hey everybody dr. o here let's talk about fermentation actually Before we jump into fermentation just want to understand that we've already covered aerobic respiration start to finish and how you can generate that 36 to 38 ATP's many organisms use something other some other inorganic substance other than oxygen as your final electron acceptor as you can see here and they're going to use what's called anaerobic respiration so I won't go into detail here but they don't have quite the concentration gradient or electrochemical gradient that we have when we use oxygen so they can't generate as much ATP as you see here the totals for anaerobic respiration are between 5 and 36 depending on the electron acceptor just a couple of quick examples here I think the nitrate and nitrite using night D nitrifying organisms in the soil are very important so they take nitrogen and change its form in the soil so there are examples of where it's important another example that's relevant in microbiology a bacteria like e-coli can if oxygen is not available can switch and start using the nitrate as a final electron acceptor that's why we have we have bacteria that are called facultative anaerobes they they prefer oxygen so they grow better in its presence but they can switch their metabolism and grow okay without oxygen as well so just a couple of quick things there but let's focus it on fermentation here so fermentation is when you use an organic final electron acceptor it's usually going to be pyruvate so where would you get pyruvate from glycolysis so these fermenters are still going to use anaerobic glycolysis the fermentation process takes that pyruvate and changes it but doesn't actually generate any more energy so the reason that you do it so why would you why and I'll show you the path in just a moment here but why would we why would we undergo fermentation what do we need to do with this Piru base let's go ahead let me show you we see the numbers real quickly fermentation is only going to release those two ATP directly that come from glycolysis but here's an example of lactic acid fermentation where you convert glucose to pyruvate using glycolysis exactly like we talked about for net gain of two ATP and you have those two NADH is produced so why would you go on what fermentation does as it turns pyruvate into lactate or lactic acid in this situation is liberate those NAD+ so here's the key to note fermentation doesn't generate any more ATP directly but without it we'd run out of eight NAD+ and we couldn't undergo glycolysis so that fermentation step isn't to generate energy directly it's to keep glycolysis going and that's why you do it and here's the thing so we have we obviously have ethanol fermentation there's lots of kinds of fermentation but in this class lactic acid fermentation is the most important one and that's because we use lactic this is how we produce lactate in our bodies in our muscles if we don't have enough oxygen so we've already covered that without oxygen we turn pyruvate into lactate or lactic acid but think about like your the the microbes that do this as well you have so the same process would happen in a bacteria that's gonna turn milk into yogurt or cheese so what happens here is when when fermenters get a hold of your milk they drop the pH and that's what causes the curdling and that's what turns milk into a solid something like yogurt or cheese so it's going to be important in our food but it's also going to be important in our you know into our health as well and that's because we want a lot of lactic acid fermenters inside our body so you think about the lactic acid fermenters that are in your gut they keep the pH low and that inhibits the growth of pathogenic bacteria we've talked about that so that's why your probiotics are dominated by lactic acid producers like lactobacillus and bifida so we want these bacteria keeping the pH in our gut low to inhibit the growth of pathogens the pathogens don't like low PHS that's why sauerkraut is if you have sauerkraut for a year it's still probably safe to eat whereas you wouldn't want cabbage sitting around for a year and then eat it the low pH is what is what protects or preserves that food this is even more important in the vaginal microbiome when you have we we always talk about the microbiome a key being diversity so most micro biomes are going to be you want them to be very diverse not the vaginal microbiome you want a minimum of 70% of the of the microbes in the vaginal microbiome to be lactic acid producers keeping the pH low and that that's what keeps the bacterial infections and those types of things away all right so those are two reasons why lactic acid fermentation is very important to our health from a microbiological standpoint last key thing I want to note here then is where does the energy go so when we're when we're done fully oxidizing glucose we've taken all the energy we generated those 36 or 38 ATP so oxidative phosphorylation aerobic respiration steals all the energy leaving low energy or useless and products fermentation takes only a tiny bit of energy away which means the end products still have the energy so I would like to say that respiration leaves useless end products fermentation leads useful in products let's go ahead and take a look at some examples here I'm just going down the right-hand side we have commercial solvents things like acetate gas alternatives like ethanol beer bread wine butter sauerkraut yogurt cheese some pharmaceuticals use mixed acid fermentation Swiss cheese's separates it the Swiss cheese is gonna use a different organism but still as you see these end products are very very useful so with fermentation you take pyruvate and you turn it into some some amazingly useful end product like I'm a big fan of cheese I'm sure some people are bigger fans of alcohol but I'll take cheese any day so that's kind of the cool thing about fermentation so fermentation they only get a little bit of energy they do fermentation in order to keep glycolysis running that's why fermentation matters but for us we can get very useful and products out of fermentation and we've been doing this for thousands of years as humans borrowing microbial fermentation for our food and now we have gas alternate et cetera I think that's kind of cool all right so that's fermentation a nutshell I hope that helps have wonderful day be blessed