Antistaphylococcal metabolite from Aureobasidium pullulans: production and characterization

Abstract

Aureobasidium pullulans (NI.3) isolated from the leaves of Dracaena reflexa variegate produced intracellular antimicrobial metabolite the yield of which was 700-800 U from about 0.7-0.85 g of dry biomass. The antistaphyloccocal metabolite showed strong activity against different Staphylococcus spp. The MICs ranged from 1.25 to 3.6 U/ml. The metabolite was only moderately sensitive to temperature. After keeping at 400C and 700C for one hour it lost only 20% and 60% of its activity respectively. However, it was completely inactivated upon exposure to 1210C for 20 min. The antistaphyloccocal metabolite was insensitive to various protein-denaturing detergents and enzymes like trypsin, proteinase K, lipase and lysozyme. The activity was fairly stable over a wide range of pH (5.7–8). When S. aureus was grown in the medium in presence of antimicrobial metabolite (10 U/ml) the number of CFU started to decrease. However, most of the cells had lost their viability after nine hours exposure. A slower killing of the S. aureus was noted when cells were kept in buffer containing antimicrobial metabolite (5 U/ml). Antimicrobial metabolite induced efflux of potassium ions from cells of Staphylococcus indicating the channel forming activity.


Keywords: Aureobasidium, antistaphylococcal activity, potassium efflux


African Journal of Clinical and Experimental Microbiology Vol. 6 (3) 2005: 177-187