Bacterial exopolysaccharides (EPSs) are important alternatives to plant polysaccharides in fermented products and exhibit antioxidant activity, which is particularly desirable for functional foods. This study evaluated the use of spent media wastewater (SMW) derived from kimchi fermentation for the production of an EPS and analyzed the characterization and antioxidant activity of the resulting EPS. The EPS concentration and conversion yields of sequential purification were 7.7–9.0 g/L and 38.6–45.1%, respectively. Fourier transform infrared spectra and NMR spectra indicated that the EPS was a linear glucan with α-(1 → 6) linkages. The EPS also exhibited thermal tolerance to high temperatures. In vitro antioxidant activity analyses indicated the scavenging activity on 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals, thiobarbituric acid reactance (TBAR), and ferric ion reducing antioxidant power (FRAP) values of 71.6–79.1, 28.2–33.0%, and 0.04–0.05 mM FeCl3, respectively. These results reveal that the EPS extracted from SMW has potential as a thermally tolerant, nontoxic, and natural antioxidant for industrial applications.

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Pine wilt disease, caused by Bursaphelenchus xylophilus (pine wood nematode), leads to severe environmental and economic damage. Here, we report the results of experiments on the biological control of pine wilt disease through termination of the insect vector of the nematode and the mechanism of the insecticidal action of Metarhizium anisopliae JEF-279 against Monochamus alternatus (Japanese pine sawyer). A combined treatment with a fungal conidia suspension and a fungal protease-containing culture filtrate caused 75.8% mortality of the insect vector. Additionally, the presence of destruxins was confirmed in the dead Japanese pine sawyer adults, and half of the 10 protein spots in proteomic analysis were identified as an actin related to muscle contraction. Based on proteomic and microscopic analyses, the infection cycle of the Japanese pine sawyer by M. anisopliae JEF-279 was inferred to proceed in the following sequence: (1) host adhesion and germination, (2) epicuticle degradation, (3) growth as blastospore, (4) killing by various fungal toxins (insecticidal metabolites), (5) immune response as defense mechanism, and (6) hyphal extrusion and conidiation. Consequently, the combined fungal conidia suspension and protease-containing culture filtrate treatment may be applied as an insecticidal agent, and flaccid paralysis is likely a major mechanism underlying the insecticidal action of M. anisopliae JEF-279 on host insects.

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Lactic acid bacteria produce various bioactive compounds widely used in human healthcare. However, studies on cryoprotective agents for the efficient storage of lactic acid bacteria after freeze-drying are still lacking. Here, we report the shelf-life extension effects of a highly efficient and eco-friendly cryoprotective agent and a cold adaptation method on Lactobacillus sakei WiKim31. Cold adaptation of L. sakei WiKim31 increased exopolysaccharide expression in response to abiotic stress. As a possible cryoprotective agent, the citrus byproduct (CP) contains a variety of sugars, amino acids, and cations, exhibiting high antioxidant activity. L. sakei WiKim31 powders formulated with CP or a mixture of soy powder (SP) and CP exhibited high cell viability at 58.3 and 76.3%, respectively, after 56 days of storage. These results indicate that CP can be efficiently used as a novel cryoprotective agent either alone or in combination with SP to improve the storage conditions of L. sakei WiKim31 and preserve it longer.