Engineered Biofilm Catalysts

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Historically, biofilms are predominantly perceived as problematic; associated with infections, dental caries, marine and reactor fouling and reduction in heat transfer. In their natural environment individual planktonic cells have the tendency to cluster together at surfaces and interfaces. Within these clusters they protect themselves from environmental and chemical stress by secreting extracellular polymeric substances (EPS) a protective and adhesive polysaccharide matrix. This EPS gives the biofilm a degree of protection against extremes of pH, temperature or the introduction of organic solvents which cannot be tolerated by individual cells. In the current global climate of searching for increasingly green approaches to the synthesis of fine chemicals and pharmaceuticals there is a growing interest in employing biotransformations: using cells to produce useful products. Although such a strategy enables the generation of enantiomerically pure compounds, the reduction of steps in a synthetic route and the possibility of eliminating environmentally detrimental catalysts, solvents and reagents, their use is problematic due to the fact that individual cells cannot in general tolerate the extreme conditions required. In this research we exploit biofilms to produce highly active Engineered Biofilm Catalysts (EBC). This is a new area as the use of biofilms in biotransformations has been largely confined to wastewater treatment and bioremediation generally by mixed microbial communities referred to as consortia. Reports of the use of biofilms for synthesis of compounds are few and far between, industrially the list of compounds generated in such a manner is little more extensive than simple compounds such as acetic acid, ethanol, butanol, 2,3-butanediol, lactic acid, fumaric acid, and succinic acid. This interdisciplinary proposal presents a novel methodology for the development and exploitation of engineered biofilm catalysts (EBC) for biotransformations relevant to the fine chemicals and pharmaceutical industries. Recently we have demonstrated the generation and utilisation of an Engineered Biofilm Catalyst (EBC). The immobilised EBC not only demonstrated unprecedented stability but proved to be a strikingly better catalyst than the free cells. As the EBC is artificially generated there is considerable scope to engineer its microstructure. We propose to explore the general application of EBC to catalysis as well as to investigate how microstructure and gene expression relate to catalytic activity. We will employ EBC using flow chemistry to generate a prototype EBC reactor for biotransformations as an exemplar for future industrial exploitation.