Preparation of β(1→3)/β(1→4)-xylooligosaccharides from red alga dulse by two xylanases from Streptomyces thermogriseus 

Abstract

Red alga dulse has xylan with the structure containing β(1→3)/β(1→4)-linkage. We previously prepared xylooligosaccharides (XOS) from dulse xylan, however, the product contains many D-xylose and less XOS having β(1→3)-linkage. To improve the efficiency of XOS production, we prepared two recombinant endo-xylanases from Streptomyces thermogriseus (StXyl10 and StXyl11). Comparing the kcat/Km value for dulse xylan, the value of StXyl10 was approximately two times higher than that of StXyl11. We then determined the suitable condition for XOS production. As a result, the dulse XOS was prepared by the successive hydrolysis of 10 mg/ml of dulse xylan by 0.5 µg/ml StXyl10 for 4 h at 50°C and then 2.0 µg/ml StXyl11 for 36 h at 60°C. The xylan was converted into 95.8% of XOS, including 59.7% of XOS having β(1→3)-linkage, and 0.97% of X1. Our study provide useful information for the production of XOS having β(1→3)-linkage.