A strain of Enterobacter tabaci β7 with high yield of indole-3-acetic acid (IAA) was screened from Wenshan, Yunnan province.At the shaking flask level, single factor experiment and response surface optimization were carried out on the fermentation process parameters, such as carbon source, nitrogen source, inoculum size, IAA precursor tryptophan, and so on.The optimal fermentation medium composition was determined as follows:galactose 6 g/L, yeast powder 2 g/L, tryptophan 500 mg/L.Under the condition of fermentation with 5% inoculum for 16 h, the highest concentration of IAA in the fermentation broth reached 276.96 mg/L, which was 13.53% higher than before.The effects of different additives, including bacteriostatic agents, protective agents, and emulsifiers, on the viable bacterial rate and IAA retention rate were studied.The most suitable additives were potassium sorbate, glycerin, and Tween-60.On this basis, after the prepared bacterial agent was stored for 24 days in the dark at 4 ℃, the viable bacterial rate reached 91.10% and the IAA retention rate reached 88.77%.
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