Algal Cultivation – Methods, Factors, Feature, Types, Uses

Algal cultivation is the process of growing microalgae. These are very small photosynthetic organisms. They use light, water and carbon dioxide. Then they grow and multiply.

During this process algal cells produce many useful substances. Protein, lipid and carbohydrate are produced. These are stored in the algal biomass.

Microalgae can be grown in freshwater. They can also grow in sea water and waste water. So algal cultivation does not need good agricultural land. This is a useful point of this process.

For algal cultivation some conditions are needed. Light, temperature, pH, CO₂, nitrogen and phosphorus are important. Mixing is also done. Aeration is done to give gas exchange and movement of medium.

Light is needed for photosynthesis. But excess light may damage the cells. Temperature is also maintained. Most algae grow well in about 15°C-30°C.

Algae are grown in open raceway ponds and closed photobioreactors. Open pond is cheaper. But contamination may occur. Photobioreactor is costly but condition can be controlled.

Cultivation may be batch, continuous or semi-continuous type. In batch culture, nutrients are given at first. In continuous culture, fresh medium is supplied continuously. In semi-continuous culture, some culture is removed and fresh medium is added.

The algal biomass is harvested after growth. It is used for biofuel, wastewater treatment and carbon capture. It is also used in food, animal feed, cosmetics and medicine.

Algae give omega-3 fatty acids, vegan protein, astaxanthin and beta-carotene. Thus algal cultivation is important for useful production and environmental work.

Algal Cultivation Methods

Algal cultivation methods are divided into two main groups. One is physical cultivation systems and other is operational feeding and harvesting modes.

A. Physical Cultivation Systems

1. Open systems or open ponds
   In this method, algae are grown in open ponds or natural water bodies. Circular ponds and long raceway ponds are used. It is the oldest and simple method. It is also low cost method for mass production. But large land area is required. Water loss by evaporation may occur. Contamination by other algae, predators and bad weather condition is common.
2. Closed photobioreactors (PBRs)
   In this method, algae are grown in closed transparent vessels. These are made up of glass or plastic. Tubular, flat-panel and bag type photobioreactors are used. In this system, light, pH, temperature and nutrients can be controlled. Biomass production is high. Contamination is less. But it is costly to build, operate and maintain.
3. Hybrid systems
   This system uses both closed and open cultivation. First clean and dense culture is grown in closed PBR. Then this culture is transferred into open raceway pond. It gives pure starting culture. After that, mass production becomes cheaper in open pond. It is also used for stress induction in some algae.
4. Adherent biofilm systems
   In this method, microalgae are not freely suspended in water. They grow attached on solid surface or membrane. The biomass forms a layer on the surface. Water use is less in this system. Harvesting is also easy. The algal biomass is removed by scraping from the surface.
5. Immobilization
   In this method, microalgal cells are trapped inside gel globules. Calcium alginate is commonly used for this. The cells remain protected inside the gel. Harvesting is very easy. The beads can be separated by simple sieving or precipitation.

B. Operational Feeding and Harvesting Modes

1. Batch cultivation
   In this method, all nutrients are added at the beginning. Algae grow in the same medium. When nutrients become exhausted, growth stops. After this, whole culture is harvested at one time. It is simple method but continuous production is not obtained.
2. Fed-batch cultivation
   This method starts like batch culture. But extra nutrients are added slowly during growth. This prevents starvation of algal cells. Due to this, the growth phase is prolonged. Cell density becomes high before final harvesting.
3. Continuous cultivation
   In this method, fresh nutrient medium is added continuously. At the same time, equal amount of culture is removed. The culture volume remains constant. It gives steady state condition. Cell density remains almost constant for long period.
4. Semi-continuous cultivation
   In this method, a fixed part of the culture is removed after some interval. Then same amount of fresh medium is added. It prevents the culture from becoming old or stagnant. Algae again enter active growth stage. It is also called repeated fed-batch cultivation.

