Marine extremophiles: a source of hydrolases for biotechnological applications

Abstract

The marine environment covers almost three quarters of the planet and is where evolution took its first steps. Extremophile microorganisms are found in several extreme marine environments, such as hydrothermal vents, hot springs, salty lakes and deep-sea floors. The ability of these microorganisms to support extremes of temperature, salinity and pressure demonstrates their great potential for biotechnological processes. Hydrolases including amylases, cellulases, peptidases and lipases from hyperthermophiles, psychrophiles, halophiles and piezophiles have been investigated for these reasons. Extremozymes are adapted to work in harsh physical-chemical conditions and their use in various industrial applications such as the biofuel, pharmaceutical, fine chemicals and food industries has increased. The understanding of the specific factors that confer the ability to withstand extreme habitats on such enzymes has become a priority for their biotechnological use. The most studied marine extremophiles are prokaryotes and in this review, we present the most studied archaea and bacteria extremophiles and their hydrolases, and discuss their use for industrial applications.

Figure 1

Phylogenetic tree showing the extremophiles and the resistant characteristics that appear in at least one species of each genera, identified with the color code. The phylogenetic tree was based on Woese et al. [28], Lang et al. [29] and Dereeper et al. [30]. The * indicates the phylogenetic branch that were according to Lang et al. [29].

Figure 2

The three major amylolytic enzymes [5].

Figure 3

(A) Enzymes involved in the hydrolysis of cellulose and (B) in xylan hydrolysis [183]. Exo-β-1,4-glucanase and cellobiohydrolase hydrolyze the glycosidic terminals releasing cellobiose units. The β-glucosidases act directly on cellulose, hydrolyzing it to glucose. The 1,4-β-glucosidase is essential to complete the hydrolysis process of the cellulose [5]. The α-d-xylosidases are exoglycosidases that act in the non-reducing end, hydrolyzing small xylo-oligosaccharides and xylobioses, releasing xylose.

Figure 4

The classifications of peptidases [5].