## 2 Experimental Section
### Enzyme Characterization  
The xylanase activities of the FCS and purified Xyl-O1 were greatest in the temperature range of 45-60 \({}^{\circ}\)C and the pH range of 5.5 to 6.0. The two samples were stable in the temperature range of 45-60 \({}^{\circ}\)C, with xylanase activity greater than 70%. The greatest FCS activity was observed at 55 \({}^{\circ}\)C, and the greatest Xyl-O1 activity was at 50 \({}^{\circ}\)C. The two enzyme samples presented the best activity at pH 6.0 in sodium acetate buffer. The activity of the two samples was greater than 90% in the pH range of 5.5 to 6.0. Other studies involving the purification and characterization of endo-\(\beta\)-1,4-xylanases from filamentous fungi have indicated that 50 \({}^{\circ}\)C is the most effective temperature for enzyme activity [33, 38, 39]. Our results are consistent with [PERSON] _et al._[40], who found that the greatest activity for a xylanase, XynG2, that was isolated from a genomic library of _A. oryzae_ KBN616 was at pH 6.0. However, its greatest enzymatic activity was at 58 \({}^{\circ}\)C, and it displayed a different Km value (5.1 mg\(\cdot\)mL\({}^{-1}\)) on birchwood as the substrate. The K\({}_{\rm m}\) values (mg\(\cdot\)mL\({}^{-1}\)) of Xyl-O1 on a soluble fraction of oat spelt and birchwood xylans were 10.05 and 3.34, respectively. The apparent K\({}_{\rm m}\) values indicated that the purified Xyl-O1 had a preference for birchwood xylan as a substrate. Birchwood xylan contains 90% xylose, whereas oat spelt xylan contains 75% xylose, 10% arabinose and 15% glucose residues. The preference of Xyl-O1 for substrates containing a higher proportion of d-xylose residues is a relevant property that can be used in the future targeting of this enzyme for alternative methods of cellulose pulp biobleaching. The Xyl-O1 enzyme activity was reduced to 86 and 8% in the presence of Hg\({}^{2+}\) at concentrations of 1.0 and 10 mmol\(\cdot\)L\({}^{-1}\), respectively. The same inhibitory effect was observed for Ag\({}^{+}\) at a concentration of 10 mmol\(\cdot\)L\({}^{-1}\). The inhibitory effects of Hg\({}^{2+}\) and Ag\({}^{+}\) on xylanase activity are known [7, 25, 41, 42]. According to [PERSON] _et al._[41], the addition of Hg\({}^{2+}\) drastically inhibits xylanolytic activity, suggesting the existence of thiol groups in the catalytic site of the enzyme. In general, purified Xyl-O1 remained stable in the presence of most of the ions that we tested. However, Mn\({}^{2+}\), which is commonly referred to as an activator of xylanase activity, showed an inhibitory effect at a concentration of 10 mmol\(\cdot\)L\({}^{-1}\) and promoted a 10% reduction in activity compared to the control. The same inhibitory effect was observed when the enzyme was pre-incubated for 40 min at 28 \({}^{\circ}\)C with the same concentration of Mn\({}^{2+}\). Conversely, [PERSON] _et al._[43] and [PERSON] _et al._[39] reported an activating effect of 10 mmol\(\cdot\)L\({}^{-1}\) Mn\({}^{2+}\) on xylanase from _A. versicolor_ and _A. awamori_ 2B.361 U2/1. Here, purified Xyl-O1 in the presence of amino acid-modifying reagents and amino acids remained relatively stable or was activated by certain reagents (Table 3). The enzyme retained 74% of its xylanolytic activity in the presence of 20 mmol\(\cdot\)L\({}^{-1}\) SDS. The reaction mixture containing 5.0 mmol\(\cdot\)L\({}^{-1}\) l-tryptophan did not have increased enzymatic activity. However, for compounds containing thiol groups, such as l-cysteine, DTT and \(\beta\)-mercaptoethanol, the xylanase activity increased by 40, 14 and 37%, respectively. The enzyme was stable in the presence of NBS and EDC reagents at concentrations of 1.0 and 5.0 mmol\(\cdot\)L\({}^{-1}\), respectively. However, the enzyme activity was completely inhibited by NBS at a concentration of 10 mmol\(\cdot\)L\({}^{-1}\) (result not shown). [PERSON] _et al._[39] also reported the inhibition of xylanase from _A. awamori_ by NBS at the same concentration.