Microbes in human welfare


Microbes play a vital role in our day to day lives. Many biological, biochemical and physiological processes are based on the action of microbes. People tend to have a narrow perception that, microbes are dangerous, but with a few exceptions like E-coli find in our gut or the yeast help in fermentation. These are just examples, microorganisms help mankind in many ways. Microbes -short form for microorganisms, are present almost everywhere both within ( body systems such as the GI system) and outside the human body (such as soil, water, air, decomposing waste). One of the major advantages that help microbes to survive even in the no man’s land is, their ability to sustain against the drastic environmental conditions. Microbes are usually found in colonies( groups)of protozoa, bacteria, fungi, viruses,  microscopic plants, viroids, and prions. Microbes have a variety of morphological, physiological and pathological (disease causation) features. This is linked with their structural and functional uniqueness capable of affecting the hosts. Fortunately, not all organisms are harmful, in fact, many of the vaccines prepared from microbes are lifesaving, for example, BCG vaccine used for tuberculosis.


Table of Contents

1. Introduction

2. Role of microorganisms in the human welfare

    2.1 Formation of curd and fermentation of dosa batter

   2.2 Microorganisms in bakery products

   2.3 Microorganisms in the beverage industry

   2.4  Microbes in the industrial products

   2.5   Microbes and antibiotics

    2.6 Microbes in the production of Chemicals, Enzymes             and other Bioactive Molecules.

   2.7 Microbes used in sewage treatment

3. Steps of sewage treatment

   3.1 Collecting wastewater:

   3.2  Odour management

   3. 3 Screening and separation

   3.4  Primary Treatment

   3. 5 Phases of secondary treatment

4. Microbes in a biogas unit

    4.1 A typical biogas plant

   4.2 Disadvantages of biogas

Various microbes


Role of microorganisms in the human welfare

Formation of curd and fermentation of dosa batter

Many hand snacks and cool dishes enriched with great taste, feel, and healthy textures are made possible because of the chemical processes mediated by many microbes, one such example is the formation of curd from milk and. Fermentation of dosa batter is another example mediated by lactobacillus.  Lactobacillus (lactic acid bacteria) help to release the lactic acid that can convert the unprocessed milk into a processed milk overnight. The production of acids by bacterium give the food products coagulated and a sour like taste. Fermentation process does not help in improving the taste but it aids in improving the look and feel, texture, puffiness of dough as a result of the production of CO2 gas by a bacillus.


Microorganisms in bakery products

Most of the bakery products work on the basic principle of the fermentation process. Bakers mix the dough properly to keep it overnight result in the fermentation by adding some yeast powder or baker’s yeast (Saccharomyces cerevisiae). Yeast makes the mixture puffed, soft and increase the quantity.


Microorganisms in the beverage industry

Alcoholic drinks like wine and beer are the breweries manufactured based on the bacterial processes fermentation and brewing. For instance, grape wine stored for years result in a fine quality product wine. Another example, the traditional drink Toddy, most popular in some parts of southern India. It is made by fermenting the sap collected from palms.  


Microbes in the industrial products

A number of beverages, antibiotics, processed foods and health drinks are produced by using the principles of microbial action. Saccharomyces cerevisiae is used for the production of fermented beverages. Fermenters are the large vessels containing colonies of growing microbes essential for the industrial production. Brewer’s yeast is the term exclusively used for the one used in beverage production. It is used for fermenting the malted cereals and fruit juices so that ethanol- a  popular form of alcohol.


Microbes and antibiotics

Microbes have centuries of history helping in the preparation of many antibiotics. In the year 1926, Alexander Fleming has successfully used original microorganisms for the production of penicillin. It was one of the life-changing event as it was identified as the best invention of the 20th century.  The word Anti is of Greek origin means “against”, and bio stands for “life”.   When Alexander Fleming was working on a column of Staphylococci bacteria he found that mould was growing in one of his unwashed culture plates. He found that there is some influence behind the chemical nature of the phenomenon. Later on, he realized the columnar growth was due to a chemical called Penicillium notatum. A complete scientific progression on the microorganisms was made by Ernest Chain and Howard Florey after many years. Penicillin was used to treat the wounded soldiers of the USA during World War II. However, the first Nobel Prize for an antibiotic invention was awarded to Fleming, Chain, and Florey in the year 1945 for their contribution. Evidently, the dead strain of other organisms such as Streptomycin, Tetracycline, Chloramphenicol, Erythromycin, Fusidic acid, and Methicillin was also used in the treatment of infections.


