Paenibacillus sp. strain HC1 xylanases responsible for degradation of rice bran hemicellulose

SummaryPaenibacillus sp. strain HC1 is the first bacterium capable of growing on rice bran hemicellulose as a sole carbon source. Two xylanases (Xyl-I and -II) were purified from the bacterial culture fluid and enzymatically characterized. Xyl-I and -II showed monomer forms with molecular masses of 30 and 18 kDa, respectively, and were most active at around pH 5.0 and 45 °C. Xylooligosaccharides were degraded to xylobiose and xylose by Xyl-I, but not by Xyl-II, suggesting that Xyl-I plays an important role in complete depolymerization of xylan. Both enzymes acted endolytically on rice bran hemicellulose, indicating that Xyl-I and -II contribute to the structure determination and practical use of the polysaccharide, an unutilized biomass in technology.