Metabolic heat coherent growth of Halomonas variabilis (HV) for enhanced production of Extracellular Polymeric Substances (EPS) in a Bio Reaction Calorimeter (BioRC)

Abstract

The optimum condition at which the halophilic salt-tolerant bacterium Halomonas variabilis (MTCC 3712) produces the maximum amount of extracellular polymeric substances (EPS) was investigated experimentally using response surface methodology based on the central composite design (CCD). Hyper-saline medium containing 1.5% w/v NaCl enriched nutrient medium with 1.5% glucose as a carbon source was used to produce about 4.74 g/L of EPS in 16 h compared to various other EPS production of this kind. The metabolic heat profile confirms net EPS production by HV was a growth-associated aerobic process. There is a good agreement between metabolic heat and Oxygen Uptake Rate (OUR). The maximum observed heat release was 2.1 W. The total protein content of the sample is 53% of the total EPS (Soluble EPS, Loosely bound EPS, and tightly bound EPS). The emulsifying and flocculating activities of the EPS were measured to explore the possibility of using the biopolymer for effluent treatment.

Keywords:

• Extracellular polymeric substances
• halomonas variabilis
• response surface methodology

Acknowledgment

The authors wish to thank Prof. Karthikeyan.R, Mepco Schlenk Engineering College for useful discussions. Director, CSIR-CLRI for the kind permission to publish this manuscript.