The Potential Biotechnological Applications of the Exopolysaccharide Produced by the Halophilic Bacterium Halomonas almeriensis

Abstract

We have studied the extracellular polysaccharide (EPS) produced by the type strain, M8 T , of the halophilic bacterium Halomonas almeriensis , to ascertain whether it might have any biotechnological applications. All the cultural parameters tested influenced both bacterial growth and polysaccharide production. EPS production was mainly growth-associated and under optimum environmental and nutritional conditions M8 T excreted about 1.7 g of EPS per litre of culture medium (about 0.4 g of EPS per gram of dry cell weight). Analysis by anion-exchange chromatography and high-performance size-exclusion chromatography indicated that the exopolysaccharide was composed of two fractions, one of 6.3 × 10 6 and another of 1.5 × 10 4 Daltons. The monosaccharide composition of the high-molecular-weight fraction was mannose (72% w/w), glucose (27.5% w/w) and rhamnose (0.5% w/w). The low-molecular-weight fraction contained mannose (70% w/w) and glucose (30% w/w). The EPS has a substantial protein fraction (1.1% w/w) and was capable of emulsifying several hydrophobic substrates, a capacity presumably related to its protein content. The EPS produced solutions of low viscosity with pseudoplastic behaviour. It also had a high capacity for binding some cations. It contained considerable quantities of sulphates (1.4% w/w), an unusual feature in bacterial polysaccharides. All these characteristics render it potentially useful as a biological agent, bio-detoxifier and emulsifier.

A statistical approach on optimization of exopolymeric substance production by Halomonas sp. S19 and its emulsification activity

“…In marine environment, most of the bacteria exclusively secrete exopolymeric substances outside the cell, which may be tightly or loosely bounded on the cell surface and assist the cell to survive (Sutherland 2001). The exopolymeric substances are composed of sugars and non-sugar components (proteins, uronic acids, sulphates and acetyl group) (Llamas et al 2012).…”

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“…Moreover, these exopolymers showed emulsifying activity to many hydrophobic substrates possibly due to their high protein content and low viscosity. Extracellular polysaccharide production by H. almeriensis 11,55 have been optimized and revealed a growth associated production of 1.7 g/L of EPS. The sulfated EPS so produced was capable of emulsifying several hydrophobic substrates and binding of metal ions.…”

“…8 Production of extracellular polysaccharides by halophilic Archaea and Bacteria has been reported by several workers and the members of the genus Halomonas have been identified as the most potential producers. [9][10][11] While the chemistry, structure and functions of microbial extracellular polymeric substances in general have been highlighted with special emphasis on microbial ecology, medicine, dairy industry, formation of biofilms, and environmental biotechnology; their role in the remediation of heavy metals, toxic compounds and dyes from the anthropogenic environments could not be ruled out. 12 Survey of literature have clearly indicated that the information pertaining to the production and characterization of extracellular polysaccharides by the wide variety of halophilic microorganisms isolated from hypersaline environments are inadequate.…”

Chemical Mutagenesis for Improvement of Production of a Biologically Active Extracellular Polymeric Substance by <i>Halomonas xianhensis</i> SUR308

“…Halophilic bacteria belonging to the genus Halomonas have been identified as potential bioresources for the production of extracellular polymeric substances (EPS) (Llamas et al, 2012;Bouchotroch et al, 2001). The unusual physical and chemical properties (Margesin and Schinner, 2001) of the EPS derived from halophilic bacteria have drawn the attention of the microbial biotechnologists to explore the potentials of EPS production at commercially viable way.…”