1. Open System Algal Cultivation Methods

Open ponds are the oldest and simple method for outdoor cultivation of microalgae. It is used for large scale production of algal biomass. This system is low cost and easy to operate.

What They Are and How They Work

• In this method, microalgae are grown in open water system. It is used from around 1950s. It is used when large amount of algal biomass is needed with less cost.
• The system may be natural water body or artificial outdoor basin. Circular ponds, tanks and long raceway channels are used. Raceway pond is common because water can be circulated easily.
• The pond is usually shallow. The depth is about 15-30 cm. This shallow depth helps sunlight to enter the water and reach the algal cells.
• Paddle wheels are used for mixing the culture. They mix water, nutrients and algal cells. This prevents settling of algae at the bottom and also helps in harvesting.

Advantages

• Open pond has simple structure. So construction cost is low. Maintenance and operation are also cheaper than closed system.
• Natural sunlight is used in this method. Only little energy is needed to run the paddle wheels. So energy requirement is low.
• Municipal or agricultural wastewater can be used as medium. Algae use nutrients present in wastewater. At the same time, wastewater treatment also takes place.

Disadvantages

• The pond is open to the environment. So other organisms can enter very easily. Other algae, bacteria, rotifers and amoebae may grow and reduce the culture.
• Temperature and weather cannot be controlled. Rain may dilute the culture. Strong sunlight, wind and bad weather may affect algal growth. Water loss by evaporation is also high.
• Biomass production is lower than closed system. Carbon dioxide supply is poor. Self-shading also occurs, where upper algal cells block light and lower cells get less light.
• Large land area is required for commercial production. More water is also needed. So this system is difficult where land and water are limited.

2. Closed System Algal Cultivation Techniques

Closed photobioreactors (PBRs) are closed artificial systems used for cultivation of microalgae. In this system, algal culture is not directly exposed to outside environment. So growth condition can be controlled in better way.

What They Are and How They Work

• In closed system, microalgae are grown inside enclosed vessels. These vessels are called photobioreactors. They are used for growing algae in controlled and almost sterile condition.
• The reactor is made up of transparent materials. Glass, plexiglass or flexible plastic are used. These materials allow light to enter inside the culture.
• The shape of PBRs may be different. They may be vertical or horizontal tubular type. They may be flat-panel type, rectangular tank type or helical coil type.
• The algal culture remains separated from outside air. So contamination is reduced. Light, temperature, pH, carbon dioxide and nutrients can be monitored and controlled.

Advantages

• Biomass production is high in closed system. Light path is short and surface area is more. So light absorption becomes better. Growth rate and cell density are higher than open ponds.
• Contamination is less because the system is closed. Other algae, bacteria, pathogens and grazing organisms cannot enter easily. So pure culture can be maintained.
• Water loss by evaporation is very low. Carbon dioxide supply is also more efficient. Gas exchange can be controlled according to need of the culture.
• The quality of biomass is more uniform. Specific and sensitive algal species can be grown. It is useful for production of high value products in pharmaceutical and nutraceutical industries.

Disadvantages

• The cost of closed system is very high. Construction of PBRs needs more money. Pumps, mixing system, cooling system and control system also increase the operating cost.
• Oxygen may accumulate inside the reactor. During photosynthesis, algae release oxygen. If oxygen becomes high, it inhibits algal growth. So degassing arrangement is needed.
• Overheating may occur in closed system. Direct sunlight can increase the temperature inside reactor. Cooling system is required to maintain proper temperature.
• Bio-fouling is another problem. Algal cells may stick on the inner wall of reactor. It blocks light penetration. Cleaning becomes difficult.
• Large scale production is difficult. It is costly and technically complex. So use of PBRs for very large biofuel production is limited.

3. Hybrid Systems

Hybrid systems are used for cultivation of microalgae by using both closed and open system. In this method, photobioreactor (PBR) and open raceway pond are used together. It is made to reduce the high cost of closed system and contamination problem of open system.

