Kluyveromyces lactis β-galactosidase immobilized on collagen: catalytic stability on batch and packed-bed reactor hydrolysis

Abstract

The aim of this study was to evaluate the catalytic characteristics and operational stability of the tetrameric Kluyveromyces lactis β-galactosidase (KLG) enzyme immobilized on collagen. The support was submitted to four different treatments: aluminum, glutaraldehyde, acetic acid, and a combination of the methods with aluminum and glutaraldehyde. The four modified supports and the enzyme, both in its soluble and immobilized forms, were studied using thermogravimetric, differential exploratory calorimetry, infrared spectroscopy, and textural analyses. Operational pH, temperature and kinetic parameters of the soluble enzyme and of derivatives were characterized. Immobilized enzyme was applied in milk and whey lactose hydrolysis, via batch and continuous processing. There was no significant reduction (p < 0.05) in immobilization yields of all derivatives with loads up to 100 mgprotein/gsupport, with yields of approximately 70%. All derivatives reached a percentage of approximately 50% of lactose hydrolysis after 17 reuse cycles in the hydrolysis of milk and whey, using batch processing. On the other hand, hydrolysis percentages higher than 50% were achieved with packed-bed reactor even after 48 h of operation. Immobilized KLG on collagen maintained its catalytic characteristics and showed good operational stability in hydrolysis processes, especially in the continuous processes with packed-bed reactor.