[Isolation, identification and agarose degradation of a polysaccharide-degrading marine bacterium Persicobacter sp. JZB09].

ABSTRACT

OBJECTIVE: To isolate and identify a versatile carbohydrate-degrading bacterium from marine environments, and characterize the extracellular agarase activity. METHODS: The I2 staining method was applied in the isolation of agarose-degrading bacteria from coastal sediments of the Jiaozhou bay nearby Qingdao city, China. The JZB09 strain was cultured in multiple media using various complex polysaccharides as the sole carbon source to test the carbohydrate utilizing abilities. The 16S rRNA gene was cloned, sequenced and analyzed to identify the taxonomic position of the strain. Crude extracellular proteins were prepared using (NH4)2SO4 precepitation method. The dialyzed enzyme extract was applied in further studies including activity testing, activity staining, and agarose degrading for oligosaccharides purifiction. Three purified oligosaccharides were individually analyzed using thin layer chromatograph (TLC) and MALDI-TOF MS method. RESULTS: The agarolytic marine bacterium, Persicobacter sp. JZB09, could use multiple complex polysaccharides as the sole carbon source and grew well on agarose, cellulose and xylan. The extracellular enzyme extract exhibits efficient and extensive degradation activity on agarose with an activity of 77.2 U/mg proteins. The extracellular agarase system (EAS) in the crude extracellular enzymes contains at least two agarose depolymerases with molecular masses of approximately 45 kDa and 70 kDa, respectively. A series of degradation products from agarose by the EAS was purified and identified as neoagaro-oligosaccharides, among which neoagarotetraose was the major product of the crude enzymatic products, which suggests that beta-agarase is the major constituent of the JZB09 EAS. CONCLUSION: The polysaccharide-degrading bacterium Persicobacter sp. JZB09 and its polysaccharide-degrading system is promising for the exploration of polysaccharide depolymerase resources including beta-agarases.