P. rhodozyma was cultured for four days at 25 °C in a 200 r·min−1 shaking incubator using the medium previously reported [20].The cells of P. rhodozyma were harvested with a centrifuge at 7200 r·min−1 for 3 min, then resuspended and washed twice with 0.1 mol·L−1 phosphate buffer at pH 7.0.