Fluidized bed microencapsulation of Lactobacillus reuteri with sweet whey and shellac for improved acid resistance and in-vitro gastro-intestinal survival

This study aimed at developing a micro-encapsulation process for Lactobacillus reuteri DSM 20016 with sweet whey powder and dietary shellac by a two-step fluidized bed granulation and top spray coating technique to enhance resistance to acid conditions and to increase bacterial survival under gastro-intestinal conditions. L. reuteri DSM 20016 was a top-spray fluid bed granulated at 50 °C with sweet whey and different thermo-protectants followed by top spray coating with an aqueous shellac solution. Moisture content and particle size of granules measured by infrared moisture balance and laser diffraction were appropriate for the encapsulation of the bacteria. Bacterial survival rates were evaluated by pour plate counting. Viabilities after granulation were 43 ± 4.5%, after 15 min shellac coating 22.69 ± 2.41% and 14.86 ± 1.29% after 30 min coating time. Endpoint bacterial count after 28 d storage at 4 °C remained equal for coated and uncoated bacteria. After incubation in gastric acid and intestinal conditions the final survival rate of coated L. reuteri DSM 20016 with 76.74 ± 24.36% was higher compared to free cells with 17.74 ± 10.51% (p = 0.0388).To conclude fluidized bed technology with a combination of sweet whey and shellac as encapsulation material offers distinct acid resistance for L. reuteri DSM 20016 and enables improved survival during gastro-intestinal transit. Hence the usage of shellac and sweet whey powder as encapsulation material improves the effectiveness of probiotic food applications.