Xylanases From Thermophilic Archaea: A Hidden Treasure

Abstract

[Abstract] Archaea are a domain of prokaryotic organisms that often inhabit extremophilic environments. Their enzymes are therefore of enormous biotechnological interest, due to their stability and activity in harsh conditions. Although bioprospection by the metagenomics of extreme environments has yielded many novel xylanases (endo-xylanases and β-xylosidades), most show a highest sequence similarity to bacteria or unculturable microorganisms and not to archaea. This graphical review focuses on the very promising but underexploited (hyper)thermophilic archaeal xylanases. There are only a few examples of xylanases isolated from culturable archaea. So far, 5 different (hyper)thermophilic archaeal strains with xylanase activity have been described, of which 4 present endo-xylanase activity and one shows both endo-xylanase and β-xylosidase activity. All of them show enzymatic activity under a high optimum temperature, neutral optimum pH (with one exception). These facts, together with the important applications of xylanases, reveal archaeal extremophilic xylanases to be a hidden treasure of biotechnology. Bioprospection of archaeal endo-xylanases constitutes a relatively unexploited field, full of potential.