Development of a high‐efficiency trans‐cinnamic acid bioproduction method by pH‐controlled separation technology

Abstract

BACKGROUND: Trans-cinnamic acid (t-CA) and its derivatives have been shown to be antioxidant and antibacterial, and can be used in food additives and flavors. However, a traditional t-CA production via chemical synthesis with a condensation reaction may not be suitable for its application in the pharmaceutical and food fields as it is not a 'green' route. This study investigated the bioconversion of L-phenylalanine (L-phe) to t-CA using engineered whole-cell Escherichia coli BL21(DE3) expressing phenylalanine ammonia-lyase (PAL, EC 4.3.1.5) as a biocatalyst. To prevent product inhibition, an in situ reaction and separation of t-CA was performed using a pH-controlled biotransformation strategy. RESULTS:A coupling reaction and separation system based on pH adjustment was proposed for improving the bioproduction of t-CA. Using this process, 39.61 g L −1 t-CA was bioproduced from 40 g L −1 of L-phe in 8 h and a high purity (>98%) of t-CA product was achieved directly without additional purification. CONCLUSION:The bioprocess developed in this study is a highly efficient method for the bioproduction of t-CA and, therefore, offers a promising alternative route for t-CA production. Separation of t-CA from the reaction mixture by adjusting the pHThe reaction mixture was obtained after a 2 h bioconversion using 20 g L −1 of L-phe and 8.52 g L −1 DCW of cells at pH 9.0 and 55 ∘ C. After cells were removed by centrifugation, the supernatants were adjusted to different pH values by using HCl, and were allowed to stand at room temperature for 20 min, and then the acidified supernatants were centrifuged again for separating the t-CA precipitate. The concentrations of L-phe and t-CA in the acidified supernatants at different pH values were analyzed by HPLC.