JOURNAL OF PURE AND APPLIED MICROBIOLOGY, December 2012. Vol. 6(4), p. Proof * To whom all correspondence should be addressed. Mob.: +91-9840856804 E-mail: mail.vidhyalakshmi@gmail.com Application of RSM to Optimize Medium For Exo Polysaccharide Production By Bacillus Sp R.Vidhyalakshmi* and C.Valli Nachiyar Department of Biotechnology, Sathyabama University, Rajiv Gandhi Salai, Chennai - 600 119, India. (Received: 18 February 2012; accepted: 21 April 2012) The combined effect of various media components for exo polysaccharide production by Bacillus spp was studied using RSM. The extracted polysaccharide showed good anti tumor activity and an attempt was made to increase the production of EPS using RSM .The temperature (30°C±1°C ) and pH value (7.0± 0.1) were kept constant throughout the experimental time. A conventional method was used to fix the best yielding substrate and Box Behnken Design was employed to design the composition of the media components. The optimal value for the critical components was obtained as follows. Sucrose -30 gm, Yeast extract -2 gm ,Calcium chloride - 4.3gm,Casamino acid -10ml/l with the predicted value of the model 10.02gm/l ±0.001. A quadratic polynomial analysis was applied for predicting the various responses of media components. Under an experiment the yield of exo polymer was 10gm/l ± 0.001. The determination coefficient (R 2 ) was 0.9813 that ensures adequate credibility of the model. Key words: Optimization , Box-Behnken design, Exopolysaccharide, Response surface methodology Media are traditionally optimized by one- at-a time strategy i.e. varying one factor while keeping all others constant. Though the conventional method is simple and easy to apply without the need for statistical analysis, designing more number of experiments is uneconomical. Using statistical methods to design an optimal medium is economical and often accurate with fewer residues. RSM is a collection of statistical techniques for designing experiments, building models, evaluating the effects of various factors and conclude with an optimal condition that gives best results. RSM has been successfully used in optimization of many Bioprocesses. Interest in exo polysaccharide producing bacteria has increased because of its importance in determining the rheological properties of dairy products and many non dairy applications (1,2) . Nitrogen limiting conditions increase the production of EPS. The effect of various stimulating agents on the production of EPS was studied by (3) . In recent years there has been a continuous search for new water soluble polysaccharides, particularly those produced by microorganisms. These polymers have been attracting interest due