Method for producing avermectins by fermentation by using air-lift loop reactor

Abstract

The invention belongs to the technical field of microbial fermentation, and particularly relates to a method for producing avermectins by fed-batch fermentation by using an air-lift loop reactor. Themethod comprises the following steps that streptomyces avermitilis is inoculated to a slant culture medium for culture, and a spore slant is taken to prepare into a spore suspension; the spore suspension is inoculated to a seed culture medium and cultured to a logarithmic growth phase; and the streptomyces avermitilis spore suspension cultured to the logarithmic growth phase is transplanted into the air-lift loop reactor provided with a fermentation culture medium for fermentation culture, and a supplementary medium is added in batches in the middle and later periods of fermentation. The method adopts the air-lift loop reactor as a fermentation vessel, optimizes the fed-batch process and the composition of the supplementary medium, effectively reduces the bacterial infection rate in the fermentation culture process, and significantly increases the titer of the avermectins in fermentation liquid.

Description

technical field [0001] The invention belongs to the technical field of microbial fermentation, and in particular relates to a method for producing abamectin by fed-batch fermentation in an airlift loop reactor. Background technique [0002] Avermectins are a group of 16-membered macrolide antibiotics with insecticidal, acaricidal and nematicidal activities, which are fermented by Streptomyces avermitilis in Streptomyces griseus. Natural abamectin contains 8 homologue components with similar structures, the main 4 species are A1a, A2a, B1a and B2a, and their total content is ≥80%; the corresponding 4 homologues with smaller proportions are A1b, A2b, B1b and B2b, the total content of which is ≤20%. Abamectin is widely used in agriculture and is a common pesticide variety. It is used as an insecticide to control Brassicaceae diamondback moth, cotton bollworm, mites, cabbage caterpillar, etc. [0003] At present, the fermentation equipment used for the fermentation and product...

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Problems solved by technology

[0003] At present, the fermentation equipment used for the fermentation and production of abamectin is a general-purpose stirring fermenter. The fermentation method is continuous fermentation, that is, all the base materials are put in at one time. The base materials are mainly high-concentration corn starch, soybean cake powder and yeast powder. , do not add materials in the middle until the tank is put into the tank. However, in order to pursue high output and low cost, too much starch, soybean cake powder and yeast powder are added in the basic material, resulting in a viscous material liquid, especially in the early stage of fermentation. Poor effect of dissolved oxygen in the culture medium

Therefore, it is necessary to increase the stirring speed and ventilation, and equip motors and stirring equipment that can provide high-speed stirring. However, higher dissolved oxygen is not required in the later stage, and the motor and stirring can be stopped. The entire fermentation process only uses relatively high-speed stirring and stirring for a short time. The motor causes waste of energy and the equipment utilization rate is not high

In the later stage, in order to prevent the liquid level from being too high, the fermentation utilization coefficient is low during batch fermentation, and the tank release coefficient is lower than 70%, which makes the overall fermentation tank equipment utilization rate low

[0004] Existing production enterprises generally use general-purpose stirring fermenters to produce abamectin, the fermentation level is low, the output is not high, and the production cost is relatively high

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