Monod kinetics to determine microorganism in bioreactors

Summary

In this video, Mules Peters explains Monod Kinetics, the most commonly used model for predicting microorganism growth. He walks through the key stages of microbial growth, including lag, log, stationary, and death phases, while focusing on the stationary phase for modeling. The video covers the Monod equation, its assumptions, and limitations, and emphasizes the role of substrate concentration and biomass in bioreactor systems. Practical applications, including the importance of secondary product formation and the need for mass balance equations, are discussed, with a focus on continuous reactors and optimization strategies for various microbial processes.

Takeaways

• 😀 Monod Kinetics is the most commonly used model to predict microorganism growth, developed by a French scientist who won the Nobel Prize in Medicine in 1965.
• 😀 The Monod equation is an empirical model, often compared to enzyme kinetics for microorganism growth.
• 😀 Microorganism growth follows four stages: lag phase, log phase (exponential growth), stationary phase (balanced growth), and death phase (decline in cell number).
• 😀 The stationary phase is crucial for the Monod model, where the rate of cell division equals the rate of cell death, indicating balanced growth.
• 😀 The Monod equation includes key parameters like maximum growth rate (μ_max), substrate concentration (S), and half-maximal growth rate (K_s).
• 😀 In the Monod model, a single limiting substrate is typically assumed, though real-life systems may require adjustments for multiple nutrients.
• 😀 Key assumptions in Monod kinetics: balanced growth, no inhibition, and Newtonian fluid behavior, which may need modification in viscous systems.
• 😀 Mass balance equations for bioreactors take into account both substrate (S) and biomass (X) flows in and out, particularly for continuous systems.
• 😀 The biomass formation rate in Monod kinetics is influenced by the yield coefficient (Y), substrate utilization rate (R_S), and cell death rate (K_d).
• 😀 For product formation, such as pharmaceuticals or biomethane, secondary metabolic products must be considered in the mass balance alongside biomass growth.
• 😀 Solving Monod kinetics equations can be complex but is simplified by assuming maximum growth rates and no inhibition, with tools like MATLAB aiding the process.

Q & A

What is the Monod Kinetics model used for?

The Monod Kinetics model is used to predict the growth of microorganisms, particularly in environments like bioreactors. It is commonly used to model the relationship between microorganism growth and substrate concentration.

Who is the Monod Kinetics model named after?

The Monod Kinetics model is named after a French scientist, Jacques Monod, who won the Nobel Prize in Medicine in 1965 for his work on enzyme kinetics.

What are the four main stages of microorganism growth?

The four main stages of microorganism growth are the lag phase, log phase (exponential growth), stationary phase (balance between cell division and death), and death (or decline) phase (exponential decrease in living cells).

What happens during the stationary phase of microorganism growth?

During the stationary phase, the rate of cell division is roughly equal to the rate of cell death, leading to a balance in the number of live and dead cells.

What does the Monod equation take into account in terms of microorganism growth?

The Monod equation incorporates the maximum growth rate (μmax), the concentration of limiting substrates (S), and the half-velocity constant (Ks) that determines when the substrate concentration is half of the maximum growth rate.

Why might Monod kinetics not fully represent real-life conditions?

Monod kinetics assumes a single limiting substrate and balanced growth, which might not be accurate in real-life scenarios where multiple limiting factors or inhibitions (like pH or temperature changes) can affect growth.

How does substrate concentration affect microorganism growth according to Monod kinetics?

According to Monod kinetics, as the substrate concentration increases, the specific growth rate of microorganisms also increases, but eventually, this rate will reach a maximum value (μmax) due to substrate limitations.

What is the importance of making assumptions in the Monod model?

Assumptions are important in simplifying complex biological systems to allow for modeling. For example, the assumption of balanced growth and no inhibition helps in using Monod kinetics to predict growth rates under specific conditions.

How do bioreactors impact the application of Monod kinetics?

In bioreactors, Monod kinetics is applied to model microorganism growth under controlled conditions where nutrient availability and other factors like oxygen or pH levels can be manipulated. However, real-life bioreactors may involve multiple substrates or limitations that complicate the model.

What is the role of secondary metabolites in bioreactor processes?

In many bioreactor processes, the primary focus is not just on biomass (e.g., yeast or bacteria), but on the secondary metabolites that microorganisms produce, such as pharmaceutical products or biomethane. The production of these metabolites requires separate mass balances.