Process engineering studies of free and micro-encapsulated β-galactosidase in batch and packed bed bioreactors for production of galactooligosaccharides

• GOS production in batch and packed bed reactors using β-galactosidase was studied.
• Free enzyme studies were conducted in mechanically agitated batch reactor.
• Optimum conditions of enzyme immobilization for packed bed reactor were determined.
• Michaelis–Menten kinetics was followed by both free and immobilized enzyme systems.
• GOS yield from packed bed reactor was higher compared to yield from batch reactor.

In the present investigation, an attempt has been made to produce galactooligosaccharides (GOS)1 from de-proteinated casein whey using free and immobilized β-galactosidase. An extensive investigation on β-galactosidase immobilization by micro-encapsulation on calcium alginate has been carried out to evaluate the optimum process parameters namely sodium alginate to enzyme ratio (SER) 2 (100:3) and calcium chloride concentration (0.3 M) with an intention to get maximum enzyme loading and retention in activity. Investigations on GOS formation in mechanically agitated batch bioreactor using free enzyme indicate that the overall observed rate can be well explained by conventional Michaelis–Menten model (Km = 195.2 kg m−3, kcat = 5.37 min−1). Effects of different operating parameters (temperature, initial substrate concentration) on reaction rate and GOS yield during batch processing have been investigated. Studies on GOS production in packed bed bioreactor using immobilized β-galactosidase indicate that although the observed rate can be well explained by Michaelis–Menten model (K′m=200.2 kg m−3K′m=200.2 kg m−3, K′cat=1.39 min−1K′cat=1.39 min−1), enzyme activity is partially blocked due to immobilization. A comparison of activation energies for both systems indicates that the immobilized enzyme system requires more active enzyme compared to its free counterpart for same GOS yield.