Efficient enzymatic conversion of lactose in milk using fungal β-galactosidase

Abstract

Abstract β-galactosidase (β-gal, E.C. 3.2.1.23) was detected in different fungal cultures and their fermentation factors were optimized, as well as β-gal was purified and characterized from the selected fungal strain. Moreover, the potential impact of fungal β-gal on free lactose-flavored milk production was investigated. Aspergillus terreus NRRL 280 showed the highest β-gal specific activity which grown at 37 °C for 7 days compared to other fungal strains. Also, A. terreus NRRL 280 showed their highest β-gal activity at the optimized growth conditions of 37 °C, pH 4.0 for 7 days. β-gal enzyme was purified from A. terreus NRRL 280 using 40-60% ammonium sulfate saturation with 22.15% yield and 1.11 purification fold. Purified β-gal exhibited their optimal activity at 60 °C, pH 6.0, and 80 min of incubation time, as well as it was is quite stable for the heat treatment. β-gal activity was significantly enhanced with 5 mM Ca2+, Mn2+ and Mg2+, while it was were sensitive to Fe3+ and EDTA. The highest lactose hydrolysis (94.16%) and 23.9 g/l of glucose were recorded for flavored raw skim milk treated with 7.0 U/l milk of β-gal at 6th day of storage period. The flavored milk made from raw full cream cow milk treated with 5.25 U/l of β-gal was recorded the highest sensorial attributes scores followed by those of made from raw skim milk with the same β-gal level. It could be concluded that using of fungal β-gal in lactose-free flavored milk may prove to be beneficial for intolerant lactose people.