Screening of Methionine-producing Bacillus Species from Nigerian Fermented Food Condiments and Effects of Some Cultural Parameters on Methionine Accumulation

Abstract

Fermented food condiments are sources of proteins and vitamins and are added as spices or sauces to food for flavour or taste enhancers. The major fermenting microorganisms, Bacillus species, produce proteolytic enzymes that hydrolyze proteins and amino acids and peptides. Methionine is the most essential amino acid for chicken feeds and can be produced by Bacillus species. The screening of methionine-producing microorganisms from Nigerian fermented food condiments and the effect of some cultural parameters on methionine accumulation were conducted. Bacterial organisms isolated from fermented food condiments, ogiri and okpeye, were screened for methionine producers on minimal solid agar medium seeded with auxotrophic Escherichia coli and in submerged medium. The effects of medium to fermenter volume ratio, inoculum size, carbon and nitrogen sources on methionine accumulation by the isolates were investigated. Of the five methionine producers recovered, two of the active isolates identified as Bacillus pumilus and Bacillus amyloliquefaciens were used for methionine production. A 20.0ml fermentation medium and 5.0% inoculum size gave the highest methionine accumulation by the Bacillus species. At 8.0% glucose and 4.0% ammonium sulphate concentrations, methionine yields of 5.22mg/ml and 5.50mg/ml were accumulated in the broth cultures of B. pumilus and B. amyloliquefaciens respectively. B. pumilus and B. amyloliquefaciens recovered from Nigerian fermented food condiments were observed to produce methionine and the optimization of some cultural parameters enhanced methionine accumulation by the Bacillus species.