Extremophilic Prokaryotic Endoxylanases: Diversity, Applicability, and Molecular Insights.

Digvijay Verma

doi:10.3389/fmicb.2021.728475

Abstract

Extremophilic endoxylanases grabbed attention in recent years due to their applicability under harsh conditions of several industrial processes. Thermophilic, alkaliphilic, and acidophilic endoxylanases found their employability in bio-bleaching of paper pulp, bioconversion of lignocellulosic biomass into xylooligosaccharides, bioethanol production, and improving the nutritious value of bread and other bakery products. Xylanases obtained from extremophilic bacteria and archaea are considered better than fungal sources for several reasons. For example, enzymatic activity under broad pH and temperature range, low molecular weight, cellulase-free activity, and longer stability under extreme conditions of prokaryotic derived xylanases make them a good choice. In addition, a short life span, easy cultivation/harvesting methods, higher yield, and rapid DNA manipulations of bacterial and archaeal cells further reduces the overall cost of the product. This review focuses on the diversity of prokaryotic endoxylanases, their characteristics, and their functional attributes. Besides, the molecular mechanisms of their extreme behavior have also been presented here.

Highlights

Specialty section: This article was submitted to Extreme Microbiology, a section of the journal Frontiers in MicrobiologyReceived: 21 June 2021 Accepted: 06 August 2021 Published: 09 September 2021Citation: Verma D (2021) Extremophilic Prokaryotic Endoxylanases: Diversity, Applicability, and Molecular Insights
A polyextremophilic endoxylanase of B. halodurans TSEV1 was successfully employed for the bleaching of kraft pulp at the higher pH of 10.0 (Kumar and Satyanarayana, 2012)
The estimated global industrial enzyme market was approximately US$ 5.6 billion during 2019, and it is projected to rise at a compound annual growth rate (CAGR) of 6.4% from 2020 to 2027,2 where xylanolytic enzymes share a significant chunk of total carbohydrases

Summary

INTRODUCTION

Specialty section: This article was submitted to Extreme Microbiology, a section of the journal Frontiers in Microbiology. Thermotoga (Bok et al, 1994; Winterhalter et al, 1995; Shi et al, 2013), Clostridium (Rani and Nand, 2000; Heinze et al, 2017), Caldicellulosiruptor (Luthi et al, 1990), Geobacillus (Sharma et al, 2007; Kumar et al, 2013b; Verma et al, 2013a), Bacillus (Mamo et al, 2006; Kumar et al, 2013a), and Streptomycetes (Bajaj and Singh, 2010) are the major genera for exhibiting thermophilic endoxylanases The majority of these bacteria have been isolated from thermophilic habitats, which could be the reason for showing the reflection of their environment in their properties (Saleem et al, 2012; Verma et al, 2019; Irfan et al, 2020). The GH-10 and GH-11 xylanases of either bacteria, archaea, or fungal origin share several common features such as both exhibiting glutamate as catalytic acid/base in their respective signature sequences and both following the retaining mechanism of catalysis (Figure 2) In both families, several extremophilic endoxylanases have been characterized.

Birchwood xylan

Findings

CONCLUSION