Alginate microcapsules as delivery and protective systems of Bacillus licheniformis in a simulated shrimp's digestive tract

This work aims to encapsulate Bacillus licheniformis, a marine probiotic, in alginate microparticles (AMPs), and the evaluation of its controlled and targeted release within a simulated shrimp digestive tract (DT). The encapsulation process was carried out using the ionic gelation technique. Both free and bacteria-loaded AMPs were physicochemically characterized by size, morphology, surface electrical charge, the survival, and the number of encapsulated bacteria after the encapsulation process, and the bacterial survival after 40-days of storage (at 4 °C and 25 °C). The in vitro release and survival studies of the bacteria were carried out using a protocol developed in our laboratory by implementing buffers of dissected organs from shrimp's DT. Results indicated that microparticles with an average size of 172–185 μm and negatively charged (−16.77 and − 17.66 mV, respectively) were obtained after using the ionic gelation method. The bacterial survival and encapsulation efficiency showed high cell viability and yield above 99%. Stability studies showed that the best storage temperature was 4 °C, in which it remained almost 100% of the bacteria viable for 15 days; however, cell viability declined to 55% survival after 30 days of storage at this temperature. Regardless of the cell viability reduction after 30 days, there are enough viable bacteria cells to be considered as a probiotic product. Release and survival studies showed that alginate particles had a protective effect on bacteria by keeping ca. 51.29% of viable probiotic within the shrimp intestine; in contrast, free bacteria only reached the shrimp intestine ca. 27.16% viable. Our results suggest that microparticles can be produced by a low-cost method that could ultimately benefit shrimp farming in a near future.