14

Humans have no anaerobic respiration, if we define this as oxidation of a substrate with an external electron acceptor other than oxygen. In humans, the terminal electron acceptor in respiration is always oxygen, which is reduced at complex IV in the respiratory chain. Alternative electron acceptors are mostly found in bacteria and archaea. I would call the ...


10

I think you will find all text books (e.g. Berg et al. Ch 16) describe glycolysis as the conversion of glucose to pyruvate, as this is how it has been defined and considered in countless biochemical papers. The subsequent reactions of pyruvate are regarded as separate metabolic steps or pathways. The title of the short review article you cite (“Lactate is ...


9

Short answer Weak organic acids are more effective for food preservation then strong mineral acids, mainly because undissociated weak acids can cross the cell membrane and disrupt cell physiology from within. Background Natural fermented, or pickled materials are traditionally cured in a brine solution (salt, water, sometimes spices and sugar). Desirable ...


9

Glycolysis needs a steady supply of NAD+ to happen - this is the driver for the anaerobic oxidation to lactate and ethanol, although this is energetically much less favorable than the complete oxidation. But without oxygen there is no other way to keep the glycolysis active for at least some energy supply. The difference is located in the enzymes available ...


6

Heterologous promoters often express genes that are toxic to the organism when expressed in too high quantities. When the genes are expressed constitutively, the organism will either grow slowly or die before they reach a high density suitable for production of the protein. As such, it is not about expressing the genes all the time, but expressing the ...


6

This study found no difference in the outcome of sauerkraut fermentation with or without iodized salt: There was no clear influence of iodized salt on microbial populations. Stable fermentations were achieved using iodized as well as non-iodized salt.


6

Your sugar substrate was sucrose. Yeast cells metabolise this by secreting an enzyme, invertase, which splits the disaccharide into glucose and fructose both of which can be fermented by yeast to produce CO2. According to this site Equal Original (blue packaging)  is a zero calorie sweetener that contains aspartame and acesulfame potassium as its sweetening ...


6

The insides of fruits are relatively anaerobic environments. Natural fermentation, as in berries that get birds intoxicated, is primarily from yeast, and it seems most likely that humans recognized this process before intentionally encouraging fermentation of anything. Natural fermentation reaching high ethanol concentrations occurs especially when berries ...


5

Short answer (A) is a possible answer and is indeed cause for fatigue, as pyruvate is needed for the Krebs cycle to run. The krebs cycle is an essential step in the generation of ATP in aerobic organisms. (B) is incorrect because NADH is never transported into the mitochondria in any organism (it is a nonsense answer). Background NADH is not transported ...


5

There are some recipes available on the web, my answer is based on this webpage and this information: The process itself is rather easy and you can either use ready bought apple juice, homemade juice or apple cider (basically unfiltered apple juice). You will need some specially cultivated yeast, baker's yeast is generally not recommended since it might ...


5

This is an interesting question (I really mean this — see below), for which a straight answer is remarkably difficult to find on the web. When I googled for it I got pages with statements that obligate anaerobic bacteria still had the electron transport chain (ETC) and ATP synthase as there were different electron acceptors other than oxygen. Yes, we know ...


5

As @bpedit indicates in his comment, this is a semantic question — i.e. one regarding the meaning and usage of words. I will explain how I and others use these words and why. If you are convinced by my logic you will wish to use them in the same way, if not you are free to use them differently. However there is no ‘universal truth’ here, and if you are ...


4

Muscle tissue is a good example of anaerobic fermentation. Lactic Acid is fermented and builds up in this tissue when we do large amounts of exercise. We use the Pyruvate molecule and LDH to produce Lactate when required but it is only for short bursts of energy in specific tissues. Try a google image search for the glycolytic pathway. Usually Aerobic and ...


4

Yes I find it somewhat ironic that in a response a recent post from the poster concerning itself with the precise definition of ‘fermentation’ I argued that this was a semantic question because of the use of the term in the English language before any biochemistry was known. I now discover that the term is used in an even looser sense than I was aware of — ...


4

The statement in your first paragraph is correct: for yeast to ferment a carbohydrate it must be fed into the glycolytic pathway which, in the case of oligomers of glucose (e.g. mannose) simply means breaking the oligomer into its constituent glucose monomers using a single enzyme. This is similar to how yeast processes sucrose: the disaccharide is ...


