Editing Malolactic fermentation (section)

===''Oenococcus''===
[[File:Malolactic inoculation and nutrient.JPG|left|thumb|Cultured ''Oenococcus oeni'' inoculum strain and "Opti-malo" nutrient additive]]
The genus ''[[Oenococcus]]'' has one main member involved in winemaking, ''O. oeni'', once known as ''Leuconostoc oeni''. Despite having the name ''Oeno[[coccus]]'', under the microscope, the bacterium has a [[bacillus (shape)]] rod shape. The bacteria is a [[Gram-positive]], [[facultative anaerobe]] that can utilize some [[oxygen]] for [[aerobic respiration]] but usually produces cellular energy through fermentation. ''O. oeni'' is a heterofermenter that creates multiple end products from the use of glucose with D-lactic acid and carbon dioxide being produced in roughly equal amounts to either ethanol or acetate. In [[reductive condition]]s (such as near the end of alcoholic fermentation), the third end product is usually ethanol while in slightly [[oxidative]] (such as early in alcohol fermentation or in an [[ullage (wine)|untopped barrel]]), the bacteria are more likely to produce acetate.<ref name="Boulton"/>

Some ''O. oeni'' strains can use fructose to create [[mannitol]] (which can lead to wine fault known as mannitol taint), while many other strains can break down the [[amino acid]] [[arginine]] (which can be present in the wine that is resting on the [[lees (wine)|lees]] after fermentation from the [[Autolysis (wine)|autolysis]] of dead yeast cells) into [[ammonia]].<ref name="Wine Micro"/>

In addition to the [[hexose]] glucose and fructose sugars, most strains of ''O. oeni'' can use the [[residual sugar|residual pentose]] sugars left behind from yeast fermentation including [[L-arabinose]] and [[ribose]]. Only around 45% of ''O. oeni'' strains can ferment [[sucrose]] (the form of sugar usually added for [[chaptalization]] that gets converted by yeast into glucose and fructose).<ref name="Wine Micro"/>

Winemakers tend to prefer ''O. oeni'' for several reasons. First, the species is compatible with the main wine yeast ''[[Saccharomyces cerevisiae]]'', though in cases where both MLF and alcoholic fermentation are started together, the yeast most often outcompetes the bacterium for nutritional resources which may cause a delay in the onset of malolactic fermentation. Second, most strains of ''O. oeni'' are tolerant to the low pH levels of wine and can usually deal with the standard [[alcohol level]]s that most wines reach by the end of fermentation. Additionally, while sulfur dioxide levels above 0.8 molecular SO<sub>2</sub> (pH dependent but roughly 35-50 ppm) will inhibit the bacteria, ''O. oeni'' is relatively resistant compared to other LAB. Finally, ''O. oeni'' tends to produce the least amount of [[biogenic amines]] (and most lactic acid<ref name="Jacobson"/>) among the lactic acid bacteria encountered in winemaking.<ref name="Boulton"/>