Extracellular Polysaccharide Produced by a New Methylotrophic Isolate

새로운 메탄올 자화세균이 생산하는 세포외 다당류

  • Lee, Ho J. (Department of Biology and Bioproducts Research Center, Yonsei University) ;
  • Kim, Si W. (Division of Environmental Engineering, Chosun University) ;
  • Kim, Young M. (Department of Biology and Bioproducts Research Center, Yonsei University)
  • 이호준 (연세대학교 이과대학 생물학과, 생물산업소재연구센터) ;
  • 김시욱 (조선대학교 공과대학 환경공학부) ;
  • 김영민 (연세대학교 이과대학 생물학과, 생물산업소재연구센터)
  • Received : 1998.11.14
  • Accepted : 1998.12.16
  • Published : 1998.12.01

Abstract

An obligately methylotrophic bacterium which produces extracellular polysaccharide (EPS) was isolated through methanol-enrichment culture technique. The isolate was aerobic, nonmotile, and gram negative rod and exibited catalase, but no oxidase, activity. Plasmid, carotenoid, and poly-${\beta}$-hydroxybutyric acid were not found. The guanine plus cytosine content of DNA was 52-56%. The isolate was found to grow only on methanol and monomethylamine. Growth was optimal ($t_d=2.4h$) at $35^{\circ}C$ and pH 6.5 in a mineral medium containing 0.5% (v/v) methanol, 25 mM phosphate, and 0.212% ammonium sulfate. Methanol was assimilated through the ribulose monophosphate pathway. Maximun amount of EPS was produced in cells growing at the mid-stationary growth phase at $30^{\circ}C$ in a mineral medium (PH 6.5) containing 1.0% (v/v) methanol in the CIN ratio of 54.7. Thin-layer chromatographic and high performance liquid chromatographic analysis revealed that the EPS was composed of glucose and galactose. EPS which was not treated with ethanol (Pbe) exhibited stable viscosity under various concentrations of salts and temperatures hut showed high viscosity at low pH. EPS precipitated with ethanol (Pae) was found to be more stable in viscosity than the Pbe at various salt concentrations, temperatures, and pH. The Pae also exhibited higher viscosity than the Pbe and xanthan gum. Scanning electron microscopy revealed that the lyophilized Pbe and Pae have a multi-layered structure and a structure of thick fibers, respectively.

Keywords

Obligate methylotrophic bacterium;methanol;extracellular polysaccharide

Acknowledgement

Supported by : 한국과학재단