Acetobacter and Gluconobacter

Many LAB found in wines can improve wine quality by metabolizing malic acid to lactic acid in a process called malolactic fermentation (MLF). This fermentation is an enzyme-mediated decarboxylation of the dicarbox-ylic acid, L (—) malic acid, to the monocarboxylic L (+) lactic acid (Amerine et al., 1980 Kunkee, 1967 Lonvaud-Funel, 1999). MLF decreases wine acidity and is particularly important in wines produced from grapes grown in cool climates, which often have high acidity (Beelman and Gallander, 1979 Kunkee, 1967, 1974). 

However, some LAB can be associated with spoilage problems including stuck alcoholic fermentations (Edwards et al., 1999 Huang et al., 1996), production of off-flavors or off-odors (Costello and Henschke, 2002 Drysdale and Fleet, 1989a Sponholz, 1993), excessive volatile acidity (VA) (Drysdale and Fleet, 1989a Huang et al., 1996), synthesis of polysaccharides responsible for ropiness (Manca de Nadra and Strasser de Saad, 1995), or other defects. 

This chapter summarizes current information regarding the bacteria important during the winemaking process including AcetobacterIGluconobacter, Lactobacillus, Oenococcus, and Pediococcus, as well as the impact these microorganisms have on wine quality and public health concerns. Furthermore, the interactions that occur between these microorganisms and S. cerevisiae and their influences on wine quality are discussed. 

A brief overview of the importance of the acetic acid bacteria (AAB) Acetobacter and Gluconobacter in winemaking is given here, but readers are directed to a comprehensive review by Du Toit and Pretorius (2002) for a more detailed discussion. 

AAB produce acetic acid through the oxidation of ethanol by two membrane-bound enzymes an alcohol dehydrogenase and an aldehyde dehydrogenase (Saeki et al., 1997). The alcohol dehydrogenase oxidizes ethanol to 

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The sugars in fruits such as grapes are feimented by yeasts to produce wines. In winemaking, lactic acid bacteria convert malic acid into lactic acid in malolactic fermentation in fruits with high acidity. Acetobacter and Gluconobacter oxidise ethanol in wine to acetic acid (vinegar). 

Giudici, P. and Masini, G. (1995). Production of gluconic acid by strains of Acetobacter and Gluconobacter in grape must Annali di Microbiologia ed Enzimologia 45, 313-319. 

Taxonomic status of AAB is complex and not well established, as it has been subjected to changes on several occasions in last 40 years. Historically, AAB were mainly classified as Acelobacler (Beijerinck, 1898) and Gluconobacter (Asai, 1935). At present, AAB taxonomically belong to family Acetobacteraceae (Asai, 1968), which is classified under the class alpha proteobacteria. AAB has 15 validated genera, and only two genera Acetobacter and Gluconobacter are reported to be associated with beer spoilage (van Vuuren Priest, 2003). 

The bacteria of this family are separated into two genera Acetobacter and Gluconobacter. The key distinguishing features according to Bergey s Manual. (De Ley et al., 1984) are as follows ... 

The bacteria of the two genera Acetobacter and Gluconobacter are obligatory aerobic microorganisms with an exclusively respiratory metabolism. Their growth, at the expense of substrates that they oxidize, is therefore determined by the presence of dissolved oxygen in the environment. All of these species develop on the surface of liquid media and form a halo or haze, less often a cloudiness and a deposit. 

Jerez vinegar is produced from sherry wines by following the traditional methods of aging in southwestern Spain. The first written references to Jerez vinegar comes from Columela in the first century ad (Tesfaye et al. 2009). After sherry wine production, the subsequent acetification process encompasses the activity of acetic acid bacteria species of the genera of Acetobacter and Gluconobacter (Caro et al. 1998). 

Gillis M, de Ley J (1980) Intra- and intergeneric similarities of the ribosomal ribonucleic acid cistrons of Acetobacter and Gluconobacter. Int J Syst Bacteriol 30 7-27 Glushakova AM, Chernov lY (2004) Seasonal dynamics in a yeast population on leaves of the common wood sorrel Oxalis acetosella L. Microbiology 73 184—188... 

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