title: [Enterobacter agglomerans B1 producing beta-galactosidase with transglycosylation activity: screening, identification, fermentation conditions, and galacto-oligosaccharides synthesis].
abstract: Galacto-oligosaccharides (GOS) are promising non-digestible oligosaccharides recognized as prebiotics. Commercial GOS containing galactose as subunit, are synthesized from lactose using the galactosyl-transferase activity of beta-galactosidase. A strain producing beta-galactosidase with transglycosylation activity was screened from the soil. Phenotypic analysis including morphology and physiology characteristics and 16S rDNA sequence analysis were carried out. Based on taxonomy results, the strain was identified as Enterobacter agglomerans B1. Medium and fermentation conditions were optimized by single factor and orthogonal experiments. The enzyme reached 9.7 U/mL in the medium (pH 7.5) containing 1% lactose, 1% yeast extract, and 0.5% peptone when cultured at 25 degrees C for 26 h. Effects of pH, temperature, lactose concentration, and reaction time on transgalactosylation by whole cells were studied. Yield of GOS reached 40.7% in 30% lactose (pH 7.5) at 50 degrees C for 12 h, as analyzed by HPLC and TLC. The results of an MS analysis showed that GOS were composed of di, tri-, and tetrasaccharides.
authors.affiliation: State Key Laboratory of Microbial Technology, National Glycoengineering Research Center, Shandong University, Jinan 250100, China. graduate531@163.com
authors.forename: Lili
authors.initials: L
authors.lastname: Lu
authors.forename: Min
authors.initials: M
authors.lastname: Xiao
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Xu
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D003470:Culture Media / Q000378:metabolism; D046508:Culture Techniques; D004754:Enterobacter / Q000201:enzymology* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D005285:Fermentation; D006031:Glycosylation; D009844:Oligosaccharides / Q000096:biosynthesis*; D012988:Soil Microbiology; D001616:beta-Galactosidase / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D003470:Culture Media; D009844:Oligosaccharides; D001616:beta-Galactosidase