Expression Of A Xylanase XYNZG From Plectosphaerella Cucumerina In Kluyveromyces Lactis And Its Application In Baking

Xylan can be hydrolyzed by xylanase to xylose, oligoxylose and some arabinose, which extensively exists in animals, plants and microorganisms. Moreover, it has considerable application prospect in the food, feed, paper making and other industries. Therefore, it has been attached great importance by the researchers both at home and abroad. At present, they are usually produced by large-scale fermentation with the yeast expression system in industrial production.In this research, the xylanase gene xynZG, from Plectosphaerella cucumerina, was expressed in Kluyveromyces lactis GG799based on integration expression vector pKLAC2by lithium chloride process. Transformant with the highest haloes was selected for the flask fermentation through5mM acetamide YCB plates and1%RBB-xylan YPD plates. SDS-PAGE and zymograms analysis indicated there was a proximately19kDa band as the expression products of gene xynZG. In this part, the fermentation mediums of recombinant strains were optimized, and the results showed that medium YLPU provided the highest activity of115U/ml at72h. This experiment successfully expressed the xylanase XYNZG using strains GG799, which laid the foundation for subsequent screening high expression strains.With the development of the living quality, people pay higher and higher attention to the field of food safety, especially for flour foods. Therefore, enzyme preparation as a kind of new green additives becomes more and more important. One of the application of xylanase in food industry is the amelioration of flour, it not only have an effect on the rheological properties of the dough, but can well improve all aspects of quality, such as increasing the volume of bread、 improve the degree of stretch of bread、delay the aging of bread and so on.Kluyveromyces lactis has been regarded as safety strains by FDA and its product can be safely applied in food industry. The xylanase XYNZG shows an apparent optimal temperature of40℃and retains approximately75%and55%of its maximum activity at35℃and25℃, respectively. These psychrophilic properties of XYNZG makes it highly suitable for use in the baking industry as it is generally optimally active at the temperatures most frequently used for dough preparation and proofing. The results of baking trials indicated the addition of XYNZG can reduce the kneading time of dough and have more positive effects on the sensory evaluation of bread. A series of results show that it has a positive influence on bread baking, which lays a foundation for developing new safely and reliably xylanase in the food industry. In addition, the mass spectrometry analysis showed the hydrolyzation products of xylan by XYNZG were mainly xylobiose and xylotriose, which further increased the xylanase XYNZG application value in the baking industry.