8th, 9th and 10th December 2014, "Of Yakult Trip And Microbiology"

On Monday, we went to Yakult factory. It's cool really. Since we are Microbiology students and know a bit (a bit? It should be a lot, isn't it? x'D) about the microbes and at least know what Lactobacillus is, it was a memorable trip! :D

Compared to before I studied Microbiology, I don't pay any attention to what is in Yakult. Going there and hearing the talk about the ingredients of Yakult, I think it's my first time knowing that there are probiotics in it. Scratch that, I just know that Yakult is actually a probiotic drink! x'D 

I can just conclude that I have never read the ingredients of Yakult before. Or maybe I did but because I do not know what Lactobacillus is, I don't bother much about it. Hehe. 

It left a big impact on me, to be honest. While drinking the free Yakult given to us that day. In my head, "There's Lactobacillus casein Shirota" in this drink" crossed my mind x'D I became more aware of their presence. 

The representative of the Yakult factory that day also remind us not to drink Yakult mindlessly. It should be drink at least once or twice a day. If not, it would be wasteful of the probiotics included in the drink. 

Probiotics are known to be good bacteria. However, if you take probiotic in excess, they might harm you. People with weak immune system shouldn't consume them too much. 

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Enough about the trip. Now we proceed to this week's lesson. 

This week, we learnt about microbial metabolism, microbial nutrition and microbial growth. 

For this week entry, I shall state informations that's not stated in the notes. Things that was discussed during class. [At least from what I managed to write in my notebook]

Microbial Metabolism 

-> Cellular respiration is a process in which energy in the nutrients in converted into energy in the form of ATP. There are three types of cellular respiration which is aerobic and anaerobic respirations and fermentation. 

-> Organism that respires by fermentation will produce ethanol however it depends on the microbe and substrate because not all fermentation process will produce ethanol as the end product. Some can produce other end products such as lactic acid and carbon dioxide. 

The products of fermentation for each different bacteria.

-> Aerobic respiration : glucose + oxygen --> carbon dioxide + energy + water [if you look closely it is the reverse reaction of photosynthesis] isn't it cool!! x'D I just realized that too! 

Photosynthesis equation

-> Other names for Citric acid cycle are Kreb cycle and tricarboxylic acid (TCA) cycle. 

-> Pyruvic acid are also known as pyruvate so they are the same thing. And pyruvate/pyruvic acid is a transition product before the final product is obtained. 

-> I found out through the Net today that two of the common types of biofuel nowadays are ethanol and biodiesel. Hence, organisms that can produce biofuels are bacteria, fungi and algae because they are able to ferment glucose into ethanol. 

-> Oil palm is the best substrate to produce ethanol because they have cellulose to ferment ethanol. [there are three basic types of EFC (Ethanol-From-Cellulose) process which is acid hydrolysis, enzymatic hydrolysis and thermochemical.]

-> Different microbes act with/ferment different substrates producing different end products. 

-> Other names for carbon fixation are Kelvin cycle and Calvin Benson cycle. [Although Dr have mentioned this before. hehe]

-> Bacteria have carboxysomes that contain enzymes that helps in carbon fixation. [I forgot this fact, to be honest. Hmmmm]

Microbial Nutrition

Dr asked us to find a way to remember the microbial nutrition since it is quite... various. Dr said it's either you remember each of the microbial nutrition or remember them by understanding them. Ah, I hope my words aren't jumbled up. x'D 

However, Dr said that this is the best table to understand/remembers them because it states the terms one by one. For example, first identify what's the energy source and then the reducing equivalent source (biosynthetic process) and then the carbon source.  

For example, I will do this randomly without looking at the correct microbial nutrition. Hehe. 

This organism, its energy source is from chemical compound (chemo-), it's reducing equivalent cource (source of electrons) is from inorganic compounds (-litho-) and it's carbon source is from organic compounds (-heterotroph). Hence, the microbial nutrition for this organism is chemolithoheterotroph. Ok? Ok. :D 

I studied this the night before the day that Dr Wan held a pop quiz (sort of) in class. I thought I have somehow mastered it (hehe) I mean, I thought I have understood it well but I was indeed wrong. During the quiz, I was not able to guess correctly what are the microbial nutritions based on the questions given D: Thank you Dr for doing the pop quiz!! Because it gave me the realization that I'm weak in determining the nutritions. I will definitely pay more attention to it!

