Is it a endogenous parasite of the algae? 

If not, you can use pasteur pipettere to isolate the single cell and culture it.

Hi Simrat,

1. By keeping small amount fo stock to purify. First destroy all other infected culture.

It seems to be ..What ever you are seeing some protozoa..if you observe in light microscope you can see even the water spraying out from the protozoa.

2. Give mild sonication (not more than 5 second at low duty cycle..for 5 times) to bring out the protozoa. But retaining the integrity of the algal cells. Keep overnight in dark. Repeated plating and separate out the single cell. Avoid broth/moisture atleast for 3 round fo plating.

Best,

Hi Pengbin and Arumugam,Thanks to both of you.

The problem is not the seed culture as i have the pure seed but it occurred when i scaled upto 320 L of culture which i can not dump but need some treatment.

Ok, I got it. If there is some problem on your culture media when you used in up scaled, as you have the pure seed culture?  Such, the media is not well sterilized?

Try 0.5ml/L insecticide (Actually we used old stock Endosulfan-Be careful now it is banned) it worked in our open pond. Alternatively you can try with  monocrotophos/ methoxyfenozide. Just to protect your experiment.

You might try to increase the pH of the culture medium to 8.5-9, at least for some time. In our hands this protects even open pond culture quite effectively.

Hi Gerd,

The pH is the best option as it doesnt have nay residual effect. i tried and see the ameoba lost spikes or are curled up, though not sure if they are dead or inactivated!

Thanks Pengbin and Arumugam.

Wich microalgae you culture? I employ UV for 1 minute in Scenedesmus spp and Chlorella vulgaris plate culture with great results.

Increase pH advised by Dr Kloeck is a good idea, similarly you can use sublethal temperature (for about 12 to 20 hours). In most of Chlorellas is about 40C - 43C. For other species and some strains of Chlorella it should be lower you must test it. However, for 320 l bioreactor it could be technical problem 

Madame Simrat,

 Try this method: Place the infected culture water containing the animal in an air tight plastic water bottle,replace all air & infuse CO2 so as to occupy some volume over the water level in the bottle,under slight pressure.This will increase CO2 level in water - will not harm the algae,but will kill the animals.Place the CO2 infused bottle in a fridge overnight & the next day,all the animals would have been killed. It is essential to place the bottle overnight,hence no light- no uptake of CO2 by plants & this CO2 kills the animals. The next day open the bottle,all the extra gas will diffuse out & your culture gets decontaminated.

I tried this method of mine when Chaetoceros culture water was infected with marine protozoans, & it was quite successful in all cases, up to 100%.