Improved xylooligosaccharides production from xylan extracted using ultrasound-assisted alcoholic deep eutectic solvent pretreatment of pineapple leaf waste

The management of agricultural wastes from agro-food processing industries is critical for sustainability, with growing attention towards utilizing green bioconversion processes. Pineapple leaf (PL) waste, a rich source of hemicellulose, is a potential feedstock for industrial xylooligosaccharides (XOS) production for better health care. In the present work, a combined alcoholic deep eutectic solvent (DES) and ultrasound (50 % amplitude, 20 min) fractionation approach was applied to PL waste, resulting in improved xylan extraction (180 mg/g biomass) from the liquid fraction of the pretreated mixture. The DES (choline chloride/ethylene glycol, 1:2) was recycled for five cycles, maintaining 93 % extraction efficiency. Biorefining of XOS from xylan extracted by ethanol precipitation of pretreated PL liquid hydrolysate and dilute nitric acid (4 %) for 1 h at 100 ℃ hydrolysis gave a maximum XOS yield (66.6 mg/g biomass) with xylobiose (24.3 mg/g biomass) as the most significant XOS. Mass balance analysis of the bioprocess revealed the effective conversion of waste biomass into bioproducts, ensuring minimal waste and maximum resource utilization. The integrated DES-ultrasound pretreatment substantiates the potential for sustainable XOS production from pineapple waste with significant biological activity.