普洱茶固态发酵中转化咖啡碱为茶碱菌株的鉴定与应用

Identification and Application of Fungal Converting Caffeine to Theophylline from Pu-erh Tea Solid-state Fermentation

目的:在普洱茶渥堆发酵中分离并鉴定能够转化咖啡碱为茶碱的有效菌株,研究其在液态发酵与固态发酵中转化咖啡碱为茶碱的能力,为高茶碱茶叶的开发提供菌种。方法:采用咖啡碱琼脂固态筛选培养基,从普洱茶渥堆发酵中筛选出2株潜在菌株,通过18SrDNA序列测定结合菌落特征、分生孢子结构对菌株进行鉴定。采用不同浓度的咖啡碱液态培养基、茶汤液态发酵和茶叶固态发酵探究潜在菌株咖啡碱转化为茶碱的能力。结果:潜在菌株分别鉴定为黑曲霉(Aspergillus niger NCBT110A)和聚多曲霉(Aspergillus sydowii NRRL250)。经富含咖啡碱的液态培养发现,黑曲霉对咖啡碱的利用有限;聚多曲霉能促使咖啡转化为茶碱。在一定咖啡碱浓度下,聚多曲霉对咖啡碱的降解率在90%以上,促使一半以上的咖啡碱转化为茶碱。聚多曲霉接种的茶汤液态发酵、茶叶固态发酵表明,聚多曲霉发酵过程中咖啡碱显著性下降(p<0.05),茶碱急剧增加;在发酵结束时,咖啡碱的降解率分别为85.43%和87.37%,茶碱含量分别为(501.2±13.55)mg/L和3.3293%±0.2463%(w/w)。在咖啡碱存在情况下,聚多曲霉能将咖啡碱大幅度转化为茶碱。结论:本研究揭示了聚多曲霉(Aspergillus sydowii NRRL250)具备将咖啡碱转化茶碱的特性,为高茶碱茶叶或茶饮料的开发提供了优异菌种。

Objective：The aim of this study was to identify fungus species capable of converting caffeine to theophylline,and to provide strain to develop high-thephylline tea. Methods：With caffeine-agar solid selective medium, 2 potential strains were screened out,and colony characteristics and conidial structure were identified by sequence determination of 18SrDNA.Based on liquid mediums with different concentrations of caffeine, tea soup submerged fermentation and tea- leaves solid- state fermentation, the ability of conversion from caffeine to theophylline of potential strains were studied. Results ： Potential strains were identified as Aspergillus niger NCBT! 10A and Aspergillus sydowii NRRL250. The secondary screening in liquid-state cultivation with caffeine showed that caffeine utilization of A. niger NCBTll0A was restrained,A, sydowii NRRL250 could convert caffeine to theophylline.In a certain caffeine concentration, caffeine degradation rate of A,sydowii NRRI250 was beyond 90% and more than half of caffeine was converted to theophylline.Tea soup submerged and sun- dried tea solid- state fermentation of A. sydowii NRRL250 showed that caffeine decreased significantly and theophylline increased sharply during A.sydowii NRRL250 fermentation（p 〈 0.05）.The caffeine degradation rates were 85.43% and 87.37% ,theophylline reached （501.2±13.55 ） mg/L and 3.3293% ± 0.2463% （w/w）, respectively.In the presence of caffeine,A.sydowii NRRL250 could convert caffeine to theophylline sharply.Conclusion ：A.sydowii NRRL250 could convert caffeine to theophylline, which provided excellent strain to develop high-thephylline pu-erh tea or tea drinks.