Multiphase Bioreactor Design

CHAPTER FIVE

ADVANCES IN THE SELECTION AND

DESIGN OF TWO-LIQUID PHASE

BIOCATALYTIC REACTORS

GARY J.LYE AND JOHN M.WOODLEY

The Advanced Centre for Biochemical Engineering, University College

London, Torrington Place, London WC1E 7JE, UK

ABSTRACT

The application of two-liquid phase biocatalysis presents some difficult

biochemical engineering challenges including the selection of an

appropriate reaction medium, reactor design and operating parameters.

These selections also have critical implications for subsequent

downstream processing operations such as phase separation and product

recovery. In this Chapter each of these areas will be discussed in the light

of progress made in recent years. With the advent of molecular biology

techniques allowing, for example, the engineering of solvent-resistant

biocatalysts, the application of two-liquid phase biocatalysis is set to

become more widespread in the coming years. Environmental constraints

may also lead to the development of alternatives to organic solvents as the

second liquid phase, which including the possibility of using room

temperature ionic liquids.

Keywords: Aqueous-organic media, multiphase biocatalysis, ionic

liquids, scale-up

INTRODUCTION

Biocatalysis offers some significant advantages over traditional chemical catalysis from
the viewpoint of both the organic chemist and the process engineer. For example, stereo-,
regio-and reaction-specific catalysts, operating under mild conditions, enable reactions
difficult to perform chemically to be carried out effectively with minimum side reactions
and by-products. In the past 30 years biocatalytic processes have come to find application
in the pharmaceutical and fine chemical industries as an alternative to chemical synthesis
for high value products (in particular optically pure compounds) and today over 100
processes are operating commercially throughout the world. However, the majority of
these processes are hydrolytic resolutions of racemic compounds to produce chiral
synthons or optically pure products. Recent developments in biocatalysis will now enable
the application of biologically mediated carbon-carbon bond forming reactions and redox
conversions which is where the real power of biocatalysis lies.