BACKGROUND Cadaverine is a natural polyamine that can replace fossil‐derived hexamethylene diamine to produce bio‐based polyamide. Despite huge developments in cadaverine bioproduction, an econo"mically attractive purification process is a highly important part of the production of high‐purity cadaverine. RESULTS This study utilized l‐lysine hydrochloride as a substrate for the production of high‐purity cadaverine via a litre‐scale integrated process incorporating fermentation, bioproduction, deprotonation, extraction and rectification. First, 8.24 U mg–1 lysine decarboxylase activity and 205 g L–1 cadaverine with a yield of 91.61% were achieved through the fermentation of low‐cost industrial culture by engineered Escherichia coli and the bioproduction of cadaverine by lysine decarboxylase. Secondly, four integrated purification methods – deprotonation‐evaporation, pH adjustment‐deprotonation‐evaporation, deprotonation‐extraction‐evaporation and deprotonation‐extraction‐rectification – were explored, and the conditions of each unit operation in the chosen method (deprotonation‐extraction‐rectification) were optimized. Then the optimized method was applied to a 2‐L purification system, resulting in 99% purity of cadaverine with a yield of 87.47%. Furthermore, the n‐butanol recovery ratio reached 91.25%, effectively avoiding the waste of resources and environmental pollution, and thus reducing purification costs. CONCLUSION The proposed experimental approach proves that this integrated process leads to the production of high‐purity cadaverine. In the 2‐L‐scale integrated process, 358.64 g cadaverine of 99% purity was produced at a cost of US$3.99 (US$1.11 per 100 g), which is far below its market price (US$784.71 per 100 g). This integrated process provides a potential way for the industrial‐scale production of bio‐based cadaverine. © 2020 Society of Chemical Industry

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Laccases have the advantages of non-specific oxidation and excellent catalytic activity. It is widely used in biomedicine, biosensor, and pollutant degradation. However, there are differences in the structure, substrate range, and fermentative expression of laccases depending on the source. In order to select a laccase with universality, we selected four representative laccases to analyze their catalytic properties from the aspects of sequence homology, isoelectric point, charged characteristics, active pocket, binding energy and the distance between the catalytic site and the substrate. The correlation analysis showed that the screening strategy was mainly based on structural analysis for a comprehensive evaluation through its activity and stability. The B. subtilis-derived laccase (CotA) with large and hydrophilic substrate binding pocket was screened out efficiently. It has the advantages of broad extent for substrates and strong alkali-resistance abilities. Therefore, this silico screening method can screen out suitable enzymes for specific application targets conveniently, which can lay the theoretical foundation for subsequent catalytic application studies.