Optimization Of The Ion-exchange Technology For The ε-poly-L-lysine Extraction By Macroporous Cation Resin And Its Industrial Application

ε-poly-L-lysine(ε-PL)is a kind of green and safe biological preservative.China has officially approved ε-PL and its hydrochloride as new food additive in 2014.The fermentation yield has reached the requirements of industrial production after many years of strain breeding and optimization of fermentation strategies.However,the domestic research on the separation of ε-PL is still not perfect,which has seriously restricted the industrialization of ε-PL.Therefore,it is important to research and develop the ε-PL separation and extraction technology.This study optimized the dynamic conditions of ion exchange based on the previous research.The extraction process with ion exchange technology as the core was established,and the stability of the process was investigated.Ultimately,the extraction process was perfectly applied to pilot production.The main results obtained in this study are as follows:(1)Based on the optimization and comparative study on the dynamic conditions of Na+-form and NH4+-form IRC-50 resin,Na+-form IRC-50 resin is considered more suitable for industrial application.The optimal dynamic conditions of Na+-form resin was that loading p H was 7,the loading rate was 5 BV·h-1,the elution concentration was 0.25 mol·L-1 Na OH and the elution rate was 2 BV·h-1.Under the optimum operating conditions,the desorption rate was above 95%,the working exchange capacity was 303.25 mg·g-1,the ε-PL purity enhanced 51.26%,and the removal rate of protein and pigment was above 60%.(2)The possibility of removing the impurity in ion exchange eluent by ion exchange was explored.By analyzing the source and nature of impurities,it was determined that the impurity was derived from fermentation,charged properties and ε-PL approximation,and the molecular weight was about 900-2000 Da.The method can partially removed impurities such as gradient elution with Na+-form IRC-50 resin,negative adsorption combined with positive adsorption,partial collection and strong acid resin.It can be seen that the isoelectric point of ε-PL and impurity are very close to each other,and it is difficult to remove the imputity by ion exchange method.(3)The effect of Na+-form IRC-50 resin on the extraction of ε-PL was studied under different scale-up.In the ten batch extraction process,the resin exchange capacity did not decrease significantly,the desorption rate was above 95%,the purity of the eluent was above 70%,and the process was relatively stable.The ion exchange unit was amplified 8 times and 27 times in laboratory scale,and the ion exchange separation performance was good after amplification.In the production process of ion exchange column with a total capacity of 5.5 m3,the ion exchange impurity removal was consistent with the laboratory results,and the loss rate of ε-PL was only about 2.62%.The appearance of the sample in the pilot production was almost white powder.The purity of the sample by HPLC was 99.21% and the results were in line with national standards.The results of mass spectrometry showed that the sample was Llysine polymer,and the degree of polymerization was 27-34.