In the fermentation industry (such as the production of antibiotics, amino acids, organic acids, and enzyme preparations),wood based Activated carbon (WPAC), due to its unique structure and properties, has become a core adsorbent in decolorization processes.
Its primary function is to remove impurity pigments and improve product purity and stability. This can be broken down into the following dimensions:
Core Function: Efficient Adsorption of Impurity Pigments in Fermentation Broth
During the fermentation process, microbial metabolism produces two main types of pigments (impurities that need to be removed). Wood-based powdered Activated carbon removes these pigments through a physical adsorption mechanism, fulfilling its core decolorization function:
Adsorption of Pigments as Microbial Metabolism Byproducts
When microorganisms (such as bacteria and fungi) synthesize target products (such as penicillin and glutamic acid), they also produce natural pigments such as flavonoids, quinones, melanin, and carotene derivatives. These pigments can give the fermentation broth a dark yellow, brown, or black color, directly affecting the appearance and purity of downstream products (such as crystals and liquid preparations). Wood powder activated carbon's high surface area (typically 800-1500 m²/g) and abundant microporous/mesoporous structure allow these pigment molecules (mostly large organic compounds) to be firmly adsorbed within its pores through van der Waals forces and hydrophobic interactions, enabling separation from the target product.
Adsorbing Pigments from Residual and Degraded Raw Materials
Plant-derived pigments (such as chlorophyll and carotenoids) contained in fermentation media (e.g., corn steep liquor, soybean meal, and molasses), or Maillard reaction pigments (such as melanoidins, formed by the reaction of amino acids and reducing sugars) produced during high-temperature sterilization and long-term fermentation, can also contaminate the fermentation broth.
Wood powder activated carbon has a broad-spectrum adsorption capacity for these pigments. Its surface polar groups (such as hydroxyl and carboxyl groups) can bind to polar sites on pigment molecules, making it particularly efficient for fat-soluble pigments with poor water solubility. However, its adsorption rate for water-soluble target products (such as amino acids and organic acids) is extremely low, ensuring high recovery of the target product. Second, Auxiliary Effects: Simultaneously Improving Fermentation Broth Purity and Compatibility with Subsequent Processes
In addition to decolorization, wood powder activated carbon can also simultaneously remove other impurities from the fermentation broth, indirectly optimizing the production process. Specifically, it can:
Remove some large molecular impurities and reduce the burden on subsequent processes.
In addition to pigments, fermentation broths also contain large molecular impurities such as proteins, polysaccharides, and nucleic acid fragments. These impurities may not only combine with pigments to form complexes (exacerbating color issues), but can also cause clogging of downstream filtration systems (such as plate and frame filtration and membrane filtration) and contamination of ion exchange resins.
The mesoporous structure of wood powder activated carbon can adsorb some small proteins (molecular weight 1,000-10,000 Da) and polysaccharides, reducing the "cake resistance" of subsequent filtration, extending the life of the membrane or resin, and reducing production costs.
Absorbing some odorous substances and improving product sensory quality.
Fermentation may produce odorous substances such as volatile organic acids (such as butyric acid) and sulfur-containing compounds (such as hydrogen sulfide). This odor can affect the sensory quality of food-grade fermented products (such as citric acid and lactic acid) or pharmaceutical-grade products (such as antibiotics). The microporous structure of wood powder activated carbon strongly adsorbs small molecule odorants, simultaneously reducing the odor of the fermentation broth and improving the sensory quality of the final product (e.g., a mild sour flavor and lack of off-flavors).
Reducing the risk of fermentation broth oxidation and improving product stability
Some pigments (such as quinones) are oxidizing and can oxidize target products (such as vitamin C and certain enzymes) during storage or subsequent processing, leading to product degradation and decreased potency.
While wood powder Activated carbon adsorbs pigments, it also removes these "oxidation promoters," indirectly improving the chemical stability of the fermentation broth and extending the shelf life of subsequent products.
Performance Advantages for the Fermentation Industry: Why Choose Wood Powder Activated Carbon?
Compared to coal-based and coconut shell-based activated carbon, wood powder activated carbon offers more targeted advantages in fermentation decolorization, further enhancing its effectiveness:
Pore size distribution is more suitable for pigment molecules: Wood activated carbon is primarily mesopore (2-50 nm), while pigment molecules in fermentation broth are mostly medium- to large-sized molecules (1-10 nm in diameter). The mesoporous structure efficiently "captures" these molecules, preventing the adsorption of small target molecules (coal-based activated carbon has a high micropore content, which easily adsorbs small target molecules and reduces recovery).
Surface polarity is milder: After activation, wood activated carbon has a moderate content of surface polar groups (hydroxyl and carboxyl groups), resulting in strong adsorption of less polar pigment molecules and weaker adsorption of more polar target products (such as amino acids and organic acids), achieving "targeted decolorization while retaining the product." Powdered form is well-suited to mixing processes: Fermentation broths are mostly liquid, and wood powdered activated carbon (typically 100-300 mesh) easily disperses in agitated systems. It has a large contact area with the fermentation broth and a rapid adsorption rate (compared to granular activated carbon, it eliminates the need for slow intrapore diffusion, shortening decolorization time by 30%-50%). It can also be quickly separated by filtration without compromising production efficiency.
Cost control: Wood raw materials are widely available (such as fir, pine, and eucalyptus), and production costs are lower than coconut shell activated carbon. It is suitable for large-scale, high-load decolorization needs in the fermentation industry (for example, antibiotic fermentation, where a single decolorization batch requires several tons of activated carbon).
But the currently widely used wood-based powdered activated carbon has significant shortcomings:
1. Non-renewable: It is discarded after a single use, and its annual procurement cost increases by 8%-12%;
2. Solid waste problem: Every ton of wood-based charcoal produces 0.3 tons of hazardous waste residue, resulting in high disposal costs and significant environmental risks;
3. Efficiency bottleneck: Decolorization rates generally remain around 95%, with limited room for improvement in light transmittance;
4. Manual dependency: The mixing tank requires dedicated personnel, and batch stability is subject to human factors.
Technological innovation: the industrial value of coal-based granular activated carbon
Compared to traditional wood charcoal, coal-based granular Activated carbon (0.8-5mm) is transforming industry practices through three core breakthroughs:
1. Recyclable Material Science
- Experimental data: After five thermal regeneration cycles, adsorption efficiency remains above 98%;
2. Natural Compatibility with Automation Systems
- The fluidized bed/moving bed process enables fully automated operation, with a DCS system monitoring adsorption saturation in real time;
3. Closed-Loop Environmental Protection
- The regeneration process generates no solid waste, and solvent recovery rates exceed 85%;
- Policy Compliance: It complies with the industrial clean production requirements of the Solid Waste Law.
Physical Advantages:
- Hard particle structure (0.8-5mm) withstands fluid impact and prevents pulverization;
- Specific pore size distribution provides a larger specific surface area (>1000m²/g).
System Compatibility:
- Compatible with existing fluidized bed/moving bed equipment, requiring minimal retrofitting;
- Wide temperature and pH tolerance range (2-11pH, <150°C).
