Production of recombinant β-galactosidase in bioreactors by fed-batch culture using DO-stat and linear control

Abstract

β-Galactosidase enzymes continue to play an important role in food and pharmaceutical industries. These enzymes hydrolyze lactose in its constituent monosaccharides, glucose and galactose. The industrial use of enzymes presents an increase in process costs reflecting in higher final product value. An alternative to enhance processes’ productivity and yield would be the use of recombinant enzymes and their large-scale fed-batch production. The overexpression of recombinant β-galactosidase from Kluyveromyces sp. was carried out in 2-L bioreactors using Escherichia coli strain BL21 (DE3) as host. Effect of induction time on recombinant enzyme expression was studied by adding 1 mM isopropyl thiogalactoside (IPTG) at 12 h, 18 h and 24 h of cultivation. Glucose feeding strategies were compared employing feedback-controlled DO-stat and ascendant linear pump feeding in bioreactor fed-batch cultivations. Linear feeding strategy with IPTG addition at 18 h of cultivation resulted in approximately 20 g/L and 17,745 U/L of biomass and β-galactosidase activity, respectively. On the other hand, although the feedback-controlled DO-stat feeding strategy induced at 12 h of cultivation led to lower final biomass of 18 g/L, it presented an approximately 2.5 increase in enzymatic activity, resulting in 42,367 U/L, and most importantly it led to the most prominent specific enzymatic activity of approximately 40 U/mgprotein. Comparing to previous results, these results suggest that the DO-stat feeding is a promising strategy for recombinant β-galactosidase enzyme production.