Question

Breakage of Yeast Cells in a Valve-Type Homogenizer For the breakage of Candida utilis yeast cells in a valve-type continuous homogenizer, it is known that the constants in Equation (3.3.2) are k = 5.91 × 10?4 MPa?a and a = 1.77 for the operating pressure range of 50 MPa < P < 125 MPa. It is desired that the extent of disruption be ?0.9. Plot how the number of passes varies with operating pressure over the pressure range of 50 to 125 MPa. What pressure range would you probably want to operate in? (Data from C. R. Engler and W. R. Campbell, “Disruption of Candida utilis cells in high pressure flow devices,” Biotechnol, Bioeng., vol. 23, p. 765, 1981.)

Short answer

The answer will depend on the specific relation given by Equation (3.3.2). By applying the extent of disruption \(\theta = 0.9\) in the equation, one can calculate the number of passes required for each pressure and subsequently make a plot. The optimal pressure range would minimize the number of passes needed to achieve the target disruption.

Step-by-step solution

Understand Equation (3.3.2)

Assuming the breakage of yeast cells follows the mathematical model given by Equation (3.3.2). By referring to the context and source given, we should understand that varying extents of disruption are achieved by varying the pressure and number of passes through the homogenizer.

Apply given extent of disruption

\(\theta = 0.9\) is the target extent of disruption that we aim to achieve. Considering this in the mathematical model, we should find a relation between the pressure and number of passes to achieve this disruption extent.

Calculate number of passes for different pressures

Using the established relation, calculate the number of passes required for each pressure within the range (50 MPa to 125 MPa) to achieve a disruption extent of \(\theta = 0.9\).

Plot and analyze

Plot the calculated number of passes versus pressure. Analyze the plot to determine the most efficient operating pressure range for achieving the desired extent of disruption. It is desirable to operate at pressures that yield the desired disruption with fewer passes.

Key concepts

Bioprocessing Engineering

Bioprocessing engineering is a specialized field that combines the principles of biology and engineering to develop efficient manufacturing processes for biological products. It involves using cells, such as yeast, bacteria, or mammalian cells, to produce substances like drugs, vaccines, or enzymes. In the context of our exercise dealing with the disruption of yeast cells, bioprocessing engineering covers the design and optimization of processes to break down the yeast cells effectively to release the desired intracellular products.

One critical aspect of bioprocessing engineering is understanding the kinetics of biological reactions and the influence of process parameters on these reactions. For example, in the disruption of yeast cells, engineers must consider the operating pressure, shear forces, cell concentration, and number of passes through equipment like a homogenizer. The aim is to maximize product yield and purity while minimizing costs and processing time, thereby contributing to a more efficient bioproduction workflow.

Homogenization Techniques

When it comes to breaking open yeast cells to extract valuable intracellular components, homogenization techniques play an essential role. Homogenization is a mechanical process that applies sheer force to disrupt cell walls, thereby releasing the contents. For yeast cells, this is typically achieved using high-pressure homogenizers, such as the valve-type continuous homogenizer mentioned in the exercise.

The process involves forcing the cell suspension through a narrow space where the cells are subjected to intense turbulence and shear forces, leading to cell disruption. The efficiency of homogenization is affected by several factors, including the operating pressure, the design of the homogenizer, the temperature, and the duration of the process. For students studying such bioprocessing engineering techniques, understanding how to optimize the homogenization process can be crucial for successful cell disruption.

Bioseparations

Bioseparations is a fundamental aspect of bioprocessing engineering that involves separating and purifying biological molecules from a mixture. After the cell disruption phase, the mixture consists of cell debris and the desired intracellular products. Effective separation techniques are required to isolate and purify these products for downstream applications.

Techniques such as centrifugation, filtration, and chromatography are commonly utilized in bioseparations. The choice of separation methods depends on factors such as the nature of the product, the degree of purity required, and the scale of the process. In our exercise scenario, after disrupting the yeast cells through homogenization, bioseparation techniques will be applied to recover the valuable components from the cell lysate.

Operating Pressure Optimization

Operation pressure optimization is an essential part of the homogenization process, where the aim is to find the balance between energy consumption and the cell disruption effectiveness. Operating at too high a pressure may lead to unnecessary energy costs, equipment strain, or even denatured products, whereas operating at too low a pressure could result in insufficient cell disruption.

In the textbook example provided, students are tasked with plotting the relationship between the number of passes and operating pressure to achieve 90% cell disruption. Through this, they can visualize the optimum pressure range that balances efficiency with resource consumption. Optimization techniques may include experimental designs to test different pressure settings or mathematical modeling to predict outcomes at various pressures, as suggested by Equation (3.3.2). Determining the ideal pressure range ensures the most efficient use of energy and time for the process, ultimately contributing to a cost-effective and sustainable bioprocessing operation.