High-Molecular-Weight Xylanase from B. pumilus US570 Strain: Purification, Characterization and Application in Banana and Orange Peels Hydrolysis and Breadmaking.

Abstract

New xylanase (XylUS570) was purified from the Bacillus pumilus US570 strain. It has a molecular mass of about 232kDa. This is the first report on the highest molecular weight monomeric xylanase produced by bacteria. The optimum pH and temperature recorded for enzyme activity were 7 and 55°C, respectively with a half-life time of 10min at 60°C. At 37°C, the enzyme retains more than 50% of its activity at a pH ranging from 6 to 9.5 for 24h. The XylUS570 exhibited a high activity on xylan, but no activity was detected for cellulosic substrates. The Vmax and Km values exhibited by the purified enzyme on beechwood xylan were 37.05 U mL-1 and 4.189mg mL-1, respectively. The XylUS570 was used in banana and orange peels hydrolysis and showed potential efficiency to liberate reducing sugars. It could be a good candidate for bio-ethanol production from fruit waste. The purified enzyme was used also as an additive in breadmaking. A decrease in water absorption, an increase in dough rising and improvements in volume and specific volume of the bread were recorded.