Screening and Characterization of Levan Secreted by Halophilic Bacterium of Halomonas and Chromohalobacter Genuses Originated from Bledug Kuwu Mud Crater

Five bacterial isolates from the genus of Halomonas and Chromohalobacter isolated from Bledug Kuwu mud crater, located in mainland Purwodadi-Grobogan, Central Java, Indonesia, have been assayed for levan production. Initial screening was conducted on modified Belgith medium using sucrose as the major carbon source, in which the colonies of levan-producing bacteria will have a slimy mucoid appearance when grown on this medium. The screening results showed only one positive bacterial species, which was Chromohalobacter japonicus BK AB18 that identified as potential levan producer. Thermal stability of the isolated levan has been charachterized by TGA, which gave approximate decomposition temperature about 211 oC. The structure of the levan has been elucidated by FTIR and NMR spectroscopies. FTIR spectrum of the isolated levan displayed high similarity to that of levan isolated from Bacillus methylotrophicus. The chemical shifts of carbon and proton NMR spectra of the isolated levan also exhibited high similiarity to those of levan isolated from Pseudomonas fluorescens and Zymonas mobils.