Abstract
The present study demonstrates exopolysaccharide production by an osmotolerant marine isolate and also describes further application of the purified polysaccharide for production of colloidal suspension of silver nanoparticles with narrow size distribution. Phylogenetic analysis based on 16S r RNA gene sequencing revealed close affinity of the isolate to Alteromonas macleodii. Unlike earlier reports, where glucose was used as the carbon source, lactose was found to be the most suitable substrate for polysaccharide production. The strain was capable of producing 23.4 gl−1 exopolysaccharide with a productivity of 7.8 gl−1 day−1 when 15% (w/v) lactose was used as carbon source. Furthermore, the purified polysaccharide was able to produce spherical shaped silver nanoparticles of around 70 nm size as characterized by Uv-vis spectroscopy, Dynamic light scattering and Transmission electron microscopy. These observations suggested possible commercial potential of the isolated strain for production of a polysaccharide which has the capability of synthesizing biocompatible metal nanoparticle.
Highlights
Exopolysaccharides are long chain biopolymers composed of repeating units of sugar moieties connected via glycosidic linkages and may be obtained from plant as well as microbial sources
Phylogenetic analysis of the strain PA2 based on 16S rRNA gene sequences revealed that it was closely related to the genus Alteromonas of the family Alteromonadaceae and was having a pairwise sequence similarity of 99.7%. with phylogenetic neighbour Alteromonas macleodii (Figure 1B) and this novel strain was designated as Alteromonas macleodii PA2
Effect of different carbon sources Most of the earlier reports on marine polysaccharide production indicated that glucose is a preferred carbon source for EPS production by Alteromonas macleodii [25,26,27]
Summary
Exopolysaccharides are long chain biopolymers composed of repeating units of sugar moieties connected via glycosidic linkages and may be obtained from plant as well as microbial sources. In recent time exploitation of marine microflora for isolation of novel bioactive molecules has gained significant interest among researchers worldwide. Marine environment is characterized by extreme physicochemical conditions and harbours unusual microbes with potential of different biotechnological applications. In order to survive in such conditions marine microbes follow some unique biochemical pathways resulting in the production of novel bioactive compounds including, exopolysaccharides [1,2]. Marine microbes tend to have significant osmotic tolerance leading to their capability of polysaccharide production at higher sugar concentration, which is very much desired for development of an economically feasible process for polysaccharide production. Biogenic production of metal nanoparticles has drawn significant interest from scientists. Mostly microbes and plant extracts [5,6]
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