Lecture 5 - Microbial growth kinetics | Biotechnology (Zoology) by ILLL, DU - Biotechnology Engineering (BT) PDF Download

 Page 1


Microbial growth kinetics 
              Institute of Life Long Learning, University of Delhi  
 
0 
 
 
 
 
NME-Zoology 
Lesson: Microbial growth kinetics 
Lesson Developer: Dr. Nidhi Garg 
                             Dr. Kiran Bala 
College/Dept: Hindu College 
                                 Deshbandhu College 
Lesson Reviewer: Dr. Shashi Chawla 
College/Dept: Department of Microbiology, Gargi College 
 
 
 
 
 
 
 
 
 
 
Page 2


Microbial growth kinetics 
              Institute of Life Long Learning, University of Delhi  
 
0 
 
 
 
 
NME-Zoology 
Lesson: Microbial growth kinetics 
Lesson Developer: Dr. Nidhi Garg 
                             Dr. Kiran Bala 
College/Dept: Hindu College 
                                 Deshbandhu College 
Lesson Reviewer: Dr. Shashi Chawla 
College/Dept: Department of Microbiology, Gargi College 
 
 
 
 
 
 
 
 
 
 
Microbial growth kinetics 
              Institute of Life Long Learning, University of Delhi  
 
1 
 
Table of Contents 
 
? Introduction 
? Nutrients for Microbial Growth  
? Growth Factors 
? Microbial Growth Curve 
? Lag Phase  
? Exponential Phase  
? Stationary Phase  
? Death Phase  
? Calculating Microbial Growth  
? Methods of measuring of Microbial Growth  
? Measurement of Cell Numbers  
? Measurement of Cell Mass  
? Open Systems or the Continuous Culturing Systems  
? The Chemostat  
? The Turbidostat  
? Factors Affecting Microbial Growth 
? Nutrient availability 
? Solutes and Water Activity  
? pH  
? Temperature 
? Pressure 
? Radiation 
? Oxygen Concentration 
? Summary  
? References  
? Exercises 
? Glossary 
 
 
Page 3


Microbial growth kinetics 
              Institute of Life Long Learning, University of Delhi  
 
0 
 
 
 
 
NME-Zoology 
Lesson: Microbial growth kinetics 
Lesson Developer: Dr. Nidhi Garg 
                             Dr. Kiran Bala 
College/Dept: Hindu College 
                                 Deshbandhu College 
Lesson Reviewer: Dr. Shashi Chawla 
College/Dept: Department of Microbiology, Gargi College 
 
 
 
 
 
 
 
 
 
 
Microbial growth kinetics 
              Institute of Life Long Learning, University of Delhi  
 
1 
 
Table of Contents 
 
? Introduction 
? Nutrients for Microbial Growth  
? Growth Factors 
? Microbial Growth Curve 
? Lag Phase  
? Exponential Phase  
? Stationary Phase  
? Death Phase  
? Calculating Microbial Growth  
? Methods of measuring of Microbial Growth  
? Measurement of Cell Numbers  
? Measurement of Cell Mass  
? Open Systems or the Continuous Culturing Systems  
? The Chemostat  
? The Turbidostat  
? Factors Affecting Microbial Growth 
? Nutrient availability 
? Solutes and Water Activity  
? pH  
? Temperature 
? Pressure 
? Radiation 
? Oxygen Concentration 
? Summary  
? References  
? Exercises 
? Glossary 
 
 
Microbial growth kinetics 
              Institute of Life Long Learning, University of Delhi  
 
