Lignin Valorisation Using Lignolytic Microbes and Enzymes: Challenges and Opportunities

Lignin is an abundant aromatic biopolymer. It hinders the extraction and degradation of cellulose and hemicellulose and the subsequent biochemical conversion of lignocellulosic wastes to fuels and chemicals. A substantial amount of research has been conducted over the past 20 years to develop novel and effective techniques to extract and recover valuable compounds of lignin. However, because of the extremely recalcitrant nature of lignin, the development of a suitable, cost-effective and efficient method of extracting lignin has been difficult. Using microbes and enzymes for the depolymerisation of lignin is an energy-efficient method. Numerous studies have been performed to develop a suitable bacterial strain that can be used to recycle all lignin-derived compounds, but designing such a strain is difficult. Several enzymes, such as peroxidase, laccase and lignin peroxidise, can also be used for lignin valorisation and be used to produce various compounds of pharmaceutical value, such as biopolymers, reuseable adsorbents, resins and biodiesels. This chapter deals mainly with various biotechnological approaches that use various microbes and enzymes for lignin valorisation in cost-effective and ecofriendly ways.