Synthesis of l-homophenylalanine via integrated membrane bioreactor: Influence of pH on yield

l-homophenylalanine can be used as a precursor for production of angiotensin-converting enzyme (ACE) inhibitor, which possesses significant clinical application in the management of hypertension and congestive heart failure (CHF). Pure chiral l-homophenylalanine can be synthesized efficiently by employing enzymatic methods. The biocatalysts used for biotransformation must be retained and reused due to their costs. Conventional processes for l-homophenylalanine production utilized dialysis bag for biocatalysts retention. Nevertheless, this could only be efficiently adopted for laboratory scale processes which possess low scale-up potential. In order to overcome this problem, integrated membrane bioreactor is highlighted for sustainable biocatalytic synthesis of l-homophenylalanine in environmentally friendly conditions which has not been explored by other researchers. The yield of biocatalytic reactions is greatly affected by the pH of the reaction solution, as enzymes are highly sensitive to pH change. Thus in this study, the influence of pH on the product yield at ambient temperature and atmospheric pressure was evaluated. By using l-phenylalanine dehydrogenase and formate dehydrogenase as the biocatalysts, it was found that pure l-homophenylalanine could be synthesized with >80% yield and an enantiomeric excess of over 99% in the integrated membrane bioreactor by adjusting the pH of the reaction solution. The optimal pH was found to be 8.5, when independent of other parameters.