Purification and Physicochemical Characterization of a Novel Thermostable Xylanase Secreted by the Fungus Myceliophthora heterothallica F.2.1.4.

Xylanases are enzymes that act in the depolymerization of xylan and that can be used in the food industry, the paper industry, and for bioenergy, among other uses. In this context, particular emphasis is devoted to xylooligosaccharides (XOS) that act as prebiotics, which, under the action of probiotic microorganisms, are capable of positively modifying the intestinal microbiota. In this sense, searching for microbial xylanases stands out as a sustainable strategy for the production of prebiotics. To date, there have been no reports in the literature regarding the purification of native xylanase from Myceliophthora heterothallica F.2.1.4. In this study, a xylanase from this fungus was purified and characterized. The xylanase, with 27 kDa, showed maximum activity at pH 4.5 and 65-70 °C. It maintained more than 80% of its residual activity when exposed to (i) temperatures between 30 and 60 °C for 1 h and (ii) pH 5-10 for 24 h at 4 and 25 °C. These high tolerances to different pH and different temperatures are important properties that add value to this enzyme. The hydrolysates of this enzyme on beechwood xylan, analyzed by HPAE-PAD, were mostly xylobiose (X2) and xylotriose (X3). Hydrolysates were also quantified, being retrieved from 234.2 mg xylooligosaccharides/g of hydrolyzed xylan for 12 h. According to the products obtained from the xylan hydrolysis and its tolerance properties of the enzyme, it has demonstrated potential for application production of xylooligosaccharides for use as prebiotics.

Biochemical characteristics and potential application of a novel ethanol and glucose-tolerant ß-glucosidase secreted by Pichia guilliermondii G1.2.

ß-glucosidases are glycoside hydrolases that-particularly those from filamentous fungi-have been extensively explored in cellulose fiber saccharification and wine quality improvement. However, these enzymes from yeast have been poorly studied. In this study, an ethanol-glucose tolerant ß-glucosidase that is secreted by Pichia guilliermondii (current name Meyerozyma guilliermondii) was purified and characterized. This enzyme exhibited an estimated molecular mass of 97 kDa and the highest activity between pH 3.5-5.5 and 55 °C. The ß-glucosidase was also tolerant to acetone, ethanol, isopropanol, and methanol up to 30% and glucose at 1 M. It was also stable up to 55 °C for 80 min, maintaining 70% of its initial activity and in a wide pH range (pH 3-10). The enzyme exhibited 90-100% of its initial activity for 72 h at 20, 25, and 30 °C in presence of 10% ethanol at pH 3.5, which is a similar condition to winemaking. Studies that identify new enzymes and describe their purification are required for oenology applications. The ß-glucosidase described herein is a promising candidate for use in the preparation of wine. Additionally, its tolerance to glucose is an important biochemical property that adds value to this enzyme and enables it to be used during the final saccharification process.