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Biocatalysts


‘Biofuels from cellulosics will transform the industrial enzymes business’


Peder Holk Nielsen Novozymes


Bavaria, which will produce ethanol from cellulosic biomass at a rate of 1000t per 4500t of wheat straw. The unit uses a directed enzyme technology that Sud Chemie started developing in 2006, with a pilot plant coming into operation in 2009.


Enzyme makers are also looking to


carbon capture process. The original enzyme selected from nature has been improved 2m-fold in performance by directed evolution. ‘(We’ve) pushed enzyme-based carbon capture technology to a level that surpassed all expectations,’ says John Nichols, Codexis’ president and chief executive.


Artificial enzymes Alternatively, by using rational design rather than high throughput screening, scientists can produce enzymes for specific applications. By using synthetic amino acids, they can make a range of artificial enzymes. ‘Artificial enzymes offer a new avenue for coordination chemistry and a distinctive approach in the development of environmentally friendly, “green” catalysts for production processes,’ says Corinna Hess, lecturer in Durham University’s department of chemistry in the UK. Researchers at the Medical Research Council Laboratory of Molecular Biology. Cambridge, UK, have developed synthetic polymer alternatives to DNA, dubbed XNAs, based on sugars. These could also provide a platform for substitutes for conventional biocatalysts. Using rational design, chemists can make enzymes that mimic natural ones. These synthetic enzymes may not be identical to those they are modelled on but they can increase their efficiencies, making them suitable for industrial scale processes. Termites, for example, are being used as a model for synthetic enzymes to produce biofuels and biochemicals from lignocellulose, which is their source of nutrients. The insects use enzymes to digest lignocellulose,


exploit directed evolution technologies for other applications. Codexis in Redwood City, California, US, which has a partnership with Shell to develop biofuel enzymes, has produced an enzyme for separating CO2


from emissions in a


breaking it down to monosaccharides. Researchers at Florida and Purdue Universities in the US believe their work on the analysis of the termite’s enzymes will open the way to developing ‘biocatalyst cocktails’ for biofuel production. The ‘Holy Grail’ for enzyme developers


and producers is to make possible artificial photosynthesis so that the sun’s energy can be harnessed to split water into hydrogen and oxygen. Hydrogen is seen as having massive promise as an energy option because it has at least two and half times as much energy per kilogram as gasoline. Splitting water with


1000t


use of enzymes to make downstream products. On the other hand, we do a lot to help our customers adapt our enzymes to their processes.’


DSM, which is involved in


downstream operations, has a joint venture with the US-based bioethanol producer POET for the development and production of cellulosic biofuels. It also provides a system under which enzymes are produced on the same site as the


Industry uses ca 150 biocatalytic processes, says NRSC-Catalysis


process in which they are being applied. ‘We believe that the on-site manufacture of enzymes will be the most economical and technically preferred solution where we make use of the on-site available utilities and raw materials,’ says a DSM official. ‘This is vertical integration at its best.’


Clariant is following a similar


Quantity of ethanol produced at Clariant’s €28m demonstration plant in Bavaria from 4500t of wheat straw


synthetic biocatalysts triggered by solar energy has been done in laboratories, but the big challenge is the creation of technologies that have the prospect of commercial development.


A key part of artificial photosynthesis


research is the development of catalytic processes for forming molecular hydrogen. In plants, this is done by hydrogenase enzymes containing a pair of iron atoms, which move electrons in the splitting process. Scientists at the Pacific Northwest National Laboratory (PNNL), Richmond, Washington, US, and other centres, have demonstrated that hydrogenases with other metal atoms can operate more quickly than their natural counterparts, offering alternative synthetic possibilities.


Future directions With such a wide range of technologies available, enzyme makers should be able to rely on the microorganisms as a long-term source of revenue and profits, without the need to diversify their businesses, particularly into downstream segments. ‘Our business model is centred on the development, manufacture and delivery of enzymes,’ says Nielsen. ‘We have no plans for forward integration into the


strategy for supplying customers with microorganisms for making enzymes on-site. The company also aims to supply customers, with the help of specialist partners, with engineering packages to set up units for making enzymes and also the plants for their processing. Some start-up companies in sectors like biofuels are concentrating on the development of molecular and processing technologies so that they can control much of the value chain. Sapphire Energy in the US, for example, which develops strains of algae, farms the microorganisms and extracts and refines the oil from them, has been modifying the genome of the algae chloroplast, the part of the cell in which photosynthesis occurs. Its technology has the potential for ‘rationally altering photosynthetic metabolism’ and ‘moving closer to commercially viable algae biofuels’, according to Sapphire. While experts in artificial


photosynthesis technologies warn that its commercial exploitation is at least 15 years away, by then other synthetic enzyme processes will have gained a significant share of the total catalysis market worldwide. This is likely to provide the impetus for further expansion of the sector, with artificial photosynthesis a likely benefactor.


Sean Milmo is a freelance science writer based in Braintree, Essex, UK.


Chemistry&Industry • November 2012 31


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