Microbes in human welfare


Imagine what would have happened if there are no microorganisms while the tonnes of waste materials are being deposited on the streetside daily.  Microbes or microorganisms are an essential part of natural scavenger system as they play a vital role in our day to day lives. Many biological, biochemical and physiological processes are based on the principles of microbial growth. More often, people tend to be narrow in their perception about the microbes just because they are dangerous and are the cause of illnesses, however, some of them are useful. Organisms like E-coli found in our gut or the yeast that help in fermentation are some of the examples of useful organisms. These are just examples because there are a number of organisms that benefit mankind in many ways. 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 such as excessive cold and heat. Microbes are usually found in colonies( groups)of protozoa, bacteria, fungi, viruses,  microscopic plants, viroids, and prions. Microbes exhibit a variety of morphological, physiological and pathological (disease causation) features and these characteristics are linked with the structural and functional uniqueness that enables them to affect the hosts easily. Fortunately, not all organisms are harmful, in fact, many of the vaccines prepared from microbes are lifesaving, for example, BCG vaccine used for tuberculosis.




Role of microorganisms in human welfare

1. Preparation of snacks,  curd and dosa batter

Many handmade snacks with great taste, feel, and healthy textures are only possible because of the chemical processes mediated by many microbes. In addition, the formation  of curd from the milk is due to the action of enzymes secreted by the processed milk overnight. Fermentation of dosa batter is another example mediated by lactobacillus. The bacteria are generally known as the lactic acid bacteria as they help to release the lactic acid which adds a slightly sour taste in addition to the coagulation into the milk. Although, fermentation process does not help in improving the taste but it helps to improve the look and feel, texture, puffiness of dough because of the production of CO2 gas by a bacillus.


2. Microorganisms in bakery products

Most of the bakery products work on the basic principle of the fermentation process. Bakers mix the dough accurately to keep it overnight. As a result, the mixture turns into a product due to the action of yeast powder or baker’s yeast (Saccharomyces cerevisiae). Yeast makes the mixture puffed, soft and increase the quantity.


3. Microorganisms in the beverage industry

Alcoholic drinks like wine and beer are the breweries manufactured on a large scale with the help of fermentation and brewing. The ingredients are kept locked for years which further adds great taste and feel. Breweries such as wine are prepared in this way. Another example, the traditional drink Toddy extracted from coconut trees and then it is fermented. It is the most popular drink in southern India. 


4. Microbes in industrial products

A number of processed foods and health drinks are manufactured by using microbial action. For the production of fermented beverages, fermenters that contains Saccharomyces cerevisiae is used. Fermenters are the large vessels containing colonies of growing microbes essential for industrial production. Another example is the brewer’s yeast which is exclusively used for fermenting the malted cereals and fruit juices into ethanol-based alcohol.


5. Microbes and antibiotics

Microbes have centuries of history as they were used in the preparation of many antibiotics. In the year 1926, Alexander Fleming had successfully used the microorganisms for the production of penicillin and he was awarded Nobel prize for such a great invention.  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. Later on, he realized that the chemical nature of the phenomenon was due to the bacterial colonies (Penicillium notatum).  Ernest Chain and Howard Florey after many years have further improved this drug. 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.


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

Chemicals like organic acids, alcohols and enzymes are artificially prepared with the help of microbes. Some of the products produced by the microbes are citric acid, acetic acid, butyric acid, lactic acid and ethanol. Furthermore, some of the bacterial strains are more commonly used in many medical and surgical treatment of diseases, for instance, streptococcus produces an enzyme-based substance called streptokinase which is used to remove the blood clots that causes heart attack in cardiac patients. Trichoderma polypore is a fungus that produces cyclosporine, an immunosuppressive agent used in organ transplantation in chronic patients. Moreover, Monascus purpurues produces a substance called Statins that 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 another class of enzymes used in storing, bottling and transferring fruit juices by keeping them clean and clear for a longer duration. Biomolecules that are predominantly used in the farming, fishery, drug manufacturing industries are also the contribution of some microbes. In agriculture, soil bacteria like Serratia can produce an opposing reaction against harmful worms.


