Molecular and Biochemical Characterization of Xylanase Produced by Streptomyces viridodiastaticus MS9, a Newly Isolated Soil Bacterium

A xylan-degrading bacterial strain, MS9, was recently isolated from soil samples collected in Namhae, Gyeongsangnam-do, Republic of Korea. This strain was identified as a variant of NBRC13106 based on 16S rRNA gene sequencing, DNA-DNA hybridization analysis, and other chemotaxonomic characteristics, and was named MS9 (=KCTC29014= DSM42055). In this study, we aimed to investigate the molecular and biochemical characteristics of a xylanase (XynC ) identified from MS9. XynC (molecular weight ≍ 21 kDa) was purified from a modified Luria-Bertani medium, in which cell growth and xylanase production considerably increased after addition of xylan. Thin layer chromatography of xylan-hydrolysate showed that XynC is an endo-(1,4)-β-xylanase that degrades xylan into a series of xylooligosaccharides, ultimately converting it to xylobiose. The and values of XynC for beechwood xylan were 1.13 mg/ml and 270.3 U/mg, respectively. Only one protein (GHF93985.1, 242 amino acids) containing an amino acid sequence identical to the amino-terminal sequence of XynC was identified in the genome of . GHF93985.1 with the twin-arginine translocation signal peptide is cleaved between Ala-50 and Ala-51 to form the mature protein (21.1 kDa; 192 amino acids), which has the same amino-terminal sequence (ATTITTNQT) and molecular weight as XynC , indicating GHF93985.1 corresponds to XynC . Since none of the 100 open reading frames most homologous to GHF93985.1 listed in GenBank have been identified for their biochemical functions, our findings greatly contribute to the understanding of their biochemical characteristics.