Integrated Downstream Processing of Lactoperoxidase from Milk Whey Involving Aqueous Two-Phase Extraction and Ultrasound-Assisted Ultrafiltration

The present work involves the adoption of an integrated approach for the purification
of lactoperoxidase from milk whey by coupling aqueous two-phase extraction (ATPE) with
ultrasound-assisted ultrafiltration. The effect of system parameters of ATPE such as type of
phase system, polyethylene glycol (PEG) molecular mass, system pH, tie line length and phase
volume ratio was evaluated so as to obtain differential partitioning of contaminant proteins and
lactoperoxidase in top and bottom phases, respectively. PEG 6000-potassium phosphate system
was found to be suitable for the maximum activity recovery of lactoperoxidase 150.70% leading
to 2.31-fold purity. Further, concentration and purification of enzyme was attempted using
ultrafiltration. The activity recovery and purification factor achieved after ultrafiltration were
149.85% and 3.53-fold, respectively. To optimise productivity and cost-effectiveness of
integrated process, influence of ultrasound for the enhancement of permeate flux during
ultrafiltration was also investigated. Intermittent use of ultrasound along with stirring (2 min
acoustic and 2 min stirring) resulted in increased permeate flux from 0.94 to 2.18 l/m2 h in
comparison to the ultrafiltration without ultrasound. The use of ultrasound during ultrafiltration
resulted in increase in flux, but there was no significant change in activity recovery and
purification factor. The integrated approach involving ATPE and ultrafiltration may prove to be
a feasible method for the downstream processing of lactoperoxidase from milk whey.