Effect Of By-Products From The Dairy Industry As Alternative Inducers Of Recombinant Beta-Galactosidase Expression

Objective The aim of the present study was to evaluate the efficiency of lactose derived from cheese whey and cheese whey permeate as inducer of recombinantKluyveromycessp. beta-galactosidase enzyme produced inEscherichia coli. TwoE. colistrains, BL21(DE3) and Rosetta (DE3), were used in order to produce the recombinant enzyme. Samples were evaluated for enzyme activity, total protein content, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis after induction with isopropyl-beta-D-1-thiogalactoside (IPTG) (0.05 and 1 mM) and lactose, cheese whey, and cheese whey permeate solutions (1, 10, and 20 g/L lactose) at shake-flask cultivation, and whey permeate solution (10 g/L lactose) at bioreactor scale. Results The highest specific activities obtained with IPTG as inducer (0.05 mM) after 9 h of induction, were 23 and 33 U/mg(protein)with BL21(DE3) and Rosetta(DE3) strains, respectively. Inductions performed with lactose and cheese whey permeate (10 and 20 g/L lactose) showed the highest specific activities at the evaluated hours, exhibiting better results than those obtained with IPTG. Specific activity of recombinant beta-galactosidase using whey permeate (10 g/L lactose) showed values of approximately 46 U/mg(protein)after 24-h induction at shake-flask study, and approximately 26 U/mg(protein)after 16-h induction at bench bioreactor. Conclusions The induction with cheese whey permeate was more efficient for recombinant beta-galactosidase expression than the other inducers tested, and thus, represents an alternative form to reduce costs in recombinant protein production.