Tailoring wine yeast for the new millennium: novel approaches to the ancient art of winemaking

Abstract

Yeasts are predominant in the ancient and complex process of winemaking. In spontaneous fermentations, there is a progressive growth pattern of indigenous yeasts, with the ®nal stages invariably being dominated by the alcohol-tolerant strains of Saccharomyces cerevisiae. This species is universally known as the `wine yeast' and is widely preferred for initiating wine fermentations. The primary role of wine yeast is to catalyze the rapid, complete and ef®cient conversion of grape sugars to ethanol, carbon dioxide and other minor, but important, metabolites without the development of off-¯avours. However, due to the demanding nature of modern winemaking practices and sophisticated wine markets, there is an ever-growing quest for specialized wine yeast strains possessing a wide range of optimized, improved or novel oenological properties. This review highlights the wealth of untapped indigenous yeasts with oenological potential, the complexity of wine yeasts' genetic features and the genetic techniques often used in strain development. The current status of genetically improved wine yeasts and potential targets for further strain development are outlined. In light of the limited knowledge of industrial wine yeasts' complex genomes and the daunting challenges to comply with strict statutory regulations and consumer demands regarding the future use of genetically modi®ed strains, this review cautions against unrealistic expectations over the short term. However, the staggering potential advantages of improved wine yeasts to both the winemaker and consumer in the third millennium are pointed out.

Glucose and Fructose Fermentation by Wine Yeasts in Media Containing Structurally Complex Nitrogen Sources

“…Troubled fermentations have been attributed to the nutritional status of grape musts, once they contain suboptimal yeast nutrients, especially assimilable nitrogen 3,17,21,32 . A common practice in the wine industry for nitrogen limited fermentation is the addition of nitrogen supplements, using inorganic salts such as diammonium phosphate 22,27 . In addition to nutritional deficiencies, grape must contains approximately equimolar amounts of glucose and fructose, which are cofermented to ethanol, with a preference for glucose 12 .…”

Microbial and Chemical Diversity of Traditional Non-Cereal Based Alcoholic Beverages of Sub-Saharan Africa

“…Documented evidence suggest that in the early stages of fermentation, fruit surfaces are dominated by non-Saccharomyces yeasts, bacteria, and filamentous fungi [73,74] but Saccharomyces yeasts dominate the microbial population at the end of fermentation in anaerobic conditions. This suggests that Saccharomyces yeasts are the most dominant alcoholic fermentation microorganisms [75][76][77]. Even in the presence of oxygen, S. cerevisiae, is the predominant yeast species responsible for the production of ethanol [78,79].…”

“…Commercial honey wine (mead) is made using pure cultures of yeasts and they produces aromatic volatile compounds that include alcohols, organic acids, esters, volatile fatty acids, carbonyl compounds, and volatile phenols [111,130]. Aromatic volatile compounds are responsible for the unique flavor of mead as well as its overall sensory characteristics [75,86].…”

Yeast: World’s Finest Chef

“…In fact, our relationship with S. cerevisiae can be traced back as far as 7,000 years ago in China, with the first fermented beverages similar to beer, and Mesopotamia, with the first wines as well as domesticated vines [11,25]. Conversely, the oldest known written account on the production of beer was found in Sumeria, modern day Iraq, in a stone tablet dating from 2,000 BC.…”