Study On Separation And Purification Of Milk Protein In Cheese Whey

Whey, which is a by-product of cheesemaking, contains an extensive range of nutritionaland biological substances. In recent years, increased cheese production has created a wheysurplus. Whey wastewater could cause severe pollution and tremendous waste problems.Therefore, how to deal with and deep process whey has become a bottleneck in Chinesecheese industry. This dissertation focuses on the separation and purification of whey proteinand lactoferrin, including pretreatment of cheese whey by thermocalcic precipitation,recovery of whey protein by ultrafiltration and separation and purification of lactoferrin byion-exchange chromatography.In order to reduce the turbidity and enhance the efficiency of ultrafiltration, cheese wheywas pretreated with thermocalcic precipitation. The optimal conditions determined by singlefactor experiment were as follows:0.28%of CaCl₂was added to the whey and pH raised to6.6⁷.0, the mixture was incubated at50℃and centrifuged at4℃. Under these conditions,the removal rate of residual fat was90%, while the turbidity of cheese whey （500nm ABS）decreased from2.74down to0.07.In order to separate whey protein by polyether sulfone with molecular weight cut-off of10000Da, single factor experiment was conducted to determine the parameter affecting themembrane separation including pressure, temperature, solid liquid ratio and pH value. Theresults showed that the optimal condition was: pressure30psi, solid liquid ratio21, pH6.0.And under this condition, the pure water permeation flux, the permeation of lactose and theretention of whey protein was32.66L/hm2,93.13%and94.65%respectively.To purify lactoferrin from cheese whey by ion exchange technology. Whey proteinconcentrate as the raw material applied to ion exchange column which was packed withCM-Sepharose Fast Flow. The optimal condition was as follows: the pretreated cheese wheywas applied to the resin, which was previously equilibrated on static state with phosphatebuffer （pH8.0） at4℃, and eluted with0.3mol/L and0.8mol/L NaClrespective in two stages.Under these conditions, lactoferrin was analyzed quantitatively by SDS-PAGE and Bandscan software. The purity of lactoferrin product reached93.6%and the total yield of lactoferrinwas29.56%. The purified sample and standard lactoferrin showed the same immunogensthrough Western Blotting.