Antimicrobial activity and optimization of Aureobasidin A production by Aureobasidium pullulans PA-2 against Escherichia coli and Staphylococcus aureus

Abstract

This work aims to separate antimicrobial lipopeptides from fermentation by Aureobasidium pullulans PA-2, and verify its antimicrobial activity and the optimum condition of lipopeptide production. Using high performance liquid chromatography (HPLC) analysis, the lipopeptides with antimicrobial activity was evaluated with the agar well diffusion test. Response surface methodology (RSM) was used to determine optimum conditions for lipopeptides from A. pullulans PA-2. The lipopeptides with antimicrobial activity in the fermentation supernatant of the PA-2 strain was found to be the Aureobasidin A (AbA). In vitro antagonistic tests showed that the minimal inhibitory concentration (MIC) of AbA against Staphylococcus aureus and Escherichia coli was 0.5 and 1.0 mg/mL, respectively. The optimal fermentation conditions were: inoculum size 6.8 % (v/v)(OD600=0.25), rotation speed 216 rpm, culture temperature 26 ℃, liquid volume 125 mL and initial pH7. Under this condition, predicting yield of the antimicrobial lipopeptides by the model was 940 mg/L, observed yield 920 mg/L, which was 51 % more than that of before optimization (610 mg/L).