In our case, we don't use yeast in production of metarhizium or trichoderma. We just use sources of C and N, which are usually readily found items such as rice broth, molasses, etc. This is then adjusted to suitable pH.

Thank you Jactone....I was wondering since yeast in aerobic fermentation will convert sugars to CO2 and water and hence depleting the fungus nutritional requirement

Possibly, you added them as source of nutrients for metarhizium into medium.

Medium should be sterile for better growth of the biocontrol agent.

Hi Geoffrey,

There are a lot of growth medium which requires the use of of yeast extract as a nitrogen source.

Except you are trying to perform any specific assay, there is no reason to add yeast cells to the liquid culture of Metarhizium or Trichoderma. In fact, as you know, they a major contaminant to industrial cultivation of fungi since you can not use antibiotics. Besides, if you are trying to produce fungi conidia think about using semi-solid fermentation with rice or corn as growth media.