An in vitro gastrointestinal model to evaluate the tolerance of encapsulated Lactobacillus and Lactococcus strains with synbiotic containing lactobionic acid via lyophilization technique to harsh gastric conditions during storage time

Abstract

Probiotics are living microorganisms that have potential health benefits for the host when administered in the correct proportions. However, for these beneficial effects to be produced, viable probiotic cells need to reach the human intestine. This study used a gastrointestinal model to represent the pH variation and gastric enzymes that are involved in the digestion process. Eight Lactobacillus strains and one Lactococcus strain were encapsulated using sodium alginate. The aim of this study was to compare free probiotic bacteria with encapsulated probiotic bacteria and determine the number of viable probiotic cells that might reach the human intestine. Microencapsulation of probiotic organisms followed the extrusion method with an alginate compound. Microencapsulated and free probiotic bacteria were inoculated into 200 ml of MRS (Man, Rogosa, Sharpe) broth. Simulated gastric juice and bile and pancreatic salt were used to test the tolerance of free Lactobacillus and Lactococcus species and microencapsulated bacteria to acid pH and enzymes. To enumerate the microencapsulated probiotic organisms, the bacteria were released from the capsules after total digestion with sodium citrate solution. The number of live bacteria (as CFU/g) was determined using the plate count method on MRS plates incubated at 37 °C for 48 h. Bacterial cell viability was determined on MRS agar duplicate plates at different dilutions. The results indicated that microencapsulation of probiotic bacteria showed improved viability over free cells when given 2 h of exposure to acidic conditions, and also for 2 h of exposure to bile and pancreatic salt. Encapsulation with alginate can protect probiotic bacteria from acidic conditions and bile salts. This study attempted also to produce synbiotic preparations with lactobionic acid using nontoxic encapsulating substances. The microorganisms used were stabilized with protective substances, and their stability during storage was checked under room temperature conditions. The final modification of the method, involving placing the capsules in a solution of skimmed milk with 5 % sucrose and 0.35 % ascorbic acid, resulted in an increase in the survival rate of some strains of microorganisms during microencapsulation and lyophilization and demonstrated stability during storage at room temperature.

Keywords: Gastrointestinal model; Lactobacillus; Lactococcus; Lyophilization; Microencapsulation; Probiotics; Sodium alginate; Synbiotic preparations.