Recent Developments on Biotechnological Applications of Diverse Fungi in Waste Biomass Conversion into Bioenergy: Challenges and Future Outlooks

The urgent need for sustainable energy has placed lignocellulosic biomass at the forefront of renewable feedstocks. Fungi represent powerful biological platforms for their valorization due to their ability to secrete a broad arsenal of hydrolytic and oxidative enzymes that depolymerize lignin, hemicellulose, and cellulose. This chapter highlights the taxonomic and functional diversity of lignocellulolytic fungi, as well as filamentous ascomycetes, white-rot basidiomycetes, anaerobic gut fungi, and extremophiles, emphasizing their interacting enzyme systems comprising hemicellulases, cellulases, lignin-modifying oxidoreductases, and so on. Also, special notice is given to advances in engineering and clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9-mediated genome editing in fungal metabolic systems, which enable targeted knock-in, knock-out, and regulatory modifications to enhance enzyme production and catalytic efficiency. Such strategies strengthen the development of fungal cell factories capable of producing customized enzyme consortia for industrial biomass degradation. In addition to the above, this chapter focuses on the integration of engineered fungi into biorefineries, techno-economic considerations, and bottlenecks such as enzyme inhibition, low titers, and scale-up challenges. Thus, fungal biotechnology, paired with genome editing, can accelerate the transition toward cost-effective biofuel production and sustainable bioeconomy pathways.