4-O-Methylglucaric Acid Production from Xylan with Uronic Acid Oxidase and Comparison to Glucaric Acid from Glucose

This study describes an enzymatic pathway to produce high purity 4-O-methylglucaric acid from xylan, an underutilized fraction of lignocellulosic biomass. Beechwood xylan was enzymatically hydrolysed using a commercial xylanase and an α-glucuronidase from Amphibacillus xylanus to form 4-O-methylglucuronic acid, which was then purified by anion exchange chromatography and subsequently oxidized to 4-O-methylglucaric acid using a recombinantly produced uronic acid oxidase from Citrus sinensis. Enzymatic oxidation with uronic acid oxidase afforded 95 % yield in 72 hours which is considerably higher than yields previously achieved using a glucooligosaccharide oxidase from Sarocladium strictum. 4-O-methylglucaric acid was isolated by precipitation and purified by recrystallization. Characterization by liquid chromatography mass spectrometry and nuclear magnetic resonance spectroscopy confirmed product identity and high purity (97.8 % w/w). 4-O-methylglucaric acid's performance as a detergent builder was compared to commercial glucaric acid. At 10 : 1 molar ratios of detergent builder to calcium, 4-O-methylglucaric acid provided similar calcium sequestration performance to glucaric acid (less than 5 % difference) at pH 7 and pH 10 in the presence of surfactants, including sodium dodecylbenzene sulfonate. Given their similar calcium sequestration performance, 4-O-methylglucaric acid could effectively substitute for glucaric acid in detergent formulations.