Bugging out over exciting enzymes found in ancient insects

February 25, 2018 |

Ancient insects’ digestion could boost biofuel development

In the United Kingdom, researchers at the University of York found that the ability of some insects to efficiently digest cellulose could be exploited for industrial processes, such as the production of sustainable low carbon fuels to cut greenhouse gas emissions associated with fossil fuel use.

According to their press release, the surprising find occurred when the team at the University of York was investigating the digestive system of firebrats who appeared on land during the Devonian Period, some 420 million years ago and had been previously shown to thrive on crystalline cellulose, the natural fiber, abundant in straw, paper and cardboard.

But until now, it was a mystery as to how firebrats were able to digest cellulose so effectively and what they found was something they didn’t expect.

Proteins, Carbs and Digestion

Dr. Federico Sabbadin, from the University of York’s Department of Biology, said, “Inside their gut the firebrats had a group of uncharacterised proteins that make up 20% of their carbohydrate digestive enzymes. On further inspection, these proteins proved to be a new class of enzyme, called lytic polysaccharide monooxygenases (LPMOs), which attack crystalline polysaccharides. Our study revealed that these enzymes are used by firebrats to greatly increase the rate of cellulose digestion.”

Previously, LPMOs were only known to occur in fungi, bacteria and viruses, but analysis of this new family showed it was widespread among invertebrates.

Professor Simon McQueen Mason, Director of the Centre for Novel Agricultural Products at the University of York’s Department of Biology, said, “These digestive LPMOs appear to have evolved from enzymes that digest a substance called chitin, which protects the respiratory system of insects. We found that these ancestral genes are essential for metamorphosis and that interfering with their function is lethal to insects. This could have important implications for the development of new methods to control disease-carrying mosquitoes and agricultural pests such as locusts.”

Chitin and chitosan are the main components of insect and crustacean exoskeletons and can also be found in most fungi and some algae. They demonstrate biocompatible and antibacterial properties. Applications include agriculture, medicine, food processing, and cosmetics.

You may have heard of chitin, as reported in NUU in April 2017 when researchers at the Russia-based Moscow Institute of Physics and Technology developed a faster, environmentally friendly way to depolymerize chitin and chitosan into low molecular weight, water-soluble oligosaccharides. Their process involves degrading chitin and chitosan by electron-beam plasma in a specially designed reactor, which reduces the time it takes to produce water-soluble oligosaccharides from days to just minutes. Conventional production is a multi-step, lengthy process that involves chemical depolymerization at high temperatures with hydrogen peroxide, organic and inorganic acids, and other “aggressive agents.” The result is large volumes of industrial wastewater.

What does this all mean for biomass and biofuels?

It means the enzymes could be adopted in industrial processes to break down cellulose into fermentable sugars for biofuel production. It could speed up the process of cellulosic digestion making biofuel production faster than ever.

This is huge news as it comes on the heels of another announcement by the same UK-based University of York, as reported by the Digest on February 19th, that scientists discovered a set of enzymes found in fungi that are capable of breaking down one of the main components of wood. The enzymes could potentially be used to sustainably convert wood biomass into valuable chemical commodities such as biofuels as well. The research showed that LPMOs are capable of breaking down xylans – carbohydrate molecules commonly found in wood biomass that are particularly resistant to degradation.

Enzymes are moving forward at a rapid pace with so much going on over the last year with enzymes. Keeping track of all these dizzying developments is tough, but a group of researchers in India created a comprehensive database of known enzymes with proven or potential applications in biofuel production, as reported in the Digest in November 2017. A total of 131 enzymes with a role in biofuel production were identified and classified into six enzyme classes and four broad application categories namely ‘Alcohol production’, ‘Biodiesel production’, ‘Fuel Cell’ and ‘Alternate biofuels’. A prediction tool ‘Benz’ was developed to identify and classify novel homologues of the known biofuel enzyme sequences from sequenced genomes and metagenomes.

Another recent development came from the U.S. Department of Energy’s National Renewable Energy Laboratory (NREL) researchers who gained new insights into how glycosylation—the natural attachment of sugars to proteins—affects a key cellulase enzyme, as reported in the Digest in December 2017. This work could be used to improve enzyme performance to better break down biomass and convert waste plant matter to renewable fuels and products. Namely, the more effective the enzyme, the more efficient and economical the process will be. The NREL research focuses on the enzyme Cel7A that breaks down cellulose in plants to sugars and sheds light on the specific functions of small sugars, or glycans, that microbes attach to their enzymes. This enzymatic modification by the addition of sugars is referred to as “glycosylation” and it is known to have a substantial impact on enzyme function.

Bottom Line

As research and important developments and advances occur with enzymes, the biofuels industry will only benefit. Biofuels has had so many challenges in the past that it has overcome but still has more to go and with the help of enzymes boosting production, speed, efficiency, it’s only good news for biofuels.

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