Controlled release of Lactobacillus rhamnosus biofilm probiotics from alginate-locust bean gum microcapsules

•High-density biofilm Lactobacillus rhamnosus probiotics cells are encapsulated.•Capsules’ stress tolerance is improved by addition of locust bean gum to alginate.•Higher freeze drying- (6×), thermal- (100×), and acid-tolerance (10×).•Cells are protected in simulated gastric juice, released in intestinal juice. Chitosan-coated alginate microcapsules containing high-density biofilm Lactobacillus rhamnosus have been previously shown to exhibit higher freeze drying- and thermal-tolerance than their planktonic counterparts. However, their cell release profile remains poor due to the capsules’ susceptibility to the gastric environment. Herein the effects of adding locust bean (LB) and xanthan (XT) gums to alginate (AGN) capsules on the stress tolerance and cell release profiles in simulated gastrointestinal fluids are investigated. Compared to the AGN-only capsules, the AGN-LB capsules exhibit improved stress tolerance (i.e. ≈6× for freeze drying, 100× for thermotolerance, 10× for acid), whereas the AGN-XT capsules only improve the acid tolerance. Importantly, the AGN-LB capsules possess the optimal cell release profile with a majority of cells released in the simulated intestinal juice than in the gastric juice. The AGN-LB capsules’ superiority is attributed to their stronger interaction with the chitosan coating and high swelling capacity, thus delaying their bulk dissolution.