Various nutrients belonging to three categories, carbon, organic nitrogen and complex organic sources, were investigated for the first time in terms of their effect on the co-production of extracellular thermostable α-amylase and β-galactosidase by Bacillus subtilis, a bacterium isolated from fresh sheep's milk. Among the organic nitrogen sources tested, tryptone and corn steep liquor favored their production. Substitution of soluble starch by various starchy substrates, such as corn flour, had a positive effect on both enzyme yields. Furthermore, a two-fold higher production of both enzymes was achieved when corn steep liquor or tryptone was used in combination with the different flours. Among the divalent cations examined, calcium ions appeared to be vital for α-amylase production. The crude α-amylase and β-galactosidase produced by this B. subtilis strain exhibited maximal activities at 135 °C and 65 °C, respectively, and were also found to be significantly stable at elevated temperatures.
- Bacillus subtilis, α-Amylase, β-Galactosidase, Thermostable, Co-production, Organic substrates