Aspergillus niger is the principal industrial fungus used for large-scale production of citric acid by submerged fermentation (using molasses or glucose) because it produces high yields of citric acid under controlled conditions.
Saccharomyces cerevisiae ferments sugars to produce ethanol (and CO2). Acetobacter aceti produces acetic acid, Methanobacterium (methanogens) produce methane, and Penicillium notatum produces the antibiotic penicillin, not acetic acid.
Molasses, a by-product of sugarcane processing, is rich in fermentable sugars and is the common substrate in distilleries for ethanol production using Saccharomyces cerevisiae.
Cyclosporin A is a fungal metabolite used as an immunosuppressive drug. Historically it was obtained from fungi such as Tolypocladium inflatum (and earlier literature refers to related species like Trichoderma polysporum).
In lactate (lactic acid) fermentation pyruvate is reduced to lactate by lactate dehydrogenase without decarboxylation, so CO2 is not released. Alcoholic fermentation involves decarboxylation of pyruvate to acetaldehyde and CO2; aerobic respiration releases CO2 via the TCA cycle.
Biological treatment uses microbes to degrade organic pollutants, thereby reducing Biological Oxygen Demand (BOD) of wastewater before discharge to protect aquatic life.
Anaerobic digestion produces biogas composed mainly of methane (CH4) and carbon dioxide (CO2); hydrogen sulphide (H2S) is also produced by sulfate-reducing bacteria in the sludge.
Process: Pasteurize milk (heat to kill pathogens) then cool to ~40–45°C. Inoculate with starter culture (Lactobacillus and Streptococcus species). These bacteria ferment lactose to lactic acid, lowering pH. Acidification causes casein (milk protein) to reach its isoelectric point and coagulate (precipitate) forming a gel network that traps water and fat — this is curd. Fermentation time/temperature determine texture and taste. Microbial cultures also contribute to flavor by producing small amounts of volatile compounds.
Milk is converted into curd through a fermentation process called lactic acid fermentation, carried out by lactic acid bacteria used as starter cultures. The primary bacteria involved are Lactobacillus bulgaricus and Streptococcus thermophilus, which are added to warm milk at approximately 40-45 degrees Celsius. These bacteria metabolize lactose, the primary sugar in milk, through anaerobic fermentation, producing lactic acid as the end product. The accumulation of lactic acid lowers the pH of the milk to approximately 4.6, creating an acidic environment. This acidic pH causes the milk protein casein to denature and coagulate, forming a solid curd while the liquid whey separates. The process typically takes 4-8 hours depending on temperature and bacterial concentration. The lactic acid bacteria also produce various enzymes and compounds that contribute to the characteristic flavor, texture, and nutritional properties of curd. The fermentation process not only converts milk into curd but also increases the bioavailability of nutrients, produces beneficial probiotics, and extends the shelf life of the product through preservation by acidity.
Microorganisms produce numerous bioactive molecules with significant medical and industrial applications. Penicillin is produced by the fungus Penicillium notatum or Penicillium chrysogenum and is a beta-lactam antibiotic that inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins and preventing peptidoglycan cross-linking. It is used to treat a wide range of bacterial infections caused by gram-positive and some gram-negative bacteria, making it one of the most important antibiotics in clinical medicine. Cyclosporin A is produced by certain fungi such as Tolypocladium and related Trichoderma species and functions as an immunosuppressive agent by inhibiting T cell activation and cytokine production. It is used clinically to prevent organ transplant rejection and to treat autoimmune diseases. Other important examples include insulin, produced by recombinant Escherichia coli through genetic engineering, which is used to treat diabetes mellitus by regulating blood glucose levels. Statins such as lovastatin, produced by fungi like Monascus and Aspergillus species, are used to lower cholesterol levels and reduce cardiovascular disease risk. Additional examples include human growth hormone produced by recombinant bacteria for treating growth disorders, and various enzymes like amylase and protease produced by microorganisms for industrial applications in food processing and detergent manufacturing.
a) Antibiotics are chemical substances that are either naturally produced by microorganisms such as bacteria and fungi or synthetically derived through chemical synthesis. These compounds possess the ability to kill or inhibit the growth of other microorganisms, particularly bacteria, by targeting essential cellular structures or metabolic processes. Antibiotics work through various mechanisms including inhibition of cell wall synthesis, disruption of protein synthesis, interference with nucleic acid replication, or disruption of metabolic pathways. They are widely used in clinical medicine to treat bacterial infections and have revolutionized healthcare by reducing mortality from infectious diseases. b) Zymology is the branch of microbiology and biochemistry that studies fermentation processes and the microorganisms and enzymes involved in these processes. It encompasses the study of how microorganisms metabolize substrates in the absence of oxygen, the biochemical pathways involved, and the practical applications of fermentation in food production, beverage manufacturing, and industrial biotechnology. Zymology includes the study of yeast fermentation in brewing and winemaking, lactic acid fermentation in dairy products, and various other fermentation processes. c) A superbug is a microbial strain, usually a bacterium, that has developed resistance to multiple classes of antibiotics, making it extremely difficult or impossible to treat with conventional antimicrobial therapy. Superbugs arise through genetic mutations that alter antibiotic targets or produce enzymes that inactivate antibiotics, and through horizontal gene transfer of resistance genes between bacterial species. Common examples include methicillin-resistant Staphylococcus aureus (MRSA) and multidrug-resistant Mycobacterium tuberculosis. The emergence of superbugs poses a serious public health threat and has led to increased research into alternative antimicrobial strategies and the development of new antibiotics.
