Potential breakthroughs for biofuel and AD

Two recent discoveries at universities in the UK and Australia could result in more efficient biofuel production and anaerobic digestion processes.

Researchers at Harper Adams University in Shropshire have claimed that anaerobic fungi found in the digestive tracts of cattle have the potential to simplify the production of chemicals or fuel from plant biomass.

Researchers from the University of New South Wales, meanwhile, have discovered that by adding red dye to coal seams and food waste, the naturally-occurring microbes produced up to 10 times their normal amount of methane gas during the anaerobic digestion process.

Gut fungi could simplify biofuel production

The current process to produce products such as bio-ethanol requires genetically-modified enzymes from aerobic fungi, such as Trichoderma and Aspergillus, to digest plant biomass, followed by fermentation of released sugars by yeast.

Professor Michael Theodorou, leader of the Agricultural Centre of Sustainable Energy Systems (ACSES) at Harper Adams University, is among a group of scientists whose paper, ‘Early-branching gut fungi possess a large, comprehensive array of biomass degrading enzymes’, was published online by the journal Science last Thursday (18 February).

Theodorou described the current process as ‘complex and not cost-effective because it requires chemical pre-treatments to remove lignin from plant biomass, prior to the two-stage microbial process’. The group aimed to find a more ‘straight-forward’ alternative.

The report showed that enzymes from anaerobic fungi, found in the gut of herbivores, were significantly better than the GM aerobic fungal enzymes at converting plant biomass to constituent sugars.

The gut fungi naturally convert plant biomass to sugars, which are then further processed as energy sources for their host animals. Theodorou commented that the fungi are able to achieve plant biomass conversion ‘effectively and without the need for pre-treatment’.

Theodorou said: “In our work we have identified hundreds of enzymes from anaerobic fungi with commercial biotechnology potential. It is because these fungi are able to survive in such a highly-competitive microbial ecosystem, where a myriad of protagonists seek to degrade plant biomass, that we believe they are so effective at their job.

“We need to invest more resources to study this group of relatively unknown microorganisms. They may hold the key to the renewable technology of effective biomass conversion. Their full potential must be explored and exploited.”

Red dye can cause tenfold increase in microbe methane production

A five-year-long research project, supported by the Australian Research Council and industry partner Biogas Energy, testing a technique for biogas production through anaerobic digestion (AD) involving the addition of small amounts of synthetic dye has also been published this week.

The study, ‘Novel phenazine crystals enable direct electron transfer to methanogens in anaerobic digestion by redox potential modulation’, conducted at the University of New South Wales (UNSW) in Australia, found that the red dye formed needle-like crystals to help the methane-producing microbes grow faster.

Researchers say the innovation could improve the economics of using woody crops and leftover food as commercial sources of AD biogas, as well potentially extending the lifespan of coal seam gas wells (such wells containing methane-rich natural gas are common in Australia, as well as countries including the US and Canada; the controversial technique of hydraulic fracturing, or fracking, is sometimes used to extract the gas from coal beds).

The report’s senior author, UNSW Associate Professor Mike Manefield, said: “Our research in the lab and in coal boreholes near Lithgow has shown that the crystals can lead to a massive leap in methane production – a tenfold increase from coal, and an 18-fold increase from food waste.”

The researchers studied a small synthetic molecule called neutral red that has been used for more than 150 years as a textile dye, or for staining cells under a microscope.

Small amounts of neutral red were injected 80 metres underground at three sites into the water-saturated coal seam. A five to tenfold increase in methane production was observed during a 12-month period.

Manefield added: “We knew [the dye] was able to shuttle electrons about and we wondered if it could deliver them directly to the microbes that produce methane. The crystals act as electron sponges, harvesting electrons from minerals and bacteria in the mixture and then transferring them with a lot of power to the methane-producing microbes, boosting their growth.”

Manefield predicts that biogas emitted by microbes will be vital for meeting the world’s future energy needs and helping reduce greenhouse gas emissions from burning other fossil fuels.

The paper on gut fungi for biomass renewable technology is available at the Science journal’s website.

The research paper on methane production can be downloaded from the Energy & Environmental Science journal site.