Principles and practice of designing microbial biocatalysts for fuel and chemical production

ABSTRACT The finite nature of fossil fuels and the environmental impact of its use have raised interest in alternate renewable energy sources. Specifically, non-food carbohydrates, such as lignocellulosic biomass, can be used to produce next generation biofuels, including cellulosic ethanol and other non-ethanol fuels like butanol. However, currently there is no native microorganism that can ferment all lignocellulosic sugars to fuel molecules. Thus, research is focused on engineering improved microbial biocatalysts for production of liquid fuels at high productivity, titer and yield. A clear understanding and application of the basic principles of microbial physiology and biochemistry are crucial to achieve this goal. In this review, we present and discuss the construction of microbial biocatalysts that integrate these principles with ethanol-producing Escherichia coli as an example of metabolic engineering. These principles also apply to fermentation of lignocellulosic sugars to other chemicals that are currently produced from petroleum.

Microbial biocatalysts in the biocatalytic processes of the degradation of organophosphorus compounds

A number of single microorganisms and microbial consortia, carrying out the destruction of organophosphorus compounds (OPC) by using their own enzymatic systems, were identified and investigated. They can use OPC as a source of nutrients such as carbon and/or phosphorus. The rate of OPC decomposition varies and depends mainly on environmental conditions (pH, temperature, availability of oxigen, etc.) and composition of native microbial community. The development of genetically modified organisms capable of degrading OPC, the immobilization of cells and the creation of artificial consortia are approaches that increase the efficiency of biodegradation of OPC.

Synthesis of oxyfunctionalized NSAID metabolites by microbial biocatalysts

The synthesis of valuable metabolites and degradation intermediates of drugs, like non-steroidal anti-inflammatory drugs (NSAIDs), are substantially for toxicological and environmental studies, but efficient synthesis strategies and the metabolite availability are still challenging aspects. To overcome these bottlenecks filamentous fungi as microbial biocatalysts were applied. Different NSAIDs like diclofenac, ibuprofen, naproxen and mefenamic acid could be oxyfunctionalized to produce human metabolites in isolated yields of up to 99% using 1 g L−1 of substrate. Thereby the biotransformations using Beauveria bassiana, Clitocybe nebularis or Mucor hiemalis surpass previous reported chemical, microbial and P450-based routes in terms of efficiency. In addition to different hydroxylated compounds of diclofenac, a novel metabolite, 3’,4’-dihydroxydiclofenac, has been catalyzed by B. bassiana and the responsible P450s were identified by proteome analysis. The applied filamentous fungi present an interesting alternative, microbial biocatalysts platform for the production of valuable oxyfunctionalized drug metabolites.ImportanceThe occurrence of pharmaceutically active compounds, such as diclofenac and its metabolites, in the environment, in particular in aquatic systems, is of increasing concern because of the increased application of drugs. Standards of putative metabolites are therefore necessary for environmental studies. Moreover, pharmaceutical research and development requires assessment of the bioavailability, toxicity and metabolic fate of potential new drugs to ensure its safety for users and the environment. Since most of the reactions in the early pharmacokinetics of drugs are oxyfunctionalizations catalysed by P450s, oxyfunctionalized metabolites are of major interest. However, to assess these metabolites chemical synthesis often suffer from multistep reactions, toxic substances, polluting conditions and achieve only low regioselectivity. Biocatalysis can contribute to this by using microbial cell factories. The significance of our research is to complement or even exceed synthetic methods for the production of oxyfunctionalized drug metabolites.