Excessive foam formation during batch and continuous fermentation is interfering with the growth and ethanol production from organism. I am keeping 200 rpm and supplying 1 LPM air in with 2L working volume in 7L bioreactor.
Though many antifoam agents are commercially available from companies such as Sigma, you can use the following compounds as de-foamers: polyalkylenglycols, alkoxylated fatty acid esters, polypropylene glycol (PPG), siloxane polymers, mineral oils, silicates. You can refer to this URL (https://microbialcellfactories.biomedcentral.com/articles/10.1186/1475-2859-5-S1-P30).
You may want to check also this (somewhat related) discussion: https://www.researchgate.net/post/Is_there_any_substitute_for_Antiform_anti-foaming_agent_used_for_fungi_cultured_in_a_fermenter