Idealized Enzyme Reactor System Notes | EduRev

: Idealized Enzyme Reactor System Notes | EduRev

 Page 1


ENZYME SCIENCE AND ENGINEERING 
PROF. SUBHASH CHAND 
DEPT OF BIOCHEMICAL ENGG  
AND BIOTECHNOLOGY 
IIT DELHI 
 
LECTURE-20 
IDEALIZED ENZYME REACTOR PERFORMANCE 
 
 
So today we shall discuss the performance of enzyme catalyzed reactors, the reactors in 
which enzyme catalyzed reactions are supposed to take place. 
 
[Refer Slide Time: 1:15] 
 
 
 
You will recall earlier we had discussed some of the salient features of different reactor 
types ranging from batch reactors, batch stirred tank reactors to continuous stirred tank 
reactor or plug flow reactors and fluidized bed reactors. In fact some of the unusual 
reactor configurations which have been proposed to catalyze to be used for carrying out 
enzyme catalyzed reaction like hollow fiber reactors also arbitrarily fall into one of those 
categories of plug flow or CSTR which were discussed. We had also seen earlier the 
factors that affect the choice of different reactor types and to recall some of the factors  
that we had talked about the most important ones are listed here like form of the enzyme.   
 
[Refer Slide Time: 2:22] 
 
 
Page 2


ENZYME SCIENCE AND ENGINEERING 
PROF. SUBHASH CHAND 
DEPT OF BIOCHEMICAL ENGG  
AND BIOTECHNOLOGY 
IIT DELHI 
 
LECTURE-20 
IDEALIZED ENZYME REACTOR PERFORMANCE 
 
 
So today we shall discuss the performance of enzyme catalyzed reactors, the reactors in 
which enzyme catalyzed reactions are supposed to take place. 
 
[Refer Slide Time: 1:15] 
 
 
 
You will recall earlier we had discussed some of the salient features of different reactor 
types ranging from batch reactors, batch stirred tank reactors to continuous stirred tank 
reactor or plug flow reactors and fluidized bed reactors. In fact some of the unusual 
reactor configurations which have been proposed to catalyze to be used for carrying out 
enzyme catalyzed reaction like hollow fiber reactors also arbitrarily fall into one of those 
categories of plug flow or CSTR which were discussed. We had also seen earlier the 
factors that affect the choice of different reactor types and to recall some of the factors  
that we had talked about the most important ones are listed here like form of the enzyme.   
 
[Refer Slide Time: 2:22] 
 
 
 
 
That is soluble, fibrous or particulate. The nature of the substrate whether it is soluble,  
particulate or colloidal, operational requirements; the control of pH in case an acid is 
produced or consumed in the reaction, reaction kinetics, carrier loading capacity,  
catalytic surface to reactor volume ratio, mass transfer characteristics, ease of catalyst 
replacement and regeneration, reactor cost and ease of fabrication. All these factors that I 
have listed here can be considered mainly under two categories. One category contains 
the factor which becomes fixed once an immobilized enzyme is prepared. That means  
the factors that are dictated by the immobilization enzyme preparation itself. For example 
form of the enzyme; the nature of the substrate is also fixed. Once the enzymatic reaction 
is defined the nature of substrate is fixed. The operational requirement is also fixed 
depending upon the nature of the enzyme catalyzed reaction whether an acid is produced 
or consumed  and pH control is a requirement. Similarly the catalytic surface to volume 
ratio is also fixed once an immobilized enzyme preparation is available. The carrier 
loading capacity also depends on the bulk density of the immobilized enzyme preparation  
and things like that. Ease of catalyst replacement and reactor cost and ease of fabrication  
are the factors which are dependent on the type of enzyme reactor. But the two important 
class of factors which I wanted to point out here is one is reaction kinetics and mass 
transfer characteristics. They are the ones which very heavily dictate the choice of the 
reactor; whether to go for a plug flow reactor or to go for a batch reactor or to go for a 
continuous stirred tank reactor are very heavily dictated by mass transfer requirements 
and reaction kinetics. I would once again point out that we have knowingly ignored heat 
transfer requirements assuming that for most of the enzyme catalyzed reaction the rate of 
reaction is very, very small and so heat transfer during the reaction is not a major critical 
factor. In certain cases if it is so, the heat transfer characteristics also must be taken into 
account. Last time I was taking we had also considered certain idealized reactor design 
parameter. That means for design of a particular type of reactor what kind of design 
parameters are important and you will recall that we had also hypothesized certain 
conditions or assumptions which define an idealized enzyme reactor system and the 
Page 3


