Screening and Analysis of Antifungal Strains Bacillus subtilis JF-4 and B. amylum JF-5 for the Biological Control of Fusarium Wilt of Banana.

PURPOSE: This study aimed to identify the antagonistic bacteria from the rhizosphere of healthy bananas that can effectively suppress the Fusarium wilt of banana, and to further investigate the inhibitory mechanism. METHOD: The primary and secondary screening techniques were implemented using the double-plate and fermentation antagonism methods. The strain was identified based on physiological and biochemical tests, 16S rRNA gene sequencing, and specific gene amplification. The effects of crude extract on the protein content, lipid peroxidation, and pectinase activity of mycelia were determined from the identified isolates. RESULTS: Two antagonistic bacteria, JF-4 and JF-5, were screened and initially identified as Bacillus subtilis (GenBank: OR125631) and B. amylum (GenBank: OR125632). The greenhouse experiment showed that the biological control efficiency of the two antagonists against the Fusarium wilt of banana was 48.3% and 40.3%, respectively. The catalase content produced by lipid peroxidation increased significantly after treatment with the crude extracts of JF-4 and JF-5 at concentrations of 0.69 µmol/L and 0.59 µmol/L, respectively. The protein and ergosterol content and pectinase activity decreased significantly. The two antagonistic bacteria might inhibit the growth of pathogens by enhancing lipid peroxidation and decreasing the synthesis of cell metabolites. Twenty compounds were identified by gas chromatography-mass spectrometry (GC-MS). B. subtilis JF-4 was further sequenced and assembled to obtain a complete circular chromosome genome of 681,804,824 bp. The genome consisted of a 4,310,825-bp-long scaffold. CONCLUSION: The findings of this study may help elucidate the mechanism behind this biocontrol isolate.

Fermentation optimization and disease suppression ability of a Streptomyces ma. FS-4 from banana rhizosphere soil.

BACKGROUND: Fusarium wilt of banana is one of the most destructive diseases in banana-growing regions worldwide. Soil-borne diseases and soil microbial communities are closely related. The screening of antagonistic bacteria from soil microorganisms in areas with Fusarium wilt of banana is of great practical significance for controlling this disease. RESULTS: A strain designated FS-4 was isolated from healthy banana rhizosphere soil in an area affected by Fusarium wilt. This strain exhibited a significant antagonistic effect on the pathogen. Pot experiments revealed that the fermentation broth of strain FS-4 not only decreased the incidence of banana Fusarium wilt, but also promoted the growth of banana seedlings. The strain was identified as Streptomyces ma. by its morphological, physiological, and biochemical characteristics and 16S rRNA gene sequence analysis. The culture and fermentation conditions for this strain were optimized by single-factor and response surface experiments. The optimum culture conditions for Streptomyces ma. FS-4 were as follows: peptone 0.5%, saccharose 2.4, 0.05% K2HPO4, 0.05% MgCl2, and 0.05% NaCl at an initial pH of 7.0; 180 g at 28 °C; and inoculation size of 6% for 62 h. The diameter of bacteriostasis circle for Bacillus subtilis reached 26.7 mm. CONCLUSION: Streptomyces ma. FS-4 is an important microbial resource as a biological agent for the control of plant pathogenic fungi and can be used to promote banana growth.

Optimization extraction, characterization and anticancer activities of polysaccharides from mango pomace.

Response surface methodology was used to optimize the extraction conditions for ultrasonic-assisted extraction of polysaccharides from mango pomace. The Optimum extraction conditions consisted of extraction temperature of 74 °C, ultrasonic power of 170 W, extraction time of 100 min, and raw material-to-water ratio of 1:40 g/mL. Under these conditions, the extraction yield was 3.71 ±â€¯0.07%. Three novel polysaccharide fractions, MG-1, MG-2 and MG-3 were purified from the crude polysaccharides by using DEAE-52 cellulose and Sephadex G-100 column chromatography. The molecular weight and monosaccharide composition of polysaccharide fractions (MPFs) were analyzed by high performance liquid gel permeation chromatography (HPGPC) and HPLC analysis, respectively. The characterizations of MPFs were conducted with FT-IR, 1H NMR and SEM. Furthermore, the anticancer activities of the polysaccharide fractions were also investigated in vitro. Results showed that MG-1, MG-2 and MG-3 exhibited significant anticancer activities against HepG2, MCF-7, A549, HeLa, A2780, HCT-116 and BGC-823 cells in a dose-dependent manner. MPFs were also showed to promote apoptosis as seen in the nuclear morphological examination study using calcein acetyl methoxy methyl easter (calcein-AM) and propidium iodide (PI) staining. This research could serve as a theoretical reference for the efficient utilization of MPFs in biomedical and functional food.