Spirulina Program LOGO
 CFPPA-HYERES Spirulina Training Program

"spirulina WORLD program"
CFPPA , 32 chemin St Lazare 83400 Hyéres - France

  13 - Problems and Solutions -

What problems can we have while the culture is growing ? Temperature and light we cannot do much about, except when they are too high, to cover the basin or add water (with the necessary mineral balance so as not to stress the alga ).
Spirulina produce sugars ( carbohydrates or saccharides) during photosynthesis. When these polysaccharides are overproduced, they are excreted through the cell walls into the culture medium. As these polysaccharides are viscous there comes a time when the Spirulina filaments get caught within them and create a polysaccharide mass. This can lead to destruction of the culture because the Spirulina thus are kept away from the nutrients of the culture medium, and they die of starvation.
One must be alert to three causes of polysaccharide overproduction - specially when high light conditions threaten photolysis. The primary cause is lack of fixed nitrogen in the medium as fixed nitrogen within the cell is used to convert the polysaccharides into proteins. When they are not converted into proteins they simply are excreted into the culture. An excess of bicarbonate or lack of sulfur in the medium also can cause overproduction of polysaccharides.
But there are other problems:

Rotifers (100µ to 2mm)

Sometimes rotifers get into the culture - and eventually consume the algae or at least much reduce their numbers.
These utterly fascinating creatures are on the animal side of the fence and hence, they consume oxygen. Remember, at night, algae consume oxygen and produce carbon dioxide. The carbon dioxide poisons animals. So, if you stop the paddlewheels at night, the algae will use up the dissolved oxygen, more oxygen won't be brought in as the paddIes are stopped; and these wonderful, but highIy annoying animals will smother to death.

Another way of getting no of rotifers is to use them. Placing a long, pocket-shaped net (with 100 µ holes), inside the basin and at right angles to the movement of the culture, you can harvest them. Cleaning the net two or three times a day will provide excellent food for young fish or shrimp
Protozoa (2µ to 1mm)

There is one extremely small protozoan shaped like a bean with a tail at each end (actually not the case at all, but the impression one gets unless he has a powerful and high quality microscope ). Its name is Bodo. It isn't poisonous to us, it doesn't really bother the algae. It probably helps the algae because of the small amount of carbon dioxide it leaves in the water. Anyway, it is practically impossible to get rid of them and keep them out of the culture -something like ants in the kitchen in summer .

But there is another protozoan which can eat Spirulina. It is the Amoeba.
R.R.Kudo describes 74 species of Amoeba. There is only one which is dangerous for man: Entamoeba histolytica.
The vegetative forms are rarely seen outside of the host's body (man, dog, and cat).
This amoeba is spread by its "egglike"cysts,which are killed in water at 45°C within one hour, and within a few seconds at 55°C. The temperature inside a solar dryer is between 50 to 65°C and drying takes about 4 hours, so if the Spirulina farmers observe normal hygiene, the risk from amoeba is extremely low.
As with other protozoans, allowing the culture temperature to go between 40 and 44 °C for one day (with the accompanying rise in pH) is very effective in eliminating amoebas of aIl kinds.

Entamoeba histolyca
The culture can be contaminated also by other algae. But because of the high salinity and high pH, the culture medium for Spirulina is not a welcome place for most other algae. At a salt concentration of 20 grams per liter nearly all algae contaminants are eliminated.

Strangely enough the diatom Navicula, a Yellow-Green alga, and the Green AIga Chlorella can be found in Spirulina cultures as they have an exceptionally wide tolerance range for pH and salinity. Fortunately, these usually live on the basin bottom and if the Spirulina culture is dense enough - so little light will penetrate to the basin bottom - these algae rarely become a real problem. If they begin to "take over the culture" one can turn off the paddlewheels, harvest or skim off the Spirulina from the top part of the culture, transferring them to another basin, and, after allowing the Chlorella or Navicula to settle to the bottom, remove the rest of the culture medium slowly and clean the basin bottom.
Clorella & Navicula
There are some Blue-Green Algae or Cyanobacteria which are toxic to man and other animaIs, but these can be discovered by viewing the culture through a microscope and identified by measuring what you see and comparing the dimensions and other features to those in a key which gives dimensions for 102 of the species in the Family Oscillatoriacae - of which Spirulina is one member. (see: Spirulina Production & Potential, Ripley D. FOX 1996 - ISBN. 2-85744-853-X)
Other toxic algae which sometimes (not always) are toxic, such as Anabaena, Aphanizomenon floss aquae, and Mycrocystis aeruginosa are easily identified, even under low magnification. Some of the toxins are complicated proteins which paralyze nerves. We believe the algae use them to protect themselves and to discourage competitors for their food sources. They don't have us in mind when they produce toxins, but we should have them in mind whenever we produce Spirulina.

0scillatoriacae, and Spirulina platensis identification keys
(based on Desikachary, 1959)

Oscillatoriacae, and Spirulina platensis identification keys
Oscillatoriacae, and Spirulina platensis identification keys
If one doesn't have the facility for testing for toxins by sophisticated biochemical and physical analyses , there is a simple biological test, using Artemia salina, otherwise known as brine shrimp (1-centimeter long salt warter crustacean which reproduces through the formation of cysts). These cysts appear like tiny brown eggs 2/10th of a millimeter in diameter. If you immerse them in a 1% salt water solution for about a day and a half at 20 to 25°C these cysts hatch into tiny Artemia nauplii which are very active swimmers. If one suspects toxins are present in a culture, one only has to add a few drops of water from this culture to a tiny aquarium (made from two microscope slides and containing these newly-hatched Artemia. If toxins are present, the nauplii will start to swim slowly in circles and die within a short time.


