Turning toxic by-product into Biofuel Booster

Here's an elegant example of turning a problem into a solution. Scientists at Brookhaven National Laboratory were studying an enzyme called ADO (aldehyde-deformylating oxygenase) that naturally produces alkanes — long carbon-chain molecules that are chemically similar to the hydrocarbons in gasoline and diesel fuel. The appeal of ADO is obvious: if you can get bacteria or algae to run this enzyme efficiently, you could produce biofuel that doesn't require any further processing before it can be used in an engine.

The catch was that the reaction kept stopping after just three to five cycles. The enzyme was essentially poisoning itself. The culprit turned out to be hydrogen peroxide: one of the electron transport proteins involved in the reaction was reacting with oxygen to generate hydrogen peroxide as a by-product, and that hydrogen peroxide was inhibiting ADO, shutting the whole process down.

A Simple Fix With a Big Impact

Once the team understood the problem, the solution was surprisingly straightforward. They introduced a second enzyme called catalase, which breaks down hydrogen peroxide into harmless water and oxygen. When both enzymes were present, the reaction didn't stop after five cycles — it ran for more than 225 cycles.

Taking this further, the researchers engineered a bi-functional enzyme by physically linking ADO and catalase together. The reasoning was that by keeping the two enzymes in close proximity, any hydrogen peroxide generated near ADO would be immediately neutralized by the attached catalase before it could build up to inhibitory levels. The results were impressive: in test tube experiments and pilot studies in bacteria, the bi-functional enzyme produced at least five times more alkane than ADO alone.

Why This Matters

Unlike ethanol, which is produced by fermenting sugars and still requires energy-intensive processing, alkanes produced biologically could potentially be used directly as fuel — extracted from the organism and pumped straight into an engine. That makes them a particularly attractive target for next-generation biofuels.

The team is now working on installing the bi-functional enzyme into algae and green plants, which could use sunlight to drive the entire process. It's a long road from lab demonstrations to industrial-scale fuel production, but solving the self-inhibition problem is a meaningful step in the right direction.

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Source: Brookhaven National Laboratory

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Environmentally friendly alternative to toxic heavy metals in paint !

An enzyme system could be an environmentally friendly alternative to toxic heavy metal drying agents in paints

 Austrian scientists have shown that an environmentally friendly enzyme, laccase, can be used to replace toxic drying agents in paint.

Currently, water-based paints contain heavy metals that dry the alkyd (polyester) resin films that are used as binding agents by catalysing the oxidative cross-linking of unsaturated fatty acid moieties in the films.

Heavy metals are often toxic, and the commonly used cobalt-based catalysts have recently proved to be carcinogenic, and so alternative materials are being sought.

Enrique Herrero Acero at the Austrian Centre of Industrial Biotechnology, Graz, and colleagues, decided to replace the heavy metal catalysts with a laccase enzyme–mediator-based, non-toxic biocatalyst. Laccases, found in fungi, bacteria and plants, can catalyse the oxidation of mainly phenolic substances, and are already used in other fields, including the food, pulp and paper, and textile industries.

Mediators are small molecules that can be used to broaden the substrate scope of an enzyme by acting as ‘electron shuttles’ between the enzyme and substrate. Herrero Acero faced a challenge in ‘selecting the most effective mediator based on a novel rapid screening procedure’.

The team used a fluorescent sensor system to measure the oxygen concentration in the film as the oxygen is consumed in the cross-linking reaction. The sensor system uses an indicator dye, immobilised in polystyrene, whose luminescence is quenched by oxygen, allowing the progress of the reaction to be monitored in both the emulsion and in the drying film.

1-Hydroxybenzotriazole proved to be an effective mediator for laccase in the oxidation of the alkyd resin, and measurements of the oxygen consumption during the reaction  showed that it proceeded by a two-phase radical mechanism, via peroxy-cross-linking. Using the novel screening technique, Herrero Acero intends to ‘search for novel mediators with higher performance and from renewable sources’.

Andrew Laws, of the University of Huddersfield, UK, and an expert in enzyme catalysis and bioorganic reaction mechanisms, says that ‘the enzyme performs remarkably well considering the environment that it is in’. He anticipates further research into the kinetics of the reaction, as it is not yet as fast as the cobalt-catalysed drying process. Both Laws and Herrero Acero expect future work to involve engineering the laccase enzyme to improve its stability and activity.

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