Efficient production of acetylated xylooligosaccharides from Hawthorn kernels by a xylanase from Paecilomyces aerugineus

Abstract

Hawthorn (Crataegus pinnatifida) kernels can be utilized as a good source for production of acetylated XOS. A GH family 10 xylanase gene (PaXyn10A) from Paecilomyces aerugineus was cloned and expressed in Pichia pastoris. PaXyn10A shared the highest identity of 77 % with a xylanase from Aspergillus niger. The highest extracellular xylanase activity of 20,100 U/mL with protein concentration of 19 mg/mL was obtained in a 5-L fermentor. PaXyn10A was most active at pH 5.5 and 55 °C, respectively. It hydrolyzed different xylans to produce mainly xylooligosaccharidess (XOS) with degree of polymerization 2–6. To produce XOS, hawthorn kernels (HK) were pretreated by steam explosion at 185 °C with 25 min, and then hydrolyzed by PaXyn10A. The highest XOS yield of 18.7 g/100 g HK with hydrolysis ratio of 66.8 % was achieved. Xylooligosaccharides from HK were heavily acetylated at positions of 2-, 3-, and 2, 3-. This is a promising strategy for utilization of HK to produce acetylated XOS in an industrial point of view.