What They Are and How They Work

• In hybrid system, cultivation is done in two phases. First phase is done in closed PBR. Second phase is done in open raceway pond.
• In first phase, algae are grown in sterile and controlled condition. Nutrients are supplied properly. In this phase, the aim is to produce healthy, dense and contamination free algal culture.
• In second phase, the culture is transferred into open raceway pond. Here some nutrients like nitrogen may be limited. This stress condition makes algae to store useful substances.
• Under stress, algae may accumulate lipids or pigments like astaxanthin. Lipids are useful for biofuel production. Astaxanthin is useful as valuable pigment.

Advantages

• Contamination risk is reduced in this system. The algal culture remains in open pond for short time only. So predators, bacteria and other algae get less time to destroy the culture.
• Productivity is higher than using only open pond. Biomass growth is done first in controlled condition. Then stress is given separately for accumulation of useful compounds.
• This system gives balance between cost and quality. It is cheaper than full closed PBR system. But it gives better and more uniform biomass than simple open pond.

Disadvantages

• Large land area is still needed. This is because open raceway pond is used in second phase. So commercial production needs much space.
• During open pond phase, evaporation occurs. Water loss is present. Carbon dioxide transfer is also less efficient than fully closed system.
• The cost is moderate. It is cheaper than only PBR system. But it is costlier than only open pond system because both types of units are needed.

4. Adherent Biofilm Systems

Adherent biofilm system is a method of microalgae cultivation. In this method, algae are not grown freely suspended in much amount of water. They grow attached on solid surface or membrane.

What They Are and How They Work

• In this system, microalgae grow on cheap and reusable support material. The support may be solid surface or membrane. The algal cells remain attached and form a biofilm.
• Large volume of liquid medium is not used. Only enough water is given to keep the surface moist. The algae grow as dense layer on the surface.
• The biofilm becomes concentrated on the support. So the biomass is already collected in one place. This makes harvesting more easy.

Advantages

• This system saves much water. Less water is needed because algae grow on moist surface. About 17 tons of water may produce 1 ton biomass in biofilm system. But suspended culture may need about 200 tons water.
• Harvesting is simple. The algal biomass can be removed by scraping. Centrifugation and chemical flocculation are not needed. Extra dehydration is also less required.
• Light penetration is better in this method. Algae are exposed on the surface. So cells get more light. Biomass productivity may increase up to about 30% than suspended culture.
• The system needs less space. The support materials are cheap and reusable. Capital and operation cost is low to moderate.
• Water loss by evaporation is low. Contamination risk is also less than many open suspended systems.

Disadvantages

• Sometimes biomass may detach from the surface. It may be washed away from the support. If wastewater is used, attached pollutants may again enter into water.
• Support material may be damaged with time. If metal surfaces are used, algal and microbial products may cause corrosion. Discolouration of the surface may also occur.

5. Immobilization

Immobilization is an alternative method of microalgae cultivation. In this method, algal cells are not freely suspended in liquid medium. The cells are trapped inside gel like globules.

What It Is and How It Works

• In immobilization, microalgae cells are physically enclosed in gel beads. The cells remain alive inside the gel. They continue growth and metabolic activity.
• Calcium alginate is commonly used for trapping the cells. It is obtained from brown marine algae. Calcium acts as binding agent and makes solid gel body around the cells.
• Immobilized microalgae are usually grown in closed columns. Fixed bed or fluidized bed system may be used. The medium passes through the immobilized algal beads.

Advantages and Applications

• Harvesting is very easy in this method. The algal cells are already present inside solid gel beads. So they can be separated by simple sieving or precipitation.
• This method is useful in wastewater treatment. Immobilized microalgae remove pollutants in short time. So it is important in bioremediation.
• It can remove ammonium nitrogen and phosphorus from wastewater. It is also used for removing pigments from textile industry effluents. Thus the method is useful for cleaning polluted water.