a) Brewer's yeast: Saccharomyces cerevisiae used in brewing and baking; ferments sugars to produce ethanol and CO2. In brewing it produces alcohol and flavor compounds; in baking CO2 leavens dough. b) Ideonella sakaiensis: A bacterium discovered to degrade PET plastic using enzymes PETase and MHETase that hydrolyze polyethylene terephthalate into its monomers; potential application in biodegradation and recycling of plastic waste. c) Microbial fuel cells (MFCs): Bioelectrochemical systems in which microorganisms oxidize organic substrates at the anode, releasing electrons that flow through an external circuit to the cathode, generating electricity; used for wastewater treatment with simultaneous energy recovery and biosensing.
Biogas plants offer multiple significant advantages for rural communities. They provide a renewable energy source in the form of biogas, which is primarily methane and can be used directly for cooking and lighting, reducing dependence on traditional fuels. The process converts animal waste and plant residue into usable fuel, thereby reducing environmental pollution and greenhouse gas emissions that would otherwise result from decomposition of organic waste. A valuable byproduct of biogas generation is nutrient-rich slurry, which serves as an excellent biofertilizer for agriculture, improving soil fertility and crop yields while reducing the need for chemical fertilizers. Biogas plants significantly reduce reliance on firewood and other biomass fuels, thereby decreasing deforestation pressure and promoting environmental conservation. The treatment of waste through biogas production improves sanitation in rural areas by managing animal and agricultural waste in a controlled manner. Additionally, biogas plants provide local energy security and economic benefits by reducing household expenditure on fuel, making them economically sustainable for rural populations. These combined benefits make biogas plants an environmentally sound and economically viable solution for rural energy needs and waste management.
Antibiotic resistance develops when bacteria are exposed to antibiotics and naturally occurring or mutated resistant variants survive and proliferate because susceptible bacteria are eliminated. The primary cause is overuse and misuse of antibiotics, including incomplete antibiotic courses where patients discontinue medication prematurely, unnecessary prescriptions for viral infections where antibiotics are ineffective, and indiscriminate use in agriculture and animal husbandry. This creates strong selection pressure favoring the survival and multiplication of resistant mutants that possess genes conferring resistance. Horizontal gene transfer mechanisms, including transfer of plasmids and transposons carrying resistance genes between bacterial cells, accelerate the spread of resistance traits across different bacterial species and populations. Poor infection control practices in healthcare settings allow resistant bacteria to spread more readily among patients. The widespread use of antibiotics in agriculture for growth promotion and disease prevention in livestock further accelerates the development and dissemination of antibiotic-resistant bacteria. Once resistance develops, resistant bacteria can persist in the environment and human population, making previously effective antibiotics ineffective for treatment, posing a serious threat to public health.
Industrial alcohol refers to ethanol produced on a large scale for industrial applications such as fuel, solvents, chemical feedstock, and other manufacturing purposes. The preparation of industrial alcohol begins with selection of feedstock, typically molasses (a byproduct of sugar refining) or starchy materials such as grains or potatoes. If starchy materials are used, saccharification is performed to convert complex starches into fermentable simple sugars through enzymatic or acid hydrolysis. The feedstock is then prepared as a sterile mash with appropriate nutrients and pH conditions. This mash is inoculated with the yeast Saccharomyces cerevisiae, which ferments the sugars through anaerobic respiration to produce ethanol and carbon dioxide gas. The fermentation is carried out under controlled temperature conditions (typically 20-25°C) to optimize yeast activity and ethanol yield while preventing contamination. After fermentation is complete, the fermented wash containing ethanol is subjected to fractional distillation to concentrate the ethanol and separate it from water and other components. Further dehydration using molecular sieves or chemical drying agents yields higher-purity industrial ethanol suitable for industrial applications. Throughout the process, careful monitoring of yeast health, maintenance of sterility to prevent contamination by unwanted microorganisms, and rectification steps ensure the production of ethanol with the required purity and quality standards for industrial use.
Bioremediation is an environmental biotechnology approach that uses living organisms, primarily microorganisms such as bacteria and fungi, and plants to degrade, detoxify, or remove pollutants and contaminants from contaminated environments. The process can be implemented through two main strategies: in situ bioremediation, where contamination is treated at the site of pollution without removing the contaminated material, and ex situ bioremediation, where contaminated soil or water is excavated or extracted and treated in a controlled facility away from the original site. Microorganisms employed in bioremediation possess enzymatic capabilities to break down various pollutants including petroleum hydrocarbons from oil spills, pesticides and herbicides, heavy metals through bioaccumulation or biotransformation, and even synthetic polymers like plastics. Bacteria such as Pseudomonas and other genera can metabolize complex organic pollutants as energy sources, converting them into less toxic or non-toxic compounds. Plants can absorb and accumulate heavy metals in their tissues through phytoremediation, or their associated rhizosphere microorganisms can degrade organic contaminants. Bioremediation is advantageous because it is cost-effective, environmentally sustainable, and can be applied to various types of contamination in soil, water, and sediments, making it an important tool in environmental restoration and pollution control.