Production of β-galactosidase for lactose hydrolysis in milk and dairy products using thermophilic lactic acid bacteria

Abstract

The aim of this work was to establish optimal conditions for the maximum production of β-galactosidase using an industrially suitable medium. Lactobacillus delbrueckii subsp. bulgaricus ATCC 11842 was cultivated in skim milk, whey and whey permeate basal media, supplemented with whey protein products, yeast extract or De Man–Rogosa–Sharpe (MRS) broth, at pH 5.6 and 43°C. All supplementations of the whey and whey permeate basal media resulted in the enhancement of the specific growth rates, rate of lactic acid production and β-galactosidase activity. However, unsupplemented skim milk gave the greatest rate of lactic acid production (3.50±0.269 mg lactic acid ml −1 media h −1) and the highest β-galactosidase activity (5.491±0.116 U activity ml −1 media); far superior to the best whey-based medium supplemented with MRS (2.71±0.176 mg lactic acid ml −1 media h −1 and 3.091±0.089 U activity ml −1 media, respectively). A technologically feasible approach for the reprocessing of the spent skim milk was tested and a conceptual process scheme is proposed.