Fermentation technology has gone beyond traditional brewing and vinegar making and become a core pillar of modern bioengineering. In contemporary bio-industry, the solid-liquid separation of fermentation broth refers to the process of precisely removing suspended solid particles and impurities (such as microbial cells, cells, cell debris, proteins, and their aggregates) using physical methods like filtration and centrifugation. Among these, filtration, as a fundamental unit operation, directly determines the product quality of downstream processes with its efficiency and precision.
Factors Affecting Filtration in Fermentation Engineering
▶ Working Principle
Broadly speaking, fermentation engineering consists mainly of upstream processing, fermentation engineering (midstream), and downstream processing. Downstream processing, which involves the separation and purifica tion of target products from the fermentation broth, often determines the final product’s quality and cost. It primarily includes four stages:
Depending on whether the target product is intracellular or extracellular, the main objectives of solid-liquid separation for fermentation broth are typically twofold:
Separation & Collection: To obtain cells (mycelium) containing the target product or clarified fermentation broth.
Impurity Removal: To remove solid impurities from the fermentation broth, laying the foundation for subsequent purification.
In filtration technology, the shape, size and density of solid particles determine the retention efficiency, settling velocity, and filtrate clarity. However, in biological fermentation, filtration rate is influenced not only by cell size but also by conditions such as medium composition, antifoam agents, fermentation duration, and pre-treatment. Among these, the characteristics of the microbial strain and the viscosity of the fermentation broth have the most significant impact.
▶ Fluid Dynamics Analysis
From a fluid dynamics perspective, we can get a classical filtration differential equation (Ruth’s equation)
Where:
q is the filtrate volume per unit area (m3/m2)
τ is filtration time (s)
dq/dτ is filtration rate (m/s)
Δpis filtration pressure differential (Pa)
r₀is specific resistance of the filter cake (1/m²)
x₀is volume of filter cake per unit volume of filtrate (m³/m³)
μis filtrate viscosity (Pa·s)
Ris filter medium resistance (1/m)
Since the relationship between filter cake volume and filtrate volume is,
Where:
V_eis filter cake volume (m³)
Vis filtrate volume (m³)
Fis filtration area (m²)
lis filter cake thickness (m),
a more intuitive formula for filtration rate can be derived:
This formula clearly reveals the influence of various parameters on filtration rate:
✓ Filtration rate is directly proportional to filtration area (F) and filtration pressure differential (Δp).
✓ Filtration rate is inversely proportional to filtrate viscosity (μ).
✓ Filtration rate decreases with higher specific cake resistance (r₀) and thicker filter cake (l).
However, due to the unique nature of biological material, real-world industrial production is far more complex than this ideal model.
The Complexity and Challenges of Fermentation Broth Filtration and Separation
Fermentation broths are often high-viscosity, high-solid-content systems. Simple physical separation frequently faces challenges such as low efficiency, low yield, and significant loss of bioactivity.
▶ Extreme Complexity of the Material System
✗ Solid Characteristics: Non-rigid particles like microbial cells are highly compressible. Under pressure, their porosity decreases, leading to a drastic decline in flow rate.
✗ Liquid Phase Characteristics: The complex composition of the filtrate, with fluctuations in viscosity, pH, etc, directly affects filtration performance.
✗ Surface Interactions: Charged biological macromolecules are prone to non-specific adsorption, causing product loss and filter media fouling.
▶ Stringent Requirements for Product Stability and Activity Preservation
✗ Shear Sensitivity: Enzymes, antibodies, etc, are sensitive to shear forces. High shear stress can easily cause denaturation and loss of activity.
✗ Temperature and pH Sensitivity: The narrow operating window limits the application of conventional methods like heating to reduce viscosity or cleaning with strong acids/bases.
▶ Mandatory Requirements for Sterile and Hygienic Design
✗ Endotoxin Control: Equipment surfaces must be smooth and free of dead legs, resistant to cleaning and sterilization, to control endotoxin levels.
✗ Cross-Contamination Prevention: Equipment must be capable of thorough cleaning and sanitization to eliminate residual contamination between bathes.
Shinkai’s Solution: High-Performance Biological Fermentation Filtration Technology
Shinkai addresses these challenges from two fronts: “equipment structure upgrade” and “process parameter optimization.” We enhance processing capacity by increasing filtration area, introducing dynamic/static cross-flow filtration, and implementing automated controls. Furthermore, through precise selection and process design, we solve problems related to high viscosity, clogging propensity, and activity preservation.
▶ Precise Selection and Equipment Upgrade
Shinkai prefers high-performance sintered metal filter media over traditional polymeric media.
✓ Overcomes Clogging and Adsorption: Utilizes the rigid surface and precise pores of metal materials to prevent cake embedding, reduce non-specific adsorption, and improve yield.
✓ High-temperature Sterilization Design: Employs high-temperature resistant materials, supporting repeated steam sterilization, breaking the temperature limitations of traditional filter media.
▶ Process Optimization and Operating Strategies
✓ Low-Shear Fluid Design: Optimizes piping and pumping components to reduce transfer shear forces and protect bioactivity.
✓ Dynamic Filtration Mode: Supports cross-flow filtration and backwashing. Utilizes tangential flow to delay cake buildup, extending cycle time and enabling online filter element regeneration.
▶ Shinkai Core Performance Specifications
✓ Exceptional Precision: Offers a wide precision range from 0.1 to 100 μm, ensuring 100% inception of solid particles with zero leakage.
✓ High-Temperature Resistance: Withstand extreme temperatures (up to 900℃), meeting requirements for high-temperature sterilization and extreme operating conditions.
✓ High Strength and Pressure Resistance: Withstands pressures up to 50 bar (forward), suitable for high differential pressure environments.
✓ Strong Corrosion Resistance: Resistant to solvents, acids and alkalis, compatible with various cleaning agents and process fluids.
✓ Extended Service Life: Excellent backwash regeneration effectiveness, with filter element lifespan up to 10 years, reducing long-term operational costs.
✓ Compliance Assurance: Strictly adheres to GMP standards, making it an ideal choice for solid-liquid separation in biopharmaceuticals and fermentation industries.
Nanjing Shinkai is committed to providing precise and reliable core components for the fermentation industry through high-standard biological fermentation filtration technology, helping your industrial systems achieve safer and more efficient operation. If your company is facing challenges in bioprocess fermentation filtration, please feel free to contact us. Let’s work together to explore the optimal solution.
www.shinkaifilter.com
Email: sales01@shinkaifilter.com
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