one strain of O. oeni has been shown to produce acrolein, it is more commonly found in wines that have been infected by strains of Lactobacillus and Pediococcus species such as L. brevis, L. buchneri, and P. parvulus. Acrolein taint has also shown to be more common in wines that have been fermented at high temperatures and/or made from grapes that have been harvested at high Brix levels. Heterofermenting species from the genus Lactobacillus, as well as some wild strains of O. oeni, have the potential to metabolize fructose (one of the main sugars in wine) into the sugar alcohols mannitol and (less commonly) erythritol. These are sweet-tasting compounds can add sweetness to a wine where it is not desired (such as Cabernet Sauvignon). Mannitol taint, described as mannite by Pasteur, in wines is often accompanied by other wine faults, including the presence of excessive levels of acetic acid, diacetyl, lactic acid, and 2-butanol, which can contribute to a "vinegary-estery" aroma. The wine may also have a slimy sheen on the surface. Fresno mold and ropiness In the mid-20th century, a cottony mycelium-like growth began appearing in the bottles of some sweet fortified wines produced in California's Central Valley. Being fortified, these wines often had alcohol levels in excess of 20% which is usually a level that discourages growth of most spoilage organisms associated with winemaking. Nicknamed "Fresno mold" due to where it was first discovered, the culprit of this growth was determined to be L. fructivorans, a species which can be controlled by sanitation and maintaining adequate sulfur dioxide levels. Some Lactobacillus and Pediococcus species (particularly P. damnosus and P. pentosaceus) have the potential to synthesize polysaccharides that add an oily viscosity to the wine. In the case of Lactobacillus, some of these saccharides may be glucans that can be synthesized from glucose present in the wine as low as 50–100 mg/L (0.005 to 0.01% residual sugar) and afflict seemingly "dry" wines. While "ropiness" can occur in the barrel or tank, it is often observed in the wines several months after they are bottled. Wines with pH levels above 3.5 and low sulfur dioxide levels are at most risk for developing this fault. Called graisse (or "grease") by the French and les vins filant by Pasteur, this fault has been observed in apple wines and cider. It can also be potentially be caused by other spoilage microbes such as