Current Scenario on Thermozymes for Plant Biomass Deconstruction and Derived Commodity Chemicals

Abstract

In the hunt for alternative energy sources, lignocellulosic biomass (LCB), such as forestry and agricultural residues, appears to be a potential raw material for transformation into useful bio-products in so-called biorefineries, as it is abundant at low/no cost. The electricity generation capacity is expected to expand from 183 GW to 800 GW by 2031-32. In contrast to demand, India's indigenous energy sources are insufficient, leaving it reliant on crude oil imports (>80%). Alternative 2G renewable energy solutions have become important due to oil geopolitics and environmental concerns. As an agrarian tropical nation, crops produce significant volumes of residues, resulting in both resource waste and a missed opportunity to increase farmer revenue. As a result, forestry and agriculture leftovers on and off the farm can be used to generate bio-energy and other platform chemicals. The recalcitrance and intricacy of cellulose fibrils intertwined with hemicellulose and lignin render lignocellulosic biomass (LCB) generally inaccessible to cellulolytic enzymes in the native state, despite being renewable and inexpensive. Bio delignification/ depolymerization with ligninases can break down such complicated materials. Further hydrolysis of LCB to convert cellulosic and hemicellulosic fractions into monomeric sugars is dependent on the costs and robust enzymes such as glycosyl hydrolases (GHs), which have multiple substrates, are more stable at high temperatures and a wide pH range, and have improved catalytic efficiency. Thermozymes, enzymes obtained from thermophilic microbes possess unique characteristics such as temperature, chemical, and pH stability. They can certainly be used in several industrial processes by replacing mesophilic enzymes. Because the process works at slightly elevated temperatures, thermostable ligninases and GHs are of special importance. The biocatalyst's stability and reusability have always been important obstacles in creating biocatalytic reactions. The challenges and potential of employing thermophiles and their derived enzymes (thermozymes) in various stages of biomass conversion into a variety of commercial chemicals are discussed in this review.