Production of (2E)-hexenal by a hydroperoxide lyase from Amaranthus tricolor and salt-adding steam distillation for the separation

(2E)-Hexenal is widely used in flavors and perfumes; however, it is mainly derived from chemical synthesis. In this study, hydroperoxide lyase (HPL) naturally originated from Amaranthus tricolor was used to catalyze the reaction to generate (2E)-hexenal from 13-hydroperoxy-9Z, 11E, 15 Z-octadecatrienoic acid (13-HPOT), and salt-adding steam distillation was used for the separation of (2E)-hexenal. A maximum yield of (2E)-hexenal that reached 1,156.4?mg?L^?1 was obtained with a high substrate concentration (40?mM 13-HPOT) under the following conditions: 10?min, pH 7.5, 20?°C, HPL 16 U?mL^?1, butylated hydroxytoluene (BHT) 1?mM, and dithiothreitol (DTT) 15?mM. Then the separation of (2E)-hexenal was conducted by salt-adding steam distillation. It was found that AlCl₃ had the greatest effect on the separation of (2E)-hexenal, followed by CaCl₂ and NaCl. The distillate yield with the addition of AlCl₃ was 93.2?%, while the distillate yield without the addition of salt was 81.2?%. The distillate concentration with AlCl₃ was 6,464.2?mg?L^?1, while the distillate concentration without the addition of salt was 4,490.3?mg?L^?1. The addition of salt improved the efficiency of the steam distillation. This study was greatly meaningful for providing a green method to the large-scale production of (2E)-hexenal.