PRODUCTION OF POLISACCHARIDES BY BACTERIAL STRAINS FROM BULGARIAN GEOTHERMAL SPRINGS: ENGINEERING PARAMETERS AT ELEVATED SCALE

References: 13th SGEM GeoConference on Nano, Bio And Green – Technologies For A Sustainable Future, www.sgem.org, SGEM2013 Conference Proceedings, ISBN 978-619-7105-06-3 / ISSN 1314-2704, June 16-22, 2013, 219 - 226 pp

ABSTRACT

Geothermal springs located in East European countries present a challenge for the search of un-described biotechnological resources. Bulgaria is rich in thermal springs with different geotectonic origin and different physical chemical properties whose habitants are slightly investigated. The study considers a bioprocess of exopolysachharide (EPS) production by thermophilic bacterium Aeribacillus palidus 418 strain isolated from Bulgarian Rupi basin. The bioreactor performance at elevated scale is studied. A small-scale 0.15 m diameter bioreactor is simulated and extrapolated 5-fold to an elevated scale of 0.75 m stirred vessel. Computational flow dynamics technique (CFD) simulation methods are employed to ensure detailed analysis of the flow patterns and distribution of process fluid flow power. The mixing performance characteristics relevant for scale-up at constant specific input power are determined. The predictions of the performance parameters are illustrated. Small-scale and large scale 2-D visualizations are elaborated and compared. It is demonstrated that scale-up by constant specific power ensures the system specific conditions required for practical production. Due to the inherent relationship of kinetic energy dissipation rate with local mass transfer rate, both the hydrodynamic and diffusion parameters at elevated scale could be determined. Deviations of dissipated power at hundred-fold volumetric scaling, i.e. between 3 dm3 and 0.3 m3 tanks, does not produce reduction in mass transfer rate and previews stable semi-tech scale performance. The results manifest the prospects for feasible sustainable production and, in view of the 3-D modeling employed, are amenable for direct implementation.

Keywords: geothermal springs, EPS, green processing, Aeribacillus palidus, bioreactor scale-up