An expansin from the marine bacterium Hahella chejuensis acts synergistically with xylanase and enhances xylan hydrolysis.

HcEXLX2 is a bacterial expansin found in a marine bacterium, Hahella chejuensis. Previously, HcEXLX2 was reported to act synergistically with a commercial cellulase preparation on the cellulose hydrolysis. The aim of the present study was to investigate the possible synergistic activity of HcEXLX2 with an endo-type xylanase from Saccharophagus degradans 2-40(T) (Xyn10C) in the hydrolysis of xylan. When 160 μg of HcEXLX2 was incubated with 12 μg of Xyn10C, the yield of reducing sugar increased 3.1 times when compared to that without HcEXLX2. The optimal temperature and pH for the synergism of HcEXLX2 with Xyn10C were 30°C and pH 7, respectively. In addition, binding experiments revealed that HcEXLX2 binds to xylan more preferentially than to Avicel. These results imply that HcEXLX2 could be used as an accessory protein to boost the activity of xylanase if its synergistic effect is strengthened at lower dosages.