Guwahati:Enzyme’s efficacy explored by IIT-G to produce biofuel from biomass

Guwahati: Researchers at the Indian Institute of Technology-Guwahati (IIT-G) have studied the utility of a specific multifunctional enzyme that can break down woody biomass for conversion into bioethanol fuel.

Researchers report that the bacterial endoglucanase enzyme, RfGH5_4 obtained from a bacterium called Ruminococcus flavefaciens, can break down woody biomass into a simple sugar that can be efficiently fermented to produce bioethanol. Can – A renewable fuel that can replace petroleum systems.

A team led by Professor Arun Goyal, Department of Biology and Bioengineering, IIT Guwahati, along with researchers from the University of Lisbon, Portugal recently published the research findings and observations in the International Journal of Biological Macromolecules.

The published paper is a research work of Prof. Arun Goyal’s doctoral student Parameshwar Vithal Gawande as part of his PhD thesis work.

Fuel production from renewable biological sources has attracted significant scientific interest in recent years due to the diminishing reserves of fossil fuels and the environmental pollution problems associated with their generation and use.

Among the many biofuels, ethanol (or ethyl alcohol) is widely studied for its positive effects on the environment. This intoxicating ingredient in spirits and beverages, which can also be used to fuel vehicles, is usually produced by fermenting raw materials containing sugar and starch – grapes, barley and potatoes.

However, there is interest in developing methods to extract bioethanol for fuel from agricultural and forestry residues and crops that are rich in carbohydrate polymers (lignocellulose) – the dry plant matter that makes up the woody part of plants.

For the industrial production of bioethanol as a fuel, lignocellulose extracted from plants is deconstructed using biological catalysts (enzymes) called cellulases, and subsequently fermented.

Endoglucanase is one such cellulase enzyme. A barrier to converting lignocellulosic biomass into bioethanol is the poor performance of these enzymes.

Additionally, lignocellulosic biomass also contains cellulose along with hemicellulose, which cannot be broken down by many endoglucanases.

The IIT Guwahati team chose Ruminococcus flavefaciens because this bacterium is found in the intestines of cows and other ruminants that have been exposed to cellulosic stress for millions of years.

The specific gene encoding the cellulase enzyme, RfGH5_4, was isolated from R. flavefaciens.

The researchers thus developed the efficient machinery of RfGH5_4 to break down cellulose and cellulosic structures into simple sugars. The bacterium possesses a group of at least 14 different multi-modular enzymes that can break down cellulose, one of which is RfGH5_4.

Explaining the research work, Prof. Arun Goyal, Department of Biology and Bioengineering, IIT Guwahati said, “We characterized the endoglucanase, RfGH5_4, and found that it hydrolyzed carboxymethyl cellulose (a laboratory-scale analogue of cellulose). as well as with normal cellulose. higher catalytic efficiency.”

“Our studies have also shown that this enzyme acts on lignocellulosic substrates from various agricultural residues such as cotton stalks, sorghum stalks, sugarcane bagasse, etc. and also interacts well with hemicellulosic substrates. In which β-glucan, lichenan, xonlogicanjam, x-glucan., xylan and carob galactomannan, “he said.

Earlier work by the IITG team on the cloning, expression and biochemical characterization of RfGH5_4 showed that this specific endoglucanase is multifunctional and catalytically efficient.

With this knowledge, they characterized the structure of the enzyme, its reaction mechanism and the structural basis of its multifunctionality. While elaborating on the properties of RfGH5_4, they further emphasized that its multifunctionality distinguishes RfGH5_4 from the plethora of other cellulases that exist in nature and are commercially available.

Elucidating the structural basis, Parameshwar Gawande, PhD Research Scholar, explained, “The structure of RfGH5_4 was determined using extensive molecular dynamics and computational approaches at IITG’s Perm-Ishan Supercomputer Facility. Some highly flexible loops were found in its core structure to make room for different carbohydrate polymers during the reaction, thus providing multi-functionality to RfGH5_4.

“Agricultural residual biomasses are discarded or burned, causing various environmental threats, including global warming and climate change. Their deconstruction by RfGH5_4 may also enhance its application in food medicine”, Prof. Goyal. said

“The presented research seeks to constructively contribute to addressing the UN’s Sustainable Development Goals (SDGs) 2030,” Prof Goyal added.

Research has shown that the multifunctional RfGH5_4 cellulase can be used for the efficient and cost-effective production of lignocellulosic bioethanol on an industrial scale.
Thus, its ability to break down cellulose and hemicellulose makes it potentially useful in various other applications such as textiles, food and pulp industry, synthesis of prebiotics, and pharmaceuticals.

The results of the research work were recently presented by Gwande at the International Conference of Biotechnology for Better Tomorrow (ICBBT-2022) in Bali, Indonesia and received the ‘Best Oral Presentation Award’.