| Cadaverine is a natural polyamine which can replace fossil-derived hexamethylene diamine to produce bio-based polyamides,helping to reduce energy crisis and mitigate environmental pollution.In this paper,lysine hydrochloride was used as a raw material to study the catalytic preparation of cadaverine hydrochloride using a permeabilized engineering E.coli strain heterologous expression of lysine decarboxylase.It solves the problems of using expensive catalysts in chemical methods to increase production costs and complex metabolic pathways and low yields of microbial fermentation methods.At the same time,in order to solve the problem that cadaverine still exists in the form of hydrochloride after the catalytic reaction,this paper uses cadaverine hydrochloride as a raw material to purify high-purity cadaverine through unit operations such as deprotonation,extraction,and rectification,which simplifies operations,reduces costs,and increases its potential for industrialization.The main conclusions of this article are as follows:(1)Firstly,the engineered strain BL21-Pcad-Cad A induced by cheap L-lysine hydrochloride instead of IPTG was constructed.Then the permeabilized cells were served as the biocatalyst for the production of cadaverine,because the enhanced permeability facilitated the mass transfer of the substrate and the release of products.In the shake flask stage,223 g / L of cadaverine can be obtained,the yield is 98.6%,and the lysine decarboxylase activity reaches 8.56 U/mg.After the replacement of industrial materials and the solution of the scale-up permeabilization process,the optimal process conditions are: 37 ℃,p H 5.6,400 g/L lysine hydrochloride,3.5 g/L permeabilized cells,0.1 m M pyridoxal phosphate.Cadaverine concentration reached 205 g/L with the yield of 92.1% after 20 h in a 2 L bioconversion system,achieving the level of industrial production.Furthermore,the costs of industrial materials for 2 L integrated strategy($2.78)was only 1/11 of the lab reagents($30.88).(2)Four integrated purification methods,which contained DeprotonationEvaporation,p H adjustment-Deprotonation-Evaporation,Deprotonation-ExtractionEvaporation,and Deprotonation-Extraction-Rectification,were explored,and the conditions of each unit operation in the selected method Deprotonation-ExtractionRectification were optimized as: deprotonation temperature 80 ℃,rotational speed 250 rpm,p H 13.5,reaction time 5 h;extraction temperature 55 ℃,rotation speed 250 rpm,extraction ratio 5:5,time 1 h;reflux ratio 1,pressure of the top 1 bar,bottom temperature 100-180 °C.Then the optimized method was applied to the 2 L purification system,resulting in a 99% purity of cadaverine with a yield of 87.47%.Furthermore,the n-butanol recovery ratio reached 91.25%.In summary,the integrated process described in this paper has greater advantages in enzyme activity,yield and cost,and provides a possible way for the industrial production of bio-based cadaverine. |
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