PART 1 - Kinetics of Substrate Utilization, Product Formation and Biomass Production in Cell Cultures

Question 1

___________ are apparatus or structures in which a chemical, biological and/or
physical process are facilitated

Answer 1

Reactors

Question 2

____________ are model systems for which the transport processes
and chemical reactions are exactly defined.

Answer 2

Ideal reactors

Question 3

For a reactor to be ideal, it must be:

Answer 3

• controlled
• analog and prototype
• mathematically modeled

Question 4

Types of ideal reactors in the context of enzymatic and culture processes:

Answer 4

• Batch operation of mixed enzyme reactor
• Continuous operation of mixed enzyme reactor

Question 5

Batch process is an ____________________ operation where the __________,_________ changes with ______.

Answer 5

unsteady state

concentration of cell mass, substrate changes with TIME

Question 6

Batch processes operate in ________________

Answer 6

closed systems

Question 7

Explain what happens in batch processes

Answer 7

substrate is added at the beginning of the process and products removed only at the end.

Question 8

What are classified as batch

Answer 8

Bioreactors with neither input nor output of liquid
or solid material

Question 9

In Batch, the mass of substrate in the reactor, M, is equal to the ________________ multiplied by the ________________.

Answer 9

substrate concentration s
liquid volume V

Question 10

Recite the initial equation of Batch Time from Mass Balance for Enzymatic Reaction

Answer 10

d(sV)/dt = -(VmaxS/Km+S)V

Since V is constant,
Take V outside the differential, and cancel from both sides

Question 11

Enzymes are subject to _______________. Accordingly, the concentration of active enzyme in
the reactor, and therefore the value of __________, may change during reaction.

Answer 11

deactivation, vmax

Question 12

Microorganisms have specific ___________ and _____ ranges at which they thrive

Answer 12

temperature, pH

Question 13

Cell growth process got two different manifestations according to the morphology of cell
involved: EXPLAIN UNI ORGANISMS AND MOLDS

Answer 13

For unicellular organisms which divide as they grow, increases in biomass are accompanied by increases in the number of cells present.

Unlike unicellular organisms, molds do not necessarily undergo cell division as the primary means of growth. Instead, they grow by
elongation and branching of their filamentous structures.

Question 14

Certain parameters/ phenomena to
consider in determining the cell population kinetics

What does it do to formulate a simple kinetic model for cellular activities

Answer 14

• characteristics of culture broth,
• nutrients and substrates used for growth and production of metabolites
• cell to cell heterogeneity
• microbial cells of different ages manifesting metabolic activities
• characterization of biochemical pathway

THEY ARE COMPLEX
They make it difficult to formulate a simple kinetic model

Question 15

Two processes are associated with cell growth

Answer 15

1. utilization of materials from the medium
   by the cells
2. generation of metabolic end products in the medium

Question 16

Define the RATE-LIMITING SUBSTRATE

Answer 16

First, it is assumed that
the concentration of all components present in the medium is sufficiently high and the rate of
reaction depends on the concentration of that component only.

Question 17

The process by which cells generate energy, involves various metabolic pathways.

Answer 17

Cellular respiration

Question 18

These are used to maintain optimal growth conditions

Answer 18

Incubators, Bioreactors, and Temperature-Controlled Environments

Question 19

What can be indicative of alterations in cell structure,
function, or health

Answer 19

Changes in the
rheological properties of cells, including viscosity,

Question 20

This refers to the study of the flow and deformation of matter, and it plays a role in understanding the mechanical properties of cells

Answer 20

Rheology

Question 21

This may contribute to the diversity observed in different phases of cellular activities.

Answer 21

Stochastic events

Question 22

This can contribute to genetic variability among cells within a population

Answer 22

Genetic drift, as
a random process

Question 23

They classified the microbial systems according to the number of components used in the
cellular representation.

Answer 23

Arnold Fredrickson and Henry
Tsuchiya

Question 24

Model classifications for mathematical representation of cell populations: ENUMERATE AND EXPLAIN EACH

Question 25

This is one perspective in which microbial cells are considered as **multicomponent systems**. These models are very complex and not used very often.

Answer 25

Structured model

Question 26

One common type of structured model in cell growth is the

Answer 26

age-structured model

Question 27

The structured model usually deals with the **kinetics of the change** in individual components present in the cells, such as

Answer 27

RNA, DNA, proteins, etc

Question 28

When cell population is treated as **one component system**, it is referred to as

Answer 28

Unstructured model

Question 29

Model assumes balanced growth where cell components **do not change with time**. Much **less complex** and much more commonly used.

