Eucalyptus xylan: An in-house-produced substrate for xylanase evaluation to substitute birchwood xylan.

Over the past decades, most studies with xylanases have used Birchwood xylan as the standard substrate for activity assays. However, recently, Birchwood xylan production was discontinued by major suppliers, creating an important demand for a substitute. Ongoing and future studies require a substrate with characteristics equivalent to the discontinued xylan, in order to enable the comparison of results. In this context, a protocol for the production of a substrate similar to the discontinued commercial Birchwood xylan is reported. Obtained from bleached Eucalyptus cellulose pulp, xylan was extracted using 4% w/v NaOH solution at 25 °C, precipitated with glacial acetic acid (HOAc), and freeze-dried. A thermal pretreatment in an autoclave for 15 min increased its solubility. The resulting xylan was characterized by infrared spectroscopy, thermogravimetry, and NMR. When assessing the activity of xylanases, the results were the same as those for commercial Birchwood xylan.