6. Batch Cultivation

Batch cultivation is a cultivation method where all nutrients are added at the beginning. After starting the culture, no fresh nutrient medium is added. The algae grow in the same medium until nutrients become exhausted.

What It Is and How It Works

• In this method, the culture vessel is filled with medium, nutrients and algal inoculum. All required substrates are supplied at first only. After this, the culture is allowed to grow.
• During cultivation, extra nutrients are not added. Only gases, acid or alkali may be added for maintaining the condition. pH, aeration and gas supply are controlled when needed.
• The algal cells use the nutrients present in the medium. After some time, nutrient level becomes low. Then the cells enter stationary phase.
• At the end, the whole culture is harvested at one time. The biomass is collected after the batch cycle is completed.

Advantages

• This method is simple and convenient. It is easy to operate and manage. It is useful in early experimental work, like testing of medium and study of algal strain.
• Contamination risk is less. Fresh medium is not added again and again. So outside organisms get less chance to enter.
• The process has a clear starting and ending point. So each batch can be recorded separately. This gives good traceability of materials and product.
• The time of one batch is relatively short. One cultivation cycle can be completed and then next batch can be started.

Disadvantages

• Productivity is lower than continuous method. The algae remain in active growth phase for limited time only. Carbon source, oxygen or nutrients become limiting after some period.
• Toxic metabolic products may collect in the medium. These substances may inhibit enzymes and reduce algal growth.
• Production is not continuous. After every batch, the vessel has to be emptied, cleaned and sterilized. This causes time loss and interruption in production.

7. Fed-Batch Cultivation

Fed-batch cultivation is a cultivation method which starts like batch culture. But in this method, fresh nutrients are added slowly during the growth period. The culture is not removed during feeding time.

What It Is and How It Works

• In this method, the culture is first started with medium and algal inoculum. After starting, nutrients or substrates are added in small amount at different time. So the culture does not face sudden nutrient shortage.
• The feeding may be done manually or by automatic system. Nutrients may be added slowly in linear or exponential way. Sometimes feeding is started when biomass becomes high or when a nutrient becomes low.
• During the feeding phase, culture medium and cells are not removed. The volume of culture may increase. The whole culture is harvested only at the end of the process.

Advantages

• This method gives high cell density. Nutrients are supplied continuously or step by step. So nutrient depletion is prevented. At the same time, too much nutrient at beginning is avoided, which may inhibit growth.
• The exponential growth phase becomes longer. The algae remain active for more time. So more biomass and product can be obtained than simple batch method.
• Feeding pattern can be controlled according to need. It can change the metabolism of culture. It is useful for production of selected products like recombinant proteins or antibiotics.
• This method is widely used in biotechnology industries. It is flexible and gives good yield. So it is considered important in bioprocess production.

Disadvantages

• Toxic by-products may collect in the medium. As culture is not removed during the run, inhibitory substances remain inside. These may reduce growth after some time.
• Contamination chance is more than batch culture. Fresh feed is added again and again. So outside organisms may enter if sterility is not maintained.
• At the end, cell density becomes very high. Harvesting and downstream processing become difficult. More biomass and product need proper handling.
• Management of the process is complex. Feeding rate must be controlled carefully. If feed is more, overfeeding occurs. If feed is less, underfeeding occurs and growth becomes slow.

8. Continuous Cultivation

Continuous cultivation is a cultivation method where fresh nutrient medium is added continuously. At the same time, same amount of culture is removed. So the volume of culture remains same.

What It Is and How It Works

• In this method, the bioreactor receives fresh medium all the time. The algal cells and used medium are also removed at the same rate. This keeps the culture in continuous growth.
• Feeding and harvesting occur together. So the culture does not become old very quickly. The condition inside the vessel remains almost constant. This condition is called steady-state.
• In continuous cultivation, cell density, nutrients and growth rate are maintained for long time. The algae remain in active physiological condition.
• There are some common types of continuous systems. Chemostat is controlled by one growth limiting nutrient. Turbidostat is controlled by cell density. In perfusion culture, cells are retained or recycled and cell free medium is removed.

