Control of Browning in Cell Subculture of Cistanche deserticola

Browning forms easily during cell culture of Cistanche deserticola. By comparing the content of phenol,browning degree and activity of polyphenol oxidase (PPO) between browning and unbrowning cells,enzymatic action of PPO was considered as the main factor of browning. The optimum pH of PPO is from 5.8 to 6.0 by determining the activity of PPO with pH from 2.0 to 8.0. The effects of inhibitors,including vitamin C (Vc),citric acid and sodium sulfite,on the activity of PPO of Cistanche deserticola were investigated at the optimum pH. These inhibitors all can restrain the activity of PPO,Vc can restrain prominently the activity of PPO,increasing its concentration. When the concentration of Vc reached 0.6 mg/L,the activity of PPO decreased to 5.1% of the optimum activity of PPO. Then the medium containing activated carbon and VC for cell subculture was obtained. The optimal B5 medium including 1.0 g/L activated carbon,3.0 mg/L Vc,1.0 mg/L IAA and 4.0 mg/L KT can effectively restrain browning of cells. The browning degree of the cells in the optimal B5 medium decreased to 21%. The cells of Cistanche deserticola grew better in the optimal medium and the maximum relative increment of cell growth (dry weight) was 25.4%.