ENZYME SCIENCE AND ENGINEERING 
PROF. SUBHASH CHAND 
DEPT OF BIOCHEMICAL ENGG  
AND BIOTECHNOLOGY 
IIT DELHI 
 
LECTURE-20 
IDEALIZED ENZYME REACTOR PERFORMANCE 
 
 
So today we shall discuss the performance of enzyme catalyzed reactors, the reactors in 
which enzyme catalyzed reactions are supposed to take place. 
 
[Refer Slide Time: 1:15] 
 
 
 
You will recall earlier we had discussed some of the salient features of different reactor 
types ranging from batch reactors, batch stirred tank reactors to continuous stirred tank 
reactor or plug flow reactors and fluidized bed reactors. In fact some of the unusual 
reactor configurations which have been proposed to catalyze to be used for carrying out 
enzyme catalyzed reaction like hollow fiber reactors also arbitrarily fall into one of those 
categories of plug flow or CSTR which were discussed. We had also seen earlier the 
factors that affect the choice of different reactor types and to recall some of the factors  
that we had talked about the most important ones are listed here like form of the enzyme.   
 
[Refer Slide Time: 2:22] 
 
 
 
 
That is soluble, fibrous or particulate. The nature of the substrate whether it is soluble,  
particulate or colloidal, operational requirements; the control of pH in case an acid is 
produced or consumed in the reaction, reaction kinetics, carrier loading capacity,  
catalytic surface to reactor volume ratio, mass transfer characteristics, ease of catalyst 
replacement and regeneration, reactor cost and ease of fabrication. All these factors that I 
have listed here can be considered mainly under two categories. One category contains 
the factor which becomes fixed once an immobilized enzyme is prepared. That means  
the factors that are dictated by the immobilization enzyme preparation itself. For example 
form of the enzyme; the nature of the substrate is also fixed. Once the enzymatic reaction 
is defined the nature of substrate is fixed. The operational requirement is also fixed 
depending upon the nature of the enzyme catalyzed reaction whether an acid is produced 
or consumed  and pH control is a requirement. Similarly the catalytic surface to volume 
ratio is also fixed once an immobilized enzyme preparation is available. The carrier 
loading capacity also depends on the bulk density of the immobilized enzyme preparation  
and things like that. Ease of catalyst replacement and reactor cost and ease of fabrication  
are the factors which are dependent on the type of enzyme reactor. But the two important 
class of factors which I wanted to point out here is one is reaction kinetics and mass 
transfer characteristics. They are the ones which very heavily dictate the choice of the 
reactor; whether to go for a plug flow reactor or to go for a batch reactor or to go for a 
continuous stirred tank reactor are very heavily dictated by mass transfer requirements 
and reaction kinetics. I would once again point out that we have knowingly ignored heat 
transfer requirements assuming that for most of the enzyme catalyzed reaction the rate of 
reaction is very, very small and so heat transfer during the reaction is not a major critical 
factor. In certain cases if it is so, the heat transfer characteristics also must be taken into 
account. Last time I was taking we had also considered certain idealized reactor design 
parameter. That means for design of a particular type of reactor what kind of design 
parameters are important and you will recall that we had also hypothesized certain 
conditions or assumptions which define an idealized enzyme reactor system and the 
assumptions were that isothermal operation, ?H is very small, uniform enzyme 
distribution, plug flow behavior or completely back mix behavior, that means you have  
one of the extreme fluid dynamics in the reactor system. Either it is a plug flow motion  
or it is a completely back mix  and nothing in between. That is what we have assumed  
and there are no mass transfer  limitations and no significant partitioning of substrate 
between bulk and the carrier phase. 
 
