Microwave and Enzyme-assisted Extraction of Grape Seed Procyanidins and Study of Their Antibacterial Activity
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Abstract:
Procyanidins of Xinjiang white grape seeds were extracted by microwave and enzyme-assisted treatments for study of their antibacterial activity. Response surface analysis was conducted, using the Box-Behnken design experiment based on the single-factor test, to investigate the influence of four main factors (solid-liquid ratio, microwave time, microwave temperature, and cellulose dosage) on the procyanidin extraction rate. The extracted procyanidin sample was purified (purity 95.6%) using AB-8 macroporous resins. The optimal extraction conditions were as follows: temperature, 60 ℃; solid-liquid ratio, 1:14.6 (g:mL); microwave time, 9 min; and cellulose dosage, 0.56 mg/mL. Under these conditions, the procyanidin extraction yield was 5.72%. The purified procyanidins could effectively inhibit the growth of Staphylococcus aureus, with an inhibition zone diameter of 19.2 mm, a minimal inhibitory concentration (MIC) of 2.5 mg/mL, and a minimum bactericidal concentration (MBC) of 5 mg/mL. After treatment with the procyanidins, the permeability of the bacterial cell membrane was increased and the cell wall was destroyed. Scanning electron microscope images of the procyanidin-treated S. aureus showed wrinked bacterial surfaces and different cell sizes .
