CULTIVATION OF MICROALGAE (ALGACULTURE)

CULTIVATION OF MICROALGAE (ALGACULTURE)

·    The first Microalgal cultivation was achieved by Martinus Willem Beijerinck in 1890 using Chlorella vulgaris.

·       Some of the important parameters for Algal cultivation are

a)     Culture medium

b)     Light

c)     Temperature (16 °C to 27 °C; Optimum – 18 °C to 24 °C)

d)     Salinity (12 g/L to 40 g/L; Optimum – 20 g/L to 24 g/L)

e)     pH (pH 7 to 9; Optimum pH – 8.2 to 8.7)

f)      Aeration and Proper mixing (Agitation)

·   The two most common methods of Microalgae cultivation are (i) Open Cultivation Systems (Open ponds, Tanks and Raceway ponds) and (ii) Controlled Closed Cultivation Systems (using different types of Bioreactors). 

(i) Open Cultivation Systems

·     One of the first attempts to Scale up and Cultivate Microalgae was achieved using Open Raceway Ponds.

·       Some of the major advantages of an Open Cultivation System are

a)     Minimal capital and operating costs

b)     Lower energy requirement for culture mixing.

·       On the downside, disadvantages includes

a)     Open systems require Large areas to Scale up.

b) Susceptible to contamination by birds, adverse weather conditions and bacterial pathogens.

c)  It is difficult to have control over growth parameters, such as evaporation, culture temperature, etc.

(ii) Closed Cultivation Systems

·       Closed Cultivation Systems referred to as closed Photobioreactors.

·    Photobioreactors are more efficient in terms of quality as they can be operated at highly controlled conditions and, therefore, can overcome the disadvantages of an Open Cultivation System.

·       Photobioreactors can be designed and optimized in accordance with the strain of choice.

·       Some of the common designs of Photobioreactors are

a)     Tubular Photobioreactors

b)     Vertical Column Photobioreactors

c)     Flat Plate Photobioreactors

·       The Closed Cultivation System utilizes relatively little space, while increasing the Light availability and greatly decreasing the Contamination issues.

·       Photobioreactors have some disadvantages such as

a)     Bio-fouling

b)     Overheating

c)     Benthic algae growth (algae that live on the surface of the bed)

d)     Cleaning issues

e)     High build-up of Dissolved oxygen resulting in growth limitation

f)      Very high capital costs for designing and operating

Methods used for Harvesting Microalgae

·       Some of the common methods used for harvesting the cultivated Microalgae are

a)     Filtration

b)     Centrifugation

c)     Flocculation

d)     Flotation