2 
 
Introduction 
Growth is defined as ?an increase in cellular constituents?. Bacterial growth is an asexual 
reproduction of a bacterium resulting in formation of two daughter cells by a process called 
binary fission. If no mutation occurs in the genome of resulting daughter cells then they are 
said to be genetically identical to the original cell. This results in the doubling of the bacterial 
population. Both daughter cells resulting from the bacterial cell division do not necessarily 
survive. But, if the number of microorganisms surviving exceeds unity on average, then the 
bacterial population is said to have undergone exponential growth. It is inconvenient to 
examine the growth and reproduction of a single bacterium because of their small size. 
Therefore, for studying microbial growth, microbiologists track changes in the total population 
number. Liquid broth is not the only medium for culturing bacteria, as biofilms or agar surfaces 
present additional alternatives.  
Nutrients for microbial growth  
The organisms require nutrients in order to obtain energy and synthesize new cellular 
components, and are essential for microbial growth. Environmental factors like temperature, 
oxygen levels, and osmotic concentration of the culture medium are important for the 
successful cultivation of microorganisms. Microorganisms require some nutrients in large 
quantities which are known as macronutrients or macroelements, while some other 
nutrients are required in small quantities and are known as micronutrients or 
microelements. The macronutrients are carbon, hydrogen, oxygen, nitrogen, phosphorus, 
calcium, sulfur, potassium, magnesium and iron. Of these 10 major nutrients carbon, 
hydrogen, oxygen, nitrogen, phosphorus and calcium are used for the synthesis of 
carbohydrates, proteins, lipids and nucleic acids.  
1. Carbon is required for the synthesis of backbone of all organic molecules. The molecules 
that serve as carbon sources normally also provide both oxygen and hydrogen atoms, and 
also act as energy sources. Reason being that they are almost always reduced and thus, 
serve as electron donors to other more oxidized molecules. The more reduced organic 
molecules have higher energy content as exemplified by lipids which on oxidation provide 
more energy than carbohydrates. Carbon dioxide (CO
2
) is an important carbon source that 
Page 4


Microbial growth kinetics 
              Institute of Life Long Learning, University of Delhi  
 
0 
 
 
 
 
NME-Zoology 
Lesson: Microbial growth kinetics 
Lesson Developer: Dr. Nidhi Garg 
                             Dr. Kiran Bala 
College/Dept: Hindu College 
                                 Deshbandhu College 
Lesson Reviewer: Dr. Shashi Chawla 
College/Dept: Department of Microbiology, Gargi College 
 
 
 
 
 
 
 
 
 
 
Microbial growth kinetics 
              Institute of Life Long Learning, University of Delhi  
 
1 
 
Table of Contents 
 
? Introduction 
? Nutrients for Microbial Growth  
? Growth Factors 
? Microbial Growth Curve 
? Lag Phase  
? Exponential Phase  
? Stationary Phase  
? Death Phase  
? Calculating Microbial Growth  
? Methods of measuring of Microbial Growth  
? Measurement of Cell Numbers  
? Measurement of Cell Mass  
? Open Systems or the Continuous Culturing Systems  
? The Chemostat  
? The Turbidostat  
? Factors Affecting Microbial Growth 
? Nutrient availability 
? Solutes and Water Activity  
? pH  
? Temperature 
? Pressure 
? Radiation 
? Oxygen Concentration 
? Summary  
? References  
? Exercises 
? Glossary 
 
 
Microbial growth kinetics 
              Institute of Life Long Learning, University of Delhi  
 
2 
 
Introduction 
Growth is defined as ?an increase in cellular constituents?. Bacterial growth is an asexual 
reproduction of a bacterium resulting in formation of two daughter cells by a process called 
binary fission. If no mutation occurs in the genome of resulting daughter cells then they are 
said to be genetically identical to the original cell. This results in the doubling of the bacterial 
population. Both daughter cells resulting from the bacterial cell division do not necessarily 
survive. But, if the number of microorganisms surviving exceeds unity on average, then the 
bacterial population is said to have undergone exponential growth. It is inconvenient to 
examine the growth and reproduction of a single bacterium because of their small size. 
Therefore, for studying microbial growth, microbiologists track changes in the total population 
number. Liquid broth is not the only medium for culturing bacteria, as biofilms or agar surfaces 
present additional alternatives.  
Nutrients for microbial growth  
The organisms require nutrients in order to obtain energy and synthesize new cellular 
components, and are essential for microbial growth. Environmental factors like temperature, 
oxygen levels, and osmotic concentration of the culture medium are important for the 
successful cultivation of microorganisms. Microorganisms require some nutrients in large 
quantities which are known as macronutrients or macroelements, while some other 
nutrients are required in small quantities and are known as micronutrients or 
microelements. The macronutrients are carbon, hydrogen, oxygen, nitrogen, phosphorus, 
calcium, sulfur, potassium, magnesium and iron. Of these 10 major nutrients carbon, 
hydrogen, oxygen, nitrogen, phosphorus and calcium are used for the synthesis of 
carbohydrates, proteins, lipids and nucleic acids.  
1. Carbon is required for the synthesis of backbone of all organic molecules. The molecules 
that serve as carbon sources normally also provide both oxygen and hydrogen atoms, and 
also act as energy sources. Reason being that they are almost always reduced and thus, 
serve as electron donors to other more oxidized molecules. The more reduced organic 
molecules have higher energy content as exemplified by lipids which on oxidation provide 
more energy than carbohydrates. Carbon dioxide (CO
2
) is an important carbon source that 
Microbial growth kinetics 
              Institute of Life Long Learning, University of Delhi  
 
