RESUMO
Aims: This study evaluated nutritional parameters for optimum methionine production Study Design: Methionine was assayed using the colorimetric method of Greenstein and Wintz (1961). Place and Duration of Study: Department of Applied Microbiology and Brewing, Nnamdi Azikiwe University, Awka, Anambra State, Nigeria, between April 2010 and November 2011. Methodology: Bacillus cereus RS 16 was previously isolated from a soil ecovar in Owerri, Nigera. It was maintained on nutrient agar (Oxoid) slants at 4ºC. Bacillus cereus 16 was confirmed by 16Sr RNA conducted at Macrogen Incoporated Korea. Methionine production was carried out in a submerged medium. A 10% (v/v) seed culture was used to inoculate a 100ml Erlenmeyer flask containing 30 ml of fermentation medium in a rotatory shaking incubator at 170 rpm and 30ºC. Growth and methionine accumulation was determined from the broth. Nutritional parameters were studied to determine optimum methionine production Results: Glucose and ammonium chloride were the best carbon and nitrogen source for Lmethionine production. Maximum methionine (4.55mg/ml) were obtained with 80.0g glucose, 20.0g ammonium chloride, 20.0g calcium carbonate, 0.1.g DL-ornithine monohydrate, 0.1g peptone, 0.5g potassium dihydrogen phosphate, 0.5g potassium hydrogen phosphate, 0.01g magnesium sulphate heptahydrate, 0.001g manganese sulphate tetrahydrate, 0.001g ferrous sulphate heptahydrate at 72h fermentation period. There was a remarkable increase of methionine level to 4.55 mg/ml after optimization compared to methionine level of 1.92 mg/ml before optimization Conclusion: This present investigation has determined optimum parameters for maximum production of L- methionine by the newly isolated mesophilic bacterium Bacillus cereus strain RS 16. This information has enabled formulation of media composition for maximum methionine production by this organism.