CONSERVATION OF TOBACCO FIELD SOIL BY MUTANT STRAIN BACILLUS PUMILUS YYFP-3 AND OPTIMIZATION OF ITS FERMENTATION CONDITIONS

This study aimed to enhance soil quality by screening strains with conservation effects in tobacco-planted soil.Bacillus pumilus YYFP was used as the starting strain, and ARTP-DES technology was employed for composite mutagenesis.The impact of the mutant strain on tobacco planting soil was evaluated, and optimal fermentation conditions were determined using response surface methodology.The results indicated that the amylase-producing activity of the high-quality mutant strain YYFP-3 was 278.77U/mL.After applying a high concentration of the YYFP-3 mutant strain in combination with organic fertilizer to tobacco-growing soil, the soil pH approached neutrality.Compared to the control group (CK), the contents of soil organic carbon, total nitrogen, available phosphorus, and available potassium increased by 20.33%, 22.06%, 74.34%, and 12.36%, respectively.The optimal fermentation conditions of the Box-Behnken design were 12.94 g/L soluble starch, 4.22 g/L calcium chloride, and 3.66% inoculum, yielding an enzyme activity of 535.50 ± 4.26 U/mL.This study demonstrated that the mutant strain YYFP-3, when used as a microbial fertilizer in combination with organic fertilizer, has the potential to enhance soil quality, reduce the need for chemical fertilizers, support the conservation of tobacco plant soils, and present promising application prospects.