Double-coated microencapsulation of honeybee endogenous probiotics as a new strategy for the biocontrol of the American foulbrood disease

Abstract

Background American foulbrood (AFB) is one of the potent and highly contagious bacterial diseases affecting honeybees of Apis mellifera and A. cerana species. Paenibacillus larvae larvae (P. l. larvae) is the causative agent of AFB. The present study evaluated a novel technique to control AFB disease, in vitro, depending on double-coated microencapsulated probiotics. Microencapsulation was performed for the preservation of five different locally isolated, honeybee endogenous lactic acid bacteria (LAB) (Lactobacillus plantarum MK780211, L. plantarum MK780215, L. kunkeei MK780216, L. kunkeei MK780218 and Lactobacillus sp. MK780212). Results Extrusion technique was used to encapsulate each strain separately in alginate beads coated with resistant starch (Hi-maize) and chitosan. Encapsulation efficiency was determined by testing the cell viability after encapsulation process, and it was ranging between 93.1 and 95.5%. The antimicrobial activity of both free and encapsulated LABs against P. l. larvae was evaluated by the agar well diffusion method. The encapsulation process decreased the activity of all the tested probiotics to some extent, except Lactobacillus sp. MK780212 which caused complete inhibition for P. l. larvae with good shelf-life expectancy time, for a month, compared to its free cells. The effect of whole capsule and its components was evaluated to ensure the activity of the tested probiotics. Conclusion The laboratory-controlled experiments revealed that the microencapsulation process with double coating can be used with some probiotics efficiently without affecting their activity.