Techniques in industrial microbiology, Biology tutorial


The medium employed to grow a microorganism is vital as it can find out the level of microbial growth and product formation. In order to maximize the competitiveness, lower cost crude materials are employed as sources of carbon, nitrogen and phosphorus. Crude plant hydroxyl salts frequently are employed as complex sources of nitrogen, carbon and growth factors.

By products from the brewing industry often are utilized due to their lower cost and greater accessibility. Other helpful sources comprise molasses and from cheese manufacture.

Culture Media:

It is a combination of nutrients employed for the cultivation of microorganisms is termed as culture medium. Culture media might be liquid (broth) or solid agar. The media can be synthetic, semi synthetic or natural. There are various kinds of media. They are:

1) Enrichment Media:

Blood and other special nutrients might be added to common purpose media to encourage the growth of fastidious microbes. Such particularly fortified media (example: blood agar) are termed as enrichment media.

2) General Purpose Media:

Media like tryptic soy broth and tryptic soy agar are termed as general purpose media as they sustain the growth of numerous microorganisms.

3) Selective Media:

This media favors the growth of specific microorganisms. For illustration bile salt or dyes such as basic fucshin and crystal violets favor the growth of gram - ve bacteria through inhibiting the growth of gram + ve bacteria. The others are endo agar, methylene blue agar, eosin and Mac Conkey agar.

4) Differential Media:

This media are such which differentiate among various groups of microbes and ever permit tentative recognition of microorganisms based on their biological features.

Blood agar is both a differential medium and an enriched one. It differentiates among hemolytic and non-hemolytic bacteria.

Media Formulation:

Each and every microbes need water, sources of carbon, mineral elements and most likely vitamin and oxygen when aerobic on a big scale, manufacturers generally use sources of cheap nutrient to prepare a medium that will require the given criteria.

1) It should produce the maximum yield of products or biomass per gram of substrate employed.

2) It should permit the maximum rate of product formation.

3) The yield of undesirable products should be minimal.

4) It should be cheap and of reliable quality.

5) It should cause minimum problems in the production procedure specifically other features as aeration, purification extraction and the waste management.

Isolation and Identification of Culture:

The isolation and recognition of microbes in the natural sources like water, food, blood and medical samples frequently need the utilization of complex media of selective, differential and so on in most of the case, the pour plate and streak. Plate methods have become indispensable tools of the microbiologist in isolating and subsequent recognition of a microbial species.

1) Spread Plate Method:

When a mixture of cells is spread out on an agar surface, employing a particularly shaped rod each and every cell grows into a completely separate colony. As each colony occurs from a single cell, each and every colony represents a pure culture. The spread plate is a simple, direct way of accomplishing this outcome.

2) Streak Plate:

The streak plate methods utilize an inoculating loop to spread cells across an agar surface. The microbial mixture is transferred to the edge of the agar plate by an inoculating loop or swab and then streaked out over the surface in one of some patterns. After the first sector is streaked, the inoculating loop is sterilized and inoculums for the second sector are attained from the first sector this is completed for the other sectors. Finally some few cells will be on the loop and single cells will drop from it as it is rubbed all along the agar surface.

3) Pour Plate Method:

The original sample is diluted some times to decrease the microbial population adequately to get separate colonies if plating. Then small volumes of some diluted samples are mixed by liquid agar which has been cooled to around 45oC, and the mixtures are poured instantly into sterile culture plates. Similar to the spread plates, the pour plates can be employed to find out the number of cells in the population.  


This Mutation is a change in the sequence in DNA (or RWA) in some RNA viruses. It is obvious that since it is the sequence of such bases that is responsible for the kind of proteins and therefore enzymes synthesized, and change in the sequence will finally lead to the change in property. The fundamental procedure for generating microbial mutants comprises exposure of cells to the action of mutagens. Mutagenic agents can either be chemical or physical. Illustrations of physical are ionizing radiation and ultraviolet light. Chemical mutagents are nitrous acid, M - methyl - N - nitro - na - guanine (NTG)

Mutation and natural selection approach is hitor mix, while, genetic engineering permits purposeful manipulation or genetic information to engineer a microorganism which can produce high outcomes of diversity of products.

Strain Selection:

The choice of microorganism for industrial process starts by the screening to determine the right candidates out of the numerous species of microbes, relatively some have the genetic information required to produce economically helpful products. The first phase in the screening of microbes is the isolation that is, getting either pure or mixed culture followed through the assessment to find out which of the microbes carry out the desired reaction or produce the desired product.

