Instituto de Ciencias de Vid y del Vino (CSIC-UR-CAR), Logroño, La Rioja, Spain.
Biotechnol Prog. 2012 Mar-Apr;28(2):327-36. doi: 10.1002/btpr.734. Epub 2011 Nov 7.
KNR4 defective recombinant wine yeast strains were previously shown to oversecrete mannoproteins during alcoholic fermentation and, depending on the genetic background, to contribute to protein stability of white wines. We have tried to get a deeper insight into the consequences of KNR4 deletion in a wine yeast strain, from both a biological and an enological standpoint, and to understand the mechanisms leading to improved mannoprotein release. In fermentation experiments, followed by aging on lees, and compared to the parent strain, the recombinant strain shows increased release of mannoproteins during the fermentation but little increase during aging. Mannoprotein release by the recombinant strain takes place mainly during the fermentation step. In contrast, autolysis of the recombinant strain keeps going after aging for 78 days. In addition, the recombinant strain is moderately flocculent, which would be interesting for the production of sparkling wines. This might be related to changes in the expression of Flo1p-regulated genes. The new biological processes affected by KNR4 deletion in wine yeasts, as revealed by this transcriptomic study are flocculation, adaptation to anaerobiosis, oxidative stress response, and ethanol tolerance, as well as FKS1 overexpression; but no overexpression was detected for genes coding for major structural mannoproteins of the cell wall.
先前的研究表明，KNR4 缺陷型重组葡萄酒酵母菌株在酒精发酵过程中会过度分泌甘露糖蛋白，并且根据遗传背景的不同，还会影响白葡萄酒的蛋白质稳定性。我们试图从生物学和酿造学的角度更深入地了解 KNR4 在葡萄酒酵母菌株中的缺失所带来的影响，并了解导致甘露糖蛋白释放改善的机制。在发酵实验中，经过酒泥陈酿后，与亲本菌株相比，重组菌株在发酵过程中释放的甘露糖蛋白增加，但在陈酿过程中增加很少。重组菌株的甘露糖蛋白释放主要发生在发酵阶段。相比之下，重组菌株的自溶作用在 78 天后的陈酿过程中仍在继续。此外，重组菌株适度絮凝，这对于生产起泡酒很有趣。这可能与 Flo1p 调控基因表达的变化有关。通过这项转录组学研究揭示了 KNR4 在葡萄酒酵母中缺失所影响的新生物学过程，包括絮凝、厌氧适应、氧化应激反应和乙醇耐受性，以及 FKS1 的过表达；但细胞壁主要结构甘露糖蛋白的编码基因没有检测到过表达。