Advantages

• This method gives high productivity. The cells remain in growing condition for long time. So biomass and product formation becomes continuous.
• Waste materials are removed with the harvested medium. So toxic metabolic products do not accumulate much. This reduces growth inhibition.
• There is less stopping of the process. The culture can run for many days or even months. Cleaning, sterilizing and starting again are not needed again and again.
• Product quality may become more uniform. This is because the culture condition is kept constant for long period.

Disadvantages

• Contamination risk is high. The process runs for long time. Fresh medium is added continuously and culture is removed continuously. So outside organisms may enter easily.
• Genetic change may also occur during long cultivation. The culture may not remain same if it is continued for long period.
• Operation is more complex than batch culture. Feed rate and harvest rate must be balanced properly. If harvesting is more, culture may be washed out.
• Traceability is poor. The product is not divided into clear batches. The culture is continuously mixed and harvested, so quality control becomes difficult.

9. Semi-Continuous or Repeated Fed-Batch Cultivation

Semi-continuous cultivation is a cultivation method between fed-batch and continuous cultivation. It is also called repeated fed-batch cultivation. In this method, some part of culture is harvested and fresh medium is added again.

What It Is and How It Works

• In this method, the culture is first started like normal batch culture. The algae grow in the medium and biomass increases.
• When the culture reaches high biomass density, some part of the culture is removed. It is done before the culture enters stationary phase. Generally about 25% to 75% of the culture volume is harvested.
• The removed volume is replaced by fresh nutrient medium. The remaining algal cells stay inside the bioreactor. These cells act as inoculum for next cycle.
• This process is repeated again and again. So the culture remains in active growth condition. It helps to maintain repeated exponential growth.

Advantages

• Regular removal of medium prevents toxic substances from accumulating. Waste metabolites are removed with harvested culture. So growth inhibition becomes less.
• Biomass yield remains more constant in this method. The culture density is not allowed to become too high. So oxygen transfer, light supply and cooling problem are reduced.
• The biochemical composition of algal cells can be controlled. Harvesting time and dilution amount can be adjusted. It helps to maintain stable growth rate and product quality.
• Light penetration becomes better after partial harvesting. Cell density decreases for some time. So remaining algal cells receive more light and growth again becomes active.
• Traceability is better than continuous method. The product can be separated into different sub-batches. This helps in quality control and finding problem in a particular cycle.
• Downstream processing becomes easier. The harvested culture is less diluted than continuous method. So biomass recovery and product processing need less effort.

Economic and Ecological Importance of Algal Cultivation

Algal cultivation is useful for economy and environment. It gives many useful products. It also helps in cleaning water and reducing pollution. Microalgae grow fast and their biomass is used in many ways.

Economic Importance of Algal Cultivation

• High value products are obtained from microalgae
  Microalgae produce protein, lipid and pigments. Astaxanthin, beta-carotene and phycocyanin are important pigments. These products are used in food, medicine and industries.
• Algal biomass is used for fuel production
  Algal biomass is used as third generation fuel source. Biodiesel, bioethanol, biomethane, biohydrogen and syngas are produced from algae. These are renewable fuels.
• Algae are used as food supplement
  Algae contain protein, vitamins and minerals. They also contain omega-3 fatty acids like EPA and DHA. So they are used as nutraceutical and dietary supplement.
• Algae are used in animal and fish feed
  Microalgae are used as feed for fish larvae, livestock, poultry and pets. They contain protein and useful fatty acids. DHA is important for growth of fish larvae.
• Algae are used in cosmetics and medicines
  Algal extracts are used in creams, lotions and sunscreens. They have antioxidant and anti-inflammatory nature. They also protect from UV light. So they are used in cosmetic and pharmaceutical products.
• Algae are used for bioplastics and biofertilizer
  Algal biomass is used for making biodegradable plastics. It can also be changed into biochar. This biochar is used as biofertilizer. It improves soil and crop growth.
• Algal cultivation gives work and saves land
  Microalgae can grow in non-arable land. They do not need good agricultural land. This helps to save crop land. It also gives work in cultivation, harvesting and processing.

