (SRS) at high temperatures
The xylanolytic potential of Rice Straw-based Consortium (RSC) was revealed by the formation of clearance zones on agarose gel supplemented with 1% birch wood xylan, when stained with 0.1% Congo Red solution

Summary

Introduction

With a rampant increase in agro-industrial activities, large quantities of agro residues are being generated worldwide. Such biomass being inexpensive and rich in polysaccharides (cellulose and hemicelluloses) can be subjected to microbial deconstruction (Singh et al, 2019) and the fermentable monosaccharides released can act as building blocks for value added products, such as chemicals, biofuels, etc (Aggarwal et al, 2017). Bacterial consortia with thermostable enzyme systems would be desirable for large scale industrial saccharification of prolonged duration due to lower possibilities of microbial contamination, reduced medium viscosity, increased solubility and surface area of substrate (Cao et al, 2014; Synowiecki., 2010; Gomes et al, 2016). Development of a thermophilic consortium can be of significance in the microbial production of thermostable xylanases for improved industrial hydrolysis of complex agroresidues

Methods

Results

Conclusion