Antistaphylococcal metabolite from Aureobasidium pullulans: production and characterization

NE Kalantar, RL Deopurkar, BP Kapadnis

 

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.

KeywordsAureobasidium, antistaphylococcal activity, potassium efflux

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