Applications and Benefits of Thermophilic Microorganisms and Their Enzymes for Industrial Biotechnology

Abstract

Thermophilic and thermotolerant microorganisms are of important economic value due to their ability to produce thermostable extracellular enzymes which have important biotechnological applications. It is known that thermophilic activities are generally associated with protein thermostability. Thus, proteins produced by thermophiles tend to be more thermostable than their mesophilic counterparts. The mechanisms of intrinsic thermostability of the protein that results in the molecular rigidity are related to a number of hydrogen and disulfide bonds, salt bridges, presence of hydrophobic amino acids and the packing of external residues. The advantage of the use of thermostable enzymes for conducting biotechnological processes at elevated temperatures are: reducing the risk of contamination by mesophilic microorganisms; decreasing the viscosity of the reaction medium; increasing the bioavailability and solubility of organic compounds; increasing the diffusion coefficient of substrates and products resulting in higher reaction rates. Several cellulases, xylanases and pectinases have been applied in biotechnological processes such as biobleaching of paper pulp, production of animal feed, production of fermentable sugars for obtaining biofuel from cellulosic wastes, fruit juice extraction and clarification, refinement of vegetable fibers, degumming of natural fibers, curing of coffee, cocoa and tobacco and also for waste-water treatment. The thermostable enzymes are produced directly from native microorganisms but, in the majority of the industrial processes, the heterologous expression the enzyme is carrying out. Here, we discuss thermophilic microorganisms and their thermostable enzyme involved with plant material degradations and the prokaryotic and eukaryotic systems for heterologous expression of those enzymes.