IIT Guwahati Discovers New Enzyme-'RfGH5 4'; Produces Bioethanol from Forest Scraps

With dwindling fossil fuel reserves and climate change wreaking havoc on the world, adopting clean strategies based on renewable energy is critical. Ethanol, also known as ethyl alcohol, can be used to fuel vehicles in addition to being used in spirits, drinks, and pharmaceutical products.

RfGH5 4, an enzyme derived from the bacterium Ruminococcus flavefaciens, effectively breaks down cellulose and hemicellulose in woody biomatter and converts it to bioethanol. This bacterium can be found in the intestines of cows and other cud-eating animals.

The enzyme RfGH5 4 was tested for efficiency by breaking down and fermenting molecules of biomasses such as cotton main stalk and small branches, sorghum stalk, sugarcane bagasse, finger millet stalk, and maize leaves into simple sugars. While chemical processes can be used to produce bioethanol fuel, it is typically produced through the fermentation of sugar, which is typically derived from fuel or energy crops such as corn, maize, wheat, and potato, among others.

The research was conducted by IIT-Guwahati and the University of Lisbon in Portugal, and the findings were published in the International Journal of Biological Macromolecules in October. The study, led by Professor Arun Goyal of IIT Guwahati's Department of Biosciences and Bioengineering, demonstrates that large amounts of organic carbon are stored in agricultural and plant biomass in the form of molecules such as cellulose and hemicellulose.

The study is significant because it can help India reduce its reliance on crude oil imports, which is currently at 85%. Domestically produced ethanol can be blended with gasoline to significantly reduce reliance on foreign sources. By 2023, India hopes to have 20% ethanol blending with gas in some areas of the country, followed by a pan-India rollout in 2025-2026.

These findings will not only convert wasted residual biomass into an effective resource to fuel cars, but can also be used in food medicine, taking one step closer to finding more sustainable alternatives to using non-renewable sources of energy. It can also be used in other industries such as food and pulp, pharmaceuticals, and textiles. "Agricultural residual biomasses are wasted or burned causing various environmental hazards including global warming and climate change.

"Their deconstruction by RfGH5 4 may also extend its use in food medicine," Professor Goyal said in a statement Tuesday. The enzyme is multifunctional and has proven to be an effective catalyst. This distinguishes it from other enzyme groups found in nature and available commercially. The enzyme was also found to be stable at temperatures ranging from 5 to 45 degrees Celsius, making it widely applicable.

"The structure of RfGH5 4 was deciphered using extensive molecular dynamics and computational approaches at IIT-Param-Ishan G's Supercomputer facility," said Parmeshwar Gavande, PhD Research Scholar and the study's first author. RfGH5 4 was discovered to have some highly flexible loops in its core structure that allow for different carbohydrate polymers to be used during the reaction, giving the enzyme multifunctionality. These findings suggest that this enzyme could help to reduce the cost of producing bioethanol on a large scale.