Characterization of lipolytic producing Proteus and Klebsiella strains isolated from fermented foods

Abstract

The aim of this research was to characterize the lipolytic producing Gram-negative, facultatively anaerobic, rod-shaped bacteria isolated from fermented foods collected in Thailand. All isolates were identified based on their phenotypic characteristics and 16S rRNA gene sequence analyses. Nine isolates (Group 1) belonged to the genus Proteus and one in Group 2 was Klebsiella based on 16S rRNA gene sequence similarity. The isolates in Group 1 (NM3-7, PR10-2, PR10-3, PR11-3, PR11-4, PR12-2, NM28-1, NM42-8 and NM42-10) were closely related to Proteus mirabilis ATCC 29906T with 99.78-100% similarity. Isolate NM42-1 in Group 2 was closely related to Klebsiella ozaenae ATCC 11296 T with 99.85% similarity. The isolates were sensitive to carbenicillin, imipenem, novobiocin, penicillin G, streptomycin, sulphoanmides, ampicillin, cephalothin, gentamicin, kanamycin and tobramycin, but they were resistant to bacitracin, clindamycin, erythromycin, tetracycline and vancomycin. Proteus isolates showed lipolytic activity for Tween 20, Tween 40, Tween 60 or Tween 80 ranging from 0.10±0.02-0.57±0.00 U/mL, whereas Klebsiella isolate exhibited 0.10±0.02 -0.24±0.04 U/mL. P. mirabilis PR11-3 exhibited the highest activity on Tween 80 at pH 8.0 when incubated for 18 h.