Chen Yonggan, Gu Fenglin, Li Jihua, He Shuzhen, Xu Fei, Fang Yiming
Spice and Beverage Research Institute, CATAS, Wanning, China College of Food Science and Technology, Huazhong Agricultural University, Wuhan, China Key Laboratory of Genetic Resources Utilization of Spice and Beverage Crops, Ministry of Agriculture, Wanning, China.
Spice and Beverage Research Institute, CATAS, Wanning, China Key Laboratory of Genetic Resources Utilization of Spice and Beverage Crops, Ministry of Agriculture, Wanning, China
Appl Environ Microbiol. 2015 Aug;81(15):4947-54. doi: 10.1128/AEM.00458-15. Epub 2015 May 15.
Vanilla beans were analyzed using biochemical methods, which revealed that glucovanillin disperses from the inner part to the outer part of the vanilla bean during the curing process and is simultaneously hydrolyzed by β-d-glucosidase. Enzymatic hydrolysis was found to occur on the surface of the vanilla beans. Transcripts of the β-d-glucosidase gene (bgl) of colonizing microorganisms were detected. The results directly indicate that colonizing microorganisms are involved in glucovanillin hydrolysis. Phylogenetic analysis based on 16S rRNA gene sequences showed that the colonizing microorganisms mainly belonged to the Bacillus genus. bgl was detected in all the isolates and presented clustering similar to that of the isolate taxonomy. Furthermore, inoculation of green fluorescent protein-tagged isolates showed that the Bacillus isolates can colonize vanilla beans. Glucovanillin was metabolized as the sole source of carbon in a culture of the isolates within 24 h. These isolates presented unique glucovanillin degradation capabilities. Vanillin was the major volatile compound in the culture. Other compounds, such as α-cubebene, β-pinene, and guaiacol, were detected in some isolate cultures. Colonizing Bacillus isolates were found to hydrolyze glucovanillin in culture, indirectly demonstrating the involvement of colonizing Bacillus isolates in glucovanillin hydrolysis during the vanilla curing process. Based on these results, we conclude that colonizing Bacillus isolates produce β-d-glucosidase, which mediates glucovanillin hydrolysis and influences flavor formation.
采用生化方法对香草豆进行分析，结果表明，在发酵过程中，葡糖香草醛从香草豆内部扩散到外部，并同时被β - d - 葡萄糖苷酶水解。发现酶促水解发生在香草豆表面。检测到定殖微生物的β - d - 葡萄糖苷酶基因（bgl）转录本。结果直接表明定殖微生物参与了葡糖香草醛的水解。基于16S rRNA基因序列的系统发育分析表明，定殖微生物主要属于芽孢杆菌属。在所有分离株中均检测到bgl，且其聚类情况与分离株分类相似。此外，接种绿色荧光蛋白标记的分离株表明，芽孢杆菌分离株能够定殖于香草豆。在分离株培养物中，葡糖香草醛在24小时内作为唯一碳源被代谢。这些分离株表现出独特的葡糖香草醛降解能力。香草醛是培养物中的主要挥发性化合物。在一些分离株培养物中还检测到其他化合物，如α - 荜澄茄烯（α - cubebene）、β - 蒎烯（β - pinene）和愈创木酚（guaiacol）。发现定殖的芽孢杆菌分离株在培养物中水解葡糖香草醛，间接证明了定殖的芽孢杆菌分离株在香草豆发酵过程中参与了葡糖香草醛的水解。基于这些结果，我们得出结论，定殖的芽孢杆菌分离株产生β - d - 葡萄糖苷酶，该酶介导葡糖香草醛水解并影响风味形成。
