title: Synthesis of alkylgalactosides using whole cells of Bacillus pseudofirmus species as catalysts.
abstract: Whole cells of alkaliphilic Bacillus pseudofirmus AR-199, induced for beta-galactosidase activity, were used for the synthesis of 1-hexyl-beta-d-galactoside and 1-octyl-beta-d-galactoside, respectively, by transglycosylation reaction between lactose and the corresponding alcohol acceptor. The product yield was strongly influenced by the initial water content in the reaction mixture. Water content of 10% (v/v) was optimal providing 3.6-36 mM hexyl galactoside from 10 to 150 mM lactose, and no secondary product hydrolysis. Product yield could be enhanced by supplementing the reaction mixture with more cells or partly replacing the product with fresh substrate, but was decreased with time to the initial equilibrium level. Cell permeabilisation or disruption resulted in increased reaction rate and higher product yield but was followed by product hydrolysis. Octyl galactoside synthesis using whole cells was optimal at water content of 2% (v/v) with a yield of 26%. The cells were immobilised in cryogels of polyvinyl alcohol for use in continuous process, where hexyl galactoside was produced with a constant yield of 50% from 50mM lactose for at least a week.
authors.affiliation: Department of Biotechnology, Center for Chemistry and Chemical Engineering, Lund University, Box 124, S-221 00 Lund, Sweden.
authors.forename: Sapna
authors.initials: S
authors.lastname: Das-Bradoo
authors.forename: Ingemar
authors.initials: I
authors.lastname: Svensson
authors.forename: Jorge
authors.initials: J
authors.lastname: Santos
authors.forename: Fatima
authors.initials: F
authors.lastname: Plieva
authors.forename: Bo
authors.initials: B
authors.lastname: Mattiasson
authors.forename: Rajni
authors.initials: R
authors.lastname: Hatti-Kaul
mesh_terms: D000438:Alcohols / Q000378:metabolism; D001407:Bacillus / Q000254:growth & development / Q000378:metabolism*; D019149:Bioreactors; D001709:Biotechnology / Q000379:methods*; D001798:Blood Proteins / Q000737:chemistry; D002384:Catalysis; D002462:Cell Membrane / Q000502:physiology; D018914:Cells, Immobilized; D059985:Cryogels; D005353:Fibronectins / Q000737:chemistry; D005696:Galactosidases / Q000378:metabolism; D005697:Galactosides / Q000096:biosynthesis* / Q000737:chemistry*; D006031:Glycosylation; D020100:Hydrogels; D006868:Hydrolysis; D007700:Kinetics; D007785:Lactose / Q000378:metabolism; D010539:Permeability; D011142:Polyvinyl Alcohol / Q000737:chemistry; D013379:Substrate Specificity; D013997:Time Factors; D014867:Water / Q000737:chemistry
chemical_list: D000438:Alcohols; D001798:Blood Proteins; D059985:Cryogels; D005353:Fibronectins; D005697:Galactosides; D020100:Hydrogels; D014867:Water; D011142:Polyvinyl Alcohol; D005696:Galactosidases; D007785:Lactose