Microencapsulation of bovine vaginal lactobacilli in alginate using emulsion-gelation: freeze-drying, storage and antimicrobial activity

Abstract

Probiotics containing autochthonous Lactic Acid Bacteria (LAB) as local treatment in the Bovine Reproductive Tract (BRT)was proposed as a sustainable alternative to prevent outcome of pathogens colonization in the postpartum uterus in cows.Microencapsulation of these LABs could improve their survival during stressing conditions and promote the intimate contact betweenthe veterinarian form and the vaginal mucosa. In this work, emulsion-ionic gelation technique was applied to encapsulate bovine LABstrains in an alginate (3%) matrix. Optical and scanning electron microscopic evaluations showed spheroidal particles (12-48 µm)with a fully charge of LAB; the average load ranged 8.98 ± 0.15 to 8.06 ± 0.21 log CFU/g. The microencapsulated lactic acid bacteria(LAB-MCs) stability was evaluated during lyophilization [in Skim Milk (SM), or Neutral Distilled Water (NDW)] and storage (at 4°Cup to 90 days). SM represented a significant high protection to the lyophilization. Also, the alginate microencapsulation improvedthe LAB strain resistance when freeze-dried in water, comparing to known sensibility of LAB free cells. L. gasseri CRL 1412 showedsimilar resistance in both, NDW (0.70 ± 0.05) and SM (0.72 ± 0.05); and their microcapsules (MCs) exhibited antagonistic activityagainst E. coli 99/14 (pathogen from Bovine metritis) when cultured together; contrary, in co-culture with empty-MCs no inhibitionwas observed. To evaluate the microencapsulation process, different parameters were estimated: Encapsulation Factor (EF) (rangedbetween 0.76 ± 0.03 and 0.85 ± 0.08) and Encapsulating Efficiency (EE) (average EE%=75%) none significant differences (LSDFishertest, P<0.05) were observed between LAB strains. Taking account the weight of the materials, the calculated average yieldwas 50.5%. The standardized encapsulation conditions allowed selected L. gasseri CRL 1412-MCs as potential systems to beincluded in formulations to restore vaginal microbiota to prevent metritis in cows