In Vitro assessment of the survivability of Lactobacillus casei DN-114 001 and Lactobacillus casei Shirota, within commercialised food matrices, in the upper gastrointestinal tract

Abstract

The aim of this study was to determine the survivability of probiotics; Lactobacillus casei Shirota and Lactobacillus casei DN-114 001, within their respective commercialised food matrices YakultÒ and ActimelÒ, during in vitro simulated gastrointestinal transit. Original and Light/Fat Free varieties of each brand were assessed to determine whether nutritional composition affected bacterial survival rate. Strains were exposed to 3 hours of simulated gastric transit at pH 2, using Hydrochloric Acid (32%) and Pepsin (3mg ml-1), followed by 2 hours of simulated duodenal transit, at pH 6.5, using Bile Salts (0.3% w/v) and Sodium Hydroxide (4M). Samples were serially diluted with PBS, spread plated onto MRS Agar and incubated at 37oC for 72 hours in a Carbon dioxide incubator (5%). Strains within all products retained viability after 5 hours of simulated gastrointestinal transit. Reductions in L. casei Shirota, within YakultÒ products (0.993 ± 0.220; Mean ± Standard Deviation), were significantly greater (P< 0.05), after 5 hours of simulated gastrointestinal transit, than reductions in L. casei DN-114 001 within ActimelÒ products (0.330 ± 0.129). No significant correlation was observed between the variety of brand (Original or Light/Fat Free) and bacterial survival rate after 5 hours of simulated gastrointestinal transit. Results suggest L. casei DN-114 001 is more capable at adapting to and surviving the inhospitable conditions of the gastrointestinal tract. However, food matrix composition may have some effect on bacterial survival as reductions of L. casei DN-114 001, within ActimelÒ Fat Free (0.428 ± 0.059), after 5 hours of simulated gastrointestinal transit were proven significant (P< 0.05), but were insignificant for L. casei DN-114 001 within ActimelÒ Original, when compared to controls. This study demonstrates that L. casei Shirota and L. casei DN-114 001, in Original and Light/Fat Free versions of YakultÒ and ActimelÒ, have the potential to survive the upper gastrointestinal tract.

Highlights

· All strains retained viability after 5 hours of in vitro gastrointestinal transit

· L. casei DN-114 001 in ActimelÒ Original showed resistance to gastrointestinal transit

· L. casei Shirota in YakultÒ products was significantly affected by gastrointestinal transit

· Composition of food matrix is potentially correlated with bacterial survivability