All the bioreactors I can found near me are either made of glass or stainless steel. People just use autoclave to sterilze them. But most of new PBR designs are using plexiglass with other plastics.  Gas sterilzation sounds troublesome and space limited.  Now I just fill our reactor with 70% alcohol, but I don't really like it.  Are there anything else I can try?  

I keep wondering how those big tubular reactors commonly seen  get sterilized. 

Thanks,