Effect of ionic strength on the foam separation of nisin from the fermentation broth

Nisin is a 34-residue peptide and it is widely used as food preservative. Different strategies for nisin purification from the complex broth have been investigated. But these methods increase the cost of nisin production, and its wide application is limited. Foam separation is an economical and effective technology for protein concentration and separation. In this paper, we utilized foam separation technology to recover nisin from fermentation broth, and studied the effect of ionic strength on the experimental system. The results showed that with ionic strength increasing, surface tension and inactivation ratio first decreased and then increased, and, however, foaming ability, foam stability, enrichment ratio and recovery first increased and then decreased. Under the conditions of the titer of nisin fermentation broth 4200 IU/ml, pH 3.0, feed liquid 250 ml, air flow rate 30 ml/min and temperature 25 °C, the maximum enrichment ratio and recovery and the minimum inactivation ratio of nisin reached 6.4, 86.44% and 9.89%, respectively, when the ionic strength was 0.41 mol/kg. Furthermore, we obtained higher nisin recovery and activity using sodium rather than potassium salt.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideResearch highlights► Foam properties first increased and then decreased with increase of ionic strength. ► Enrichment ratio and recovery of nisin first increased and then decreased. ► Inactivity ratio of nisin first decreased and then increased. ► E, R and inactivation ratio of nisin were affected by ionic strength and ion types.