Cost-effective plant-based medium for enhanced spore production of B. amyloliquefaciens CN12 for biofertilizer application

In this study, endospore-forming bacteria were isolated, screened, and characterized from samples collected in Tan Phu protection forest for potential use in biofertilizer application. Twelve endospore-forming bacteria showed the ability to produce indole-3-acetic acid were evaluated. Based on the relative enzyme activity, siderophore production, phosphate and potassium solubilization, strain CN12 was selected. Strain CN12 was identified as Bacillus amyloliquefaciens based on 16 S rRNA gene sequencing. The liquid culture medium using inexpensive substrates was optimized for increasing its endospore production. The medium consisted of 10% mung bean sprouts extract solution, 0.87% molasses, 0.12% urea, and 0.06% MgSO₄ produced the spore yield of 5.53 ± 3.5 (× 10⁸ CFU/mL) for strain CN12. Malabar spinach plants treated with strain CN12 showed significantly increases of 39.4 ± 8.9 to 77.6 ± 11.8 g in fresh weight, 17.1 ± 3.0 to 65.8 ± 17.2 cm in plant height, and 2.9 ± 0.9 to 6.8 ± 2.3 g in root weight compared to the control. These observations revealed that strain CN12 is a promising candidate for biofertilizer production.