Table 4.
Summary and comparison of different cell disruption and extraction methods.
| Method | Advantages | Disadvantages | Scalability | Remarks |
|---|---|---|---|---|
| CELL DISRUPTION METHODS | ||||
| Mechanical methods | Species independent, effective, no product contamination | |||
| Bead milling | Simple and efficient | Less efficient for bacteria | From lab to industrial scale | |
| Homogenization | Well-established in industry for other applications | Less suitable for filamentous fungi | To industrial scale | |
| Ultrasound | Continous operation possible | Heat generation and radical formation | Large scale not possible | |
| Physical methods | Limited scalability | |||
| Decompression | Gentle technique, minimizes chemical and physical stresses, and heat development | Less suitable for cell with tough cell wall, e.g., yeast, fungi and spores | Potentially larger scales | |
| Osmotic shock | Gentle technique, microorganims with cell walls are only weakened, not destroyed | High costs of additives | Smale scale only | |
| Microwaves | No drying necessary, quick, and inexpensive | Heat development, free radicals | Industrial scale for other applications | |
| Pulsed electrical field | Cell suspension has to be free of ions, cell disruption decreases gradually | Potentially larger scales | ||
| Drying | Easily scalable | Energy demands depend on method, potentially very energy intensive, yeasts and plant cell only poorly affected | Industrial scale for other applications | Crucial for effective downstream processing, conservative effect |
| Chemical methods | Contamination of the products, unsuitable for some applications | |||
| Solvents | Possibly combines cell disruption and extraction | Cell walls of most microorganisms are usually impermeable to most solvents, large amounts of solvents necessary | Industrial scale | |
| In situ transesterifica-tion | Combines cell disruption, lipid extraction and transesterification | Chemical modification of the product –> suitable for analytical means or biodiesel production | Easily scalable | |
| Enyzmes | Mild reaction conditions, substrate specific, environmental friendly, safe for food applications | Specific enzyme cocktails needed for every microorganism, possible very expensive | Large scale application possible but dependent on enzyme costs | |
| EXTRACTION METHODS | ||||
| Classical methods | Established procedures | Requires high amounts on solvents | Analytical to industrial scale | |
| Soxhlet | automated systems available, combinable with other methods | requires a lot of time and high amounts of solvents, not suitable for thermosensitive compounds | Analytical to large scale | |
| Bligh and Dyer | Requires less solvents than Folch methods, also wet samples extractable | The unmodified method underestimates significantly lipid content for samples with < 2% lipid content | Analytical to large scale | |
| Folch | Standard technique for total lipid extraction, very liable | Needs dry samples, higher amounts of solvents than Bligh and Dyer | Analytical to large scale | |
| Pressurized liquid extraction | Enhanced extraction performance due to enhanced solubility and mass transfer properties, 5-fold faster and requires 20-fold less solvent than Bligh and Dyer, automated | High investment costs | Potentially large scale | |
| Supercritical fluid extraction (CO2) | Extraction can be performed at low temperatures, enabling a gentle extraction of thermosensitive compounds, protection against oxidation, environmental friendly | Moisture content of the sample hinders extraction efficiency, high investment costs | Industrial scale for other applications | |