[Refer Slide Time: 6:15] 
 
 
 
These are the basic assumptions which define our ideal enzyme reactor and the reactor  
design parameters. That means the parameter which we should define initially before we 
go on to design any particular reactor was “tau”, the space time in the reactor; initial 
substrate concentration, enzyme loading, E
0
. In the case of continuous operation, the 
information about the deactivation rate constant is also required, k
d
. Then the temperature 
of operation, pH control and these are the reaction conditions. Other design parameters 
are fractional conversion and productivity and reactor capacity.  
 
[Refer Slide Time: 7:08] 
Page 4


ENZYME SCIENCE AND ENGINEERING 
PROF. SUBHASH CHAND 
DEPT OF BIOCHEMICAL ENGG  
AND BIOTECHNOLOGY 
IIT DELHI 
 
LECTURE-20 
IDEALIZED ENZYME REACTOR PERFORMANCE 
 
 
So today we shall discuss the performance of enzyme catalyzed reactors, the reactors in 
which enzyme catalyzed reactions are supposed to take place. 
 
[Refer Slide Time: 1:15] 
 
 
 
You will recall earlier we had discussed some of the salient features of different reactor 
types ranging from batch reactors, batch stirred tank reactors to continuous stirred tank 
reactor or plug flow reactors and fluidized bed reactors. In fact some of the unusual 
reactor configurations which have been proposed to catalyze to be used for carrying out 
enzyme catalyzed reaction like hollow fiber reactors also arbitrarily fall into one of those 
categories of plug flow or CSTR which were discussed. We had also seen earlier the 
factors that affect the choice of different reactor types and to recall some of the factors  
that we had talked about the most important ones are listed here like form of the enzyme.   
 
[Refer Slide Time: 2:22] 
 
 
 
 
That is soluble, fibrous or particulate. The nature of the substrate whether it is soluble,  
particulate or colloidal, operational requirements; the control of pH in case an acid is 
produced or consumed in the reaction, reaction kinetics, carrier loading capacity,  
catalytic surface to reactor volume ratio, mass transfer characteristics, ease of catalyst 
replacement and regeneration, reactor cost and ease of fabrication. All these factors that I 
have listed here can be considered mainly under two categories. One category contains 
the factor which becomes fixed once an immobilized enzyme is prepared. That means  
the factors that are dictated by the immobilization enzyme preparation itself. For example 
form of the enzyme; the nature of the substrate is also fixed. Once the enzymatic reaction 
is defined the nature of substrate is fixed. The operational requirement is also fixed 
depending upon the nature of the enzyme catalyzed reaction whether an acid is produced 
or consumed  and pH control is a requirement. Similarly the catalytic surface to volume 
ratio is also fixed once an immobilized enzyme preparation is available. The carrier 
loading capacity also depends on the bulk density of the immobilized enzyme preparation  
and things like that. Ease of catalyst replacement and reactor cost and ease of fabrication  
are the factors which are dependent on the type of enzyme reactor. But the two important 
class of factors which I wanted to point out here is one is reaction kinetics and mass 
transfer characteristics. They are the ones which very heavily dictate the choice of the 
reactor; whether to go for a plug flow reactor or to go for a batch reactor or to go for a 
continuous stirred tank reactor are very heavily dictated by mass transfer requirements 
and reaction kinetics. I would once again point out that we have knowingly ignored heat 
transfer requirements assuming that for most of the enzyme catalyzed reaction the rate of 
reaction is very, very small and so heat transfer during the reaction is not a major critical 
factor. In certain cases if it is so, the heat transfer characteristics also must be taken into 
account. Last time I was taking we had also considered certain idealized reactor design 
parameter. That means for design of a particular type of reactor what kind of design 
parameters are important and you will recall that we had also hypothesized certain 
conditions or assumptions which define an idealized enzyme reactor system and the 
assumptions were that isothermal operation, ?H is very small, uniform enzyme 
distribution, plug flow behavior or completely back mix behavior, that means you have  
one of the extreme fluid dynamics in the reactor system. Either it is a plug flow motion  
or it is a completely back mix  and nothing in between. That is what we have assumed  
and there are no mass transfer  limitations and no significant partitioning of substrate 
between bulk and the carrier phase. 
 
