New robust enzymes for bioplastic production

Nature will be the main hunting ground for Isabel Arends and her research team in their efforts to uncover novel enzymes with very special properties. These new enzymes must be capable of producing bio building blocks for bioplastics. “With enzyme technology we can even make bioproducts that are water resistant and durable.”

Today’s production of building blocks for plastics is based on fossil fuels and chemical processes. “These building blocks can be produced in a more environmentally friendly way by using bio-ethanol as a starting compound, in combination with enzymes,” says Isabel Arends, professor in Biocatalysis and Organic chemistry at the Delft University of Technology. AkzoNobel, the industrial project partner for this BE-Basic project and a market player in the production of monomers for plastics, stands behind this idea.

That enzymes can endure much tougher conditions than micro-organisms is often the main consideration in opting for enzymatic processes, as in the pre-treatment of cellulosic feedstocks, for example. Enzymes are also more easy to condition and train so that they can cope with extreme conditions such as the presence of organic solvents, high salt levels or high temperatures. “That’s why you can make the same building blocks by using enzymes instead of via chemical pathways. The true advantage is that enzymes allow us to perform the process in an atom-efficient way. ”Our goal is to develop novel enzymes that convert bio-ethanol into building blocks for durable bulk plastics.”


Promising places

Nature is a good source in which to look for these novel enzymes. Postdoc Özlem Erol-Hollmann has already taken samples from many different locations, ranging from the North Sea and the harbour of Rotterdam to the Botanical gardens at Delft and Texel. “The most promising places to take sample from are the places were micro-organism are exposed to some form of stress,” says Arends. In industrial and salty environments the bacteria are already trained to cope with more extreme conditions and have developed specialised enzymes to survive. “In these locations we have a good chance of finding something really new; the dream of every researcher. Finding new enzymes also gives us the opportunity to build up new intellectual property. That is a big advantage over existing enzymes, which are protected by patents.”

The scientists got an initial idea of what such an enzyme would look like in theory from the literature. With the corresponding DNA-code they developed a kind of probe that they could use to search for enzyme variants in the total DNA pool found in their soil and water samples. “We call it ‘DNA-mining’. Once we find the DNA that codes for enzyme variants, we can produce that enzyme in the lab using molecular biological techniques and test whether it is able to convert bio-ethanol,” Arends explains.

Screening for activity

The screening assays designed to test the newly found enzymes in terms of activity are developed by postdoc Dr. Marina Faiella. “Together we are looking at more than a thousand enzymatic variations, which all have to be tested. Therefore we are developing high-throughput screening methods based on a colour reaction that indicates whether an enzyme is displaying the required activity. We want to be able to screen ninety-six variants at the same time.” This is still a qualitative method. The second step of the screening will be a thorough quantitative analysis of the conversion with more advanced analytical equipment.

For this high-throughput screening (HTS) work the department of Biotechnology has arranged a specially dedicated lab in Delft. “Our HTS-lab has the safety level ML II, which is necessary for working with metagenomes from environmental samples. Because the samples must not leave the lab space, we have also our screening robot, plate readers and chromatograph inside.” Research in Delft is in full swing and Arends’s group is ready to discover the first enzymes. “If we succeed AkzoNobel will have a blueprint for an entirely new and sustainable process based on bio-ethanol and enzymes. It will be green, clean, and waste free.”


January 2010