Dr also said that we have to have good imaginations too when determining the microbial nutritions. For example, based on one of the questions that day... This organism lives on the mountain where there are no other microbes surrouding it --> from there we can know that since there are no other microbes around it that it can feeds on, thus it should be an organism that can produce its own food! 

Microbial Growth

-> The purpose of studying the growth of microbes is because when we know what can kill/help the survive, we can control the factors of their survival such as the temperature and pH in order to either stop or slow down their cell productions. 

-> The growth of microbes are not determined by its sizes but by the number of cells. 

-> When to use the terms "tolerant" and "-phile"?

tolerant : when the condition is very near to "optimum". 

-phile : when the condition is at "optimum". 

-> One of the physical requirements for microbial growth is water activity. What is meant by water activity?  

Water activity (a_w): The amount of water needed/found in substrate that is just right or enough for the microbes to grow. 

 Water in food that is not bound to food molecules can support the growth of bacteria, yeast, and mold. The term water activity (a_w) refers to this unbound water.

The water activity of a food is not the same thing as its moisture content. Although moist foods are likely to have greater water activity than are dry foods, this is not always so. In fact, a variety of foods may have exactly the same moisture content and yet have quite different water activities.

The water activity (a_w) of a food is the ratio between the vapor pressure of the food itself, when in a completely undisturbed balance with the surrounding air media, and the vapor pressure of distilled water under identical conditions. A water activity of 0.80 means the vapor pressure is 80 percent of that of pure water. The water activity increases with temperature. The moisture condition of a product can be measured as the equilibrium relative humidity (ERH) expressed in percentage or as the water activity expressed as a decimal.

Most foods have a water activity above 0.95 and that will provide sufficient moisture to support the growth of bacteria, yeasts, and mold. The amount of available moisture can be reduced to a point that will inhibit the growth of microorganisms.

Water activity can also be used to predict the spoilage of food which is by knowing the water activity that is suitable for the bacteria or any other microbes to enhance its growth. This can be prevented by reducing the water activity of the food as much as possible! 

Water activity (a_w) has its most useful application in predicting the growth of bacteria, yeast, and mold. For a food to have a useful shelf-life without relying on refrigerated storage, it is necessary to control either its acidity level (pH) or the level of water activity (a_w) or a suitable combination of the two. This can effectively increase the product's stability and make it possible to predict its shelf life under known ambient storage conditions.

Food can be made safe to store by lowering the water activity to a point that will not allow pathogens such as Clostridium botulinum and Staphylococcus aureus to grow in it. The table below illustrates the water activity (a_w) levels that can support the growth of particular groups of bacteria, yeast, and mold.

And this is some of the water activity that is suitable/optimum for the microbes~ 

The range of water activity in food that can enhance the growth of some microorganisms. 

I read about this from here :- 

http://www.foodsafetysite.com/educators/competencies/general/bacteria/bac5.html

Dr also gave us an example by asking us a question. She said that the water activity for ..

(i) bacteria : 0.91-0.97 
(ii) fungus : 0.81-0.88 
(iii) honey : 0.9 

So which of the stated can survive in low amount of water? The answer is fungus! As you can see the water activity it requires to grow is rather low compared to bacteria and honey. 

Not to forget, organisms that can withstand extreme dryness are called xerophiles~ 

-> Barophiles are organisms that can live at high pressure. 

Dr test our understanding about the temperature range by asking us a question. 

Pyrolobus fumarii can survive at 110 degree Celcius. What will happen to it when in low temperature? 

It will die. Die instantly. It will instantly die at low temperature, not inactive because it cannot survive in temperature below than 110 degree celcius. 

I guess that's all from me! I think entry like this is much more informative in form of my understanding, right doctor? Hee. I may have misunderstood the purpose of the reflective journal. x'D 


P/S
Thank you for reminding us to study hard, Dr :) I will do my best!!