Answer 29

Unstructured Model

Question 30

This consider individual cells, in recognition of the fact that **cells in a population** – a pure culture – are **different** and are most often formulated as a population balance model.

Answer 30

Segregated Model

Question 31

These models form an important class and describe the *biomass* as **consisting of several variables** (such as NADH, precursors, metabolites, ATP, biomass).

Answer 31

Unsegregated structured models

Question 32

The real condition of the living system is

Answer 32

a structured, segregated one

Question 33

In ideal conditions, the cell growth kinetics is assumed to be in the

Answer 33

unsegregated, unstructured mode

Question 34

This is typically prepared by using a seed culture in a liquid medium.

Answer 34

Inoculum

Question 35

It is the period where the individual bacteria are maturing and not yet able to divide.

Answer 35

Lag phase

Question 36

The log phase is sometimes called

Answer 36

the logarithmic phase or the exponential phase.

Question 37

It is the period characterized by cell doubling and the growth rate is independent of nutrient and substrate concentration.

Answer 37

Log phase/ Exponential phase

Question 38

No net growth of cell numbers or cell mass. *Secondary metabolites* like **alkaloids** and **glycosides** are produced.

Answer 38

Stationary Phase

Question 39

This phase shows an **exponential decrease** in the number of living cells in the media while nutrients are depleted. The rate of cell decline is ___________.

Answer 39

The death phase **first-order**

Question 40

Batch process is ________________ operation where the concentration of cell mass, substrate changes with time.

Answer 40

an unsteady state

Question 41

This is a type of chemical reactor that operates continuously, provides thorough mixing.

Answer 41

Continuous Stirred-Tank Reactor (CSTR)

Question 42

This is used in a variety of industrial processes for chemical reactions where **steady-state** conditions are desired.

Answer 42

CSTR

Question 43

CSTR is also called

Answer 43

Chemostat

Question 44

Purpose of mixing

Answer 44

to maintain homogeneity in the fermentation broth

Question 45

In the **steady- state** condition, the concentration of any component in the vessel is ___________ of time.

Answer 45

independent

Question 46

Ideal Chemostat Models

Answer 46

--

Question 47

Monod Chemostat Models

Answer 47

--

Question 48

Sterile feed means

Answer 48

X0 = 0

Question 49

Cell mass productivity

Question 50

Explain the plot of XSS, SSS, DXSS versus the dilution rate D.

Question 51

At D_washout, ________ will remain present in the reactor.

Answer 51

no cell

Question 52

At Dwashout, _______, where washout of cells will take place

Answer 52

X→0

Question 53

It should be noted that ______ < 𝐷𝑤𝑎𝑠ℎ𝑜𝑢𝑡 ≤ ______

Answer 53

𝐷𝑚𝑎𝑥 𝜇𝑚𝑎𝑥

Question 54

If a mixed microbial culture contains both slow-growing and fast-growing microorganisms, then by adjusting the **dilution rate**_______ than the __________ of slow-growing but ______ than that of fast-growing, it is possible to separate fast-growing organisms from the slow-growing organisms.

Answer 54

higher Dwashout less

Question 55

Advantages of Chemostat

Answer 55

- Growth rate can be controlled and maintained indefinitely. So one can operate the log phase of growth for the maximum cell mass production for the infinite period of time. - Effect of growth-limiting substrate can be easily monitored. - The chemostat can be used to study the period of unbalanced growth, which occurs during the transition period between steady states at different growth rates. The formation of some plant metabolite is found to increase during the transition of phases. - Results obtained are reliable and reproducible.

Question 56

Disadvantages of Chemostat

Answer 56

- The major problem of chemostat is cell washout. It is difficult to operate at Dmax because it is very close to Dwashout - Cell growth over long periods can cause mutation or contamination

Question 57

Bioreactors are operated continuously in a few bioprocess industries such as

Answer 57

- brewing, - production of bakers’ yeast - waste treatment

Question 58

In CSTRs, if the vessel is well mixed, the product stream has ____________ composition as the liquid in the reactor.

Answer 58

the same

Question 59

Therefore, when continuous reactors are used with ___________________, the catalyst is _________________ from the vessel in the product stream.

