Lactose nano-probe optimized using response surface methodology.

A lactose nano-probe has been developed by immobilization of PsBGAL onto gold nanoparticles (AuNps). It is helpful for severe lactose intolerants for quality check of lactose hydrolyzed milk and estimation of hidden lactose present in variety of food products. Optimization of PsBGAL immobilization onto AuNps using spacer arm (cysteamine-glutaraldehyde) was carried out by response surface methodology (Box-Behnken design). The process has led to immobilization of enzyme onto AuNps with an efficiency of 140.81%. AuNp-PsBGAL was characterized using transmission electron microscopy, scanning electron microscopy and Fourier transform infrared spectroscopy. Immobilized enzyme showed broad temperature and pH optima and a significant enhancement in catalytic efficiency (V(max)/K(m)) with respect to soluble PsBGAL. AuNp-PsBGAL was stable under dried conditions than wet conditions for 6 months with loss of 10.2% and 87.53%, respectively. It has reusability of over five batchwise uses, with almost no loss in activity. Hill's coefficient was found to be 1.71 corresponding to lactose concentration ranging from 0.1% to 2.0%.