Bal Jyotiranjan, Yun Suk-Hyun, Yeo Soo-Hwan, Kim Jung-Mi, Kim Beom-Tae, Kim Dae-Hyuk
Department of Molecular Biology, Department of Bioactive Material Sciences, Institute for Molecular Biology and Genetics, Chonbuk National University, Jeonju, Jeollabuk-do, 561-756, Korea.
Fermented Food Science Division, Department of Agrofood Resource, NAAS, RDA, Wanju-gun, Jeollabuk-do, 565-851, Korea.
Appl Microbiol Biotechnol. 2017 Mar;101(5):2093-2106. doi: 10.1007/s00253-016-8042-2. Epub 2016 Dec 14.
The brewing of makgeolli, one of Korea's most popular alcoholic beverages that is gaining popularity globally, is facilitated by nuruk, a traditional Korean cereal starter. The nuruk microbiome greatly influences the fermentation process as well as the nutritional, hygienic, and aromatic qualities of the product. This study is a continuation of our efforts to examine nuruk biodiversity at a depth previously unattainable. In this study, microfloral dynamics in wheat-based nuruk C, composed of traditional ingredients such as barley, green gram, and wheat and fermented under various internal moisture contents of 20% (C20), 26% (C26), and 30% (C30), was evaluated using 454 pyrosequencing during the 30-day fermentation process. Rarefaction analysis and alpha diversity parameters indicated adequate sampling. C20 showed the greatest fungal richness and diversity, C20 and C26 exhibited similar bacterial richness and diversity, while C30 had low fungal and bacterial richness. Fungal taxonomic assignments revealed that the initial moisture content caused selective enrichment of Aspergillus candidus with a decreasing trend during fermentation, whereas Saccharomycetales sp. exhibited increasing relative abundance with increasing moisture content from day 6 of the fermentation process. Depending on initial moisture level, changes in bacterial communities were also observed in the genera Streptomyces, Bacillus, and Staphylococcus, with decreasing trends whereas Saccharopolyspora exhibited a sigmoidal trend with the highest abundance in C26. These findings demonstrate the possible impact of initial moisture content of nuruk on microfloral richness, diversity, and dynamics; this study is thus a step toward our ultimate goal of enhancing the quality of nuruk.
马格利酒是韩国最受欢迎的酒精饮料之一，目前在全球范围内越来越受欢迎，其酿造过程由韩国传统谷物发酵剂—— nuruk 辅助完成。nuruk微生物群对发酵过程以及产品的营养、卫生和香气品质有很大影响。本研究是我们在以前无法达到的深度上检查nuruk生物多样性的努力的延续。在本研究中，使用454焦磷酸测序技术评估了以小麦为基础的nuruk C在30天发酵过程中的微生物群落动态，nuruk C由大麦、绿豆和小麦等传统成分组成，并在20%（C20）、26%（C26）和30%（C30）的不同内部水分含量下进行发酵。稀释分析和α多样性参数表明采样充足。C20显示出最大的真菌丰富度和多样性，C20和C26表现出相似的细菌丰富度和多样性，而C30的真菌和细菌丰富度较低。真菌分类学分析表明，初始水分含量导致白色念珠菌选择性富集，在发酵过程中呈下降趋势，而酵母目在发酵过程第6天起随着水分含量增加相对丰度增加。根据初始水分水平，链霉菌属、芽孢杆菌属和葡萄球菌属的细菌群落也发生了变化，呈下降趋势，而糖多孢菌属呈S形趋势，在C26中丰度最高。这些发现证明了nuruk初始水分含量对微生物丰富度、多样性和动态的可能影响；因此，本研究朝着我们提高nuruk质量的最终目标迈出了一步。
