Laboratory studies of sludge digestion. - Illinois State Water Survey

Alcohol to aldehyde 11.7 Calories
Alcohol to acetic acid 23.8 Calories
Alcohol to CO2 + CH4
43.5 Calories
But aerobic combustion of this molecule to water and carbon dioxide
would yield 328.6 Calories. This difference in energy is reflected in
the greater amount of food which must be utilized anaerobically to
maintain a culture; thus according to Lesser, 117 Pasteur's data indicate
the need of 8 to 9 grams of sugar to give one gram of yeast aerobically,
but 80 to 90 grams of sugar are needed under anaerobic conditions.
From the above characterization of strict anaerobes, it is clear that
free oxygen does not play a part in their respiratory oxidations, using
this word, of course, with its modern connotations to include dehydrogenation,
electron transfer, etc. Much literature has accumulated in
recent years on the subject of biological oxidations.
During the years 1858 to 1883, Moritz Traube 200 advocated a peroxide
theory, with water as an essential medium and hydrogen peroxide
formed from it as the active agent; that is, oxygen oxidized only a
hydrogen of the water molecule and all subsequent oxidation was effected
by the liberated OH. However, later work by Engler and Wild 60
and by Bach 4 showed that other peroxides could also be formed; thus
substance A reacting with oxygen produced AO2, a peroxide or moloxide,
which in turn could oxidize more A or a second substance B:
A + AO2 = 2AO or B + AO2 = BO + AO.
Meantime Hoppe-Seyler 93 and Baumann 14 advanced the idea that molecular
oxygen was resolved by nascent hydrogen or other reducing agent
into an atom of active oxygen and a molecule of water, the type equation
being MH2 + O-O + H2O = M + H2O + H2O2. This idea arose
from anaerobic studies in which hydrogen evolution often occurred,
and Hoppe-Seyler showed that hydrogen absorbed on palladium in
water could effect many oxidations in the presence of oxygen, such as
the production of phenol from benzine, of benzoic acid from toluene,
etc. Similar views, postulating the resolution of the oxygen molecule
into two active atoms, were reached also by Clausius 43 and by Van't
Hoff. 206
Engler and Weissburg 59 distinguished two classes of oxidations
by peroxide formation; the simple case of a substance not only inducing
oxidation but also itself being oxidized; for example, benzoyl-hydrogen
peroxide reacting with benzaldehyde,
C6H5CHO + O2 = C6H5CO.O.OH, and
C6H5CO.O.OH + C6H5CHO = 2C6H5COOH;
and the case of a third substance, not ordinarily oxidized, but in which
oxidation is produced by the peroxide of an autoxidizable substance;
for example, indigo oxidation by benzoyl-hydrogen peroxide,
C6H5CO.OH +. indigo = C6H5COOH + indigo oxidation
products.
Many peroxide-yielding substances are now recognized, including metals
like iron and zinc, non-metals like hydrogen and phosphorous,' and
various organic molecules such as hydrocarbons, terpenes, alcohols,
59