Production of Lacto-<i>N</i>-triose II and Lacto-<i>N</i>-neotetraose from Chitin by a Novel β-<i>N</i>-Acetylhexosaminidase Expressed in Pichia pastoris
Yihao Liu, Qiaojuan Yan, Junwen Ma, Shaoqing Yang, Ting Li, Zhengqiang Jiang
Abstract
An unstudied β-N-acetylhexosaminidase (HaHex74) from Haloferula sp. was expressed in Pichia pastoris. HaHex74 displayed the highest similarity (61%) with a β-N-acetylhexosaminidase from an uncultured Bacteroidetes bacterium. The recombinant P. pastoris secreted the highest enzyme activity of 3500 U mL–1 after incubation for 168 h in a 5-L fermenter. HaHex74 showed an optimal pH and temperature of 6.5 and 45 °C, respectively. HaHex74 displayed high transglycosylation activity, showing a maximal conversion ratio of 13.1% (7.1 g L–1), which is by far the highest conversion ratio for the synthesis of lacto-N-triose II (LNT2) from N-acetyl chitobiose. Thus, an efficient strategy for the production of high value-added LNT2 and lacto-N-neotetraose (LNnT) from chitin by enzyme cocktails was first developed in a 5-L reactor. As a result, the contents of LNT2 and LNnT reached 8.6 and 2.0 g L–1, respectively. The novel and environmentally friendly bioprocess may greatly promote the production of LNT2 and LNnT from chitin.