An improved process for biocatalytic asymmetric amine synthesis by in situ product removal using a supported liquid membrane

Chiral amines are important building blocks in the pharmaceutical industry, and the biocatalytic synthesis of these compounds using ω-transaminases has been increasingly studied in recent years. In principal, asymmetric synthesis of chiral amines from a prochiral ketone is the preferable route, but it is often hampered by an unfavourable equilibrium position and product inhibition. An effective method for product removal is therefore necessary to drive the reaction towards product formation. In a recent study (Rehn et al., 2014) [29] we reported on the successful use of a supported liquid membrane (SLM) for the in situ product removal (ISPR) of (S)-α-methylbenzylamine (MBA) produced by Arthrobacter citreus ω-transaminase present in immobilized Escherichia coli cells. In the present work, we thoroughly discuss the factors influencing the performance of the SLM system and considerations for its successful use. Moreover, the system is further improved by implementing continuous control of the reactor pH using the amine donor substrate, and regeneration of the SLM unit at regular intervals to maintain the extraction performance, allowing the accumulation of 1.0 M (121 g/l) product in the stripping phase during operation for 91 h.