Fermentation tanks as biological reactor, is providing good response to environment for microbial fermentation, to complete the core equipment of Biocatalysis reactions to be a product of production tasks. This article is designed for volume 40M3, height to diameter ratio of 2.8, the initial water temperature 16 ° c, export the design conditions of water temperature 28 ° c, design a suitable ventilation citric acid production from fermentation tanks. The appliance uses the cooling device for vertical type cooling snake pipe, due to the speed of water flow in a pipe, high heat transfer coefficient, and played the role of the bezel. Mixing unit with six curved blade turbine type stirrer, which deliver high energy, high dissolved oxygen rate, has the role of enhanced heat transfer process. Under design conditions on fermentation of geometric size calculation, determine the type of tank materials and heads and head and tank connection methods, calculation of tank wall thickness of wall thickness and head, such as determining the fermentation tank other attachments, overall design layout to the fermentation tanks, to achieve process requirements, so as to improve production efficiency and quality of fermentation products. Fermentation tanks as biological reactor, is providing good response to environment for microbial fermentation, to complete the core equipment of Biocatalysis reactions to be a product of production tasks. This article is designed for volume 40M3, height to diameter ratio of 2.8, the initial water temperature 16 ° c, export the design conditions of water temperature 28 ° c, design a suitable ventilation citric acid production from fermentation tanks. The appliance uses the cooling device for vertical type cooling snake pipe, due to the speed of water flow in a pipe, high heat transfer coefficient, and played the role of the bezel. Mixing unit with six curved blade turbine type stirrer, which deliver high energy, high dissolved oxygen rate, has the role of enhanced heat transfer process. Under design conditions on fermentation of geometric size calculation, determine the type of tank materials and heads and head and tank connection methods, calculation of tank wall thickness of wall thickness and head, such as determining the fermentation tank other attachments, overall design layout to the fermentation tanks, to achieve process requirements, so as to improve production efficiency and quality of fermentation products.