Encapsulation of an Agrobacterium radiobacter extract containing d-hydantoinase and d-carbamoylase activities into alginate–chitosan polyelectrolyte complexes: Preparation of the biocatalyst

Alginate–chitosan polyelectrolyte complexes (PECs) have been used for the first time as a suitable matrix for coimmobilisation of enzymes to reproduce a multistep enzymatic route for production of d-amino acids. Encapsulation of a crude cell extract from Agrobacterium radiobacter containing d-hydantoinase and d-carbamoylase activities into the PECs with negligible leakage from the formed capsules was accomplished. All results in this study indicate that the preparation of the biocatalyst (preparation method and chitosan characteristics) play a key role in the biocatalyst's properties. The most suitable biocatalysts were prepared using a chitosan with a medium molecular weight (600 kDa) and a degree of deacetylation of 0.9. For all of the preparation conditions under study, an encapsulation yield of around 60% was achieved and the enzymatic activity yields ranged from 30 to 80% for d-hydantoinase activity and from 40 to 128% for d-carbamoylase activity relative to the activities of the soluble extract. All of the biocatalysts were able to hydrolyze l,d-hydroxyphenylhydantoin into p-hydroxyphenylglycine with yields ranging from 30 to 80%.