Thomas K C, Hynes S H, Ingledew W M
Department of Applied Microbiology and Food Science, University of Saskatchewan, Saskatoon, Canada.
Appl Environ Microbiol. 1994 May;60(5):1519-24. doi: 10.1128/aem.60.5.1519-1524.1994.
The effects of osmoprotectants (such as glycine betaine and proline) and particulate materials on the fermentation of very high concentrations of glucose by the brewing strain Saccharomyces cerevisiae (uvarum) NCYC 1324 were studied. The yeast growing at 20 degrees C consumed only 15 g of the sugar per 100 ml from a minimal medium which initially contained 35% (wt/vol) glucose. Supplementing the medium with a mixture of glycine betaine, glycine, and proline increased the amount of sugar fermented to 30.5 g/100 ml. With such supplementation, the viability of the yeast cells was maintained above 80% throughout the fermentation, while it dropped to less than 12% in the unsupplemented controls. Among single additives, glycine was more effective than proline or glycine betaine. On incubating the cultures for 10 days, the viability decreased to only 55% with glycine, while it dropped to 36 and 27%, respectively, with glycine betaine and proline. It is suggested that glycine and proline, known to be poor nitrogen sources for growth, may serve directly or indirectly as osmoprotectants. Nutrients such as tryptone, yeast extract, and a mixture of purine and pyrimidine bases increased the sugar uptake and ethanol production but did not allow the population to maintain the high level of cell viability. While only 43% of the sugar was fermented in unsupplemented medium, the presence of particulate materials such as wheat bran, wheat mash insolubles, alumina, and soy flour increased sugar utilization to 68, 75, 81, and 82%, respectively.
研究了渗透保护剂（如甘氨酸甜菜碱和脯氨酸）及颗粒物质对酿酒酵母（葡萄汁酵母）NCYC 1324发酵高浓度葡萄糖的影响。在20℃生长的酵母从最初含有35%（重量/体积）葡萄糖的基本培养基中每100毫升仅消耗15克糖。向培养基中添加甘氨酸甜菜碱、甘氨酸和脯氨酸的混合物可使发酵的糖量增加至30.5克/100毫升。通过这种添加，在整个发酵过程中酵母细胞的活力维持在80%以上，而在未添加的对照中则降至12%以下。在单一添加剂中，甘氨酸比脯氨酸或甘氨酸甜菜碱更有效。将培养物孵育10天后，添加甘氨酸时活力仅降至55%，而添加甘氨酸甜菜碱和脯氨酸时分别降至36%和27%。有人认为，已知作为生长氮源较差的甘氨酸和脯氨酸可能直接或间接充当渗透保护剂。诸如胰蛋白胨、酵母提取物以及嘌呤和嘧啶碱混合物等营养物质增加了糖的摄取和乙醇的产生，但不能使细胞群体维持高细胞活力水平。在未添加培养基中仅43%的糖被发酵，而诸如麦麸、小麦糖化不溶物、氧化铝和大豆粉等颗粒物质的存在分别将糖的利用率提高到68%、75%、81%和82%。
