Application of Aspergillus sydowii NRRL250 to Degrade Caffeine in Pu-erh Tea

Pu-erh tea is produced by a solid-state fermentation. The natural microbiota presented in pu-erh tea influence caffeine level. In previous study, one effective fungi was selected from pu-erh tea and identified as Aspergillus sydowii NRRL250, which could lead caffeine degradation. In this paper, A. sydowii NRRL250 was inoculated into a liquid medium with different initial caffeine concentrations (600, 1200 and 1800 mg/L of caffeine, respectively) to explore caffeine degradation products. The solid-state fermentation of sun-dried tea leaves and submerged fermentation of tea infusion were carried out to investigate the application of A. sydowii NRRL250 through an inoculation. Samples were collected periodically, and the contents of caffeine, theophylline, 3-methylxanthine and theobromine were determined by HPLC. In the substrate tests, caffeine degraded drastically, theophylline and 3-methylxanthine were detected and increased obviously with the degradation of caffeine, and theobromine was not detected. In the solid-state and submerged fermentation, caffeine decreased radically (p<0.05), only about 4.14±0.771 mg/g and 157.8±10.21 mg/L of caffeine were remained, respectively. And theophylline had a dramatic increase (p<0.05), 28.29±2.463 mg/g and 501.2±13.55 mg/L of theophylline were produced in the end of the fermentation. 3-Methylxanthine also increased significantly (p<0.05) in the fermentation. Theobromine remained stable without significant change (p>0.05). Compared with the submerged fermentation without caffeine addition, the extra addition of caffeine could enhance the productions of theophylline and 3-methylxanthine significantly (p<0.05). Therefore, theophylline and 3-methylxanthine were the main degradation products from caffeine, caffeine concentration had a significant (p<0.05) effect on the productions of theophylline and 3-methylxanthine. And A. sydowii NRRL250 had great application potential to produce decaffeinated and high-theophylline tea through an inoculation