OK, I tried to find out imformation on the net about superattenuation, couldn't find much. I did a search of science direct, without much luck.
fount this article - "Beer spoilage bacteria and hop resistance" by Kanta Sakamoto 2003
Beer has been recognized for hundreds of years as
a safe beverage. It is hard to spoil and has a remarkable microbiological stability. The reason is that beer
is an unfavorable medium for many microorganisms
due to the presence of ethanol (0.5 10% w/w), hop
bitter compounds (approximately 17 55 ppm of isoa-acids), the high content of carbondioxide (approximately 0.5% w/w), the low pH (3.8 4.7), the extremely reduced content of oxygen ( < 0.1 ppm) and
the presence of only traces of nutritive substances
such as glucose, maltose and maltotriose. These latter
carbon sources have been substrates for brewing yeast
during fermentation. As a result, pathogens such as
Salmonellae typhimurium and Staphylococcus aureus
do not grow or survive in beer (Bunker, 1955).
However, in spite of these unfavorable features, a
few microorganisms still manage to grow in beer.
These, so-called beer spoilage microorganisms, can
cause an increase of turbidity and unpleasant sensory
changes of beer. Needless to say that these changes
can affect negatively not only the quality of final
product but also the financial gain of the brewing
companies.
A number of microorganisms have been reported
to be beer spoilage microorganisms, among which
both Gram-positive and Gram-negative bacteria, as
well as so-called wild yeasts. Gram-positive beer
spoilage bacteria include lactic acid bacteria belonging to the genera Lactobacillus and Pediococcus.
They are recognized as the most hazardous bacteria
for breweries since these organisms are responsible
for approximately 70% of the microbial beer-spoilage
incidents (Back, 1994). The second group of beer
spoilage bacteria is Gram-negative bacteria of the
genera Pectinatus and Megasphaera. The roles of
these strictly anaerobic bacteria in beer spoilage have
increased since the improved technology in modern
breweries has resulted in significant reduction of
oxygen content in the final products. Wild yeasts do
cause less serious spoilage problem than bacteria but
are considered a serious nuisance to brewers because
of the difficulty to discriminate them from brewing
yeasts.
