Cheng Tiantian, Zhao Jinrong, Zhang Tuo, Ba Genna, Fan Qicheng, Sun Yuanzheng, Zhang Guangfu, Sadiq Faizan Ahmed, Sang Yaxin, Gao Jie
Inner Mongolia Yili Industrial Group Limited by Share Ltd, Hohhot 010080, China.
Department of Food Science and Technology, Hebei Agricultural University, Baoding, Hebei 071000, China.
Int J Food Microbiol. 2025 Jul 15;442:111345. doi: 10.1016/j.ijfoodmicro.2025.111345.
Kefir grains serve as natural dairy starter cultures, surviving in high-altitude environments with low temperatures and limited oxygen, while maintaining robust fermentation capabilities. In this study, we reconstructed a synthetic microbial community (SMC) within the kefir microbial ecosystem and explored the strategies that keep this SMC stable and functioning within the complex environment. We investigated the interactions among kefir species by comparing their symbiotic capabilities, milk acidification properties, and fermentation profiles during growth in both individual cultures and co-cultures across various media. Additionally, to deepen our understanding of system-level responses within the SMC, we integrated metabolomics with pure culture techniques to elucidate the mechanisms that enable coexistence among SMC members. The composition of the SMC in fermented milk was determined through co-cultivation assessments and flavor profile analysis, which identified the key members as Lactobacillus kefiranofaciens CZ22, Lactococcus lactis CZ19, and Saccharomyces cerevisiae Y8. The fermented milk produced by SMC shared identical volatile compound profiles with traditional kefir milk, including seven alcohols, seven aldehydes, six ketones, five esters, two carboxylic acids, two ethers, one acyl compound, and five miscellaneous volatile compounds. Our findings revealed that the coexistence mechanism among these three species is based on cross-feeding interactions. Lc. lactis CZ19 provides L. kefiranofaciens CZ22 with amino acids such as tyrosine, proline, and arginine, promoting its growth. Moreover, S. cerevisiae Y8 supplies primary metabolic products, including purines, pyrimidines, and nucleotides, to L. kefiranofaciens CZ22, facilitating the coexistence of all three species. During the fermentation process of the SMC, L. kefiranofaciens CZ22 maintained high abundance and accelerated acidification and enhanced flavor volatiles in milk. The SMC we constructed effectively maintained the core kefir species and fermentation performance of kefir starter cultures, simplified the complex fermentation system and laid the groundwork for the modernization and improvement of the production process. This study systematically elucidates the coexistence strategies employed by synthetic microbial systems in fermented milk production, while enhancing our understanding of microbial interactions in traditional fermented foods.
开菲尔粒作为天然的乳制品发酵剂，能在低温、低氧的高海拔环境中存活，同时保持强大的发酵能力。在本研究中，我们在开菲尔微生物生态系统内构建了一个合成微生物群落（SMC），并探索了在复杂环境中保持该SMC稳定和发挥功能的策略。我们通过比较开菲尔菌种在不同培养基中的单独培养和共培养过程中的共生能力、乳酸酸化特性及发酵谱，研究了它们之间的相互作用。此外，为了更深入地了解SMC内的系统水平反应，我们将代谢组学与纯培养技术相结合，以阐明使SMC成员能够共存的机制。通过共培养评估和风味特征分析确定了发酵乳中SMC的组成，其中关键成员为开菲尔糖乳杆菌CZ22、乳酸乳球菌CZ19和酿酒酵母Y8。SMC产生的发酵乳与传统开菲尔乳具有相同的挥发性化合物谱，包括七种醇、七种醛、六种酮、五种酯、两种羧酸、两种醚、一种酰基化合物和五种其他挥发性化合物。我们的研究结果表明，这三种菌种之间的共存机制基于交叉喂养相互作用。乳酸乳球菌CZ19为开菲尔糖乳杆菌CZ22提供酪氨酸、脯氨酸和精氨酸等氨基酸，促进其生长。此外，酿酒酵母Y8为开菲尔糖乳杆菌CZ22提供嘌呤、嘧啶和核苷酸等初级代谢产物，促进了所有三种菌种的共存。在SMC的发酵过程中，开菲尔糖乳杆菌CZ22保持高丰度，加速了酸化并增强了乳中的风味挥发物。我们构建的SMC有效地维持了开菲尔发酵剂培养物的核心菌种和发酵性能，简化了复杂的发酵系统，为生产工艺的现代化和改进奠定了基础。本研究系统地阐明了合成微生物系统在发酵乳生产中采用的共存策略，同时增进了我们对传统发酵食品中微生物相互作用的理解。
