AUTHOR=Verma Digvijay , Satyanarayana Tulasi 

TITLE=Xylanolytic Extremozymes Retrieved From Environmental Metagenomes: Characteristics, Genetic Engineering, and Applications

JOURNAL=Frontiers in Microbiology

VOLUME=Volume 11 - 2020

YEAR=2020

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2020.551109

DOI=10.3389/fmicb.2020.551109

ISSN=1664-302X

ABSTRACT=Xylanolytic enzymes have extensive applications in paper, food and feed, pharmaceutical, and biofuel industries. These industries demand xylanases that are functional under extreme conditions like high temperature, acidic/alkaline pH, and others, which are prevailing in bioprocessing industries. Despite the availability of several xylan-hydrolyzing enzymes from cultured microbes, there is a huge gap between what is available and that industries require. DNA manipulations as well as protein engineering techniques are also not quite satisfactory in generating xylan-hydrolyzing extremozymes. With the compound annual growth rate (CAGR) of 6.6% of xylan hydrolyzing enzymes in the global market, there is a need for xylanolytic extremozymes. Therefore, metagenomic approaches have been employed to uncover the hidden xylanolytic genes that were earlier inaccessible in culture-dependent approaches. An appreciable success has been achieved in retrieving several unusual xylanolytic enzymes with novel and desirable characteristics from different extreme environments using functional and sequence-based approaches of metagenomics. Moreover, the Carbohydrate Active enZYmes (CAZy) database includes approximately four hundred GH-10 and GH-11 unclassified xylanases. This review discusses sources, characteristics, and applications of xylanolytic enzymes obtained through metagenomic approaches and their amelioration by genetic engineering techniques.