A study of the separation of proteins from multicomponent mixtures by a semi-batch foaming process

Foam fractionation offers an attractive method of separating/concentrating proteins (or their mixtures) from dilute solutions which are typical of many dairy, food and biological process streams. Experiments were conducted to obtain the values of the average bubble size, gas holdup, interfacial area, the bulk phase concentration and the heat of desorption (which determines the concentration of adsorbed components) in the liquid solution using a 75 mm diameter, 530 mm long glass column fitted with a stainless steel sparger for bubble generation. The mass transfer coefficient for Bovine Serum Albumin (BSA), K, was determined from the analysis of the concentration of foam and feed at different times using the above mentioned parameters. The values vary with the feed concentration, i.e. K = 4.34 × 10^-6 mol cal^-1 cm^-2 s^-1 at 60 mg l^-1 and K = 3.62 × 10^-6 at 25 mg l^-1. The separation performance, expressed as enrichment ratio, selectivity and percentage recovery, was investigated for a binary and ternary protein mixtures of BSA, α-lactalbumin and lactoferrin. The effects of the operating factors, i.e. air flow rate, initial feed protein concentration ratio, bubble size and solution pH on separation performance were examined. The results provided some guidelines in producing a fraction, enriched in the target protein lactoferrin, from its mixture with other proteins.