Microbes  in the production of Chemicals, Enzymes and other Bioactive Molecules

Certain chemicals like organic acids, alcohols and enzymes are artificially prepared with the help of microbes. Some of them are citric acid, acetic acid, butyric acid, lactic acid, ethanol, etc. In addition, certain bacterial strains are used in many medical and surgical treatments of diseases, for instance, streptococcus produces an enzyme-based substance called streptokinase is used to remove the blood clot causing heart attack in cardiac patients. Trichoderma polypore is a fungus that produces cyclosporine, an immunosuppressive agent used in organ transplant patients. A fungus, Monascus purpurues produces the substance called Statins. Statins assist in reducing the cholesterol levels in our body.  Microbes can also help in the production of enzymes like lipases  used in the manufacturing of detergents.  Pectinases and proteases are the enzymes used in storing, bottling, transferring fruit juices while they can keep them clean and clear for a longer duration. Many biomolecules present in the environment can be produced artificially by culturing them. Biomolecules are predominantly used in the farming, fishery,drug manufacturing  industries and other commercial ventures. Soil bacteria like Serratia can produce an opposing reaction against harmful worms, so they are useful in agriculture.


Microbes used in sewage treatment

Garbage is an unresolved issue globally. Each year, India generates more than 62 million tonnes of waste encompassing both recyclable and non-recyclable items. Wate accumulates in a rapid pace with the annual rise of 4%, so, waste gets doubled every 20 years. Fortunately, most of the waste is biodegradable (can be degraded by biological organisms like bacteria, fungus, virus etc). If this waste is poorly managed by throwing near streets and suburbs, it is going to cause a disaster in the form of many communicable diseases. Garbage is thrown in the streets combined with the rainwater to enter the aquatic sources such as ponds and rivers. The sewage and the garbage released everyday cause water pollution. So, the best way is to treat it by using sewage treatment plants (STPs) which filters, processes, and converts into less polluting products. STPs use microorganisms to decompose the waste before treating them.


Steps of sewage treatment

It is the process in which contaminants from domestically used water and municipal water is removed by using physical, chemical, biological means. The products released after the sewage treatment is called sewage sludge. Sewage treatment requires a systematic processing of waste through a series of biological, mechanical and chemical processes. Let us discuss the stages of sewage treatment.

1. Collecting wastewater:

Collecting wastewater, wastes, and sewage is everyone`s responsibility. The wastewater is collected in a closed septic tank or a waste receiving tank. The collected water is then directed to a treatment plant through underground drainage systems or by exhauster tracks.


2.  Odour management:

Since the mixture is the combination of biological, inorganic, chemical substances, it starts decomposing quickly resulting in the foul smell. By using some chemicals, the bad odour can be neutralized to make it easy for the screening and separation.


3. Screening and separation:

During this phase, wastes are segregated into various types. There are a number of materials in the wastes. Some of them are nappies, cotton buds, scissors, glass pieces, and biological products, plastics, diapers, rags, sanitary items, face wipes, broken bottles or bottle top etc. After the segregation, the waste must be free from clogging by solid materials hence a proper segregation of solid matter is important. The solid wastes removed from the wastewater will be shifted to landfills.


4. Primary Treatment

Primary treatment involves the separation of the residual macrobiotic solid matter by pouring the wastewater into big tanks. This will allow the solid matter to settle down at the bottom of the tanks. The resulting sludge -lowest residue is removed by large machinery scrappers. After this, the collected solids are pushed into the centre of the cylindrical tanks and later pumped out of the tanks for further treatment.  After removing the sludge, the water at this stage is called primary effluent. In the next stage, the primary effluent is pumped for secondary treatment.


