BORON BASED SEPARATIONS FOR IN-SITU RECOVERY OF L-ERYTHRULOSE FROM TRANSKETOLASE-CATALYZED CONDENSATION

In this article we report on the application of in situ product remova l (ISPR) (the concurrent recovery of a product during the product form ation process) as a means of improving the productivity of bioconversi ons. The Escherichia coli transketolase-catalyzed condensation of glyc olaldehyde with beta-hydroxypyruvate to yield L-erythrulose (and carbo n dioxide) was chosen as a model system. Those ISPR methods based on p henylboronate-diol interactions showed greatest potential for use as a selective means of removing L-erythrulose from the reaction medium. S oluble, insoluble, and immobilized boronates were investigated. Concen trations of free phenylboric acid of 100 mM and above were toxic to tr ansketolase, thus rendering the use of these methods unsuitable for IS PR. However, one of the immobilized phenylboronate resins (Affi-Gel 60 1(R)) was not toxic to the enzyme, although significant levels of nons pecific binding of both substrates were observed. When ISPR was perfor med on the model reaction using this resin with substrate feeding, it proceeded to completion. (C) 1997 John Wiley & Sons, Inc.