Insight

In industries including biotechnology, biopharmaceuticals, bioenergy, food and feed production, efficient recovery of intracellular compounds is a core link running through R&D and large-scale manufacturing. Intracellular products such as proteins, lipids and pigments determine the core value of bio-based products, and directly affect the functionality, stability and economic efficiency of final goods. Taking fermentation processes as an example, microorganisms including bacteria, yeasts and algae are widely applied to synthesize high-value intracellular substances. Algal protein has become an important raw material for animal feed and fortified functional foods; microbial lipids can be further converted into renewable biofuels; and various natural pigments and functional proteins show broad application prospects in pharmaceutical, food and cosmetic sectors. Nevertheless, most target products are enclosed within rigid cell walls and cell membranes. Achieving efficient and controllable cell disruption and product release while preserving the activity and structural integrity of target compounds has become an inevitable technical challenge for downstream processing.

Among diverse cell disruption technologies, high-pressure homogenization has evolved from its traditional applications in emulsification and homogenization into one of the pivotal techniques for intracellular compound extraction. During high-pressure homogenization, cell suspension passes through the narrow gap of a homogenizing valve under instantaneous high pressure. Combined effects of strong shear force, impact force and cavitation are generated to effectively rupture cell walls and membranes. As an entirely physical process, it requires no additional chemical reagents, unlike extraction methods relying on chemical solvents or biocatalysis. This eliminates risks posed by solvent residues to product safety and alleviates environmental impacts, complying with the trend of green and sustainable development in modern biomanufacturing.

Furthermore, high-pressure homogenization delivers prominent advantages in processing efficiency, scalability and process controllability. By adjusting homogenization pressure, cycle times and processing temperature, technicians can conduct targeted disruption on different microbial cells such as Gram-negative bacteria, Gram-positive bacteria, yeasts and algae. It enables full release of intracellular substances while minimizing damage to the structure and bioactivity of target products. This parameter-adjustable and result-predictable feature is particularly critical for industrial production. Cell disruption protocols established at laboratory scale can be smoothly scaled up to pilot and commercial production without fundamental modifications to the process flow.

Against the backdrop of rising requirements for yield, cost control and sustainability in biomanufacturing, high-pressure homogenization has been increasingly adopted for intracellular protein extraction, microbial lipid recovery and natural pigment release. It serves as an efficient alternative to conventional chemical and enzymatic methods, and is reshaping cell disruption — a seemingly basic yet indispensable downstream unit operation. The following sections elaborate on the working mechanism, key influencing factors and application performance across various cell systems, and explore how this technology can create greater value in modern bioprocessing.

High-pressure homogenization is a physical cell disruption method with a straightforward fundamental principle, yet it features highly integrated engineering design and energy utilization to inflict intense and controllable damage on cellular structures within an extremely short period. In a standard process, cell suspension is pressurized by a high-pressure pump and forced through a precisely engineered homogenizing valve with an ultra-narrow clearance. As the fluid rushes through the valve orifice and undergoes instant pressure relief, multiple powerful physical effects occur simultaneously.

First, dramatic pressure drop and rapid flow velocity variation generate substantial shear force, which acts as the primary driving force to break cell walls and membranes. Second, intense turbulence formed within the narrow channel triggers frequent collisions between cells, as well as between cells and equipment inner walls, further compromising cellular structural integrity. In addition, cavitation takes place in local low-pressure zones, characterized by the formation and instantaneous implosion of microbubbles. This process releases massive energy and imposes additional mechanical impact on cell walls. The combined actions of shear, impact and cavitation enable efficient disruption of various cell types without chemical reagents or biocatalysts.

Compared with other cell disruption approaches, high-pressure homogenizers excel in process controllability and excellent scalability. Regulation of homogenization pressure, cycle times and feed concentration allows flexible adaptation to bacteria, yeasts, algae and other cell types. It maximizes the release of intracellular proteins, lipids and pigments while maintaining the structural stability and bioactivity of target substances. Featuring stable continuous operation and easy industrial scale-up, this technology has become a highly competitive solution for cell disruption in downstream biomanufacturing workflows.

Numerous research findings and industrial practices have verified that rational selection of pressure settings and homogenization cycles enables high-efficiency rupture of cell walls and membranes, facilitating the release of proteins, lipids, pigments and other high-value intracellular products. This technology has achieved particularly mature applications in microalgae processing. In studies on Porphyridium disruption for extraction of intracellular B-phycoerythrin and functional proteins, the influences of operating pressure and cycle times on disruption efficiency were systematically investigated. The results indicated that at approximately 1000 bar, chloroplast membranes were only slightly damaged, and partial water-soluble proteins in the cytoplasm were released, while the recovery of chloroplast-localized B-phycoerythrin remained low. When the pressure exceeded 1000 bar, cell membranes and chloroplast membranes were thoroughly disrupted, leading to a remarkable increase in B-phycoerythrin release. This demonstrates that high-pressure homogenization not only realizes cell disruption, but also enables fine regulation on the release of different intracellular components via pressure adjustment, creating technical feasibility for targeted recovery of desired products.

