should be simple. you can just add some coltrimazole, nystatin or any other comercial antifungal.

You can use

1- Direct isolation under the microscope By picking up a single filament and directly inoculated in a test tube on 19 BG11 nutrient medium solidified with 1% agar.

2- Serial dilution technique until isolating single species

3- Streak plate method

Professors Kuhar and Hussein both present solid recommendations which are valid. You may want to make serial dilutions and then select single pure colonies and keeping several to assurance you can discard any contaminated colonies.

I would suggest identifying your contaminant and targeting any amendment based on your specific issue.

You can use a combination of these suggestions and test out what works under you condition.

Thanks for your responses

I will consider your recommendations for my experiment

Regards