USING DIFFERENT EXPRESSION INDUCERS TO OBTAIN RECOMBINANT β-GALACTOSIDASE

The β-galactosidase is used in lactose enzymatic hydrolysis and it is widely used in food industry to prepare low lactose milk and dairy products. The costs involved in applying enzymes in industrial processes are still high and an alternative to reduce the product value is to produce the enzyme in the recombinant form, using inexpensive inducers for enzymatic expression. The objective of this study was to evaluate the effect of different inducers for Kluyveromyces marxianus β-galactosidase expression in Escherichia coli. Luria-Bertani-grown (LB) cultures of E. coli strain BL21 (DE3) were used to express the recombinant enzyme. Isopropyl β-D-1-thiogalactopyranoside (IPTG) and lactose were used as expression inducers at different concentrations (0.05 and 0.5 mM of IPTG and 1, 10, and 20 g/L of lactose). β-Galactosidase expression, enzymatic activity, and protein concentration were verified. The highest specific activity of the enzyme in soluble fraction was approximately 39.13 U/mgprotein when using 10 g/L of lactose after 27-h induction. After 6-h induction, using 10 g/L and 20 g/L, there was no significant difference (p ≤ 0.05) in the activity values, whereas the lowest specific activity was with IPTG. Thus, these results showed the benefits of using lactose as a low cost and toxicity inductor.