Anaerobic Fermentation,Inoculated Fermenters,Acetogens,Anaerobic Fermenters

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	Anaerobic Fermentation - In anaerobic fermentation, a provision for aeration is usually not needed. But in some cases, aeration may be needed initially for inoculum build up. In most cases, a mixing device is also unnecessary; while in some cases initial mixing of the inoculum is necessary. Once the fermentation begins, the gas produced in the process generates sufficient mixing. The air present in the headspace of the fermentor should be replaced by CO₂, H₂, N₂ or a suitable mixture of these; this is particularly important for obligate anaerobes like Clostridium.
The fermentation usually liberates CO₂ and H₂, which are collected and used, e.g., CO₂ for making dry ice and methanol, and for bubbling into freshly inoculated fermenters. In case of acetogens and other gas utilizing bacteria, O₂free sterile CO₂ or other gases are bubbled through the medium. Acetogens have been cultured in 400 I fermenters by bubbling sterile CO₂ and 3, kg cells could be harvested in each run. Recovery of products from anaerobic fermenters does not require anaerobic conditions. But many enzymes of such organisms are highly O₂, sensitive. Therefore, when recovery of such enzymes is the objective, cells must be harvested under strictly anaerobic conditions.