4

Conversion of lactose to galactose and glucose is a part of the bacterial metabolism of lactose. So digested lactose would work. In fact, it should work for all kinds of 6-carbon sugars as lactic acid is produced from pyruvate (end product of glycolysis). See Wikipedia:lactic acid fermentation.


3

Yes, it is possible to reuse yeast in both beer and wine fermentation - commercial brewers do it all the time for cost savings and batch reproducibility, and although I'm not as familiar with making wine, many sites including this one say it's perfectly fine, as long as the viability of the cells is high enough. The yeast aren't necessarily in stress-...


3

Suppose the cellular pool has $x$ATP before starting glycolysis. In the initial phosphorylation steps, we use up two ATP to get the total tally at $(x-2)$ATP. The following steps yields $4$ ATP which brings the final total to $(x+2)$ATP. Assuming the cell is performing fermentation, the two additional $NADH$ formed will not be contributing to any ATP gain. ...


3

Remember that glycolysis yields 2 NADH as well as 2 net ATP. This NADH can be used to a terminal electron acceptor to produce an end product with a net gain of ATP. End-products of fermentation can include lactate, acetate, butyrate, propionate and ethanol, all of which generate different amounts of additional ATP. The exact pathways involved vary ...


3

Fruit Moonshine is quite desirable :) Peel the bananas. Good workflow here: http://www.moonshiners.club/banana-moonshine-recipe/ It takes considerable work especially in large quantities. Furthermore, check legality and read up on methanol poisoning. Don't poison yourself!


3

Although there is no net oxidation or reduction in glycolysis, a constant supply of NAD+ is (paradoxically) required in order for glycolysis to continue. Otherwise, the glyceraldyde-3-phosphate dehydrogenase reaction (GAPdh) could not generate 1,3-diphosphoglycerate. So how is the NADH generated in the GAPdh reaction converted back to NAD+? Both alcohol ...


3

Well, I’m not sure I should answer this, as your question is predicated by an incorrect supposition: Acetoacetyl-CoA is a C3 unit. 3-Hydroxybutyryl-CoA / Butyryl is a C4 unit. Not according to Kegg: However, my answer is worthwhile if I explain how I found this out. One way to check this sort of thing is to go to the Kegg website and search for the ...


2

I don't have a definitive answer to this, but a little over a decade ago I was in an undergraduate lab that had a similar thing happen - a small amount of metabolism of a "control" group of bacteria fed artificial, sugar/calorie free sweeteners instead of sugar. Our running theories at the time were: Contamination. Always a problem in laboratory ...


2

I think the reason as to why glucose concentration is faster in the aerobic case than the anaerobic one, is perfectly explained by Chris. To summarize:- The energy requirement of the organism in both the condition remains more or less constant. Since aerobic respiration generates more energy per glucose,(38ATP) it takes more time for the same ...


2

Almost certainly not. Species occupy different niches due to their differing growth rates and tolerances. Interspecies quorum sensing and the symbiotic relationship that implies do exist(see: lichen), but open-air inoculation is unlikely to produce them. Why would the Brettanomyces simply kill time waiting for 'their turn'? It's likely they don't grow as ...


2

generally, lactic acid bacteria (LAB) are the ones you should be looking at for milk-based fermentation products. although sometimes species like bifidobacterium are added, which is of a completely different phylum. also, for cheese production, or the Dutch variety I am familiar with anyway, you would need fungi as well. the lactobacillales order is not ...


2

I think only b.) is true. a. I cannot find evidence that maltose is toxic to yeasts (and I would hardly believe it, because it is a glucose dimer), however I found evidence, that yeasts might need the presence of oxygen to process maltose. 1977 - The Requirement of Oxygen for the Utilization of Maltose, Cellobiose and D-Galactose by Certain Anaerobically ...


2

Yes there are, though I had to dig a lot to find them. They are called strictly fermentative bacteria. Lactic acid bacteria (Lactobacillales (Firmicutes)) ferment glucose through pyruvate to lactate using the glycolytic pathway, and include the genera Streptococcus, Lactococcus, Lactobacillus, and Leuconostoc. From Madigan et al. 2014 Brock biology of ...


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