Optimization of fermentation media for enhanced amino acids production by bacteria isolated from natural sources

The present study is designed to investigate the enhanced production of amino acids by bacterial strains isolated from different natural sources including sewage water, fresh milk, honey, yoghurt and soil. Sixty five bacterial isolates from these natural sources were isolated and nineteen isolates were found to be producers of amino acids. These isolates were grown in different fermentation media to enhance amino acid production. Out of nineteen, five bacterial isolates were good producers of methionine, cysteine, glutamic acid and valine. On the basis of 16SrRNA nucleotide sequences these organisms were identified as Bacillus anthracis, Bacillus cereus, Escherichia coli H, Escherichia coli M2 and Bacillus sp. The optimum temperature for the growth of B. anthracis and E. coli was found to be 37 degree C, while B. cereus and E. coli showed optimum growth at 30 degree C. Bacillus sp. showed its optimum growth at 39 degree C. B. anthracis, E. coli H and Bacillus sp. showed optimum growth at pH 7, while optimum pH for growth of B. cereus was 6. E. coli M2 showed its maximum growth at 8. The maximum amount of cysteine and methionine produced by B. anthracis were 13.28g/l and 12.52 g/l in GM2 and urea based medium UM4 fermentation media, respectively. B. anthracis was also capable to produce 9.6g/l of glutamic acid and 4.08 g/l of valine in UM1 medium. B. cereus produced maximum cysteine (11.4g/l) and glutamic acid (11.06g/l) in UM1 medium, while maximum amount of methionine (11.2g/l) was produced in UM4 medium. Maximum valine produced was 12.9g/l in GM2 medium. Maximum cysteine and valine produced by E. coli were 11.6 g/l and 7.6 g/l in UM1, while maximum amount of methionine and glutamic acid produced was 13 g/l and 10.2 g/l in GM2 medium. The maximum amount of lysine produced was 1.2 g/l in UM2. Maximum amount of cysteine, glutamic acid and valine produced by E. coli M2 were 9.7 g/l, 12.5 g/l and 8.24 g/l, respectively in UM1 medium. E. coli M2 produced 12.6g/l of methionine in UM2. Bacillus sp. S6 produced 10.0 g/l of cysteine in UM2, and 8.12g/l methionine in GM2. Maximum concentration of glutamic acid and valine produced was 9.6 and 8.07 g/l in UM1. To conclude the indigenously isolated bacterial isolates can be employed for overproduction of the industrially important amino acids.