title: A standard quantitative method to measure acid tolerance of probiotic cells.
abstract: The aim of this work was to develop a standard quantitative method to measure the acid tolerance of probiotic cells when exposed to a simulated gastric fluid. Three model strains of different cell concentrations were exposed to a standard simulated gastric fluid of fixed volume. The fluid pH ranged from pH 1.5 to 2.5. In general, the death kinetics followed an exponential trend. The overall death constant, k (d), for all strains was found to be in a power relationship with the pH value and the initial cell concentration, and it can be expressed as k(d)=k(AII) (pH(-9.0)N(0)(-0.19)) where k (AII) is defined as the acid intolerance indicator and N (0) is the initial cell concentration (CFU/ml). This equation was validated with the experimental data with an average R (2) of 0.98. The acid intolerance of cells can be quantitatively expressed by the k (AII) values, where higher value indicates higher intolerance. In conclusion, a standard quantitative method has been developed to measure the acid tolerance of probiotic cells. This could facilitate the selection of probiotic strains and processing technologies.
authors.affiliation: Centre of Materials and Minerals, School of Engineering and Information Technology, Universiti Malaysia Sabah, 88999 Kota Kinabalu, Sabah, Malaysia. chan@ums.edu.my
authors.forename: Eng-Seng
authors.initials: ES
authors.lastname: Chan
authors.forename: Peh-Phong
authors.initials: PP
authors.lastname: Lee
authors.forename: Pogaku
authors.initials: P
authors.lastname: Ravindra
authors.forename: Kamatan
authors.initials: K
authors.lastname: Krishnaiah
authors.forename: Wan-Ping
authors.initials: WP
authors.lastname: Voo
mesh_terms: D015169:Colony Count, Microbial; D005744:Gastric Acid; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D007779:Lactobacillus acidophilus / Q000187:drug effects / Q000254:growth & development; D007780:Lacticaseibacillus casei / Q000187:drug effects / Q000254:growth & development; D050296:Microbial Viability; D008954:Models, Biological; D019936:Probiotics