A modelling study on skimmed milk lactose hydrolysis and beta-galactosidase stability using three reactor types.

摘要

The hydrolysis of lactose in skimmed milk and beta-galactosidase inactivation studies were carried out in three different devices - bioreactor, sonicator and homogeniser - to evaluate the performance of such reactors that have different operational systems. The experiments were carried out using beta-galactosidase produced from Kluyveromyces marxianuslactis. At the optimum process conditions obtained from the experiments performed in bioreactor, sonicator and homogeniser, 89%, 90% and 54% of lactose were hydrolysed and the enzyme lost its activity by 14%, 13% and 24%, respectively, at the end of the processing time of 30 min. The commercial milk lactose content (1 g/L lactose) was reached at 60 min for bioreactor and sonicator. After evaluation of the data, it was found that the kinetics of hydrolysis and enzyme inactivation could be represented by a first-order kinetic model and a single-step non-first-order enzyme inactivation kinetic model, respectively, for all process conditions applied. The activation energy for hydrolysis reaction and the enzymatic inactivation energy values were also calculated