Hi Zamra,

Unusual foaming may happen in different conditions, contamination by bacteria or fungi, that produce biosurfactants, especially if aseptic techniques were not strictly followed. Release of extracellular polysaccharides or proteins by stressed Chlorella cells (especially at extreme pH levels), which can lead to foam formation. And also increased aeration or agitation, if present, can also enhance foaming in contaminated or EPS-rich cultures. Microscopic examination of the foaming culture and the pink medium could confirm the presence of foreign microorganisms. Use autoclaved and sterile containers for storing media and apply aseptic handling throughout. Monitor pH, temperature, and light conditions during both culturing and storage.