Abstract
A moderately halophilic bacterium, Halomonas marina HMA 103 (MTCC 8968) accumulating intracellular polyesters also produced significant amount of exopolysaccharides (EPS) under batch-culture. Production of EPS by the bacterium was more or less parallel with the growth in modified basal synthetic medium. During growth, it produced 0.46 g/L of EPS after 50 h of incubation and was accompanied by the complete utilization of glucose from the medium. EPS production was maximum in 2% (w/v) glucose followed by sucrose and maltose and was positively influenced by yeast extract, beef extract and peptone. Optimum concentrations of sulfate and phosphate for EPS production were 2.4% (w/v) and 0.03% (w/v) respectively. High concentration (10% w/v) of NaCl stimulated both growth and EPS production by H. marina HMA 103. Characteristically, this EPS is a heteropolymer of glucose and mannose and the Fourier Transform Infrared (FTIR) spectrum showed distinct absorption peaks at 3424.2, 1638.7, 1122.9 and 622.3 cm-1 indicating the presence of free hydroxyl, phenyl or carbonyl groups of carbohydrate. Further, the detailed physico-chemical analysis will indicate the significance and potential importance of this EPS in biotechnology.
Highlights
Halophilic bacteria that require 3-15% NaCl for satisfactory growth (Kushner, 1988) are widely distributed throughout the hypersaline environment and have been recognized as valuable sources of new biomolecules including exopolysaccharides (Margesin and Schinner, 2001)
Halomonas marina HMA 103 (MTCC 8968), the moderately halophilic heterotrophic bacterium previously isolated from solar slatterns of Odisha, India produced characteristic opaque, slimy colonies with profound accumulation of extracellular polysaccharides (EPS) when grown on Ventosa’s agar medium containing 5 to 10% NaCl
Growth and production of extracellular polysaccharide by H. marina HMA 103 was influenced by the presence different carbon sources like glucose, sucrose, fructose, maltose, acetate, citrate and malonate in the medium
Summary
Halophilic bacteria that require 3-15% NaCl for satisfactory growth (Kushner, 1988) are widely distributed throughout the hypersaline environment and have been recognized as valuable sources of new biomolecules including exopolysaccharides (Margesin and Schinner, 2001). These exopolysaccharides (EPS) play important role in the attachment of bacteria with substrates, development of biofilms, adsorption of nutrients, conservation of enzymes, defense against attack and protection against changes in physicochemical conditions (Wotton, 2004). Extensive search for EPS with novel properties have described several species of moderately halophilic bacteria belonging to the genus Halomonas. Novel species viz. H. ventosae (MartínezCánovas et al, 2004), H. anticariensis (MartinezCanovas et al, 2004) and H. almeriensis (MartinezCheca et al, 2005; Llamas et al, 2012) deserve special mention for synthesizing copious amounts of exopolysaccharides in culture
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