Similar conclusions have been drawn from research on Chlorella kessleri, a microalga rich in proteins, carbohydrates and lipids with great potential as a functional raw material. Algal suspensions were processed under homogenization pressures of approximately 400 bar, 800 bar and 1200 bar respectively. The results showed that protein release increased significantly with elevated pressure and more homogenization cycles. This fully proves the high efficiency of high-pressure homogenization in treating microalgae with rigid cell walls, and confirms that pressure and cycle count are core parameters determining extraction performance.

Differentiated responses of various microalgae to high-pressure homogenization are closely related to the composition and thickness of their cell walls. For instance, red algae possess complex, thick cell walls composed of cellulose, xylan, mannan fibers and abundant matrix polysaccharides, which generally require higher operating pressure for effective disruption. By contrast, green algae such as Chlorella and Parachlorella have cell walls mainly consisting of cellulose and proteins, which are more vulnerable to mechanical forces. This explains why customized parameter design is necessary for different algal species in industrial applications.

Beyond microalgae, high-pressure homogenization is also well-suited for disruption of yeast and bacterial cells. Studies on Saccharomyces cerevisiae have proven that treatment at around 800 bar can effectively break its cell walls primarily composed of β-glucan and chitin, achieving efficient release of intracellular proteins. Some researches combine high-pressure homogenization with other physical pre-treatment methods: pre-weakening cell wall structures prior to homogenization reduces the required operating pressure while improving overall disruption efficiency. This strategy shows great potential for energy conservation and protection of heat-labile products. In industrial-scale scenarios, high-pressure homogenizers have been successfully applied to extract bio-based materials from recombinant Escherichia coli. These cases fully validate the application potential of this technology in continuous large-scale production.

Overall, the pressure required for high-pressure homogenization correlates positively with the mechanical strength of cell walls and membranes. Microalgae with the thickest cell walls generally demand the highest pressure, followed by yeasts, while bacteria with weaker mechanical resistance require the lowest pressure. Its advantages of adjustability, scalability and wide adaptability make high-pressure homogenization a core cell disruption technology across biopharmaceuticals, biofuel production, functional food manufacturing and other fields.

Despite its outstanding performance as an optimized cell disruption technique, high-pressure homogenization still faces technical and engineering challenges in practical production. These issues do not diminish its value, but call for systematic process optimization and integrated strategies to further tap its technical potential during process design and scale-up.

The first challenge lies in disruption selectivity. Essentially a non-selective physical treatment, high-pressure homogenization subjects cells to comprehensive rupture under pressures ranging from several hundred to over a thousand bar. Intracellular proteins, lipids, nucleic acids and cell debris are released simultaneously under combined shear force, turbulence and cavitation. While thorough product release improves total recovery yield, it increases the workload for subsequent clarification, filtration and purification. Instead of simply raising operating pressure, the practical solution is to enhance process controllability through refined design. Regulating homogenization pressure, cycle times and feed concentration can achieve semi-selective disruption to preferentially release cytoplasmic components and avoid excessive damage to organelles. In addition, coupling high-pressure homogenization with membrane filtration, centrifugation or continuous clarification systems removes large cell debris immediately after disruption, lowering the difficulty of downstream separation.

Excessive energy consumption is another prominent concern. Sustained high pressure and flow velocity lead to considerable power consumption during continuous industrial operation. This issue is negligible at laboratory scale, but directly raises operational costs and carbon footprint in pilot and commercial production. To address this problem, efforts are focused on cutting invalid energy loss. Combining mild pre-treatment such as enzymatic hydrolysis and osmotic stress can partially weaken cell wall structures beforehand, so that equivalent disruption efficiency can be achieved at reduced pressure (e.g., from 1200 bar down to 800 bar). Equipment optimization including improved valve seat design and flow channel layout, as well as the adoption of intelligent control systems, also helps reduce energy consumption per unit product while guaranteeing disruption efficiency.

Heat generation during processing is a major constraint for heat-labile products. Mechanical energy is rapidly converted into thermal energy under high pressure and repeated cycles, resulting in temperature rise of feedstock. This may cause denaturation and activity loss of enzymes, therapeutic proteins and other thermosensitive substances. Mature solutions include integrating on-line cooling modules such as heat exchangers into the system, and optimizing process routes to cut redundant cycles. Currently, the mainstream industrial strategy adopts moderate pressure with fewer cycles, which controls heat accumulation within a safe range while balancing disruption efficiency and product quality.

Moreover, techno-economic analysis and life cycle assessment should be implemented at the early stage of process development. Systematic evaluation of different pressure schemes, equipment configurations and operation modes in terms of cost, energy consumption and environmental impact enables enterprises to strike a rational balance between higher recovery yield and lower operational cost, and select the most sustainable technical route.

In summary, high-pressure homogenization has become one of the most representative physical cell disruption technologies for intracellular compound extraction. Compared with traditional methods using organic solvents or enzymatic reactions, this purely physical technique features high efficiency, continuous operability and excellent scalability. It reduces environmental burdens while enabling efficient recovery of proteins, lipids and other high-value products. Proven reliable across food, biotechnology and biopharmaceutical industries, this technology will gain broader applications with continuous equipment upgrading, digital and automated transformation, as well as synergistic integration with pre-treatment and separation technologies. Further improvements in product stability and overall cost reduction can be anticipated. As biomanufacturing advances toward greenization and large-scale production, high-pressure homogenization will play an increasingly vital supporting role in the extraction of intracellular compounds.