Question: Sic1 is an inhibitor in which species of yeast used in winemaking and breadmaking?
Context: Thiolutin is a sulfur-containing antibiotic, which is a potent inhibitor of bacterial and yeast RNA polymerases.  It was found to inhibit "in vitro" RNA synthesis directed by all three yeast RNA polymerases (I, II, and III).  Thiolutin is also an inhibitor of mannan and glucan formation in "Saccharomyces cerevisiae" and used for the analysis of mRNA stability.  Studies have shown that thiolutin inhibits adhesion of human umbilical vein endothelial cells (HUVECs) to vitronectin and thus suppresses tumor cell-induced angiogenesis in vivo. Saccharomyces pastorianus is a yeast used industrially for the production of lager beer, and was named in honour of Louis Pasteur by the German Max Reess in 1870.  This yeast's complicated genome appears to be the result of hybridisation between two pure species in the "Saccharomyces" species complex, a factor that led to difficulty in establishing a proper taxonomy of the species. Sic1, a protein, is a stoichiometric inhibitor of Cdk1-Clb (B-type cyclins) complexes in the budding yeast "Saccharomyces cerevisiae".  Because B-type cyclin-Cdk1 complexes are the drivers of S-phase initiation, Sic1 prevents premature S-phase entry.  Multisite phosphorylation of Sic1 is thought to time Sic1 ubiquitination and destruction, and by extension, the timing of S-phase entry. Prosol S.p.A. is an Italian biotechnology company headquartered in Madone, Lombardy region, Italy.  Founded in 1974, it primarily develops and markets nutritional ingredients for the food industry and livestock area, especially yeast and yeast extracts, nucleotides, ribonucleic acid, probiotics and natural enhancers.  Prosol has an in-house developed technology and its plants cover an area of 28000 sq. m, employing about 38 people and working both in domestic and international markets.  The company is the original developer and distributor of Biosprint, an active dry yeast used for animal nutrition, and Ribomix, Ribocare, Levimaxi, Brist, Ribonucleic acid trademarks for human nutrition.  The company has received the ISO, GMP+, IFS and OHSAS 18001 certifications. A stuck fermentation occurs in brewing beer or winemaking when the yeast become dormant before the fermentation has completed.  Unlike an "arrested fermentation" where the winemaker intentionally stops fermentation (such as in the production of fortified wines), a stuck fermentation is an unintentional and unwanted occurrence that can lead to the wine being spoiled by bacteria and oxidation.  There are several potential causes of a stuck fermentation-the most common are excessive temperatures killing off the yeast or a must deficient in the nitrogen food source needed for the yeast to thrive.  Once the fermentation is stuck, it is very difficult to restart due to a chemical compound released by dying yeast cells that inhibit the future growth of yeast cells in the batch.  At the winery winemakers take several steps to limit the possibility of a stuck fermentation occurring, such as adding nitrogen to the must in the form diammonium phosphate or using cultured yeast with a high temperature and alcohol tolerance.  These steps that winemakers may take to prevent a stuck fermentation will each have their own subtle or dramatic effect on the resulting flavors and quality of the wine. The role of yeast in winemaking is the most important element that distinguishes wine from grape juice.  In the absence of oxygen, yeast converts the sugars of wine grapes into alcohol and carbon dioxide through the process of fermentation.  The more sugars in the grapes, the higher the potential alcohol level of the wine if the yeast are allowed to carry out fermentation to dryness.  Sometimes winemakers will stop fermentation early in order to leave some residual sugars and sweetness in the wine such as with dessert wines.  This can be achieved by dropping fermentation temperatures to the point where the yeast are inactive, sterile filtering the wine to remove the yeast or fortification with brandy to kill off the yeast cells.  If fermentation is unintentionally stopped, such as when the yeasts become exhausted of available nutrients, and the wine has not yet reached dryness this is considered a stuck fermentation. Saccharomyces cerevisiae is a species of yeast.  It has been instrumental to winemaking, baking, and brewing since ancient times.  It is believed to have been originally isolated from the skin of grapes (one can see the yeast as a component of the thin white film on the skins of some dark-colored fruits such as plums; it exists among the waxes of the cuticle).  It is one of the most intensively studied eukaryotic model organisms in molecular and cell biology, much like "Escherichia coli" as the model bacterium.  It is the microorganism behind the most common type of fermentation.  "S. cerevisiae" cells are round to ovoid, 5–10 μm in diameter.  It reproduces by a division process known as budding. A portmanteau inhibitor is a drug that is a combination of two drug molecules, each of which is itself a type of inhibitor.  The term was coined in 2007 by University of Minnesota researchers who designed and synthesized a combination HIV reverse transcriptase inhibitor and an integrase inhibitor, and was further used in 2011 by a team of researchers combining an integrase inhibitor with a CCR5 entry inhibitor. A yeast expression platform is a strain of yeast used to produce large amounts of proteins, sugars or other compounds for research or industrial uses.  While yeast are often more resource-intensive to maintain than bacteria, certain products can only be produced by eukaryotic cells like yeast, necessitating use of a yeast expression platform.  Yeasts differ in productivity and with respect to their capabilities to secrete, process and modify proteins.  As such, different types of yeast (i.e. different expression platforms) are better suited for different research and industrial applications. Flor (Spanish and Portuguese for "flower") is a winemaking term referring to a film of yeast on the surface of wine and which is important in the manufacture of some styles of sherry.  The flor is formed naturally under certain winemaking conditions, from indigenous yeasts found in the region of Andalucía in southern Spain.  Normally in winemaking, it is essential to keep young wines away from exposure to air by sealing them in airtight barrels, to avoid contamination by bacteria and yeasts that tend to spoil it.  However, in the manufacture of sherries, the slightly porous oak barrels are deliberately filled only about five-sixths full with the young wine, leaving "the space of two fists" empty to allow the flor yeast to take form and the bung is not completely sealed.  The flor favors cooler climates and higher humidity, so the sherries produced in the coastal Sanlúcar de Barrameda and El Puerto de Santa María have a thicker cap of flor than those produced inland in Jerez.  The yeast gives the resulting sherry its distinctive fresh taste, with residual flavors of fresh bread.  Depending on the development of the wine, it may be aged entirely under the veil of flor to produce a fino or manzanilla sherry, or it may be fortified to limit the growth of flor and undergo oxidative aging to produce an amontillado or oloroso sherry.
Answer: Saccharomyces cerevisiae