[Refer Slide Time: 6:15] 
 
 
 
These are the basic assumptions which define our ideal enzyme reactor and the reactor  
design parameters. That means the parameter which we should define initially before we 
go on to design any particular reactor was “tau”, the space time in the reactor; initial 
substrate concentration, enzyme loading, E
0
. In the case of continuous operation, the 
information about the deactivation rate constant is also required, k
d
. Then the temperature 
of operation, pH control and these are the reaction conditions. Other design parameters 
are fractional conversion and productivity and reactor capacity.  
 
[Refer Slide Time: 7:08] 
 
 
That is the maximum reaction capacity assuming that the enzyme reaction follows a 
maximum reaction velocity, that is zero order profile and the productivity of that kind of 
the reactor will be your reaction capacity. Ultimately the performance will be dictated 
very heavily by enzyme kinetics. If we consider ….. (7:35) enzyme reactor we can safely 
say that Michaelis Menten kinetics provides us a basis for carrying out a universally 
accepted kinetics for enzyme catalyzed reactions and so therefore we will assume in most 
cases v is equal to  
 
    v = k
2
E
0
S/K
m
+S 
 
Wherever we are talking of immobilized enzyme we must also clearly understand that 
these two terms k
2
 and K
m
 are denoted by prime indicating only that they are  
immobilized enzyme  parameters and not the soluble parameters.  
 
[Refer Slide Time: 8:10] 
 
Page 5


ENZYME SCIENCE AND ENGINEERING 
PROF. SUBHASH CHAND 
DEPT OF BIOCHEMICAL ENGG  
AND BIOTECHNOLOGY 
IIT DELHI 
 
LECTURE-20 
IDEALIZED ENZYME REACTOR PERFORMANCE 
 
 
So today we shall discuss the performance of enzyme catalyzed reactors, the reactors in 
which enzyme catalyzed reactions are supposed to take place. 
 
[Refer Slide Time: 1:15] 
 
 
 
You will recall earlier we had discussed some of the salient features of different reactor 
types ranging from batch reactors, batch stirred tank reactors to continuous stirred tank 
reactor or plug flow reactors and fluidized bed reactors. In fact some of the unusual 
reactor configurations which have been proposed to catalyze to be used for carrying out 
enzyme catalyzed reaction like hollow fiber reactors also arbitrarily fall into one of those 
categories of plug flow or CSTR which were discussed. We had also seen earlier the 
factors that affect the choice of different reactor types and to recall some of the factors  
that we had talked about the most important ones are listed here like form of the enzyme.   
 
[Refer Slide Time: 2:22] 
 
 
 
