Synthesis, Production, and Biotechnological Applications of Exopolysaccharides and Polyhydroxyalkanoates by Archaea

Abstract

Extreme environments, generally characterized by atypical temperatures, pH, pressure, salinity, toxicity, and radiation levels, are inhabited by various microorganisms specifically adapted to these particular conditions, called extremophiles. Among these, the microorganisms belonging to the Archaea domain are of significant biotechnological importance as their biopolymers possess unique properties that offer insights into their biology and evolution. Particular attention has been devoted to two main types of biopolymers produced by such peculiar microorganisms, that is, the extracellular polysaccharides (EPSs), considered as a protection against desiccation and predation, and the endocellular polyhydroxyalkanoates (PHAs) that provide an internal reserve of carbon and energy. Here, we report the composition, biosynthesis, and production of EPSs and PHAs by different archaeal species.

Resistance of extremely halophilic archaea to zinc and zinc oxide nanoparticles

“…Our recent study by Das et al (2014) indicated that Haloferax strain BBK2 was also resistant to cadmium (Cd) and accumulated 21.08 and/or 15.19 % of Cd in the presence of 0.5/1 mM Cd. Haloferax is known to produce exopolysaccharide (EPS) which protects the cells from direct contact with the metals and hence its resistance (Poli et al 2011). Halococcal cells resist lysis when suspended in low-osmolarity solutions (3.5 % NaCl) (Mani et al 2012;Legat et al 2013).…”

Biocompounds from Haloarchaea and Their Uses in Biotechnology

“…PHAs are polyesters composed of hydroxy fatty acids, synthesized and stored as insoluble inclusions in the cytoplasm [76]. They serve as intracellular storage material of carbon source and energy.…”

“…The enzymes responsible for this reaction are PHA synthases. Therefore, it is considered that the key enzymes for PHA production are the polyester synthases [76,78,80]. In the Bacteria domain, where these kind of proteins have been studied extensively, they are divided into four classes depending on the subunit composition and their substrate [76,77,80].…”

“…The difference lies in the substrate specificity: while class I PHA synthases utilize CoA thioesters of various 3-hydroxy fatty acids comprising 3-5 carbon atoms, class II PHA synthases use CoA thioesters of 3-hydroxy fatty acids with 6-14 carbon atoms [76,80].…”

Polyhydroxybutyrate as Bio-Degradable Plastic – A Review

“…Marine bacteria have recently attracted attention as potentially useful candidates for the production of PHAs.. The main advantage of biodegradable polymers is that anaerobic microbes completely degraded to water, carbon dioxide and methane in various environments such as soil, sea, lake water and sewage and so it is disposable without harm to the environment (12).Although a few kinds of marine bacteria have been investigated for PHA production under some marine conditions, characterization have not been done in details of the resultant PHAs Haloferax, Haloarcula, Natrialba, Haloterrigena, Halococcus, Haloquadratum, Halorubrum, Natronobacterium, Natronococcus and Halobacterium some Haloarchaeal species have found to be efficient producer of PHB (13).Bacterial genera like Beneckea and Vibrio have been found to be first reported potent producers of PHA isolated from marine sediments (14).…”