Effect of carbon and nitrogen sources on growth of Bifidobacterium animalis Bb12 and Lactobacillus delbrueckii ssp. bulgaricus ATCC 11842 and production of β-galactosidase under different culture conditions

In this study, the effect of various carbon sources such as lactose, glucose and galactose and nitrogen sources such as yeast extract, peptone, casein hydrolysate, tryptone, ammonium sulphate and MRS broth (control) on growth of Bifidobacterium animalis BB12 and Lactobacillus delbrueckii ssp. bulgaricus and production of β-galactosidase (β-gal) by these organisms were evaluated. The medium for carbon source contained 3.5% yeast extract, 0.3% K2HPO4, 0.1% KH2PO4, 0.05% MgSO4.7H2O, 0.03% L-cysteine and 4% of lactose, glucose or galactose was supplemented as a carbon source. Similarly, the medium for nitrogen source contained 4% lactose, 0.3% K2HPO4, 0.1% KH2PO4, 0.05% MgSO4.7H2O, 0.03% L-cysteine and 3.5% of yeast extract, peptone, casein hydrolysate, tryptone, ammonium sulphate or MRS broth as a nitrogen source was added. In general, lactose, glucose and galactose were found to be suitable for β-galactosidase production. The highest level of β-gal activity of 73.66 unit/mL was produced by B. animalis Bb12 and 48.63 unit/mL by L. delbrueckii spp. bulgaricus ATCC 11842 in the presence of galactose as the carbon source. The strains were able to utilize a wide range of nitrogen sources such as yeast extract, peptone, casein hydrolysate, tryptone and ammonium sulphate. B. animalis Bb12 produced the highest level of β-gal in MRS broth and yeast extract produced the highest level of β-gal by L. delbrueckii spp. bulgaricus ATCC 11842.