Accumulation of poly (3-hydroxybutyrate) by Microbacterium barkeri DSM 20145

Authors : Srividya SHIVAKUMAR

Pages : 225-232

View : 11 | Download : 5

Publication Date : 2012-12-01

Article Type : Research Paper

Abstract :A gram-positive bacterium that accumulated polyinsert ignore into journalissuearticles values(3-hydroxybutyric); acid insert ignore into journalissuearticles values(PHB); was isolated from petrol bunk soil. From its morphological and physiological properties and the nucleotide sequence insert ignore into journalissuearticles values(about 1.5 kb); of its 16S rDNA, it was identified as Microbacterium barkeri DSM 20145. Based on the available literature, this is the first report of PHB accumulation by Microbacterium sp. The isolate accumulated 0.6 g/L, or 29.7%, of PHB under growth conditions in a nitrogen-deficient medium containing glucose and yeast extract insert ignore into journalissuearticles values(4:1 ratio);, with maximum production by 48 h. The capacity of the isolate to produce PHB under different carbon and nitrogen sources was also investigated. The strain produced appreciable levels of PHB by utilizing hemicellulosic sugars such as glucose, xylose, and arabinose, as well as disaccharides such as lactose and sucrose, alternative carbon sources like wheat bran and carboxymethyl cellulose, and organic acids such as propionic acid, with maximum production achieved using xylose insert ignore into journalissuearticles values(1.7 g/L, 68%);. Among the nitrogen sources tested, peptone supported maximum production insert ignore into journalissuearticles values(1.4 g/L, 16%);, followed by casein insert ignore into journalissuearticles values(0.9 g/L, 22.6%); and sodium nitrate insert ignore into journalissuearticles values(0.4 g/L, 26.4%);, although the PHB yield was not appreciably high. The addition of xylose to the nitrogen-deficient medium increased the values of PHB yield insert ignore into journalissuearticles values(g/L); by 2.5 and the PHB accumulation insert ignore into journalissuearticles values(% dry cell weight); by 2.3; the replacement of yeast extract in the medium with peptone increased the PHB yield insert ignore into journalissuearticles values(g/L); by 2.05. The isolated polymer was highly soluble in chloroform and peaked sharply at 235 nm upon digestion with concentrated H2SO4. This study adds a new species to the family of PHB producers.
Keywords : Key words Microbacterium barkeri DSM 20145, poly 3 hydroxybutyrate, formation, carbon and nitrogen sources