Bihar Board - Class 12 Biology - Chapter 10: Microbes in Human Welfare Long Answer Question

Q.1. Describe the kind of food that would have lactic acid bacteria. Mention their useful applications.

A.1. Lactic Acid Bacteria(LAB) of the Lactobacillus species is most commonly found in food items such as curd and yogurt. During the formation of curd, a small amount of curd is added to milk which acts as an initiator. Microbes present in the starter rapidly multiply at suitable temperatures, thereby causing the conversion of milk into curd. The LAB releases acids during the growth curdle and digest the milk protein partially which thereby facilitates the digestibility of the milk protein. Few of its applications are:

• Enhances the nutritional quality of milk by increasing vitamin B-12 content

• Regulates disease-checking microbes in the stomach

Q.2. Describe the procedure involved in Sewage treatment?

Ans: The following technique is performed for the treatment of sewage waste:

i) Primary Treatment- This entails physically separating suspended materials in settling tanks in order to reduce BOD. The raw sewage is routed into massive open tanks where it is subjected to anaerobic digestion to remove the solid fraction.

ii) Secondary Therapy- Secondary treatment relies on microbial activity, either aerobic or anaerobic. Secondary treatment techniques include:

1. Sand filters for filtration

2. Process of aeration

Application of oxidation ponds:

3. After drying, the sludge that collects after secondary treatment is disposed of, and the efferent is allowed to be used for tertiary treatment.

iii) Tertiary Treatment- This treatment comprises chemical treatment to eliminate inorganic chemicals as well as pathogenic microorganisms. Chlorination is the most common disinfection procedure.

Q.3. What is Biogas? How is it produced & Name the microbes invaded in Biogas production?

Ans: Biogas is the gas produced by anaerobic fermentation of waste biomass. It is made up of methane, CO2, hydrogen, nitrogen, oxygen, and hydrogen sulphide, among other things. Microbes that are often employed in the production of biogas-

i) Hydrolytic Bacteria, such as cellulosomes, clostridium, etc.

ii) Bacteria that produce hydrogen sulfide, such as Syntrophomonas wolfei

iii) Methanobacterium Omelianskii is an example of a methanogenic bacteria.

The biogas plant is fed by a concrete tank. The slurry is covered with a floating cover, which continues to rise when gas is created in the tank owing to microbial activity. The biogas plant includes an output that connects to a pipe that distributes biogas to surrounding residences. Microbes transform the organic part of biodegradable organic solid waste and trash into energy in the form of biogas and humus during biogas production.

CO + H₂O → CO₂ + H₂

CO₂ +4H₂ → CH4 + 2H₂O

CH3OH → CH4 +  02

Q.4. How do Biofertilizers enrich the fertility of soil? How do cyanobacteria act as biofertilizers?

Ans: Microorganisms employ biological channels to improve soil fertility for optimal crop development, and they are referred to as "BIOFERTILIZERS." These microorganisms can boost crop output in one of two ways.

i) By removing nitrogen from the atmosphere

ii) Insoluble fertilizer solubilization

iii) By promoting the growth of plants.

iv) Through phosphorus absorption.

v) By allowing plant remnants to decompose.

Anabaena, a cyanobacterium found in the leaf cavity of the water fern Azolla, fixes nitrogen from the air and excretes nitrogenous compounds into the leaf cavity.

Q.5. How does primary sludge differ from activated sludge? What type of changes in the sludge is carried out in an anaerobic sludge digester? Give the composition of biogas produced in the sewage treatment plant.

Ans: Primary sludge is made up of all solids, such as soil and small stones, that settle in the settling tank during sewage treatment. The sediment of bacterial flocs in the settling tank following biological treatment is known as activated sludge. Slime and fungal filaments bind bacteria together to form flocs. A portion of the activated sludge is used as inoculum in the aeration tank, and the rest is sent to the anaerobic sludge digester, which is a big tank. Other bacteria that grow anaerobically in this tank consume the bacteria, fungus, and cellulose in the sludge.

Q.6. Microbes can be used to decrease the use of chemical fertilizers & pesticides. Explain how this can be accomplished?

Ans: Chemicals are used to combat plant diseases and pests in modern society, however, these chemicals are poisonous and exceedingly damaging to humans and the environment. In agriculture, for example, there is a form of pest control that depends on natural predation rather than pesticides, such as To control butterflies, caterpillars, and other insects, a bacteria are known as Bacillus thuringiensis (Bt) is provided as dried spores in sachets that are mixed with water and sprayed onto sensitive plants such as brassicas, where the larvae are consumed. The toxin is released in the intestines of larvae, killing them. The bacterial sickness kills the caterpillar but does not harm other insects.

Q.7. Discuss the main ideologies crucial in the biological control of diseases and pests.

A.7. The fundamental idea is it is natural and eco-friendly. It involves the utilization of entities to monitor the community of pests and pathogens in an ecosystem. An example is Trichoderma, it is an antagonist which acts against certain soil-borne plant pathogens. Likewise, Penicillin hinders the growth of Staphylococcus and hence has been used in the penicillin production to check several bacterial pathogens. Baculovirus in genus Nucleopolyhedrovirus is used as a biological control agent for the species-specific narrow-spectrum insecticidal application. Bacillus thuringiensis is used to control insects as it acts as a biopesticide. The complete biological regulation of pests is recognised to be much more advantageous in an ecologically sensitive area.