Preparation of bacterial cells and culture
A loop of bacterial cells from a slant culture of a fresh nutrient agar was cultivated in nutrient broth by shaking at 180r.p.m. for 24h at 25°C. The fresh culture (3mL) was placed into another Erlenmeyer flask with nutrient broth. Then they were incubated on a rotary shaker at 180r.p.m. for 48h at 25°C, standardized to a density equivalent of approximately 1 × 109CFUmL−1.