3 
does not supply hydrogen. The organisms can be classified based on their mode of 
obtaining nutrition (Table 1).  
Table 1: The different modes or method of obtaining nutrition by 
different organisms.  
Mode of 
Nutrition 
Characteristics 
Autotrophs The autotrophs are organisms that can synthesize their own food. 
They are mainly the plants, algae, phytoplanktons and certain 
fungi. 
Photoautotrophs The plants and algae that utilize the energy from sunlight are 
known a photoautotrophs. 
Lithoautotrophs These organisms utilize the energy from inorganic compounds. 
Heterotrophs These are organisms that cannot fix carbon and use organic 
carbon for its growth and development. Heterotrophs are further 
divided into two categories based on how they obtain energy. 
Photoheterotroph These are the heterotrophs that utilize light as energy source. 
Chemoheterotroph These are heterotrophs that utilizes inorganic/organic energy 
sources. 
 
  
The autotrophs produce organic compounds like fats, carbohydrates, and proteins from 
inorganic carbon dioxide. These reduced carbon compounds are used as energy sources by 
autotrophs and are responsible for providing the energy in food which is consumed by the 
heterotrophs. Ninety-five percent or more of all types of living organisms are heterotrophic. 
Not all microorganisms use carbon dioxide as their sole source of carbon but utilize more 
complex reduced molecules like glucose that serve both as a source of carbon and energy. 
Many microorganisms can utilize any naturally occurring organic molecule. For example, 
Page 5


Microbial growth kinetics 
              Institute of Life Long Learning, University of Delhi  
 
0 
 
 
 
 
NME-Zoology 
Lesson: Microbial growth kinetics 
Lesson Developer: Dr. Nidhi Garg 
                             Dr. Kiran Bala 
College/Dept: Hindu College 
                                 Deshbandhu College 
Lesson Reviewer: Dr. Shashi Chawla 
College/Dept: Department of Microbiology, Gargi College 
 
 
 
 
 
 
 
 
 
 
Microbial growth kinetics 
              Institute of Life Long Learning, University of Delhi  
 
1 
 
Table of Contents 
 
? Introduction 
? Nutrients for Microbial Growth  
? Growth Factors 
? Microbial Growth Curve 
? Lag Phase  
? Exponential Phase  
? Stationary Phase  
? Death Phase  
? Calculating Microbial Growth  
? Methods of measuring of Microbial Growth  
? Measurement of Cell Numbers  
? Measurement of Cell Mass  
? Open Systems or the Continuous Culturing Systems  
? The Chemostat  
? The Turbidostat  
? Factors Affecting Microbial Growth 
? Nutrient availability 
? Solutes and Water Activity  
? pH  
? Temperature 
? Pressure 
? Radiation 
? Oxygen Concentration 
? Summary  
? References  
? Exercises 
? Glossary 
 
 
Microbial growth kinetics 
              Institute of Life Long Learning, University of Delhi  
 
2 
 
Introduction 
Growth is defined as ?an increase in cellular constituents?. Bacterial growth is an asexual 
reproduction of a bacterium resulting in formation of two daughter cells by a process called 
binary fission. If no mutation occurs in the genome of resulting daughter cells then they are 
said to be genetically identical to the original cell. This results in the doubling of the bacterial 
population. Both daughter cells resulting from the bacterial cell division do not necessarily 
survive. But, if the number of microorganisms surviving exceeds unity on average, then the 
bacterial population is said to have undergone exponential growth. It is inconvenient to 
examine the growth and reproduction of a single bacterium because of their small size. 
Therefore, for studying microbial growth, microbiologists track changes in the total population 
number. Liquid broth is not the only medium for culturing bacteria, as biofilms or agar surfaces 
present additional alternatives.  
Nutrients for microbial growth  
The organisms require nutrients in order to obtain energy and synthesize new cellular 
components, and are essential for microbial growth. Environmental factors like temperature, 
oxygen levels, and osmotic concentration of the culture medium are important for the 
successful cultivation of microorganisms. Microorganisms require some nutrients in large 
quantities which are known as macronutrients or macroelements, while some other 
nutrients are required in small quantities and are known as micronutrients or 
microelements. The macronutrients are carbon, hydrogen, oxygen, nitrogen, phosphorus, 
calcium, sulfur, potassium, magnesium and iron. Of these 10 major nutrients carbon, 
hydrogen, oxygen, nitrogen, phosphorus and calcium are used for the synthesis of 
carbohydrates, proteins, lipids and nucleic acids.  
1. Carbon is required for the synthesis of backbone of all organic molecules. The molecules 
that serve as carbon sources normally also provide both oxygen and hydrogen atoms, and 
also act as energy sources. Reason being that they are almost always reduced and thus, 
serve as electron donors to other more oxidized molecules. The more reduced organic 
molecules have higher energy content as exemplified by lipids which on oxidation provide 
more energy than carbohydrates. Carbon dioxide (CO
2
) is an important carbon source that 
Microbial growth kinetics 
              Institute of Life Long Learning, University of Delhi  
 
