|Fermentation types are classified into different classes based on various aspects like based on feeding substrate to fermenter, based on need of supply of aeration, based on need of light etc. Based on feeding substrate to fermenter, Batch fermentation, Continuous fermentation and Fed-batch fermentation are the key modes. In batch fermentation, every material for process of fermentation including substrate, inoculum and all the process parameters are set and filled in a fermenter and the process is set on and until the total process comes to an end neither substrate is added into fermenter nor product is taken out of fermenter. In fed-batch mode we find both modes of operations of batch and continuous modes, where substrate is added at fixed time intervals during the fermentation process. Based on need of supply of aeration there are aerobic fermentation and anaerobic fermentation. Aerobic fermentations: even though called fermentation, many large-scale fermentation processes are carried out in presence of aerobic conditions where, the contents present in fermenter are agitated with the help of agitator and with the help of spargers by forcing sterilized air into the fermenter. Anaerobic fermentation: apart from intense need and presence of agitator and sparger to supply aeration, rest of the configuration of the fermenter is as same as aerobic fermentation. But the presence of agitator is made compulsion for the even distribution of temperature, pH, viscosity, nutrients etc. along the medium in the fermenter. Anyways, micro aerophilic conditions to anaerobic conditions are needed to initiate the growth of the microbe in the fermenter. Based on need of light a. photo fermentation (only photosynthetic bacteria can undergo) and Dark fermentation. Photofermentation is a process of conversion of organic substances to other utilisable energy compounds following a series of biochemical reactions carried out by a specific group of bacteria named Photosynthetic bacteria, which only proceeds in the presence of light. Dark fermentation in every way it is similar to that of photofermentation, but in aspect of need of light, dark fermentation does not need any light to initiate the reactions and a diversified group of microbes are involved in dark fermentation.
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