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 VLB120DC 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 À1 aq day À1 with a maximum of 70 g L À1 aq day À1 and biomass concentrations of 45 g BDW L À1 aq have been achieved over long continuous process periods (!50 days) without reactor downtimes.

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The current industrial production of polymer building blocks such as ε‐caprolactone (ε‐CL) and 6‐hydroxyhexanoic acid (6HA) is a multi‐step process associated with critical environmental issues such as the generation of toxic waste and high energy consumption. Consequently, there is a demand for more eco‐efficient and sustainable production routes. This study deals with the generation of a platform organism that converts cyclohexane to such polymer building blocks without the formation of byproducts and under environmentally benign conditions. Based on kinetic and thermodynamic analyses of the individual enzymatic steps, a 4‐step enzymatic cascade in Pseudomonas taiwanensis VLB120 is rationally engineered via stepwise biocatalyst improvement on the genetic level. It is found that the intermediate product cyclohexanol severely inhibits the cascade which could be optimized by enhancing the expression level of downstream enzymes. The integration of a lactonase enables exclusive 6HA formation without side products. The resulting biocatalyst shows a high activity of 44.8 ± 0.2 U gCDW−1 and fully converts 5 mm cyclohexane to 6HA within 3 h. This platform organism can now serve as a basis for the development of greener production processes for polycaprolactone and related polymers.

We utilized a photoautotrophic organism to synthesize 1,2-propanediol from carbon dioxide and water fueled by light. A synthetic pathway comprising mgsA (methylglyoxal synthase), yqhD (aldehyde reductase), and adh (alcohol dehydrogenase) was inserted into Synechocystis sp. PCC6803 to convert dihydroxyacetone phosphate to methylglyoxal, which is subsequently reduced to acetol and then to 1,2-propanediol. 1,2-propanediol could be successfully produced by Synechocystis, at an approximate rate of 55 μmol h g . Surprisingly, maximal productivity was observed in the stationary phase. The production of 1,2-propanediol was clearly coupled to the turn-over of intracellular glycogen. Upon depletion of the glycogen pool, product formation stopped. Reducing the carbon flux to glycogen significantly decreased final product titers. Optimization of cultivation conditions allowed final product titers of almost 1 g L (12 mM), which belongs to the highest values published so far for photoautotrophic production of this compound.