Reutilization of soybean by-product for biomass production of Bacillus amyloliquefaciens and evaluation of its antifungal potential against Fusarium

Recently, Bacillus amyloliquefaciens has been recognized as a potential biocontrol agent for protecting crops against significant diseases. Thus, biomass production of this bacterium has received much interest. However, most previous studies have used commercial nutrient broth as a C/N source for fermentation. This study evaluated the potential reuse of various agricultural by-products, and soybean pulp by-product (SPBP) was identified as a suitable substrate for the fermentation of B. amyloliquefaciens EB.CK9. Experimental results showed that strain EB.CK9 grew best in a culture medium containing 1.75% SPBP, 0.05% MnSO4, and 0.1% KH₂PO₄, with an initial pH of 7. Cultivation was carried out at a temperature of 36°C, 200 rpm for 36 hours, and the biomass concentration reached up to 14.29 × 108 CFU/ml (shake flask condition). The production of B. amyloliquefaciens EB.CK9 in a bioreactor system resulted in a higher biomass concentration of 9.56 × 10¹¹ CFU/ml with a reduced fermentation time (10 hours). After fermentation in the bioreactor system, the antifungal activity of EB.CK9 biomass was evaluated and demonstrated promising antifungal potential against Fusarium incarnatum (56.25%), Fusarium solani (68.75%), and Fusarium oxysporum (67.50%). The study results highlight the potential for reusing agricultural by-products in the development of B. amyloliquefaciens EB.CK9-based products, open up opportunities for the development of indigenous bioproducts from endophytic bacteria, which can support the sustainable cultivation of durian.