Characterization of an acetyl esterase from Myceliophthorathermophila C1 able to deacetylate xanthan

Screening of eight carbohydrate acetyl esterases for their activity towards xanthan resulted in the recogni-tion of one active esterase. AXE3, a CAZy family CE1 acetyl xylan esterase originating from Myceliophthorathermophila C1, removed 31% of all acetyl groups present in xanthan after a 48 h incubation. AXE3 activ-ity towards xanthan was only observed when xanthan molecules were in the disordered conformation.Optimal performance towards xanthan was observed at 53¿C in the complete absence of salt, a condi-tion favouring the disordered conformation. AXE3-deacetylated xanthan was hydrolyzed using cellulasesand analyzed for its repeating units using UPLC–HILIC–ELSD/ESI–MS. This showed that AXE3 specificallyremoves the acetyl groups positioned on the inner mannose and that acetyl groups positioned on theouter mannose are not removed at all. After a prolonged incubation at optimal conditions, 57% of allacetyl groups, representing 70% of all acetyl groups on the inner mannose units, were hydrolyzed.