Oligosaccharide oxidase for the enzymatic synthesis of glucosaminic acids

d-Glucosaminic acid is a valuable amino acid useful in food and medical applications. It is a highly sought after enantiopure molecule important for the synthesis of drugs and glycopeptides. Current enzymatic synthesis pathways to d-glucosaminic acid carry disadvantages such as low product yield and long reaction times. Herein, the Auxiliary Activity 7 chito-oligosaccharide oxidase from Lentinus brumalis, LbChi7A, was shown as a potent biocatalyst capable of efficiently converting d-glucosamine (GlcN) and N-acetyl-d-glucosamine (GlcNAc) to their respective C1-acids. The substrate specificity of LbChi7A towards GlcN and GlcNAc enabled the conversion of at least 90% GlcN to d-glucosaminic acid and 100% GlcNAc to N-acetyl-d-glucosaminic acid within 60 min. LbChi7A inhibition by the hydrogen peroxide co-product was not detected, even at 860 mM. This single enzymatic conversion offers a clean and efficient process to produce industrially relevant glucosaminic acids, including d-glucosaminic acid and N-acetyl-d-glucosaminic acid. Supplementary Information The online version contains supplementary material available at 10.1007/s10529-026-03721-9.