Do you mean “axenic”? Axenic means that only a single species or strain is present in a culture (absence of any other living organism).

To get an axenic Chlamydomonas culture, you use sterile (autoclaved) Chlamydomonas medium and inoculate it with an already axenic Chlamydomonas culture. If your current culture is not axenic, the simplest way is to obtain an axenic Chlamydomonas culture from others rather than trying to make your culture axenic.

Only if you use a unique strain/species of Chlamydomonas, you should try to clean it because it is not as easy as you might think. Here is one paper on this topic:

Banerjee et al. (2012) A Simple Novel Agar Diffusion Method for Isolation of Indigenous Microalgae Chlamydomonas sp. CRP7 and Chlorella sp. CB4 from Operational Swampy Top Soil. Indian J Microbiol. 52(4):710-712.

thanks a lot Dr. Armin Hallmann i mean anoxic sorry which means no oxygen in media

Oh, okay, you meant “anoxic”.

To produce hydrogen, Chlamydomonas reinhardtii is grown first in tris-acetate-phosphate algal growth medium (TAP) and then in sulphur-depleted TAP medium (TAP-S). The TAP medium provides all the necessary nutrients (nitrogen, carbon, sulphur and trace elements) for C. reinhardtii to grow efficiently. Anaerobic conditions are imposed by sulphur deprivation, which requires an exchange of the algal growth medium from TAP to TAP-S by centrifugation or dilution. Of course, after this step the medium lacks an important component, the sulphur, which is essential for growth; therefore, it is not possible to start with TAP-S.

Sulphur deprivation results in metabolic changes within C. reinhardtii, with an initial accumulation of starch and breakdown of endogenous protein and fat. It also reduces photosynthetic rates as sulphur is required to repair PSII damage. The result is that O2 evolution gradually decreases while respiration levels are maintained, causing the culture to become anaerobic. The algal cells have the ability to switch to an anaerobic fermentative metabolism which involves both the use of solar energy to break down water, generating adenosine triphosphate and H2, and the breakdown of starch into formic acid, ethanol, acetic acid, malic acid, carbon dioxide and H2.

See the following papers:

• Tamburic B, Zemichael FW, Maitland GC, Hellgardt K. Parameters affecting the growth and hydrogen production of the green alga Chlamydomonas reinhardtii. Int J Hydrogen Energ 2011;36:7872-6.
• Hallenbeck PC, Benemann JR. Biological hydrogen production: fundamentals and limiting processes. Int J Hydrogen Energy 2002;27:1185e93
• Gorman DS, Levine RP. Photosynthetic electron transport chain of Chlamydomonas reinhardtii, v. purification and properties of cytochrome 553 and ferredoxin. Plant Physiol 1966;41:1643e7.

Thanks Dr. Armin, but i'd like to ask you 1- is it possible to make anaerobic chlamydomonas  with anoxic media without TAP-S media?

2-can Basel Bold media and Basel Bold without slphur work as TAP and TAP-S

Thanks in advane