Ecological Importance of Algal Cultivation

• Algae are used in wastewater treatment
  Microalgae clean wastewater. They use excess nitrogen and phosphorus. They also remove organic pollutants and heavy metals. This helps to reduce water pollution.
• Algae help in carbon dioxide removal
  Microalgae take carbon dioxide (CO₂) during photosynthesis. They can also use CO₂ from industrial gases. This helps in reducing greenhouse gas.
• Algae remove medicinal pollutants
  Some algae remove pharmaceutical pollutants from water. Antibiotics, painkillers and steroids can be absorbed or degraded. So toxic compounds become less in aquatic habitat.
• Algae are used as pollution indicators
  Microalgae are sensitive to toxic substances. Their growth changes when water is polluted. So they are used to know water quality and ecosystem health.
• Algae help in saving freshwater
  Microalgae can grow in wastewater, sea water and brackish water. So freshwater use becomes less. This is useful where freshwater is limited.

Different Harvesting Techniques of Algae

Harvesting of algae is the process by which algal biomass is separated from culture medium. It is an important step after algal cultivation. Different methods are used because algal cells are small and remain suspended in water.

A. Physical Harvesting Techniques

1. Centrifugation
   In this method, algal culture is rotated at high speed. The separation occurs on the basis of density. Heavy algal cells move away from the centre and settle. It is fast and efficient method. Recovery of biomass is high. Chemicals are not needed in this method. But it needs high energy. Machine cost is also high. Sometimes shear force may damage algal cells.
2. Filtration
   In this method, algal culture is passed through filter or porous membrane. Gravity, pressure or vacuum may be used. The water passes out and algal biomass remains on the filter. It is simple and economical method. Chemical use is absent. Biomass and water recovery is good. But the process may be slow. Very small algal cells are difficult to filter. Filter pores may become clogged.
3. Flotation
   In this method, air or gas bubbles are passed through the culture. The bubbles attach with algal cells. Then algal cells come to the surface and are removed by skimming. Dissolved air flotation (DAF), dispersed air flotation (DiAF), electrolytic flotation and ozone flotation are different types. This method is efficient and needs less space. But sometimes chemicals are needed for stable floc formation. Coagulants or surfactants may be used.
4. Natural sedimentation
   It is the simplest method. The algal culture is kept undisturbed in tank. Due to gravity, algal cells slowly settle at the bottom. It is very cheap method. No special machine is needed. But it takes long time. The biomass concentration is low. Spoilage of biomass may occur during long settling time.

B. Chemical and Biological Harvesting Technique

1. Flocculation
   In this method, flocculants are added to the algal culture. These substances neutralize the negative charge of algal cells. Then cells come together and form large clumps called flocs. Flocculation may be chemical or biological. In chemical flocculation, salts of iron, aluminium or other chemicals are used. In bio-flocculation, natural biopolymers or microbes are used. It is quick and low energy method. It is useful for large scale harvesting. But chemical flocculants may remain with biomass. Separation of these chemicals is sometimes difficult. The process is also affected by pH of the medium.

