Sequential extraction and organosolv pretreatment of halophytes: unlocking biomass recalcitrance for bio-based production.

The growing demand for sustainable bioresources has given prominence to lignocellulosic biomass as a possible alternative. Halophytes offer a specific advantage in this context, because they can grow on non-arable land with minimal freshwater requirements. To our knowledge, this is the first study to integrate organosolv fractionation to either Soxhlet extraction (SLE) or subcritical water extraction, (SWE) at 140 °C, as pretreatment strategies, into a single sequential process applied to halophyte biomass allowing the recovery of bioactive molecules from halophyte biomass. The spent fibers underwent organosolv fractionation under varied process conditions (180-200 °C, 15-60 min, 40-60% v/v ethanol) and were subsequently evaluated for bioenergy production via anaerobic digestion. Organosolv fractionation generates separate lignin and hemicellulose streams, which can be further converted into value-added products. Either extraction methodology effectively facilitated subsequent biomass fractionation. SLE-pretreated fibers attained > 96.4% hemicellulose removal in 87.5% of the tested conditions and 78.1% delignification. SWE-pretreated fibers exhibited slightly lower hemicellulose removal at higher (60% v/v) ethanol content and 69.3% delignification. Crucially, SWE fibers demonstrated superior bioenergy potential, achieving a methane yield of 336 mL-CH4/gVS, and complete saccharification in 62.5% of tested conditions. Our findings highlight the potential of synergistic pretreatment strategies in an integrated biorefinery approach, which valorizes halophytes as a sustainable feedstock for bio-based applications.