Because of the ubiquity of microbes, they can be isolated from natural sources example: rotten vegetable, soil, water, sewage and so on. The isolate considered for industrial application should carry out the procedure economically and thus the choice of the culture to be employed is a compromise between the productivity of the organism and the financial constraint of the product. A few of the criteria employed in selection the desired cultures are:

Hybridization: It is the artificial construction of a double stranded nucleic acid through complementary base pairing of the two single-stranded nucleic acid. It is a significant process employed in recombinant DNA technology for the recognition of specific gene. Genetic recombination in fungi can be attained through haploid strains for ascopores or basidiospores and then made to giving new strains.

In a number of lower fungi, hybridization occurs through the use of pure sexual cycle that as well makes sure that strains have enhanced performance. The hybridization of yeasts and higher fungi needs three main steps.

  • Sporulation
  • Spore formation
  • Hybridization

Recombinant DNA Technology:

It is the Invitro incorporation of the segments of genetic material from one cell to the other cell. The technology of generating a genetically engineered bacterium is summarized beneath:

1) The nutritional need of the organism should be from a much cheap source.

2) The strain must be capable to protect itself against the contamination.

3) It should be stable and amenable for the genetic manipulation.

4) This should encompass a high productivity that is; the rate at which substrates are transformed to products should be high. Furthermore, it should provide a yield of product per unit time.

5) It should be simple to extract the desired product after the bioconversion method.

6) It should be appropriate for the kind of procedure to be employed.

7) It should not react by means of the equipment.

Methods of Natural Selection:

It might be possible to design the isolation process in such a manner that producers might be recognized at the isolation phase for illustration in assay for antibiotic production, where as in other cases, random isolation should be made and producers recognized at the subsequent phase. Several methods of natural selections are as follows:

1) Enrichment culture: This is a method resultant in an increase in the number of target organisms associating to the number of other kinds in the original medium. The method comprise taking a mixed population and providing conditions either appropriate for the growth of the desired organism by the provision of a specific substrate or through inclusion of certain inhibitors. The growth of the desired organisms outcome in the modification of medium and therefore modifies the selective force that might let growth of other organisms resultant in succession. The selective force might be re-established by inoculating the enriched culture into similar fresh medium. Such sub culturing might be repeated quite a few times prior to the dominant; organism is isolated through spreading a small innoculum of the enriched culture on solid medium. The time of sub culturing must correspond to the time if desired organism is dominant.

2) Screening for antibiotic production: The detection of antimicrobial action might be attained through growing a potential producer on an agar plate in the presence of organisms against which the antimicrobial action is needed production of the antibiotic is pointed out by inhibition of the test organism. Otherwise, the isolate might be grown in liquid culture and the cell-free broth can be attained through centrifugation or filtration.

3) Screening for polysaccharide production: Microbes producing polysaccharide (dextranxanthan) have been isolated from the diverse environment. Though, the property of exopolysccharide production is hard to apply in choosy force.

It is expected to isolate for carbohydrate industrial waste that is anticipated to be rich in the desired organism. Isolates from these environments might then be grown on appropriate media and producers identified through mucilageneous appearance of the isolate. The suspected isolate might then be grown in liquid culture and the property of the polysaccharide assessed. 

i) Source of the donor genetic material: DNA having the genetic code for the property to be transferred into a bacterium from cells or it might be synthesized.

ii) Production of hybrid DNA molecule: The donor genetic material of a bacteriophage or plasmid. This is attained through the use of two enzymes; restriction endonucleases and ligase.

iii) Incorporation of hybrid DNA to host cell: This is termed as transformation or transfection. It comprises introduction of phage hybrid DNA into the host cell. The most common method for transformation based on treating the recipient bacterium with CaCl2 to make the membrane permeable to the DNA. The recipient bacteria are able of receiving the recombinant DNA molecules on the basis of just one bacterium per molecule. If bacteria are transformed, a mixture of bacteria of different genotypes is generated. Each bacterial cell is able of binary fission, yielding a colony of similar cells possessing equal genetic and thus physiological characteristics once a colony by the proper phenotype is recognized, the bacteria in it can be grown in a limitless quantity to recognize the gene.

Culture Maintenance:

Industrial microbes should be maintained in such a manner as to remove:

  • Contamination
  • Genetic change
  • And retain viability

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