7. Microbes used in sewage treatment

Garbage is an unresolved issue in the country and the world. Each year, India generates more than 62 million tonnes of waste encompassing both recyclable and non-recyclable items. Domestic and industrial wastes are accumulated at as high as 4% per annum, which means it gets doubled every 20 years. Fortunately, most of the waste is biodegradable (which can be decomposed by biological organisms ). If the waste is poorly managed by throwing near streets and suburbs, they turn disastrous because they can cause serious communicable diseases. Garbage that is thrown on the streets gets mixed with the rainwater which ultimately travels into the major aquatic sources to cause water pollution. The best way to manage such wastes is by treating them with sewage treatment plants (STPs) which filters, processes, and converts the most polluted stuff into less polluting products. STPs use microorganisms to decompose the waste before treating them.


Steps of sewage treatment

Sewage treatment is the process by which the contaminants from domestically used water and municipal wastes are being eliminated with the help of physical, chemical, biological means. It is the systematic processing of the wastes through a series of biological, mechanical and chemical processes. The products released after the sewage treatment are called sewage sludge. Let us discuss the stages of sewage treatment.


A. Collecting wastewater

Collecting sewage is everyone`s responsibility. Wastes are collected in a closed septic tank or a waste receiving tank and then directed to a treatment plant via underground drainage systems or exhauster tracks. Care should be taken not to allow the wastes getting mixed with freshwater sources. 


B.  Odour management

Since the collected mixture contains an aggregate of biological, inorganic, and chemical substances, it starts decomposing quickly to produce a foul smell. By using some chemicals, the bad odour can be neutralized so that it will be easy to handle them in the next stage i,e  screening and separation.


C. Screening and separation

During the screening and separation, waste is segregated into various types.  Some of the most commonly found wastes include nappies, cotton buds, scissors, glass pieces, and biological products, plastics, diapers, rags, sanitary items, face wipes, broken bottles and bottle tops. After the segregation of different types of wastes,  they become free from clogging as most of the solids are removed. Following this, the mixture should be safely moved to landfills through a pipeline.


D. 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 that is collected at the bottom is removed by large machinery scrappers and then they are pushed into the cylindrical tanks which can later be pumped out of the tanks for further treatment.  The residual product at this stage is called the primary effluent which is later subjected to the secondary treatment.


E. Secondary treatment

The primary effluent must be subjected to a series of mechanical and biological treatments and then pushed to a large aeration tank. The agitators in the tank create a vigorous mechanical agitation force that will disperse the compact molecules and material inside the water. Such forceful agitation will eventually help the aerobic microbes to grow and cultivate.  The growing columns of microbes will suppress the biological oxygen demand (BOD) as most of the oxygen is being utilized by them during the aerobic respiration. BOD is a parameter which is defined as the amount of dissolved oxygen required by the aerobic biological organisms to break down the 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 the secondary treatment, the water flows into a tank with paddles that provide a moderate force against the waste. The paddle movements slowly mix and bring the waste into larger particles called flocs. The aerobically processed effluent is then passed through the settling tank where flocs get settled down (sedimentation) to generate an ‘activated sludge‘.


E. Inoculation

The last phase is the inoculation during which, 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 the biological activity of microbial flora. It is being used as a fuel in both domestic and commercial purposes and is the cheapest source than any other fule as it doesn’t require a lot of raw materials aside from domestic waste. In the biogas unit, microbes in action produce different types of gases as their end-products. The decomposition of cattle dung or domestic waste can produce methane along with CO2 and H2 gases in different proportions.  The mixture of all these gases is called methanogens that produce Methanobacterium. Methanobacterium helps to decompose the dung into gases.  The cattle dung (gobar)  is commonly used as a raw material in biogas production as it is a good catalyst for the growth of methanogens. Methanogens can be found in the cattle`s stomach where a lot of cellulosic material is found. The bacterium in the methanogens helps to digest and metabolize the cellulose present in the cattle`s feed . 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 installed 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 gas pipe unit is also connected which finally lead to a gas- holder( holding chamber). The gas holding chamber is further connected into the gas control valve that receives the gas which could be connected to 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. Having said that, biogas contains methane, carbon dioxide, hydrogen, nitrogen, and hydrogen sulfide in which  50 – 70% is methane, CO2 gas about 30-40% and 10-20 % other components. At a 50% methane content, the calorific value of biogas is 4,429 kcal/m3.





  1. It suits only 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.



Further reading


Role of microorganisms in biofertilizers


Sewage treatment                                                      


Kingdom monera


Autotrophs and heterotrophs



  1. Name the human body system that normally has bacterial flora.

  2. Name some of the biological processes where microorganisms play an important role.

  3. Explain the role of microbes used in sewage treatment

  4. Describe the phases of sewage treatment.

  5. What is biogas? Explain briefly about a typical biogas plant.

  6. Explain the gaseous composition of biogas.





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