Desalting of dairy product streams using countercurrent dialysis

Abstract

The desalting of protein solutions using membrane-based diafiltration is a well-established technology within the dairy industry. These processes, however, consume a significant volume of water and generate a large volume of waste. In this study, the use of continuous countercurrent dialysis for the desalting of bovine lactoferrin downstream of chromatographic purification was compared with conventional batch diafiltration. Experimental results showed that a dialysate to feed ratio of 2.1 allowed for a 200-fold reduction in salt concentration, corresponding to 99.5 % salt removal for a 6 %wt. salt solution. As a comparison, between 5.3 and 6 diavolumes were needed to achieve a similar result with dialysis. Performance could be maintained for over 8 h in the presence of either 3 %wt. or 6 %wt. lactoferrin. The NaCl concentration in the dialysate outlet was also high, allowing potential reuse for the upstream chromatographic elution step. Detailed mass balance calculations suggested a saving of up to 77 % in fresh water and 46 % in NaCl consumption when an integrated process was used, compared to the process where batch diafiltration was employed. The outcomes suggest that the use of continuous countercurrent diafiltration could assist dairy manufacturers to reduce cost and increase sustainability.