German scientists have taken an important step toward creating more sustainable chemical processes following their success in manufacturing biocatalysts suitable for industrial applications from photosynthetically active microorganisms.
Plant biochemist Marc Nowaczyk and microbial biochemist junior professor Robert Kourist, both of the Ruhr-Universität Bochum, Bochum, Germany, are leading the research.
The two believe that photoautotrophic organisms — those that gain their energy from light — could be the key to a successful move away from fossil fuel sources. Their particular focus is on cyanobacteria, which only require light, water, nutrient salts and carbon dioxide to synthesize enzymes.
Cyanobacteria are aquatic and are believed to be one of the oldest organisms on the planet. Many Proterozoic oil deposits are attributed to the activity of cyanobacteria. They also are important providers of nitrogen fertilizer in the cultivation of rice and beans.
The scientists are using this sustainable and renewable approach to develop what they have termed “green cell factories.”
Using cyanobacteria, the researchers manufactured enzymes that, in turn, can serve for producing valuable pharmaceutical substances. To do this, they added genes for enzyme synthesis into the microorganisms.
“A particularly important observation was that cell components of cyanobacteria do not interfere with the catalytic activity,” notes Kourist. “Using photosynthesis for the production of industrial enzymes from carbon dioxide and water is a novel and environmentally friendly approach,” he adds.
Many catalytic processes result not only in the desired product, but also in a number of byproducts that must be painstakingly filtered out. Chemical reactions often generate two substances whose chemical structures behave like image and mirror image, so-called enantiomers. Using the cyanobacteria, the researchers succeeded in generating primarily one structure — an important requirement for many pharmaceutical applications. They published the results in the journal Microbial Cell Factories.
“Our results show that the introduction of foreign genes is straightforward. Cell components from Synechocystis did not interfere with the stereoselective transformations, underlining the usability of photoautotrophic organisms for enzymes production. Given the considerable commercial value of recombinant biocatalysts, cyanobacterial enzyme expression thus has the potential to complement existing approaches to use phototrophic organisms for the production of chemicals and biofuels,” note the authors in their conclusion.
However, widespread future application calls for improved efficiency. This requires faster-growing cyanobacteria that don’t need costly freshwater for growth.
“Several cyanobacterial strains have an outstanding potential for this purpose,” says Nowaczyk. The team from Bochum already is looking for ways to optimize the cell factories, specifically by improving photosynthetic electron transport.
In a similar approach, the European Union-funded Peroxicats project aims to develop novel and robust peroxidases and peroxygenases to replace the harsh chemicals currently used in industrial oxidation processes.
“The research done by the Peroxicats team is expected to give the European chemical sector a toolbox of both novel and more robust enzymes of potential use as alternatives in specific industrial applications,” says project coordinator Ángel T Martínez, from the Spanish Research Council (CSIC), Madrid.
Thanks to the sort of new genetic engineering tools being used at Bochum, enzymes and other proteins can be produced in a large-scale and at low cost by isolating or synthesizing the corresponding genes and introducing them into suitable producing hosts. Fungi are particularly good sources for these enzymes; part of the research has been dedicated to finding novel fungi from specific habitats. So far, 100 strains of interest have been screened for the production of peroxidize-type of enzymes.
The Peroxicats research team also has been able to determine the mechanism used by the enzymes to transform a wide range of chemicals in potentially interesting reactions. “These results will become available for pilot or industrial scale evaluation thus strengthening the penetration of biotech solutions in the European chemical sector,” adds Martínez.
“Unlike other harsh reagents currently added to bring about chemical reactions, enzymes act as efficient biocatalysts in nature, are non-hazardous, biodegradable and derived from renewable resources,” he says. “Their industrial use is therefore translated into societal benefits in terms of a decrease in energy consumption or more environmentally friendly processes and goods, among others.”
The enzymes have a huge range of potential industrial applications, including: oxygenation/hydroxylation of aromatic bulk hydrocarbons; plant cell-wall delignification; manufacture of flavors for food and beverages; degradation of phenolic and non-phenolic aromatic pollutants; organic synthesis; and the production of polymers and biologically active compounds.
Seán Ottewell is Chemical Processing's Editor at Large. You can e-mail him at firstname.lastname@example.org