The main indicators for optimization of the fermentation process are:
(1) Maximum product yield (or maximum output)
(2) Maximum economic benefits
(3) Lowest cost
(4) Product quality is the best
The determination of fermentation termination time is a comprehensive consideration of the above indicators:
The canning time is determined based on the criteria of high productivity, low cost and high profit.
Principles for judging the end point of fermentation
According to the fermentation type and production target, the fermentation end point is determined.
For fermentation varieties whose fermentation and raw material costs account for the main part of the entire production cost, the main pursuit is to improve productivity (kg/m3·h), yield (kg product/kg substrate) and fermentation coefficient (kg product/tank volume m3·fermentation cycle h) )
The cost of downstream extraction and refining accounts for the main part and the product price is relatively expensive. In addition to requiring high yield and fermentation coefficient, it also requires high product concentration.
Production capacity (or productivity, yield): refers to the accumulation of products per unit 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, and fermentation time unit is h.
Factors affecting canning time
The reasonable tanking time is determined by experiments, that is, the productivity and product cost of the fermentation tank are calculated based on the product output obtained at different fermentation times, and the time with high productivity and low cost is used as the tanking time.
1. Economic factors
The time to obtain maximum productivity at the lowest cost is the optimal fermentation time.
The fermentation cycle is shortened and the utilization rate of the equipment is improved, but the increase in product output per unit volume of fermentation broth is limited.
As the time is extended, the average productivity decreases, while power consumption, management expenses, equipment consumption and other expenses are still increasing, so the product cost increases.
2. Product quality factors
If the fermentation time is too short, too many unmetabolized nutrients will remain, which is not conducive to extraction and separation.
If the fermentation time is too long, the bacteria will autolyze, releasing bacterial proteins or enzymes in the body, changing the properties of the fermentation liquid, increasing the difficulty of filtration, prolonging the filtration time, and destroying some unstable products.
Too long or too short will cause the product quality to decrease and the content to increase.
3. Special factors
Abnormal conditions: bacterial infection, metabolic abnormalities (slow sugar consumption, etc.).
In order to avoid losses, the time of placing the tank can be advanced or delayed to save.