Whole-cell filamentous fungal biocatalysts for biodiesel production: Mechanistic insights, process integration, and industrial perspectives

Biodiesel has emerged as a sustainable alternative to fossil-derived fuels, while whole-cell filamentous fungal biocatalysts have attracted increasing attention because of their intrinsic lipase activity, lipid accumulation capacity, and adaptability to heterogeneous feedstocks. Distinct from existing reviews, this review develops an integrated mechanism-to-process-to-industry perspective on fungal whole-cell biodiesel production. Literature was systematically retrieved from major databases using predefined inclusion and exclusion criteria, and recent advances were critically synthesized across strain engineering, catalytic mechanisms, bioprocess development, substrate utilization, reactor engineering, and industrial implementation. Particular attention is given to the relationships among lipase function, fungal morphology, metabolic regulation, mass transfer, and process conditions, and their effects on catalytic performance and stability. Major challenges, including mass-transfer limitations, methanol toxicity, catalyst deactivation, feedstock variability, and scale-up constraints, are evaluated together with corresponding mitigation strategies. Comparative analysis of catalytic performance, catalyst lifetime, reactor operation, techno-economic factors, and environmental impacts highlights the trade-offs among fungal whole-cell, immobilized-enzyme, and conventional catalytic routes. Emerging strategies involving synthetic biology, integrated biorefineries, process intensification, green reaction media, and AI- and digital-twin-assisted process optimization are discussed, alongside opportunities for integration with renewable energy systems. From an industrial perspective, pilot-scale demonstrations, reactor scalability, catalyst lifetime, process monitoring, downstream processing, by-product valorization, and techno-economic and life-cycle assessment are critically examined. Finally, a prioritized research roadmap is proposed, distinguishing near-term priorities in standardized performance evaluation, catalyst-lifetime assessment, feedstock and reactor optimization, and process-level validation from longer-term goals in intelligent process control, modular biorefineries, and lifecycle-scale industrial deployment.