 
That is soluble, fibrous or particulate. The nature of the substrate whether it is soluble,  
particulate or colloidal, operational requirements; the control of pH in case an acid is 
produced or consumed in the reaction, reaction kinetics, carrier loading capacity,  
catalytic surface to reactor volume ratio, mass transfer characteristics, ease of catalyst 
replacement and regeneration, reactor cost and ease of fabrication. All these factors that I 
have listed here can be considered mainly under two categories. One category contains 
the factor which becomes fixed once an immobilized enzyme is prepared. That means  
the factors that are dictated by the immobilization enzyme preparation itself. For example 
form of the enzyme; the nature of the substrate is also fixed. Once the enzymatic reaction 
is defined the nature of substrate is fixed. The operational requirement is also fixed 
depending upon the nature of the enzyme catalyzed reaction whether an acid is produced 
or consumed  and pH control is a requirement. Similarly the catalytic surface to volume 
ratio is also fixed once an immobilized enzyme preparation is available. The carrier 
loading capacity also depends on the bulk density of the immobilized enzyme preparation  
and things like that. Ease of catalyst replacement and reactor cost and ease of fabrication  
are the factors which are dependent on the type of enzyme reactor. But the two important 
class of factors which I wanted to point out here is one is reaction kinetics and mass 
transfer characteristics. They are the ones which very heavily dictate the choice of the 
reactor; whether to go for a plug flow reactor or to go for a batch reactor or to go for a 
continuous stirred tank reactor are very heavily dictated by mass transfer requirements 
and reaction kinetics. I would once again point out that we have knowingly ignored heat 
transfer requirements assuming that for most of the enzyme catalyzed reaction the rate of 
reaction is very, very small and so heat transfer during the reaction is not a major critical 
factor. In certain cases if it is so, the heat transfer characteristics also must be taken into 
account. Last time I was taking we had also considered certain idealized reactor design 
parameter. That means for design of a particular type of reactor what kind of design 
parameters are important and you will recall that we had also hypothesized certain 
conditions or assumptions which define an idealized enzyme reactor system and the 
assumptions were that isothermal operation, ?H is very small, uniform enzyme 
distribution, plug flow behavior or completely back mix behavior, that means you have  
one of the extreme fluid dynamics in the reactor system. Either it is a plug flow motion  
or it is a completely back mix  and nothing in between. That is what we have assumed  
and there are no mass transfer  limitations and no significant partitioning of substrate 
between bulk and the carrier phase. 
 
[Refer Slide Time: 6:15] 
 
 
 
These are the basic assumptions which define our ideal enzyme reactor and the reactor  
design parameters. That means the parameter which we should define initially before we 
go on to design any particular reactor was “tau”, the space time in the reactor; initial 
substrate concentration, enzyme loading, E
0
. In the case of continuous operation, the 
information about the deactivation rate constant is also required, k
d
. Then the temperature 
of operation, pH control and these are the reaction conditions. Other design parameters 
are fractional conversion and productivity and reactor capacity.  
 
[Refer Slide Time: 7:08] 
 
 
That is the maximum reaction capacity assuming that the enzyme reaction follows a 
maximum reaction velocity, that is zero order profile and the productivity of that kind of 
the reactor will be your reaction capacity. Ultimately the performance will be dictated 
very heavily by enzyme kinetics. If we consider ….. (7:35) enzyme reactor we can safely 
say that Michaelis Menten kinetics provides us a basis for carrying out a universally 
accepted kinetics for enzyme catalyzed reactions and so therefore we will assume in most 
cases v is equal to  
 
    v = k
2
E
0
S/K
m
+S 
 
Wherever we are talking of immobilized enzyme we must also clearly understand that 
these two terms k
2
 and K
m
 are denoted by prime indicating only that they are  
immobilized enzyme  parameters and not the soluble parameters.  
 
[Refer Slide Time: 8:10] 
 
 
 
The first and probably the most simplest reactors is the batch reactors. The batch reactor 
can be used both for soluble enzyme as well as for immobilized enzyme. 
 
[Refer Slide Time: 8:35] 
 
 
 
You can carry out a batch reactor in a stirred mode or in a packed bed mode with using 
total recycle and on the right hand side is the characteristic profile of the reaction species 
that is the substrate and product with reference to time. The substrate concentration drops  
and ultimately depending upon the extent of conversion which we require, the product 
concentration increases. A typical profile; it can change from reaction to reaction. If the 
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