The purpose is to change the preserved strain from dormant state to logarithmic growth state, so that the strain can quickly adapt to the needs of expanded culture. The operation is to inoculate the preserved strain on the solid slope.

Seed expansion culture: the purpose is to obtain enough high-quality seeds for inoculation in fermentation tanks in production workshops through step-by-step expansion culture.

Flow chart of fermentation engineering (because it can't be illustrated, it has to be drawn simply):

Strain preservation → slant seeds → triangular flask liquid culture → seed tank → fermentor → separation and purification of fermentation liquid → finished product.

The step of preserving strains → inclined seeds is called "activation"; Inclined seeds → triangular flask liquid culture → seed tank is called "expanded culture". The size and number of seed pots depend on the number of seeds needed for production, but the number of times of seed pots (called "seed pot series") should not be more than 4 times, preferably not more than 3 times, because each expansion needs to be followed by one seed, which will increase the probability of miscellaneous bacteria pollution and the probability of strain variation and degradation.