Questions and Answers
Which contaminant is not a type of algae?
Maintaining a pH above 10 is beneficial for managing green algae.
True
What is a method used to manage aquatic insects in algae cultures?
Nettin in situ or preharvest screening
To avoid unexpected nutrient deficiencies, regular tests on __________ concentration should be conducted.
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Match the type of organism to its corresponding management method.
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What is the primary goal of culture monitoring?
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Regular microscopic examination does not include checking for contaminating organisms.
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What is one benefit of using pulse amplitude modulated fluorometry (PAM)?
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High salinity is important for managing __________ species of Dunaliella.
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Match the contaminant to its management strategy.
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What is a disadvantage of excavated ponds?
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Above ground concrete ponds are expensive.
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What is a characteristic of excavated ponds?
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PVC ponds may contain _______________ as plasticizing agents.
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What is an advantage of CPE ponds?
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Carbonator increases algae growth.
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Match the type of pond with its construction factor:
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Above ground concrete ponds are suitable for _______________ algae.
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What is a disadvantage of PVC ponds?
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What is a characteristic of Above ground concrete ponds?
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What is a major challenge during the scale-up of Spirulina sp. cultures?
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Chlorella can be used to derive inoculum from existing culture ponds.
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What percentage of the total production costs do nutrients account for?
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The production of Spirulina from flask cultures to raceway ponds can take at least _____ weeks.
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Match the algae species with their respective characteristics concerning inoculum sourcing:
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Which type of medium is typically used for health food applications?
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Why is culturing microalgae in outdoor ponds a preferred method?
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Deep ponds are a type of outdoor pond used for culturing microalgae.
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What are the advantages of using several small ponds for culturing microalgae?
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A well-mixed, intensive system can achieve high __________ density.
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Match the following microalgae species with their suitability for outdoor ponds:
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What is a disadvantage of using a large outdoor pond?
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The source and quality of water are important factors to consider when selecting a site for an outdoor pond.
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A natural source of __________ is desirable for outdoor ponds.
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Why is it important to consider the final product when culturing microalgae in outdoor ponds?
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What is an advantage of using raceway ponds?
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Study Notes
Culturing Microalgae in Outdoor Ponds
- Outdoor ponds are a cost-effective method for culturing microalgae, particularly in tropical climates.
- Suitable microalgae species for outdoor pond culture include Spirulina platensis, Chlorella vulgaris, Haematococcus pluvialis, Dunaliela salina, and Phaeodactylum tricornutum.
Pond Design and Construction
- Shallow, unlined, and unmixed ponds are used for microalgae culture.
- Pond size and shape can vary, including circular, raceway, and deep ponds.
- Several small ponds can be used to avoid culture problems and reduce the impact of contamination.
- Pond size and climatic conditions, such as temperature, rainfall, and sunlight, must be considered in pond design.
Pond Mixing
- Turbulent flow is necessary to prevent cell settling and thermal and oxygen stratification.
- Velocities of 5.0 cm/s are sufficient for small ponds, but higher velocities (20-30 cm/s) are required for larger ponds to maintain mixing.
- Paddle wheels can be used to create mixing in raceway cultures.
- Higher energy inputs are required for more intense mixing, increasing operational costs.
Relationship between Pond Mixing and Depth
- Algae require light, and high cell density can lead to light absorption in the upper layers of the pond.
- Shallow ponds are desirable for uniform light intensity, but may not be suitable for all species.
- A balance between optimizing culture depth for photosynthetic efficiency and enhancing mixing/turbulence is necessary for maximum productivity.
Pond Construction Materials
- Excavated ponds are cheap but have sloping walls that can lead to contamination.
- Above-ground concrete ponds are expensive but provide a constant depth.
- PVC linings can inhibit algae growth and may contain harmful chemicals.
- CPE linings do not inhibit algae growth but may not be approved for food use in some countries.
Strain Selection
- Microalgae strains should be selected based on their biochemical composition, temperature tolerance, and resistance to mechanical and physiological stress.
Scale-Up
- Scale-up of microalgae cultures involves diluting the inoculum through successive volumes up to the production pond.
- Two methods for scale-up include using small laboratory flask cultures and deriving the inoculum from existing culture ponds.
- Spirulina and Dunaliela can be scaled up using existing culture ponds, while Chlorella and Haematococcus require axenic cultures.
Culture Medium
- Culture medium should be designed to meet the specific requirements of the microalgae species being cultured.
- Cost of nutrients can account for 10-30% of total production costs.
- Recycling medium with remaining nutrients can reduce environmental problems and costs.
Pond Management
- Control and management of contaminants, such as bacteria, viruses, fungi, other algae, zooplankton, insects, and airborne material, is essential.
- Operating the culture system as a batch culture, restarting with fresh inoculum, and providing conditions favorable to the desired species can help manage contaminants.
Contaminant Management
- Contaminants can include green algae, non-carotenogenic species, unicellular green algae, aquatic insects, brine shrimps, and amoeba.
- Management strategies include maintaining specific conditions, such as pH and salinity, and using methods like netting, screening, and ammonia treatment to control contaminants.
Culture Monitoring
- Regular microscopic examination can detect abnormal morphological changes and contaminating organisms.
- Routine testing of nutrient concentrations and monitoring pH and oxygen levels can provide an early warning system for nutrient deficiencies or other issues.
- Pulse amplitude modulated fluorometry (PAM) can determine the physiological state of the algae.
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Description
This quiz covers the basics of culturing microalgae in outdoor ponds, including the advantages and disadvantages of different pond types and algae species. Learn about the benefits and challenges of outdoor microalgae cultivation.
