Simultaneous and selective decarboxylation of l-serine and deamination of l-phenylalanine in an amino acid mixture—a means of separating amino acids for synthesizing biobased chemicals

•Selective conversions of l-serine using l-serine decarboxylase or l-phenylalanine using l-phenylalanine ammonia-lyase in a mixture of amino acids.•Simultaneous conversions of l-serine using l-serine decarboxylase and l-phenylalanine using l-phenylalanine ammonia-lyase.•Performance of l-serine decarboxylase is not detrimentally affected by the reaction of l-phenylalanine ammonia-lyase.•Performance of l-phenylalanine ammonia-lyase is positively affected by the reaction of l-serine decarboxylase.

Amino acids (AAs) obtained from the hydrolysis of biomass-derived proteins are interesting feedstocks for the chemical industry. They can be prepared from the byproduct of biofuel production and agricultural wastes. They are rich in functionalities needed in petrochemicals, providing the opportunity to save energy, reagents, and process steps. However, their separation is required before they can be applied for further applications. Electrodialysis (ED) is a promising separation method, but its efficiency needs to be improved when separating AAs with similar isoelectric points. Thus, specific conversions are required to form product with different charges. Here we studied the enzymatic conversions which can be used as a means to aid the ED separation of neutral AAs. A model mixture containing l-serine, l-phenylalanine and l-methionine was used. The reactions of l-serine decarboxylase and l-phenylalanine ammonia-lyase were employed to specifically convert serine and phenylalanine into ethanolamine and trans-cinnamic acid. At the isoelectric point of methionine (pH 5.74), the charge of ethanolamine and trans-cinnamic acid are +1 and –1, therefore facilitating potential separation into three different streams by electrodialysis. Here the enzyme kinetics, specificity, inhibition and the operational stabilities were studied, showing that both enzymes can be applied simultaneously to aid the ED separation of neutral AAs.