A bacterium in mushroom crop residue can contribute to greener and cheaper biofuel production, according to new research.

A team of engineers recently discovered that a naturally occurring bacterium, Thermoanaerobacterium thermosaccharolyticum TG57, can directly convert cellulose, a plant-based material, to biobutanol.

“The production of biofuels using non-food feedstocks can improve sustainability and reduce costs greatly.”

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He Jianzhong, associate professor from the civil and environmental engineering department at the National University of Singapore Faculty of Engineering, and his colleagues first discovered the novel TG57 strain in 2015. They went on to culture the strain to examine its properties.

“The production of biofuels using non-food feedstocks can improve sustainability and reduce costs greatly. In our study, we demonstrated a novel method of directly converting cellulose to biobutanol using the novel TG57 strain. This is a major breakthrough in metabolic engineering and exhibits a foundational milestone in sustainable and cost-effective production of renewable biofuels and chemicals,” He explains.

Traditional biofuels are produced from food crops. This approach is costly and competes with food production in the use of land, water, energy, and other environmental resources.

Many scientists believe biofuels produced from unprocessed cellulosic materials such as plant biomass, as well as agriculture, horticultural, and organic waste could meet growing energy demands without increasing greenhouse gas emissions resulting from the burning of fossil fuels. These cellulosic materials are in great abundance, environmentally friendly, and economically sustainable.

Among various types of biofuels, biobutanol offers great promise as a gasoline substitute because of its high energy density and superior properties. It can directly replace gasoline in car engines without any modification. However, commercial production of biobutanol has been hampered by the lack of potent microbes capable of converting cellulosic biomass into biofuels. The current technique is costly and requires complicated chemical pre-treatment.

The new technique could potentially be a game-changing technology for cost effective and sustainable biofuel production.

Spent mushroom compost—typically composed of wheat straw and saw dust—is the residual compost waste mushroom farming generates. To obtain the unique TG57 strain, researchers left the microorganisms in the waste to evolve naturally for more than two years.

The fermentation process is simple, and doesn’t require complicated pre-treatment or genetic modification of the microorganisms. When the researchers add cellulose, the bacterium simply digests it to produce butanol as the main product.

Moving forward, the research team will continue to optimize the performance of the TG57 strain, and further engineer it to enhance biobutanol ratio and yield using molecular genetic tools.