Regioselective synthesis of mannobiose and mannotriose by reverse hydrolysis using a novel 1,6-alpha-D-mannosidase from Aspergillus phoenicis

摘要

A novel 1,6-alpha-D-mannosidase was produced by Aspergillus phoenicis grown on a commercial manno-oligosaccharide preparation in liquid culture. The enzyme hydrolysed only alpha-D-Manp-(l->6)-D-Manp and did not act on alpha-D-Manp-( 1 -> 2)-D-Manp, or alpha-D-Manp( 1-> 3)-D-Manp. The 1,6-alpha-D-mannosidase was used for synthesis of manno-oligosaccharides by reverse hydrolysis reaction. The highest yields, expressed as percentages (w/w) of total sugar, were approx21% mannobiose and approx5% mannotriose, and they were obtained with 45% (w/w) initial mannose concentration at pH 4.5 after 12 days incubation at 55degC. The disaccharide and trisaccharide products were separated and their structures determined by methylation analysis. Only 1-6 linkages were found in both of them.