Bauer Rolene, Volschenk Heinrich, Dicks Leon M T
Department of Microbiology, Stellenbosch University, 7600 Stellenbosch, South Africa.
J Biotechnol. 2005 Sep 10;118(4):353-62. doi: 10.1016/j.jbiotec.2005.04.015.
Wine production is characterized by a primary alcoholic fermentation, conducted by Saccharomyces cerevisiae, followed by a secondary malolactic fermentation (MLF). Although most lactic acid bacteria (LAB) have the ability to metabolize L-malate, only a few species survive the high ethanol and SO2 levels in wine. Wines produced in colder viticultural regions have a lower pH than wines produced in warmer regions. The decarboxylation of L-malate in these wines leads to an increase in pH, more organoleptic complexity and microbiological stability. MLF is, however, difficult to control and problems often occur during filtering of such wines. Pediococcus spp. are known to occur in high pH wines and have strong malolactic activity. However, some pediococci synthesize exocellular polysaccharides, which may lead to abnormal viscosity in wine. In this study, the malolactic gene from Pediococcus damnosus NCFB1832 (mleD) was cloned into S. cerevisiae and co-expressed with the malate permease gene (mae1) of Schizosaccharomyces pombe. Expression of the mleD gene was compared to the expression of two other malolactic genes, mleS from Lactococcus lactis MG1363 and mleA from Oenococcus oeni Lal1. The genetically modified strain of S. cerevisiae decreased the level of L-malate in grape must to less than 0.3 gl(-1) within 3 days. This is the first expression of a malolactic gene from Pediococcus in S. cerevisiae.
葡萄酒生产的特点是首先由酿酒酵母进行酒精发酵，随后进行二次苹果酸-乳酸发酵（MLF）。尽管大多数乳酸菌（LAB）都有代谢L-苹果酸的能力，但只有少数菌种能在葡萄酒的高乙醇和二氧化硫水平下存活。在较寒冷葡萄种植区生产的葡萄酒的pH值低于较温暖地区生产的葡萄酒。这些葡萄酒中L-苹果酸的脱羧作用会导致pH值升高、感官复杂性增加以及微生物稳定性提高。然而，MLF难以控制，在过滤此类葡萄酒时经常出现问题。已知片球菌属会出现在高pH值的葡萄酒中，并且具有很强的苹果酸-乳酸活性。然而，一些片球菌会合成胞外多糖，这可能会导致葡萄酒出现异常的粘度。在本研究中，将有害片球菌NCFB1832的苹果酸-乳酸基因（mleD）克隆到酿酒酵母中，并与粟酒裂殖酵母的苹果酸通透酶基因（mae1）共表达。将mleD基因的表达与另外两个苹果酸-乳酸基因的表达进行了比较，这两个基因分别是乳酸乳球菌MG1363的mleS和酒类酒球菌Lal1的mleA。转基因酿酒酵母菌株在3天内将葡萄汁中L-苹果酸的水平降低到低于0.3 g l-1。这是片球菌的苹果酸-乳酸基因在酿酒酵母中的首次表达。
