Covalent immobilization of halohydrin dehalogenase for efficient synthesis of epichlorohydrin in an integrated bioreactor.

Halohydrin dehalogenase (HHDH)-mediated dehalogenation of 1,3-dichloro-2-propanol (1,3-DCP) is a key step in the chemoenzymatic synthesis of epichlorohydrin (ECH) from glycerol. In this study, a covalent immobilization strategy was employed to enhance the stability of Agrobacterium tumefaciens HHDH using epoxy resin ES-103B as a carrier. Under optimal conditions, the activity recovery of ES-103B-immobilized HHDH (HHDH@ES-103B) was 62.4% and the specific activity was 1604 U/g. The HHDH@ES-103B exhibited excellent thermostability, with a half-life of 68.6 days at 40°C, which is 8.0-times higher than that of the free HHDH. A semicontinuous biotransformation of 1,3-DCP to ECH was performed using HHDH@ES-103B as biocatalyst in a recirculating packed bed reactor (RPBR), resulting in an ECH yield of 94.2%, with an average productivity of 5.2 g/L/h. The RPBR system exhibited a high operational stability and even after 50 cycles of reaction, it retained > 90% of the initial conversion. Furthermore, an integrated bioprocess based on in situ product recovery (ISPR) was developed in RPBR to overcome product inhibition. The integrated bioreactor equipped with an external macroporous adsorption resin HZD-9 column led to another 1.6-fold increase in ECH productivity to 8.46 g/L/h. This improved stability and reusability of HHDH@ES-103B demonstrated its potential for the biotransformation of 1,3-DCP to ECH. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 34:784-792, 2018.