Stimulation of Lysine Accumulation in the Broth Culture of Bacillus Species Isolated from Nigerian Fermented Food Condiments Using Agro-products

Abstract

Fermented food condiments serve as taste enhancers in African diets and these products are broken down during fermentation by microorganisms to proteineous substances, releasing free amino acids like lysine. Lysine, an essential amino acid added to animals feed, is produced by Bacillus species. This study was undertaken to evaluate the stimulatory effects of agro-products on lysine production by Bacillus species isolated from fermented food condiments. The effects of synthetics carbon sources: Sucrose, maltose, galactose, glucose, lactose, fructose, and nitrogen sources: KNO3, NH4NO3, NH4Cl, (NH4)2SO4 on lysine production by Bacillus subtilis and Bacillus licheniformis were examined. The influence of non-synthetic carbon sources: cassava, cocoyam, yam, plantain, millet, corn, potato, rice and nitrogen sources: soybean, cotton seed, cowpea, bambara nut, groundnut on lysine accumulation by the Bacillus species, were studied. Medium containing carbon and nitrogen sources (2:1), was inoculated with the Bacillus sp and incubated for 72h on a shaker at 160rpm and 30°C. Lysine was determined from the broth culture. The Bacillus species produced lysine levels above 0.6mg/ml in all the synthetic medium except lactose and galactose medium of Bacillus licheniformis. A maximum yield of 1.0 mg/ml was accumulated by Bacillus licheniformis in a medium of fructose and (NH4)2SO4. The use of non-synthetic carbon and nitrogen sources stimulated lysine yields by the Bacillus species. Lysine accumulations of 3.63mg/ml and 3.73mg/ml were observed in culture broths of Bacillus subtilis and B. licheniformis respectively, containing rice hydrolysates and defatted groundnut meals. The stimulatory effect of agro-products on lysine production by the Bacillus species has proved that they are good substrates for use in the fermentation industry.