Recovery of ergosterol and vitamin D2 from mushroom waste - Potential valorization by food and pharmaceutical industries

Background: A large amount of mushroom waste is generated during mushroom production (accounting for up to 20% of total production) and is mainly composed of mushrooms that do not meet the specifications set by retailers because of misshapen caps and/or stalks. Mushrooms are notable for their ergosterol (a precursor of vitamin D2) content which is converted to vitamin D2 after exposure to natural or artificial ultraviolet (UV) irradiation. Therefore, mushroom waste could be used as a source for the recovery of both ergosterol and vitamin D2 which could be valorized by both pharmaceutical and food industries. Scope and approach: The current review presents a comprehensive summary of research performed regarding the extraction, purification and determination of ergosterol and vitamin D2 (ergocalciferol) from mushroom matrices. Additionally, studies related to the impact of sample preparation and especially of drying methods on the retention of ergosterol and vitamin D2 are presented. Finally, the potential valorization of mushroom waste sterols by food and pharmaceutical industries is discussed. Key findings and conclusions: Ergosterol and vitamin D2 contents vary among different mushroom species. Sample drying is a crucial step that precedes sterol extraction and has a significant impact on the retention of ergosterol and vitamin D2. The extraction of sterols from mushrooms can be conducted by either conventional (e.g., Soxhlet extraction) or non-conventional methods (e.g., ultrasound-assisted extraction (UAE), microwave-assisted extraction (MAE), deep eutectic solvents (DES) extraction, supercritical fluid extraction (SFE), and pressurized liquid extraction (PLE)) or their combination. The application of non-conventional methods such as UAE and MAE facilitate in shorter extraction times than the conventional methods. The valorization of mushroom extracts enriched in ergosterol and vitamin D2 by both pharmaceutical and food industries requires further work.