Microbial biofilms: new catalysts for maximizing productivity of long-term biotransformations.
The performance of biocatalytic reactions is often hampered by product and/or substrate toxicity and short-term reaction times due to instable biocatalysts. Microbes in biofilms show a remarkable resistance against biocides and form stable communities. In nature, especially in environments characterized by harsh conditions such as heavily contaminated sites, cells grow pre-dominantly in biofilms, which enable them to cope with physiological stress. This robustness was utilized to design a bioprocess concept based on catalytic biofilms for stable long-term transformations of toxic reactants. Sixty-nine bacterial strains have been screened to find organisms suitable for biofilm-based biotransformations. This included host strains important for recombinant enzyme expression and strains isolated from biofilters or contaminated soils. Nearly all organisms with bioremediation potential showed good biofilm forming capacities. Pseudomonas sp. strain VLB120DeltaC was chosen as a model organism due to its excellent biofilm forming capacity and its well-studied capability of catalyzing asymmetric epoxidations. A tubular reactor was used for the biotransformation of styrene to (S)-styrene oxide as a model reaction. The process was stable for at least 55 days at a maximal volumetric productivity of 16 g/(L(aq) day) and a yield of 9 mol%. In situ product extraction prevented product inhibition of the catalyst. Biofilm physiology and dynamics are characterized during the biotransformation and limitations and advantages of this reaction concept are discussed.
Gross
Rainer
R
Department of Biochemical and Chemical Engineering, University of Dortmund, Emil-Figge-Str. 66, 44221 Dortmund, Germany.
Hauer
Bernhard
B
Otto
Katja
K
Schmid
Andreas
A
D018441:Biofilms; D019149:Bioreactors; D001709:Biotechnology / Q000295:instrumentation / Q000379:methods; D001711:Biotransformation; D002384:Catalysis; D004852:Epoxy Compounds / Q000737:chemistry / Q000378:metabolism*; D011549:Pseudomonas / Q000145:classification / Q000502:physiology*; D020058:Styrene / Q000378:metabolism*; D013997:Time Factors
D004852:Epoxy Compounds; D020058:Styrene; C013690:styrene oxide