title: Heterologous expression of glycoside hydrolase family 2 and 42 β-galactosidases of lactic acid bacteria in Lactococcus lactis.
abstract: This study characterized a glycoside hydrolase family 42 (GH42) β-galactosidase of Lactobacillus acidophilus (LacA) and compared lactose hydrolysis, hydrolysis of oNPG, pNPG and pNPG-analogues and galactooligosaccharides (GOSs) formation to GH2 β-galactosidases of Streptococcus thermophilus (LacZ type), Lactobacillus plantarum and Leuconostoc mesenteroides subsp. cremoris (both LacLM type). Beta-galactosidases were heterologously expressed in Lactococcus lactis using a p170 derived promoter; experiments were performed with L. lactis crude cell extract (CCE). The novel GH42 β-galactosidase of Lb. acidophilus had lower activity on lactose, oNPG and pNPG but higher relative activity on pNP analogues compared to GH2 β-galactosidases, and did not transgalactosylate at high lactose concentrations. Temperature and pH optima for lactose hydrolysis varied between GH2 β-galactosidases. oNPG and pNPG were the preferred substrates for hydrolysis; in comparison, activity on pNPG-analogues was less than 1.5%. GH2 β-galactosidases formed structurally similar GOS with varying preferences. The diversity of lactic acid bacteria β-galactosidase activity in L. lactis CCE can be exploited in future nutritional or therapeutic applications.
authors.affiliation: Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, AB, Canada. cschwab@ualberta.ca
authors.forename: Clarissa
authors.initials: C
authors.lastname: Schwab
authors.forename: Kim I
authors.initials: KI
authors.lastname: Sørensen
authors.forename: Michael G
authors.initials: MG
authors.lastname: Gänzle
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D003001:Cloning, Molecular; D004795:Enzyme Stability; D015870:Gene Expression; D006026:Glycoside Hydrolases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D007779:Lactobacillus acidophilus / Q000201:enzymology / Q000235:genetics; D048191:Lactiplantibacillus plantarum / Q000201:enzymology / Q000235:genetics; D013294:Lactococcus lactis / Q000235:genetics*; D007785:Lactose / Q000378:metabolism; D007934:Leuconostoc / Q000201:enzymology / Q000235:genetics; D009598:Nitrophenylgalactosides / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D048249:Streptococcus thermophilus / Q000201:enzymology / Q000235:genetics; D013379:Substrate Specificity; D013696:Temperature
chemical_list: D001426:Bacterial Proteins; D011994:Recombinant Proteins; C055012:2-nitrophenylgalactoside; D009598:Nitrophenylgalactosides; C059200:4-nitrophenylgalactoside; D006026:Glycoside Hydrolases; D007785:Lactose