Bioinformatics & Modeling, R&D Digital Innovation, Chr. Hansen A/S, 2970, Hørsholm, Denmark.
Theoretical Biology and Bioinformatics, Science for Life, Utrecht University, Utrecht, the Netherlands.
Nat Commun. 2023 Dec 21;14(1):8348. doi: 10.1038/s41467-023-41059-2.
Cheese fermentation and flavour formation are the result of complex biochemical reactions driven by the activity of multiple microorganisms. Here, we studied the roles of microbial interactions in flavour formation in a year-long Cheddar cheese making process, using a commercial starter culture containing Streptococcus thermophilus and Lactococcus strains. By using an experimental strategy whereby certain strains were left out from the starter culture, we show that S. thermophilus has a crucial role in boosting Lactococcus growth and shaping flavour compound profile. Controlled milk fermentations with systematic exclusion of single Lactococcus strains, combined with genomics, genome-scale metabolic modelling, and metatranscriptomics, indicated that S. thermophilus proteolytic activity relieves nitrogen limitation for Lactococcus and boosts de novo nucleotide biosynthesis. While S. thermophilus had large contribution to the flavour profile, Lactococcus cremoris also played a role by limiting diacetyl and acetoin formation, which otherwise results in an off-flavour when in excess. This off-flavour control could be attributed to the metabolic re-routing of citrate by L. cremoris from diacetyl and acetoin towards α-ketoglutarate. Further, closely related Lactococcus lactis strains exhibited different interaction patterns with S. thermophilus, highlighting the significance of strain specificity in cheese making. Our results highlight the crucial roles of competitive and cooperative microbial interactions in shaping cheese flavour profile.
奶酪的发酵和风味的形成是由多种微生物活性驱动的复杂生化反应的结果。在这里，我们使用含有嗜热链球菌和乳球菌菌株的商业发酵剂，研究了在长达一年的切达干酪制作过程中微生物相互作用在风味形成中的作用。通过使用一种实验策略，即从发酵剂中去除某些菌株，我们表明嗜热链球菌在促进乳球菌生长和塑造风味化合物特征方面起着至关重要的作用。通过有系统地排除单个乳球菌菌株的受控牛奶发酵，结合基因组学、基因组规模代谢建模和宏转录组学，表明嗜热链球菌的蛋白水解活性缓解了乳球菌的氮限制，并促进了新的核苷酸生物合成。虽然嗜热链球菌对风味特征有很大的贡献，但乳球菌乳脂亚种也通过限制双乙酰和乙酰基的形成发挥了作用，否则过量时会产生异味。这种异味控制可以归因于乳球菌乳脂亚种通过柠檬酸代谢途径将柠檬酸从双乙酰和乙酰基重新定向到α-酮戊二酸，从而避免了异味的产生。此外，密切相关的乳球菌 lactis 菌株与嗜热链球菌表现出不同的相互作用模式，突出了菌株特异性在奶酪制作中的重要性。我们的研究结果强调了竞争和合作微生物相互作用在塑造奶酪风味特征中的关键作用。
