Effects of mixed culture fermentation of Bacillus amyloliquefaciens and Trichoderma longibrachiatum on its constituent strains and the biocontrol of tomato Fusarium wilt.

AIMS: To study the effects of mixed culture fermentation (MCF) of Bacillus amyloliquefaciens and Trichoderma longibrachiatum on its constituent strains and the application values for agricultural production, with the intention of developing efficient and environmentally friendly biocontrol agents. METHODS AND RESULTS: In this study, an in vitro antifungal growth experiment showed that the inhibitory rate of the MCF broth on pathogenic fungi (Fusarium oxysporum f. sp. lycopersici, Botrytis cinerea, Trichothecium roseum and Colletotrichum gloeosporioides) was less than that of B. amyloliquefaciens culture fermentation (BCF). Moreover, the content and gene expression of lipopeptide antibiotics were also lower than that in the BCF group. However, the pot experiments based on irrigation with appropriately diluted fermentation broth showed that the biocontrol effect of MCF on tomato Fusarium wilt was significantly higher than that of TCF (T. longibrachiatum culture fermentation) and BCF, and was approximately 15.79% higher than that of the BTF group which made by mixing equivalent amounts of BCF and TCF. In MCF broth, two micro-organisms antagonized and coexisted, and the growth of T. longibrachiatum was inhibited. Using transcriptomic analysis, we speculated that MCF can upregulate the expression of genes related to carbon and nitrogen metabolism, oxidation-reduction activity, sporulation, environmental information response and chemotaxis, and biosynthesis of secondary metabolites of B. amyloliquefaciens, which might enhance the nutrient substances metabolism and competitiveness, survival ability, colonization and adaptability to the environment to increase its biocontrol potential. CONCLUSIONS: Mixed culture fermentation could promote the more reasonable and effective utilization of biocontrol micro-organisms though improving biocontrol effect, enhancing strains survival and competitiveness, increasing beneficial metabolites, combined with resistance induction or synergistic control. SIGNIFICANCE AND IMPACT OF THE STUDY: Using MCF agronomically utilizes biocontrol agents in an efficient way, which has a good potential for commercial implementation and could reduce production costs.

Structural characteristics and anticancer/antioxidant activities of a novel polysaccharide from Trichoderma kanganensis.

A novel water-soluble polysaccharide designated as TPS was isolated from the fermentation mycelia of Trichoderma kanganensis. TPS had a weight-average molecular mass of 3.074 × 105 Da, and the monosaccharide composition was consisted of Man (45.5%), GlcA (5.5%), Glc (10%), and Gal (39%). The major backbone of TPS was →6-α-d-Galp-1→5-ß-d-Manf-1→5,6-ß-d-Manf-1→5,6-ß-d-Manf-1→, and the side chains are α-d-Glcp-1→4-α-d-Glcp-1→, ß-d-Galf-1→, and α-d-Glcp-1→. In addition, we demonstrated that TPS was non-toxic in normal cells (LO2 cells) and inhibited the proliferation of mouse colon cells (CT26 cells). TPS also showed free radical scavenging activity against hydrogen peroxide. Overall, these results suggested that TPS from Trichoderma kanganensis may have potential application in biomedical fields.

Polysaccharide produced by Bacillus subtilis using burdock oligofructose as carbon source.

In this study, a polysaccharide, BP, was produced by Bacillus subtilis using burdock oligofructose as a carbon source. The polysaccharide BP was isolated from burdock fermented through B. subtilis by hot water extraction, ethanol precipitation, anion exchange and gel filtration chromatography. The molecular weight of BP was determined to be 1.533 × 107 g/mol, and is composed of mannose, rhamnose, glucose, galactose, and arabinose in the ratio of 1:0.12:17.16:0.69:1.10. Furthermore, BP is made up of a backbone structure of (1→6)-linked α-d-glucopyranosyl residues substituted at the O-3 position with α-d-glucopyranosyl branches. In vitro, BP inhibited A549 cell proliferation and increased reactive oxygen species production, thus, promoting the apoptosis of cells. Moreover, BP up-regulated the expression of caspase-3 and the corresponding protein, indicating that it activates the caspase-3 pathway. These findings suggest that the potential of BP as a supplement or drug to treat cancer.