Whole-cell catalysts hydrolysis reactions

Recombinant whole cells in particular turned out to be very attractive for bio-transformations in which more than one recombinant enzyme is needed such as redox reactions with in situ cofactor regeneration or hydrolysis with mrdtiple enzymes. With respect to the latter one, the dynamic kinetic resolution of hy-dantoins by a whole-cell catalyst that simultaneously overexpresses a racemase, a hydantoinase and a carbamoylase is a popular and industrially relevant example (Scheme 2.8) [23,24]. These cells convert a racemic hydantoin (an easily accessible substrate) to the corresponding enantiomerically pure d- or L-amino add with both high conversion and enantioselectivity. 

Scientists at Shell began work onthe enantioselective hydrolysis of racemic amides in the early 1990s 5]. Enzyme mediated hydrolysis of racemic N 1 phenylethylace tamide 2 using whole cells of Arthrobacter sp. enabled the production of enantio merically pure (S) 1 and (f ) 2 (Figure 14.2). The use of whole cells was not optimal and long reaction times were required to obtain pure (R) 2, as the selectivity of the catalyst was not very high. 

In a number of instances, whole-cell preparations have been preferred as catalysts for selected hydrolysis reactions in most of these cases the micro-organisms are easy to grow and simple to handle and are utilized because of the low cost involved. These cases will be integrated into the discussion as and when appropriate. 

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