Microbiology,

Lec. 11

Fermentations.

Fermentation = All ATP production is via substrate-level phosphorylation
Organic compounds are e- donors and organic intermediates (= breakdown products) are e- acceptors. Because part of the original substrate acts as the e- dump, fermentations yield many fewer ATPs than respiration.

In nature one can find fermentative microbes wherever there is a paucity of terminal e- acceptors. Many microbes can also switch from respiration to fermentation in their own metabolisms. For example, when yeast cells are added to fruit juice, they initially carry out aerobic respiration and then switch to fermentation as the O2 runs out.

Fermentation of sugar to ethanol: Draw on Board

Other Fermentations

Show figure "fate of pyruvate" (same info. is in Table 8.2 in the book)

point out industrial products and some of the fermentations that we already talked about when we discussed Propionibacterium, Bifidobacterium, and the lactic acid bacteria etc. See lecture Lecture 6.....

Many fermentations don't involve sugars.... show Table 8.3.....

Examine a few fermentations in a little more detail...
some are quite complex: Figure 20.24

Figure 20.20 conversion of lactic acid to propionic acid by Propionibacterium. Note CO2 production.

A neat variation on the theme of e- flow in fermentations is the "Stickland Reaction" as carried out by members of the genus Clostridium...
overall rxn.:
2 glycine + alanine + ADP + Pi ----> 3 acetate + 3 NH4+ +ATP
Figure 8.6

Anabolic reactions in cells are almost always linked to catabolic reactions (via ATP, reducing power and common pathways). We will not spend a lot of time memorizing individual pathways, but I'd like you to understand the overview of how anabolic and catabolic pathways are linked.

Figure 10.1 in the book gives an overview of this linkage in autotrophs and heterotrophs. Remember that ATP and NADH are also needed to build macromolecules.

Figure 11.1 gives a global overview of anabolic reactions in a typical bacterium (E. coli).