title: Reduction of sulfide, ammonia compounds, and adhesion properties of Lactobacillus casei strain KE99 in vitro.
abstract: The ability of Lactobacillus casei strain KE99 to reduce sulfide, ammonia, and to adhere to bio-surfaces was characterized and compared with three lactobacillus reference strains. Sulfide reduction by strain KE99 in MRS broth increased exponentially after 10-h growth and reached a maximum (>300 ppm reduction) within 48 h. KE99 demonstrated a maximum reduction of sulfide under anaerobic (341 ppm) growth conditions at pH 6.0-8.0 range. Maximum anaerobic reduction of sulfide was demonstrated by L. casei 393 at pH 7.0 (272 ppm); L. rhamnosus at pH 8.0 (277 ppm); and L. reuteri at pH 7.0 (244 ppm). KE99 reduced sulfide more (p < 0.0001) in MRS broth spiked with Na2S (374 ppm) than (NH4)2S (340 ppm) salts. Ammonia reduction by strain KE99 and the three lactobacillus reference strains in MRS broth was low. Ammonia reduction reached a maximum within 36 h and remained unchanged over extended incubations of 48 h to 72 h or further. KE99 reduced ammonium sulfate (37 ppm) more readily than the nitrate (31 ppm), hypophosphate (29 ppm), or chloride (20 ppm) salts of ammonia. KE99 and the three reference strains of lactobacilli demonstrated avid binding to Bio-coat (Cn type-I, Cn type-IV, laminin, fibronectin), Matrigel, and Caco-2 cell monolayers in vitro. The number of lactobacilli binding to Caco-2 was estimated at 74/cell with strain KE99, which was significantly higher compared with 40/cell (p < 0.0001), 26/cell (0.0001), and 64/cell (p < 0.002) with L. casei 393, L. reuteri, and L. rhamnosus, respectively. The interaction of KE99 to immobilized Cn type-I was saturable and reached an equilibrium within 1 h at room temperature. KE99 binding to Cn type-I occurred at a wide pH range and was biphasic with maximum binding at pH 5.5 and 7.5. Inhibition and binding-displacement experiments with different salts and sugars suggested that the KE99 binding to immobilized Cn type-I may involve a combination of electrostatic and lectin-type interactions. KE99 effectively detached the Cn-adherent E. coli O157:H7 in the range of 55% (ATCC43895) to 76% (ATCC43894). The binding-displacement values for L. casei 393, L. reuteri and L. rhamnosus to detach Cn-adherent E. coli O157:H7 (ATCC43894) were 66 +/- 4%, 59 +/- 2%, and 64 +/- 2%, respectively. Also, a reconstituted solution of the freeze-dried KE99 preparation effectively detached the Cn-adherent E. coli O157:H7 in a dose-dependent manner that reached a binding-displacement equilibrium of 85% at a 1% wt/vol KE99 concentration.
authors.affiliation: Center for Antimicrobial Research, California State Polytechnic University, 3801 West Temple Avenue, Pomona, California 97168, USA. asnaidu@csupomona.edu
authors.forename: A S
authors.initials: AS
authors.lastname: Naidu
authors.forename: X
authors.initials: X
authors.lastname: Xie
authors.forename: D A
authors.initials: DA
authors.lastname: Leumer
authors.forename: S
authors.initials: S
authors.lastname: Harrison
authors.forename: M J
authors.initials: MJ
authors.lastname: Burrill
authors.forename: E A
authors.initials: EA
authors.lastname: Fonda
mesh_terms: D000641:Ammonia / Q000378:metabolism*; D000821:Animal Feed; D000818:Animals; D001422:Bacterial Adhesion / Q000502:physiology*; D001667:Binding, Competitive; D018938:Caco-2 Cells; D019453:Escherichia coli O157 / Q000472:pathogenicity / Q000502:physiology; D006801:Humans; D007778:Lactobacillus / Q000378:metabolism / Q000502:physiology; D007780:Lacticaseibacillus casei / Q000378:metabolism* / Q000502:physiology; D010084:Oxidation-Reduction; D019936:Probiotics; D013440:Sulfides / Q000378:metabolism*
chemical_list: D013440:Sulfides; D000641:Ammonia