3 
does not supply hydrogen. The organisms can be classified based on their mode of 
obtaining nutrition (Table 1).  
Table 1: The different modes or method of obtaining nutrition by 
different organisms.  
Mode of 
Nutrition 
Characteristics 
Autotrophs The autotrophs are organisms that can synthesize their own food. 
They are mainly the plants, algae, phytoplanktons and certain 
fungi. 
Photoautotrophs The plants and algae that utilize the energy from sunlight are 
known a photoautotrophs. 
Lithoautotrophs These organisms utilize the energy from inorganic compounds. 
Heterotrophs These are organisms that cannot fix carbon and use organic 
carbon for its growth and development. Heterotrophs are further 
divided into two categories based on how they obtain energy. 
Photoheterotroph These are the heterotrophs that utilize light as energy source. 
Chemoheterotroph These are heterotrophs that utilizes inorganic/organic energy 
sources. 
 
  
The autotrophs produce organic compounds like fats, carbohydrates, and proteins from 
inorganic carbon dioxide. These reduced carbon compounds are used as energy sources by 
autotrophs and are responsible for providing the energy in food which is consumed by the 
heterotrophs. Ninety-five percent or more of all types of living organisms are heterotrophic. 
Not all microorganisms use carbon dioxide as their sole source of carbon but utilize more 
complex reduced molecules like glucose that serve both as a source of carbon and energy. 
Many microorganisms can utilize any naturally occurring organic molecule. For example, 
Microbial growth kinetics 
              Institute of Life Long Learning, University of Delhi  
 
4 
Burkholderia cepacia is capable of utilizing over 100 different carbon compounds while 
Actinomycetes can degrade amyl alcohol, paraffin, and even rubber. Over the course of 
time microorganisms have evolved the ability to even metabolize xenobiotics like 
pesticides, insecticides, petrochemicals etc. 
2. Nitrogen is required for the synthesis of amino acids, purines, pyrimidines, some 
carbohydrates and lipids, enzyme cofactors etc. Nitrogen in amino acids can be directly 
utilized by microorganisms, while ammonia is incorporated directly by enzymes like 
glutamate dehydrogenase or glutamine synthetase and glutamate synthase.  Bacteria like 
cyanobacteria and Rhizobium are able to reduce and assimilate atmospheric nitrogen by 
using the nitrogenase system. 
3. Phosphorus is a component of nucleic acids, nucleotides like ATP, phospholipids, some 
proteins, several cofactors, and other cell components. Inorganic phosphate is used as a 
source of phosphorus and incorporated directly by all microorganisms. Low phosphate 
levels are known to limit microbial growth in several aquatic environments.  
4. Sulfur is required for the synthesis of amino acids like cysteine and methionine, biotin, 
some carbohydrates, and thiamine. Majority of microorganisms use sulfate as a source of 
sulfur while a few others obtain sulfur from cysteine. 
The rest of the four macroelements exist as cations in the cell and perform different functions 
as mentioned in the table 2 below.  
Table 2: The major functions of certain macroelements existing as 
cations in biological systems. 
Cation Function of the Cation 
Potassium (K
+
) It acts as a cofactor for a number of enzymes, example 
protein synthesis. 
Calcium (Ca
2+
) It performs several functions in the biological system one of 
which is providing heat resistance of bacterial endospores. 
Magnesium (Mg
2+
) It acts as a cofactor for several enzymes, it complexes with 
ATP and contributes towards stabilizing ribosomes and cell