Factors Influencing Algal Growth

The following are the important factors influencing algal growth–

1. Light– Light is required for photosynthesis. In low light, growth becomes slow. In very high light, photoinhibition occurs. Photosynthetic parts become damaged. Red and blue light also affect cell division and nutrient uptake.
2. Temperature– Temperature controls many activities of algal cell. Photosynthesis and enzyme action depend on it. Most commercial algae grow well in 15°C-30°C. Very high temperature destroys chlorophyll and culture may die.
3. Carbon– Carbon is required in large amount. It forms about 50% of dry biomass of microalgae. It is obtained from CO₂, flue gas and soluble carbonates.
4. Nitrogen– Nitrogen is needed for proteins. It is also needed for nucleic acids and enzymes. When nitrogen is less, growth becomes poor.
5. Phosphorus– Phosphorus is needed for DNA, RNA and ATP. It takes part in energy transfer. Less phosphorus reduces cell division.
6. Micronutrients and vitamins– Magnesium, iron, zinc, cobalt, manganese and molybdenum are required in small amount. They help in enzyme activity. Some algae need B12, thiamine and biotin.
7. pH– pH affects enzyme action. It also affects ion availability in water. Most microalgae grow in pH 6.0-8.0. Marine algae prefer slightly alkaline medium.
8. Salinity– Salinity affects water balance of algal cell. Freshwater algae do not grow properly in salty water. Some algae grow in high salt water. They store glycerol for protection.
9. Mixing and aeration– Mixing keeps algal cells suspended. It prevents settling at bottom. It gives light and nutrients to all cells. Aeration gives CO₂ and removes extra oxygen.
10. Biological contamination– Other organisms may enter the culture. Bacteria, other algae, pathogens, rotifers and amoebae may be present. They compete for food or eat algal cells. Sometimes the whole culture is lost.

