I. Overview of fermentation endpoints

The main indicators for the optimisation of the fermentation process are:

(1) Maximum product yield (or maximum yield)

(2) Maximum economic benefits

(3) Minimum cost

(4) The best product quality

The determination of fermentation termination time is a combination of the above indicators:

High productivity, low cost and high profit are the guidelines for determining tank release time.

Second, the principle of judgement of the end of fermentation

According to the type of fermentation and production target, judge the fermentation end point.

– For fermentation and raw material costs account for the main part of the overall production costs of fermentation varieties, the main pursuit of increased productivity (kg/m3-h), yield (kg product/kg substrate) and fermentation coefficient (kg product/tank volume m3-fermentation cycle h)

– The downstream extraction and refining costs are the main part and the product is more expensive, requiring high product concentration in addition to high yield and fermentation coefficient.

Production capacity (or productivity, yield): refers to the amount of product accumulation per tank volume of fermentation broth per unit time:

Productivity unit: generally g / (L-h) or kg / (m3-h), product concentration unit is g / L or kg / m3, fermentation time unit is h.

Factors affecting the release time

Reasonable release time is determined by the experiment, that is, according to the product yield obtained from different fermentation time to calculate the productivity of the fermenter and product cost, using high productivity and low cost time, as the release time.

1. Economic factors

– The time with the lowest cost to get the maximum productivity is the most suitable fermentation time.

– Shorten the fermentation period, the equipment utilisation increases, but the growth of product yield per unit volume of fermentation broth is limited.

– Extending the time, the average productivity decreases, while power consumption, overhead expenditure, equipment consumption and other costs are still increasing, thus increasing the product cost.

2. Product quality factors

– If the fermentation time is too short, too much unmetabolised nutrients remain, which is not conducive to extraction and separation.

– If the fermentation time is too long, the bacterium will autolyse, release the bacterial proteins or enzymes in the body, change the nature of the fermentation liquid, increase the difficulty of filtration, prolong the filtration time, and destroy some unstable products.

– Too long or too short will make the product quality decrease and content increase.

3、Special factors

– Anomalies: bacterial staining, abnormal metabolism (slow sugar consumption, etc.).

– In order to avoid losses, you can save it by releasing the tank in advance or after the delay.