There will be bacteria in the culture basin, just as there are bacteria everywhere. The special risk is that people infected with pathogenic bacteria may contaminate the culture. Fortunately the preferred pH for most of our pathogenic bacteria, as weIl as yeasts and molds, lies between 6.0 and 8.0, so it is highly unlikely that they would grow in the culture of Spirulina. In the event that the basin contains pathogens disease-producing for man or that someone introduces them in handling the filter cake during harvesting, these pathogens are killed by heat - by the temperatures reached during the drying process, whether it be sun-dried, or spray-dried, or mix-drying. And the fact of being dry, especially when dried rapidly, also reduces the number of viable bacteria.


The most resistant viruses are killed by heat of 75 °C or less for one hour. At higher temperatures the time required diminishes rapidly, so sun, spray, or mix-drying guard against viral contaminations. Most viruses are inactivated in 20 minutes at 50 to 60°C.

Everything seems to be going along all right. The water in the basin is getting greener every day.

Toxin producing "algae"

Sometime there is confusion between Spirulina and toxin-producing "algae"
FOR MORE DETAILS SEE the Letter: Rebutal to the Editor of the Straits Times

When should I harvest ? (Solution for control measurement of density-culture):

A sixteenth century Vatican astronomer named Secchi was interested in light. He also was interested in how the intensity of light diminishes when passing through a column of water. He invented a simple instrument for measuring the amount of microscopic suspended matter in water ..essentially a graduated measuring stick with a white disk attached to the end of it. When submerged in the water to the depth where the white disk disappears one knows that light from above, penetrating down to the white disk, and returning by reflection to the surface but being extinguished just as it reaches the surface is "stopped" by being absorbed by microscopic particles within the water. The depth of the disk then gives a measure of turbidity, or the concentration of Spirulina in the culture. The distance from the surface to the white disk is called the Secchi depth or optical density.
We can extrapolate roughly from this to determinate the number of filaments and the dry weight of spirulina per liter.
Secchi disk
A plastic Centimeter ruler to the zero end of which you glue a 2-cm diameter white disk at right angles to the ruler (one version of the instrument invented by SECCHI to determinate the optical density of a solution).
Note that the light goes down to the disk and back again. The real density is only half of the apparent density

Sources: from TECHNAP/CREDESA french document "GUIDE de PRODUCTION de la SPIRULINE: http://www.ifrance.com/credesa

When the Secchi depth is between 1,5 and 2 centimeters it is time to harvest - removing the algae from the culture until the Secchi disk is visible down to about 4 centimeters depth.
Under good conditions this means that you can harvest 1/6 to 1/3 of the culture daily - checking each day to see that the optical density climbs up to where it was the day before. If not, one must harvest a smaller quantity or less often. Likewise, if the optical density is greater - that means the Secchi depth is less than the day before - one can harvest a greater quantity or more often.
After harvesting one must return to the culture medium the chemicals which have been removed by the algae for their growth. For each kilogram of Spirulina harvested one must add 1.4 grams of magnesium (as 14.2 grams of magnesium sulfate); 7.6 g of phosphorus (as 42.72 g of dipotassium hydrogen phosphate); 5.25 g of sulfur (as 18.46 g of dipotassium sulfate); 1.0 g of calcium (as 2.77 g of calcium chloride); 4.88 g of sodium chloride (as sea salts, which can be added up to 8 or 10 grams per liter and which contain the necessary micro-elements such as manganese, zinc, copper, chromium, boron, selenium, and molybdenum); 120 g of nitrogen (as 260.86g of urea); 0.47g of iron (as 2.35 g of iron sulfate); plus 470 g of carbon from 1723.5 g of carbon dioxide or 3291.3g of sodium bicarbonate.
When harvesting, the concentrated Spirulina that rests on top of the filter screen is called the filter cake. The water which has gone through the filter screen is called the filtrate - this is retumed to the culture basin. The filter cake on the filter screen is about 85 to 90% water. This water is reduced by squeezing, pressing, by vacuum, or by being placed on a vibrating screen before going to the drying process. This filter cake still contains around 70% humidity and the drying process must take this humidity down to between 3 and 9% - 9% being the maximum allowed by the Indian Standard Alga Spirulina, Food Grade Specification, 1991. There is less degradation when kept over a long period if this maximum level is brought down to 5 or 7%.

And, of course, the dried product must be protected against oxygen, light, and temperature beyond the normal ambient temperature. The best way to do this is to put it into mylar-coated plastic bags - the mirror-shiny side inside - and the bag completely filled and heat-sealed to keep out air. If the bag is completely filled, the very small amount of air left inside becomes absorbed by the Spirulina and this brings the plastic into close contact with the algae - this is called a shrink fit.

- Introduction ] CD-ROM Spirulina for Reducing Malnutrition - Historic of the World ]
- SPIRULINA Composition  ]   [  - Texcoco Lake Story  ]
 [ -  
WHERE SPIRULINA is found ] [  - Basins  ]   [  - Photosynthesis ]  
- SPIRULINA Production  ]  [  - Laboratory ]  [  - Harvestings ]
- Mix-drying SPIRULINA ]   [  - Starting ]  [ Problems and Solutions  ] 
[  -
- Why should we grow SPIRULINA ? : for nutrition and health ]
- Public Information-paper on SPIRULINAuseful links ]


WEBMASTER Site'' http://Spirulina.online.fr '' mailto:''Webmaster'' (Updated: November 2005)