What is in-situ adsorption fermentation technology?

The so-called in-situ adsorption fermentation technology is a technology that removes products from the fermentation broth through adsorption separation during the fermentation process. It is essentially a coupling of the fermentation process and the adsorption separation process, with the purpose of removing the product inhibition effect.

The process of removing products during the reaction is called in situ Product Removal (ISPR). ISPR is achieved by coupling biological reactions with biological separation processes, that is, reaction-separation coupling.

After implementing ISPR technology, since the product is removed in time, the production process can be strengthened in the following three aspects:

(1) Overcome product inhibition and continuously synthesize the product at the maximum rate ;

(2) Minimize losses such as degradation or escape (such as volatilization) of the product during the conversion process;

(3) Reduce downstream separation steps.

ISPR technology can only target extracellular products because current biochemical separation technology cannot remove intracellular products without affecting cell viability.

In addition to removing the inhibition of target products, ISPR technology can also be used to remove by-products that have inhibitory effects on biochemical reactions in situ, such as ethanol, lactic acid, etc.

The basis for the design of the separation process in ISPR technology: the difference in physical and chemical properties between the target product and the environmental medium and the biocompatibility of the separation process (the separation process does not affect the activity of the biocatalyst).

Freeman et al. proposed five basic product characteristics to select an appropriate separation process, including:

(1) Volatility (boiling point less than 80 ℃);

(2) Hydrophobicity (log Poct>0.8);

(3) Molecular weight (less than 1000 Da);

(4) Chargeability;

(5) Affinity to specific substances, etc.

Five main separation technologies can be used to separate products in situ:

(1) Evaporation: including stripping, (vacuum) distillation and membrane-based pervaporation or permeation Membrane distillation (transmembrane distillation).

(2) Extraction: including water-organic two-phase, aqueous two-phase or supercritical liquid extraction. A membrane can be added to the interface between oil and water, that is, perstraction.

(3) Molecular osmosis: including dialysis, electrodialysis, reverse osmosis, nanofiltration, etc.

(4) Adsorption: including hydrophobic adsorption, affinity adsorption, ion exchange, etc.

(5) Precipitation: Charged products can combine with oppositely charged substances to produce precipitation and achieve separation, such as organic acids and calcium (lime) precipitation.