Classical Lay Summary by Ragothaman Yennamalli.

Stone-washed jeans were a rage in the 1970s and 1980s – so much so that pumice stone, which is used to achieve the finish, became hard to obtain. Since jeans are made of denim, which is primarily cotton and cotton is made of cellulose polymers, it was identified that an easier alternative to pumice stones was to use cellulases, also known as enzymes. These are a broad class of proteins that break down polymeric strands. These enzymes that chew on complex polymeric structures of sugars, also known as polysaccharides, are broadly known as cellulases. One such sugar polymer is cellulose. Thus, the denim industry moved away from pumice stones by using cellulases to achieve the same stone-washed effect. This process is now known as bio-stoning.

These enzymes are produced by microorganisms – both bacteria and fungi – so that complex polysaccharides, made of either five-carbon sugar units or six-carbon sugar units, that are abundant in nature can be cut into smaller pieces. These smaller pieces are called oligosaccharides and eventually they are further broken down into the basic-building block of polysaccharides, i.e., glucose, a six-carbon sugar unit. Glucose is an essential power source for all organisms.

In addition to their usefulness in the textile industry, cellulases have very broad and important applications in industries such as food processing and pulp/paper manufacturing – these enzymes are used as a cocktail to create the desired product. One of the major uses of cellulases currently is in the production of biofuel/bioethanol, fuel produced from plant sources. This is because cellulases are pretty good at what they do: producing glucose from polymeric sugars. Each molecule of glucose produced is made up of six carbons and can be converted into three molecules of ethanol, consisting of two carbons. In many countries, including Brazil and the USA, simple polysaccharides like cane sugar and cornstarch are used with cellulases to produce bioethanol. Most recently, with increasing fuel demands and a focus on sustainable models of generating fuel, bioethanol production using cellulases is seen as the key to clean energy. Biophysics and Biophysical techniques help at each step for us to achieve this goal.

There are a variety of subcategories of cellulases, and each have a specific role or action in degrading the polymeric cellulose in the plant cell wall. Imagine, you hold a handful of uncooked spaghetti and if the task were to break it down to smaller bits, you can use a multitude of tools to achieve the result. In the same way, the microfibrils in the plant biomass that hold the cellulose needs various types of cellulases to work together in breaking down the cellulose to glucose. For example, some cellulases specifically chew up by making a nick in the middle of the polymer (Endoglucases), others do it from ends of the polymer (Exoglucanases), and others use the products of the former and further chew it down to smaller bits (Cellobiohydrolase and Beta-Glucosidase). One of the bottlenecks of cellulose degradation has been reducing its crystalline property with temperature and pressure to an easily digestible amorphous form. In the last decade, a new class of enzymes have been identified that act on crystalline form of the polysaccharide, called as Lytic Polysaccharide Monooxygenases or LPMOs. Cocktails that have LPMOs are known to boost glucose yields. Interestingly, the action of these LPMOs have been characterized in detail using biophysical techniques such as atomic force microscopy, x-ray crystallography, NMR spectroscopy, cation-exchange chromatography, and other techniques. Thus, biophysics and biophysical techniques aid in multiple ways ranging from the clothes we wear to generating clean energy sources for our vehicles.