Production of Extracellular Polymeric Substances by Halophilic Bacteria of Solar Salterns

Moderately halophilic aerobic bacteria were isolated from 31 soil and 18 water samples collected from multipond solar salterns of Gujarat, Orissa, and West Bengal, India. A total of 587 bacterial isolates with distinct morphological features were obtained from these samples following dilution and plating on MH agar medium supplemented with NaCl. The isolates were screened for growth associated extracellular polymeric substances (EPS) production in MY medium under batch culture. In all, 20 isolates were selected as potent ones producing more than 1？g/L of EPS. These EPS producing isolates were characterized in detail for their morphological, physiological, and biochemical features and tentatively identified as members belonging to the genera Halomonas, Salinicoccus, Bacillus, Aidingimonas, Alteromonas, and Chromohalobacter. Apart from EPS production, these isolates also hold promise towards the production of various biomolecules of industrial importance. 1. Introduction Multipond solar salterns used for industrial production of marine salts by evaporation of sea water represent hypersaline environments which are popular habitats for studying halophilic bacteria and have great potential towards industrial and biotechnological applications [1, 2]. The diversity of halophilic bacteria so far isolated and characterized is categorized into four different classes according to NaCl requirement for their growth and includes slight halophiles, moderate halophiles, extreme halophiles, and border line halophiles. The halotolerant bacteria on the other hand do not require NaCl for their growth but can tolerate a high salinity [3–5]. Halophilic diversity of solar salterns has been studied quite extensively across the globe and reviewed by several authors [6–8]. However, only very few studies have been made on the halophilic bacterial community in coastal solar salterns of India [9, 10], which deserves special attention for exploration and commercial exploitation of these microbial resources. Extracellular polymeric substances (EPS) are one of the industrially important compounds produced by a wide variety of marine microorganisms. Due to growing biotechnological interest [11], production of bacterial EPS has become an attractive field of research. EPS is used as thickeners, emulsifiers, and suspending agents in food, pharmaceuticals, and petroleum industries. They are also used as adhesives in detergents, textiles, papers, paints, and beverages industries. Moreover, EPS are used as metal removers and bioabsorbers in oil recovery, mining, and petroleum industries