(582bc) Exopolysaccharides and Thermostable Proteins From Thermophile

Exopolysaccharides and thermostable proteins from thermophile

Jia Wang¹, David R. Salem^{1, 2}, and Rajesh K. Sani¹

¹Department of Chemical and Biological Engineering, SDSM&T, Rapid City, SD 57701                ²Department of Materials and Metallurgical Engineering, SDSM&T, Rapid City, SD 57701

Recently thermophilic microorganisms have been recognized as potential producers of exopolysaccharides (EPSs) having novel and unusual characteristics and functional activities. Thermophiles have several advantages for EPSs production compared to mesophiles e.g., short fermentation period, decrease in viscosity at high temperatures, and non-pathogenic products.  Thermophilic EPSs have unique structures and chemical-physical characteristics which could be exploited for several applications in the near future.  In addition, thermostable proteins synthesized by thermophilic bacteria play important roles in survival of these thermophiles under harsh environmental conditions.  The knowledge on the structural and functional properties of EPSs and thermostable proteins from thermophiles is very limited.  We therefore isolated several thermophilic Bacillus and Geobacillus from the deep biosphere of the Homestake Gold Mine and local compost facilities. 

One of the isolate, Geobacillus sp. (WSUCF1) produced unique type of EPSs.  WSUCF1 genome revealed the presence of 25 ORFs of glycosyltransferases that are responsible for the biosynthesis of polysaccharides. Among the various carbon sources, cellobiose was found to be the most appropriate carbon source for EPSs production (60.47 mg EPS/L) when grown in a batch reactor at 60°C.  The EPSs were isolated using ethanol precipitation and purified. The chemical-physical analyses of the EPSs revealed 94.31% carbohydrate and 5.68% protein and trace amount of nucleic acids.  Fourier Transform Infrared and Nuclear Magnetic Resonance spectroscopy results showed several unique features of the EPS isolated from WSUCF1 including the presence of large number of methyl ketones. Further characterizations of EPSs from WSUCF1 in-terms of determination of molecular weight, identification of sugar components, optical rotation value, differential scanning calorimetry (DSC) and thermogravimetrical analysis (TGA) are continuing. Additionally, thermostable proteins produced by WSUCF1 are currently being characterized.  The EPSs and thermostable proteins of WSUCF1 strain have given an evidence for their potential applications in industrial processes.  Future investigations of the EPSs and thermostable proteins from WSUCF1 will likely reveal more functional properties in regard to new opportunities in various industrial fields including bio-based polymeric materials.