Screening and Characterization of Putative Probiotic Lactobacillus Strains from Honey Bee Gut (Apis mellifera)

Abstract

The objective of this work was to isolate, identify and characterize lactobacilli strains from the intestinal tract of honey bees as putative probiotics. We obtained eighty-five isolates. At the end of screening based on physiological properties, 17 isolates were pre-selected and their resistance to gastrointestinal stress was evaluated. Twelve (12) with good resistance after 3 h exposure to low pH values (pH2, pH3) were subjected to determination of their in vitro BSH activity. The research of the bsh-A, bsh-B, Bsh1 and Bsh-Lp1 genes encoding the BSH enzyme was also conducted. Four isolates (H46, H82, H21 and H28) were resistant, seven others tolerant (H6, H15, H47, H24, H67, H44, H80) and only one was sensitive (H63) to oxgall bile salt. Determination of BSH activity revealed that all strains hydrolyze bile salts, with a preference for oxgall as opposed to Taurodeoxycholate. H15 and H47 isolates showed the highest BSH activities, which were 103.82 ± 12.93 U/mg and 98.53 ± 2.86 U/mg, respectively, with no significant difference (p>0.05). Only the bsh-Lp1 gene was amplified in isolate H24 and H28. None of the strains showed the bsh-1, bsh-A or bsh-B genes. After sequencing bsh-Lp1 gene of H24 and H28, the BSH proteins deduced from the complete ORF showed high similarity with those of GenBank database. Antimicrobial activity revealed the inhibition zone against pathogenic and food spoilage bacteria. Isolates were identified based on the sequencing of 16S rRNA encoding gene as Lactobacillus plantarum (75%) and Lactobacillus paraplantarum (25%).