Meredith's Notes

Oenococcus Oeni (old name: Leuconostoc oenos)

    12/4/07 

    Notes from: http://genome.jgi-psf.org/draft_microbes/oenoe/oenoe.home.html

• Lactid Acid bacterium.

• Gram Positive

• Naturally occuring in fruit mash.

• Carries out malolactic conversion in wineries.

  • Secondary fermentation in wine product

• One of the most acid/alcohol tolerant.

• Facultative anaerobe.

• "On the basis of 16S rRNA sequence, Dicks et al. (2) proposed a reclassification of Leuconostoc oenos into a new genus, Oenococcus oeni. O. oeni shares relatively little DNA homology with the other genera in the Leuconostoc branch of the LAB (1). Woese argued that O. oeni is an example of a fast-evolving microorganism (7). Subsequent comparisons of RNA polymerase genes contradicted this view (5). Whole genomic comparisons between O. oeni and the nonacidophilic Leuconostoc mesenteroides (also sequenced as part of the LABGC project) will help resolve this issue and shed light on the evolution of this unusual branch." <----RE-WORD WHEN I GET THE TIME

• Ability to convert malate to lactose, called malolactic coversion.

  • Invovles uptake of malate, its decarboxylation to L-lactic acid and CO2, export of end products.

  • Produces energy in form of proton motive force (storing of energy as a combination of a proton and voltage gradient across a membrane).

    Notes from: http://www.lbl.gov/Science-Articles/Archive/JGI-wine-making-genome.html

• De-acidifies wine after initial fermentation.

• Converts MALIC acid into LACTIC acid (malolactic fermentation)

  • It aids in taste, aroma, and texture of wine and plays a role in spoilage and taint.

  •  Saccharomyces cerevisiae, the most commonly used yeast in wine, doesn't metabolize malic acid

  • The malolactic fermentation process is carried out spontaneously by the O. oeni which is tolerant of the wine's ethanol and acid.

  • oeni grows slowly. If the process is not timed to start right after the alcohol fermentation, the process can be very slow.

    Extra information?:

•     Lactic Acid Bacteria Genome Consortium (LABGC)

  • Oenococcus oeni genome to be sequenced at JGI under the U.S. Department of Energy's Microbial Genome Program.

  • Scientists plan to use this sequence to advance genomic study of lactic acid bacteria. They wish to gain a more complete understanding of the microbes' physiology and genetic make-up, specifically in relation to their roll in the fermentation of foods and beverages.

  • Learning about these things will also aid in the understanding of their roll in food preservation and safety, for the sake of the health of animals and humans.

12/6/07 

Notes from: http://mic.sgmjournals.org/cgi/content/abstract/148/1/325

•  Performs malolactic fermentation, converting L-malate to L-lactate and carbon dioxide, in wines
• Consumes carbohydrates via the heterolactic pathway. In the first steps of hexose metabolism(The chemical reactions and pathways involving a hexose, any monosaccharide with a chain of six carbon atoms in the molecule) two molecules of NAD(P)⁺ are consumed, which must be regenerated in later reactions.
• Recent studies have shown that O. oeni grows poorly under aerobic conditions with glucose as the only carbohydrate in the medium

• O₂ inactivates the enzymes of the ethanol-forming pathway, one of the two pathways which reoxidizes NAD(P)⁺

  ^{in the catabolism of glucose. This means the glucose cannot be catabolised in aerobic conditions. However, if fructose is added, the catabolism rate increases to be at apporoximately the same level as anaerobic catabolis.}

   

   

12/9/07

Notes from: http://winebusinessmonthly.com/Winemaking/webarticle.cfm?ref=rn&dataId=49280

• GRAM POSITIVE!

   

• Facultative anaerobe. (Normally use oxygen but can live without it)
• heterofermentative (convert glucose to equal molar amounts of lactic acid, CO₂ and ethanol or acetate).
• By converting malic acid (tricarboxylic or possessing three acid groups) into lactic acid (dicarboxylic), O. oeni may be desirable because it reduces a wine's acidity and contributes new flavors and aromas.
• O. oeni is the primary species used commercially to conduct MLF because of its acid tolerance and the flavor profile produced
• When to inoculate O. oeni into wine is debated between researchers.
• It has been shown that the conversion of malic to lactic acid produces ATP
• MLF** is responsible for the procustion of diacetyl  which produces "nutty" aromasin wine. It also produces esters which give wine a "fruity" nose.
• Finally, MLF increases body or mouthfeel, possibly due to the production of polyols (glycerol, erythritol).

**MLF - malolactic fermentation