Characterization of a biofilm membrane reactor and its prospects for fine chemical synthesis.

Biofilms are known to be robust biocatalysts. Conventionally, they have been mainly applied for wastewater treatment, however recent reports about their employment for chemical synthesis are increasingly attracting attention. Engineered Pseudomonas sp. strain VLB120 Delta C biofilm growing in a tubular membrane reactor was utilized for the continuous production of (S)-styrene oxide. A biofilm specific morphotype appeared in the effluent during cultivation, accounting for 60-80% of the total biofilm irrespective of inoculation conditions but with similar specific activities as the original morphotype. Mass transfer of the substrate styrene and the product styrene oxide was found to be dependent on the flow rate but was not limiting the epoxidation rate. Oxygen was identified as one of the main parameters influencing the biotransformation rate. Productivity was linearly dependent on the specific membrane area and on the tube wall thickness. On average volumetric productivities of 24 g L(aq) (-1) day(-1) with a maximum of 70 g L(aq) (-1) day(-1) and biomass concentrations of 45 g (BDW) L(aq) (-1) have been achieved over long continuous process periods (>or=50 days) without reactor downtimes.