Abstract
Bacillus siamensis LDR was tested for its potential as a biocontrol agent against the phytopathogenic fungi Curvularia lunata BM and Ganoderma sp. TB4. Fermentation of B. siamensis LDR for the production of antifungal compound was performed in modified Czapex-Dox broth using hanjeli (Coix lacryma-jobi L.) starch as carbon source. The Bacillus siamensis LDR inoculum was 105 CFU/ mL, and fermentation was conducted for up to 16 days. Antibiosis assay conducted to test the antifungal activity of filtrate medium. The results showed inhibition of C. lunata BM and Ganoderma sp. TB4 were 47.08% and 85.99%, respectively on 14th day of fermentation. Antifungal assay of the crude extract from filtrate medium revealed growth inhibition of C. lunata BM (60.70%) and Ganoderma sp. TB4 (65.25%). Thin layer chromatography of the crude extract revealed pink-colored spots indicative of lipopeptide compounds. Analysis of the crude extract by ultraperformance liquid chromatography-mass spectrometry was tentatively identified as iturin A, bacillomycin F, and surfactin.
Highlights
The Bacillus siamensis LDR culture was grown in modified Czapex-Dox broth (CDB) medium containing 3 g NaNO3, 1 g K2HPO4, 0.5 g MgSO4, 0.5 g KCl, 0.01 g FeSO4, 15 g agar (Kusanggraeni et al 2021) and supplemented with 2 g hanjeli as a carbon source in 1,000 mL distilled water
The modified CDB medium was inoculated with 105 CFU/mL B. siamensis LDR, and bacterial growth was measured at 7 and 14 days using total plate counts (TPC)
Bacillus siamensis LDR can produce antifungal compounds when grown in a modified CDB medium with hanjeli starch as the carbon source
Summary
Agriculture is one of the most important national economic sectors in Indonesia. Palm oil and coffee are important agricultural commodities that contribute to Indonesian’s foreign exchange (FAO 2017). The agricultural sector is facing many problems, especially plant disease caused by infections of pathogens, such as fungi. Fungal infections can adversely affect agricultural products and lower their economic. Santoso I et al.: Antifungal compound of Bacillus siamensis LDR value (Almeida et al 2019). The most devastating phytopathogenic fungi affecting palm oil plantations are Ganoderma sp. Attacks palm seedlings and cause leaf blight or leaf spots disease (Agustika et al 2019), and it infects other important crops, such as corn (Garcia-Aroca et al 2018) and rice (Majeed et al 2015). The diseases caused by fungal infection should be controlled
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