Preparation of Inoculum for Fermentation Process

Microorganisms for industrial production are usually sourced naturally from their natural habitat or purchased in their pure forms from culture collection organizations such as the American Type Culture Collection (ATCC). After their purchase or isolation, the industrial microbes must be prepared through inoculum preparation techniques which activate these organisms prior to their usage for fermentation. Microbial inoculum has to be prepared from the preservation culture so that it can be used for the actual fermentation process. The aim of inoculum preparation is to select industrial microorganisms with high productivity and to minimize low productive, mutant strains for a particular fermentation process. Since profit making and cost reduction are two critical issues in any industrial microbiology process, it is important to use industrial microbes with higher biomass production and higher product yield so that the production process can be optimized appropriately with minimal or no loss. Several steps are usually involved in inoculum preparation.

First generation culture is prepared from the preservation culture on agar slants which is then sub-cultured to prepare “working culture” of the organism. At this stage the microorganisms (inoculums) start growing. In small scale fermentation processes, the working culture is normally used as the actual inoculum for the fermentation process. But for large scale fermentation processes, inoculum preparation involves additional steps that go beyond the working culture. Secondly, sterile saline water or liquid nutrient medium containing glass beads is added to the agar slants and shaken so that microbial suspension is prepared. This microbial suspension is transferred to a flat bed bottle which contains sterile agar medium. The microorganisms (inoculums) are allowed to grow by incubating the bottle. Thirdly, the microbial cells from the flat bed bottles are transferred to a shaker flask containing sterile liquid nutrient medium and is placed on a rotary shaker bed in an incubator. Microorganisms grow at a rapid rate due to aeration. Fourthly, microbial cells from the shaker flask can be used as seed culture which are then added to a small fermenter and allowed to grow for about 1-2 days. This simulates conditions that exist in the larger fermenter to be used for the industrial production of metabolites that are of economic importance. Finally, the microorganisms (inoculums prepared) are transferred to the main fermentation vessel containing essential fermentation media; and the fermentation process is allowed to run for the stipulated time and environmental condition required for optimal biomass formation and product yield.


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