Aqueous extraction of glucuronoxylans from chestnut wood: New strategy for lignin oxidation using phthalocyanine or porphyrin/H2O2 system

Hardwood 4-O-methylglucuronoxylans (MGX) are classically isolated by a delignification step, using a sodium chlorite solution, followed by alkaline extraction, an efficient, although potentially polluting process. In this work, we propose a chlorine-free environmentally-friendly process for MGX extraction from Castanea sativa Mill. Chestnut sawdust was first delignified using metalled phthalocyanine or porphyrin in presence of hydrogen peroxide. Then, MGX were easily extracted by hot water. This protocol, repeated with different incubation times and temperatures, led to the selective extraction of acetylated MGX with decent yields reaching 12%. The best results were obtained after delignification using iron tetrapyrrole macrocycles. However, lower degrees of polymerization of MGX were observed in comparison to the classical method, suggesting that this new process affects the structures of xylans.