5. Phases of secondary treatment

1. The primary effluent is subjected to a series of mechanical and biological treatments. The primary effluent is being pushed to a large aeration tanks. The agitators in the tank create a vigorous mechanical agitation force against the primary effluent. The process of agitation will disperse the compact molecules and material inside the water which will eventually help the aerobic microbes to grow and cultivate.

2. Furthermore, microbes help to reduce the biological oxygen demand (BOD) as most of the oxygen is being utilized by them. BOD is a parameter defined as the amount of dissolved oxygen required by the aerobic biological organisms to break down organic material in a given water sample at a certain temperature over a specific time period. Rise in the  BOD  indicates there is still a lot more pollutants remaining in the effluents. During this stage, the water flows into a tank with paddles. Paddles provide a moderate force against the waste . to slowly mix and bring into larger particles called flocs. The aerobically processed effluent is passed through the settling tank where flocs get settled down (sedimentation) to generate an ‘activated sludge‘.

4. In the next stage, inoculation is done, During this phase,  a part of activated sludge is added to the aeration tank and the rest of the sludge is subjected to anaerobic sludge digestion. The anaerobic bacteria help in processing the waste to produce methane, and carbon dioxide gas. The resulting gas can be used as biogas. The final effluent after anaerobic processing is released into rivers and streams.


Microbes in a biogas unit



Biogas is the gas produced by biological activity (microbial). It is a mixture of many gases, predominantly methane gas. Biogas is being used as a fuel in both domestic and commercial purposes. It is the cheapest source as it doesn’t require a lot of raw materials apart from domestic waste. Microbes produce different types of gaseous as their end-products and the type of gas produced depends upon the microbes and the organic substrates they utilize.  During the chemical process of fermentation of dough, cheese making and beverage production  CO2 is released as an endproduct. However, the decomposition of cattle dung or domestic waste can produce methane along with CO2 and H2 gases.  The mixture of all these are called methanogens, and the bacterium responsible for such phenomenon is known by the name Methanobacterium.  The excreta or dung (gobar) of cattle is commonly used as a raw material in biogas production. This is because cattle dung can encourage the growth of methanogens. methanogens can be found in the cattle`s stomach where a lot of cellulosic material is present. The bacterium will help to digest and metabolize the cellulose present in the cattle`s feed thereby help in the nutrition of cattle. After the metabolism, the end products of cellulose digestion is nothing but the dung. Cattle dung has to be processed in through a gobar gas plant.


A typical biogas plant

A typical biogas unit has an underground concrete tank at the depth of 10-15 feet. Wastes such as cow dung, sewage slurry or bio-wastes are dumped into this reservoir. As seen in the image( left-top of the image )  there is a mixing tank through which the mixture of raw materials is added and mixed well. The mixture will then pass through the inlet pipe to reach the inlet tank (reservoir). There is a partition wall in the middle of the reservoir where the excess of dung is connected to the overflow tank that receives the overflown dung. Into the partition wall, a pipe unit called gas pipe unit is connected. Into the gas pipe unit, a gas holder chamber is linked. The gas holder chamber is further connected to the gas control valve that can be directly received into the inlet of a gas stove or an electric unit. After the production of gas, the leftover slurry is removed through another outlet and may be used as fertilizer. As already discussed above, biogas composed of methane, carbon dioxide, hydrogen, nitrogen, and hydrogen sulfide. Methane has about 50 – 70%, CO2 gas about 30-40% and 10-20 % other components. At a 50% methane content, calorific value of biogas is 4,429 kcal/m3.


  1. It suits only village and complete rural settings.

  2. The rate of production is slow.

  3. Not a suitable method for industrial and large scale modes.

  4. Cannot be used for equipment that requires high voltage and high-end functionalities.

  5. Needs intensive work while filling, removing and transferring the raw material and end products.





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