title: High yield production of a soluble bifidobacterial β-galactosidase (BbgIV) in E. coli DH5α with improved catalytic efficiency for the synthesis of prebiotic galactooligosaccharides.
abstract: The bifidobacterial β-galactosidase (BbgIV) was produced in E. coli DH5α at 37 and 30 °C in a 5 L bioreactor under varied conditions of dissolved oxygen (dO2) and pH. The yield of soluble BbgIV was significantly (P < 0.05) increased once the dO2 dropped to 0-2% and remained at such low values during the exponential phase. Limited dO2 significantly (P < 0.05) increased the plasmid copy number and decreased the cells growth rate. Consequently, the BbgIV yield increased to its maximum (71-75 mg per g dry cell weight), which represented 20-25% of the total soluble proteins in the cells. In addition, the specific activity and catalytic efficiency of BbgIV were significantly (P < 0.05) enhanced under limited dO2 conditions. This was concomitant with a change in the enzyme secondary structure, suggesting a link between the enzyme structure and function. The knowledge generated from this work is very important for producing BbgIV as a biocatalyst for the development of a cost-effective process for the synthesis of prebiotic galactooligosaccharides from lactose.
authors: Department of Food and Nutritional Sciences, The University of Reading , PO Box 226, Whiteknights, Reading, Berkshire, RG6 6AP, United Kingdom.
authors: Ali
authors: A
authors: Osman
authors: George
authors: G
authors: Tzortzis
authors: Robert A
authors: RA
authors: Rastall
authors: Dimitris
authors: D
authors: Charalampopoulos
mesh_terms: D001644:Bifidobacterium / Q000201:enzymology*; D055162:Biocatalysis; D019149:Bioreactors; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D005690:Galactose; D007785:Lactose / Q000378:metabolism; D009844:Oligosaccharides / Q000096:biosynthesis*; D056692:Prebiotics; D011994:Recombinant Proteins / Q000096:biosynthesis*; D014169:Transformation, Bacterial; D001616:beta-Galactosidase / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism
chemical_list: D009844:Oligosaccharides; D056692:Prebiotics; D011994:Recombinant Proteins; D001616:beta-Galactosidase; D007785:Lactose; D005690:Galactose