Termites are renowned for devouring wood. Now, bacteria in one termite species鈥� guts have been shown to break down toxic creosote, which is used to preserve wood. The finding could be useful for turning harmful, chemically treated wood waste into biofuels.
Termites鈥� guts are tiny bioreactors teeming with microbes that allow the insects to digest tough lignin and cellulose in wood. Previous studies suggest that these gut microorganisms could be key to turning lignocellulose 鈥� the of renewable carbon on the planet 鈥� into biofuels via anaerobic digestion.
Anaerobic digester systems commonly use methane-producing microbes in the absence of oxygen to convert food waste or sewage into biogas, a mixture comprising mostly methane with a bit of carbon dioxide. But converting woody plants is difficult because most microorganisms struggle to break up lignocellulose. Throw toxic wood preservers into the mix and it becomes even harder.
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Now, Sameh Ali and Jianzhong Sun at Jiangsu University, China, have found that bacteria living in Coptotermes formosanus 鈥� known as a 鈥渟uper-termite鈥� for its large colonies and voracious appetite for wood 鈥� can decontaminate wood that contains creosote while breaking down lignocellulose, making it easier for anaerobic bioreactors to then convert it into biofuels.
The researchers isolated bacteria from the termites鈥� guts and selected four species that they found could decompose creosote. They then grew these bacteria together in liquid cultures. When creosote-soaked sawdust was treated with the bacterial mixture for 12 days, it completely removed two toxic chemicals found in creosote: naphthalene and phenol. Lignocellulose content was also reduced.
The resulting product was then anaerobically digested, revealing that the bacterial pre-treatment boosted biogas and methane yields by around 58 per cent and 83 per cent respectively. 鈥淚f it is possible to scale the experiments up, the approach may be useful for recycling treated wood,鈥� says Nathan Lo at the University of Sydney, Australia.
Creosote, which can be carcinogenic, has long been used to protect timber against rot and wood-eating insects. Railway sleepers, telephone poles and fence posts are often permeated with it. However, such wood waste can be dangerous to recycle or burn. It usually ends up in landfill, but even there it releases pollutants into the atmosphere or ground.
鈥淐reosote-treated wood necessitates appropriate processing in order to eliminate pollution and public health risks,鈥� says Ali. He suggests that converting it into biofuels using bacteria offers 鈥渁 unique, sustainable decontamination solution鈥�.
Bioresource Technology
