Identification Of Cellobiose Transporter In Celllolytic Fungus Aspergillus Niger

Complete hydrolysis paradigm and partial cellulose hydrolysis coexist universally in cellulolytic fungi.Aspergillus niger,which is one of the main industrial producers of lignocellulolytic enzymes,is charactered for its abundant extracellularβ-glucosidase and known for its rapid complete hydrolysis for cellulose.However,there is no evidence that Aspergillus niger can directly transport cellobiose.The study is aimed at verifying the existing of cellobiose transporter in Aspergillus niger,which is important for understanding the mechanism of cellulose utilization by Aspergillus niger and the function of six intracellular β-glucosidases.Because Saccharomyces cerevisiae YPH499 does not contain cellobiose transporters and intracellular β-glucosidase,it cannot grow on cellobiose as the sole carbon source,which allow us to verify the transport properties of the transporters.Genes encoding putative transporters were separately transformed into a recombinant S.cerevisiae host YP-βG expressing intracellular β-glucosidase GH1-1 in YPH499.The main results of the research are as follow:1 The results of sequence homology and gene transcriptional level analysis induced by different carbon indicate that three suger transporters in Aspergillus niger B2,An CT79,An CT26 and An CT46,could transport cellobiose.2 Of the three recombinant yeasts,only YP-βG-CT79 can grow on cellobiose as the sole carbon source,indicating An CT79 is a cellobiose transporter.3 Yeast YP-βG-CT79 can grow on cellotriose,cellotetraose and cellopentaose,indicating An CT79 is a cellodextrin transporter.The identification of cellobiose transporters in the cellulolytic fungus Aspergillus niger B2 provides valid evidence for the existence of partial cellulose hydrolysis in Aspergillus niger,implying six intracellular β-glucosidases may functionally expression in Aspergillus niger.What’s more,investigation for cellobiose transporter of Aspergillus niger will deepen understanding the regulation mechanism for lignocellulolytic enzymes production..