Study On The Separation Of Nisin From The Fermentation Broth Of Lactococcus Lactics By Adsorption

Nisin is a bacteriocin of bactericidal activity against Gram positive bacteria and is commonly used as a food preservative in the food industry. At present, nisin is produced through fermentation by certain strains of Lactococcus lactis. It is the important step to separatie nisin from the fermentation broth. In the study, resins produced in China were chosen as the adsorbents. The kinetics and energetics of the anionic resins were studied.1. The adsorption and desorption of nisin from the fermentation broth by macroporous resins and anionic resins were studied. The adsorption quantities of the macroporous resin D4006 was 190 000IU/g and H103 was 124 000IU/g; 70%(v/v) ethanol solution (pH2～3) was chosen as the desorbent for nisin desorption; In the dynamic adsorption and desorption test, as for D4006,the pierce time was 43 min, and reached the balance time in 42.5h; as for H103,the pierce time was 85 min, and reached the balance time in 45.67h. The highest elute concentration of nisin appeared within 100min.The adsorption quantities of the anionic resin D113 was 120 000IU/mL and D4006 was 129 000IU/mL; 5%KCl (pH2～3) was chosen as the desorbent. The final recovery of nisin on D113 and D151 were 45.6% and 20.9%, respectively. In the dynamic adsorption and desorption test, the balance time was 20h and the highest elute concentration of nisin appeared in 2.5h. The activities of nisin separated by D113 was 15453IU/ml.2. The ion exchange kinetics for nisin onto D113 was developed. The results showed that it was the particle diffusion control (PDC) when 50r/min, 100r/min and 150r/min. As for D113, it was controlled by PDC at 40℃,50℃and by film diffusion control (FDC) at 25℃.3. The thermodynamics of nisin adsorption on D113 was studied. At 25℃,40℃and 50℃, the equilibrium data for the adsorption of nisin were correlated with the Langmuir type isotherm equations. The enthalpy of adsorption was above zero of D113 at 25℃,40℃and 50℃, the process of adsorption was an endothermic process. Temprature has little effect on the adsorption process.4. The effects of surfactant on on desorption of nisin from fermentation broth was studied. As for D4006, 59.2% and 61.8% of nisin was desorbed by using 2% (v/v)Tween-80 and 0.2% ( g ml-1) PEG20000, respectively. As for H103, with the addition of 2%(v/v)Tween-80 and 4% (g ml-1) PEG20000 the nisin desorption rates were 57.6% and 60.4%. Compared with the desorption rates without any surfactant, the nisin desorption rates increased approximately 20% both the two resins.