Answer 59

freely suspended cells or enzymes continuously withdrawn

Question 60

Characteristic operating parameters for continuous reactors are

Answer 60

- dilution rate D defined in - average residence time τ. T = V/F D = F/V

Question 61

The different phases of growth are more readily distinguished when the ____________________ is plotted against _______; alternatively, a _________ plot can be used.

Answer 61

logarithm of viable cell concentration time semi-log

Question 62

During the ___________ immediately after inoculation of the culture, the rate of growth is essentially _______.

Answer 62

lag phase zero

Question 63

This also refers to a period of time when the change of cell number is zero

Answer 63

Lag phase

Question 64

Cells use this phase to adapt to their new environment.

Answer 64

lag

Question 65

In this phase, **new enzymes or structural components** may be synthesized but the concentration of cells _______________.

Answer 65

Lag phase **does not increase**

Question 66

The length of this lag period depends on many factors such as

Answer 66

- the type and age of the microorganisms, - the size of the inoculum, - culture conditions

Question 67

This phase is where *growth starts* for the **inoculated cell culture**

Answer 67

Acceleration phase

Question 68

The *cell number* starts to **increase**, and the division rate increases to reach a ____________

Answer 68

Acceleration phase maximum

Question 69

During this period, growth achieves its maximum rate.

Answer 69

Growth phase or exponential growth phase

Question 70

If growth is exponential (which is the most often case), the growth phase appears as a _______________ on a semi-log plot.

Answer 70

straight line

Question 71

Growth slows down due to _______________ or build-up of ____________________

Answer 71

Decline phase nutrient exhaustion inhibitory products.

Question 72

During this period, cell growth ceases. No further cell growth can be observed

Answer 72

Stationary phase

Question 73

The transition between the **exponential phase** and the **stationary phase** involves a period of _____________________ during which the various cellular components are synthesized at ___________________.

Answer 73

unbalanced growth unequal rates

Question 74

Consequently, cells in the stationary phase have a chemical composition ___________ from that of cells in the exponential phase.

Answer 74

different

Question 75

At this phase, cells lose _________ or are destroyed by ______

Answer 75

Death phase viability lysis

Question 76

Death occurs either because of the depletion of the _________________, or the accumulation of ______________.

Answer 76

cellular reserves of energy toxic products

Question 77

Cell growth is considered to be a

Answer 77

**first-order** *autocatalytic* reaction

Question 78

time required for the cell population to double

Answer 78

Doubling time

Question 79

Starting with a cell concentration of 𝑁0, the concentration at 𝑡 = 𝑡𝑑 is

Answer 79

N=2𝑁0. or X=2X0

Question 80

Doubling time is a valid representation of the growth rate only when

Answer 80

μ is constant

Question 81

This represents an **approximation** where the *average cellular synthesis activities* are **not affected** by the *growing cell population* as the coordination is relatively **perfect**.

Answer 81

Balanced growth kinetics

Question 82

In an environment **favorable for growth**, *cells **regulate** their metabolism* and *adjust the **rates** of various internal reactions* so that a condition of _______________ occurs.

Answer 82

balanced growth

Question 83

Under this type of kinetics, the **composition** of the biomass *remains constant*.

Answer 83

Balanced growth

Question 84

A balanced growth signifies that the cell is able to modulate the effects of _____________________ and keep the **biomass composition steady** *despite changes in environmental conditions*.

Answer 84

external perturbations

Question 85

Balanced Growth A cell can grow in size or mass in numbers. Hence, **unstructured models** can be used for the

Answer 85

bio-phase characterization

Question 86

For the biomass composition **to remain constant** during growth, the _________________________ in the culture must be **equal** to the cell ______________________

Answer 86

*specific rate of production of each component or N* *specific growth rate*, μ

Question 87

Balanced growth cannot be achieved if __________________affect the ________________. In most cultures, balanced growth occurs at the same time as _________________.

Answer 87

environmental changes rate of growth exponential growth.

Question 88

In ______________ organisms, the progressive doubling of cell number results in a ____________________in the population.

Answer 88

unicellular continually increasing rate of growth

Question 89

A bacterial culture undergoing balanced growth mimics a ______________________________

Answer 89

first-order autocatalytic chemical reaction.

Question 89

Balanced growth Hence, the rate of the cell population increase at any particular time is **proportional** to the ___________________ of bacteria present at that time.

Answer 89

number density (CN)