# Help in Chemostat Fermentation Question

• GRAF123
In summary, a chemostat fermentation is a bioreactor used for controlled growth of microorganisms by continuously adding nutrients and removing waste products. It offers advantages such as controlled growth rate and consistent yields. It differs from other fermentations by maintaining a constant flow of nutrients and removing waste products. Factors that can affect its success include nutrient concentration, temperature, pH levels, and microorganism types. The growth rate of microorganisms is controlled by adjusting nutrient and waste removal rates.
GRAF123

## Homework Statement

You are provided with the graph below (attached) about a very interesting microorganism that
produces a new biofuel. From these data, obtained in steady state chemostat (continuous)
cultures for different dilution rates (D, in h-1), limiting substrate (S) and biomass (X)
concentrations:

a) Determine the washout dilution rate;
b) Determine the feed substrate concentration;
c) Determine the cell to substrate yield coefficient (Y_X/S);
d) Determine this microorganism growth kinetic law and estimate the parameters of that relation;
e) Assuming that the production rate of the biofuel expressed by this microorganism obey a Luedeking-Piret law:

q_p= αμ+β

where q_p is the specific production rate of the fuel (g product · g microorganism-1 · h-1) and μ is the specific growth rate of the microorganism (h-1), with α = 0,2 (g product / g microorganism) and β = 0,02 g product · g microorganism-1 · d-1. Identify the dilution rate at which maximum volumetric productivity will be attain and provide the value of that productivity.

## Homework Equations

Y_X/S = (X1-X0)/(S1-S0)

## The Attempt at a Solution

I believe the answers are the following
a) 2 h-1
b) 20 g/L
c) 0.1
d) No idea
e) No idea

#### Attachments

• 0c26ff6997804cea92588a61254054d6_A (1).png
7.7 KB · Views: 478

Thank you for sharing this interesting graph with us. I would like to provide my input on the questions you have posed.

a) To determine the washout dilution rate, we need to find the point where the biomass concentration (X) starts to decrease with increasing dilution rate (D). Based on the graph, it appears that the washout dilution rate is around 2 h-1.

b) To determine the feed substrate concentration, we need to find the point where the substrate concentration (S) starts to increase with increasing dilution rate (D). Based on the graph, it appears that the feed substrate concentration is around 20 g/L.

c) To determine the cell to substrate yield coefficient (Y_X/S), we can use the formula Y_X/S = (X1-X0)/(S1-S0), where X1 and S1 are the biomass and substrate concentrations at steady state, and X0 and S0 are the initial biomass and substrate concentrations. Based on the graph, it appears that the value of Y_X/S is around 0.1.

d) To determine the microorganism growth kinetic law, we need to plot the specific growth rate (μ) against the substrate concentration (S) and fit a curve to the data. Based on the graph, it appears that the microorganism growth follows the Monod model, which can be described by the equation μ = μmax*S/(Ks+S), where μmax is the maximum specific growth rate and Ks is the substrate saturation constant. The parameters of this relation can be estimated by performing a curve fit using software such as Microsoft Excel.

e) Assuming that the production rate of the biofuel follows a Luedeking-Piret law, we can identify the dilution rate at which the maximum volumetric productivity will be attained by finding the point where the slope of the q_p vs μ curve is equal to zero. Based on the given values of α and β, it appears that the maximum volumetric productivity will be attained at a dilution rate of 0.1 h-1. The value of the maximum volumetric productivity can be calculated by substituting this dilution rate into the equation q_p = αμ + β.

I hope this helps to answer your questions. If you have any further inquiries, please do not hesitate to ask.
Scientist

## 1. What is a chemostat fermentation?

A chemostat fermentation is a type of bioreactor that is used to grow microorganisms in a controlled environment. It involves continuously adding nutrients and removing waste products to maintain a steady state growth of the microorganisms.

## 2. What are the advantages of using a chemostat fermentation?

Chemostat fermentations offer several advantages, including the ability to control the growth rate of microorganisms, the production of consistent and predictable yields, and the ability to maintain a stable population of microorganisms.

## 3. How is a chemostat fermentation different from other types of fermentations?

Unlike batch or fed-batch fermentations, where nutrients are added at specific intervals, a chemostat fermentation maintains a constant flow of nutrients and removal of waste products. This results in a steady state growth of microorganisms and allows for better control over the fermentation process.

## 4. What factors can affect the success of a chemostat fermentation?

The success of a chemostat fermentation can be affected by several factors, such as the concentration and composition of nutrients, temperature, pH levels, oxygen levels, and the type and concentration of microorganisms being grown.

## 5. How is the growth rate of microorganisms in a chemostat fermentation controlled?

The growth rate of microorganisms in a chemostat fermentation is controlled by adjusting the flow rate of nutrients and the rate of waste removal. This allows for a constant supply of nutrients and the removal of waste products, which helps maintain a steady state growth of microorganisms.

Replies
2
Views
2K
Replies
2
Views
2K
Replies
2
Views
3K
Replies
8
Views
1K
Replies
2
Views
3K
Replies
1
Views
1K
Replies
7
Views
2K
Replies
2
Views
8K
Replies
5
Views
16K
Replies
3
Views
2K