References

1. 5 2.1.2 Microalgae growth factors Algal activity is affected by several factors that can motivate or inhibit its growth. The mos – Repository IHE Delft Institute for Water Education. (n.d.).
2. Gabrielyan, D. A., Sinetova, M. A., Gabel, B. V., Gabrielian, A. K., Starikov, A. Y., Voloshin, R. A., Markelova, A., Savinykh, G. A., Shcherbakova, N. V., & Los, D. A. (2026). A reliable semi-continuous cultivation mode for stable high-quality biomass production of Chlorella sorokiniana IPPAS C-1. Phycology, 6(1), 4. https://doi.org/10.3390/phycology6010004
3. Smith, K. (2024). A review on using photobioreactors for the cultivation of microalgae for biodiesel production. NHSJS Reports, 1.
4. A comprehensive review on algal nutraceuticals as prospective … (n.d.).
5. Jaryal, S. J., Sharma, A. K., Lamba, B. Y., & Patel, A. (2025). A comprehensive review on microalgae based astaxanthin: Bioprocess optimization, technological barriers, industrial applications and future roadmap. Frontiers in Marine Science, 12, 1644644. https://doi.org/10.3389/fmars.2025.1644644
6. A review on microalgae cultivation and harvesting, and their biomass extraction processing using ionic liquids – PMC. (n.d.).
7. Iakovidou, G., Itziou, A., Tsiotsias, A., Lakioti, E., Samaras, P., Tsanaktsidis, C., & Karayannis, V. (2024). Application of microalgae to wastewater bioremediation, with CO2 biomitigation, health product and biofuel development, and environmental biomonitoring. Applied Sciences, 14(15), 6727. https://doi.org/10.3390/app14156727
8. Eppendorf SE. (n.d.). Bioprocess operation modes: Batch, fed-batch, and continuous culture – Eppendorf US.
9. Narala, R. R., Garg, S., Sharma, K. K., Thomas-Hall, S. R., Deme, M., Li, Y., & Schenk, P. M. (2016). Comparison of microalgae cultivation in photobioreactor … – Frontiers.
10. Narala, R. R., Garg, S., Sharma, K. K., Thomas-Hall, S. R., Deme, M., Li, Y., & Schenk, P. M. (2016). Comparison of microalgae cultivation in photobioreactor, open raceway pond, and a two-stage hybrid system. Frontiers in Energy Research, 4, 29. https://doi.org/10.3389/fenrg.2016.00029
11. Comprehensive engineering and biophysical dynamics of microalgal cultivation: Systems, kinetics, species taxonomy, and biorefinery applications. (n.d.).
12. Kumar, G., Huy, M., Bakonyi, P., Bélafi-Bakó, K., & Kim, S.-H. (2018). Evaluation of gradual adaptation of mixed microalgae consortia cultivation using textile wastewater via fed batch operation. Biotechnology Reports, 20, e00289. https://doi.org/10.1016/j.btre.2018.e00289
13. Integrated hybrid Nested-bottled photobioreactor for enhanced … (n.d.).
14. Ramlee, A., Rasdi, N. W., Wahid, M. E. A., & Jusoh, M. (2021). Microalgae and the factors involved in successful propagation for mass production. Journal of Sustainability Science and Management, 16(3), 21-42.
15. Marine microalgae and their industrial biotechnological applications: A review – PMC. (n.d.).
16. Archimede Ricerche Srl. (n.d.). Microalgae – Archimede Ricerche.
17. Microalgae derived astaxanthin: Research and consumer trends and industrial use as food – PMC. (n.d.).
18. Microalgae for high-value products towards human health and … (n.d.).
19. Microalgae: A promising source of valuable bioproducts – PMC. (n.d.).
20. Sánchez Sáez, E. (2025). Microalgae: Omega-3, cultivation, nutraceutical and cosmetic benefits – AINIA. AINIA.
21. Allmicroalgae. (n.d.). Our species of microalgae produced – Allmicroalgae.
22. Hena, S., Bhatelia, T., Leinecker, N., & Shah, M. (2026). Parametric studies and semi-continuous harvesting strategies for enhancing CO2 bio-fixation rate and high-density biomass production using adaptive laboratory-evolved Chlorella vulgaris. Microorganisms, 14(2), 324. https://doi.org/10.3390/microorganisms14020324
23. Dehiba, B., Carmen, G.-P., Antonio, P. J., & El-Amine, A. S.-M. (2023). Prediction of microalgae growth kinetics in semi-continuous culture from batch culture experiments. Egyptian Academic Journal of Biological Sciences, C. Physiology & Molecular Biology, 15(1), 185-193. https://doi.org/10.21608/EAJBSC.2023.288623
24. Hairabedian, G. (2023). Semi-continuous cultivation mode works! – ALGECO. ALGECO.
25. Ummalyma, S. B., Sirohi, R., Udayan, A., Yadav, P., Raj, A., Sim, S. J., & Pandey, A. (2022). Sustainable microalgal biomass production in food industry wastewater for low-cost biorefinery products: A review. Phytochemistry Reviews. https://doi.org/10.1007/s11101-022-09814-3
26. Quiroz, D., McGowen, J. A., & Quinn, J. C. (2025). Techno-economic analysis of microalgae cultivation strategies: Batch and semi-continuous approaches. Algal Research, 90, 104109. https://doi.org/10.1016/j.algal.2025.104109
27. Mehlitz, T. H. (2009). Temperature influence and heat management requirements of microalgae cultivation in photobioreactors [Master’s thesis, California Polytechnic State University]. Digital Commons @ Cal Poly.
28. Chowdury, K. H., Nahar, N., & Deb, U. K. (2020). The growth factors involved in microalgae cultivation for biofuel production: A review. Computational Water, Energy, and Environmental Engineering, 9(4), 185-215. https://doi.org/10.4236/cweee.2020.94012
29. Chowdury, K. H., Nahar, N., & Deb, U. K. (2020). The growth factors involved in microalgae cultivation for biofuel production: A review. Computational Water, Energy, and Environmental Engineering, 9(4), 185-215. https://doi.org/10.4236/cweee.2020.94012
30. Allman, T. (2020). The difference between batch, fed-batch, and continuous processes – INFORS HT. INFORS HT.