ENZYMATIC-SYNTHESIS WITH MAINLY UNDISSOLVED SUBSTRATES AT VERY HIGH-CONCENTRATIONS

This review describes a recently developed method for enzymatic synthe sis with mainly undissolved substrates at very high concentrations. At the end of the reaction, up to 80% (w/w) reaction mixture is product, a fact which is promising in terms of industrial applications and lar ge-scale systems. In comparison with other approaches for enzymatic pe ptide synthesis, this method gives a very high mass of product combine d with good reaction yields and rates. We will analyze the historical development from two different directions which have been reported; th ese are described with terms like ''solid-to-solid conversion'' and '' heterogenous eutectic mixtures''. The reaction requires and takes plac e in a liquid phase which, however may be of very small volume. This r eview analyzes in detail the function of additional water or organic s olvents (around 10% w/w). The liquid phase formed is usually dependent on these third components; however, it can also result from a eutecti c two-substrate mixture, We summarize what is known so far about the t hermodynamics and kinetics. Finally, the possibility for and main prob lems of scale up are discussed. (C) 1998 Elsevier Science Inc.