| Lysine is one of the three basic amino acids.However,human and animal can't synthesize it in body.It also plays an important role in growth and metabolism in human and animal,and often is used as food additives and feed additives.Among all kinds of amino acids,the production and consumption of lysine is only next to glutamic acid,ranking second.China has now become the world's largest lysine market.In 2015,the total output of lysine was 1.1 million tons,and the total market supply reached 0.8 million tons in domestic.The 98% content lysine was about 9.1 to 9.3 RMB per kg,and the 70% content was about 5.3 to 5.5 RMB per kg in first quarter of 2017.The development of the separation and purification of lysine has become a new hotspot because of its important role in many fields,market requirement and price difference.In this paper,a new type of lab-made bacterial strain was used to ferment and produce lysine,and the separation process of downstream was studied.The most commonly used ion-exchange resin method was adopted.The process data of lysine separation was explored for the target of choosing the best resin,the best adsorption and desorption conditions.Finally,the static and dynamic adsorption principle and process of ion exchange separation of lysine were analyzed.The main conclusions are listed as follows:(1)In the analyzing test methods,optimization and verification of test conditions were conducted in determining of lysine and glucose concentrations with methods such as ninhydrin colorimetry,OPA pre-column derivatization with HPLC,and differential method with HPLC.The corresponding standard curves were established,and the correlations of the curves were good.(2)Seven kinds of resins were screened.Static experiments showed that the adsorption capacity of 001×7 ion exchange resin for 5 g/L lysine was 0.0751 g/g,and the desorption rate was 96.33%.Moreover,the 001×7 resin had a high selectivity to lysine,and hardly adsorbed glucose.Thus 001×7 ion exchange resin was chosen to conduct a further study for lysine adsorption.(3)The influencing factors of static adsorption of lysine by 001×7 resin were investigated,and the optimum adsorption conditions as follows: lysine solution volume was 100 m L,pH was 3.5-4.5 and adsorption time was 2 h.In this condition,the adsorption capacity was up to 0.09 g/g wet resin.The influencing factors of static desorption process were also investigated by using ammonia solution as the desorption reagent,and the optimum desorption conditions as follows: the ammonia concentration was 1 mol/L,volume was 100 mL,and desorption time was 4 h,finally the desorption rate reached 96.8%.The optimal static adsorption and desorption conditions could provide data reference for subsequent dynamic adsorption.(4)The adsorption isotherms of lysine by 001×7 resin under different temperatures and pH were investigated,and Freundlich model and Langmuir model were used to explain the adsorption process of lysine.The adsorption process was more accord with the Langmuir isotherm adsorption process,which belonged to monolayer adsorption.The effects of temperature and pH on the adsorption kinetics of the resin were investigated,and the results showed that the pseudo-second-order equation could simulate the adsorption process of lysine well.(5)The influencing factors of dynamic adsorption and desorption of lysine by 001×7 resin were investigated,such as sample concentration,flow rate and elution flow rate.The optimum conditions as follows: the sample concentration was 25 g/L-40 g/L,flow rate was 2.5 m L/min,and the elution flow rate was about 2.5 m L/min.(6)The dynamic adsorption of glucose indicated that the resin adsorption to glucose was physical absorption only,and it could be easily washed down.Based on the use of more than 10 consecutive times of 001×7 resin column,the result showed that the properties of 001×7 resin are stable and are applicable to continuous separation of lysine. |
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