This study presents a sequential biorefinery strategy for the sustainable valorisation of whole mandarin peel (MP) combining high-intensity focused ultrasound (HIFU) and enzymatic hydrolysis (EH) at high solids loading (10% DW/v). Both processes were independently evaluated to select favourable operating conditions prior to integration, thereby enhancing industrial relevance compared to studies focused solely on peel fractions. Selected HIFU conditions yielded 16 mg GAE/g DW (67% of conventional solvent extraction, CSE) with enhanced antioxidant activity (82% DPPH inhibition) while reducing both extraction time and solvent use by 87% and 94%, respectively. Phenolic profiling revealed enrichment in polymethoxylated flavones and extracts showed selective cytotoxicity toward cancer cell lines without affecting non-tumoral HaCaT cells. EH of untreated MP using Viscozyme released up to 52.7 g/100 g DW sugars and enriched the residual solids in protein (up to 19.6%). In the sequential configuration, EH of HIFU-treated solids yielded 20.9 g/L sugars with Viscozyme alone, increasing to 40.1 g/L upon Cellic® CTec2 supplementation (73% of standalone EH), reflecting reduced sugar availability after HIFU co-extraction. These results demonstrate selective fractionation of phenolics and fermentable sugars from whole MP under intensified conditions and provide process-level insight into ultrasound–enzyme integration, highlighting the decisive influence of LPMO-containing enzyme systems on saccharification performance.
García-Aparicio et al. (Mon,) studied this question.