Response to oxidative stress ofCoriolus versicolor induced by exogenous hydrogen peroxide and paraquat

Manganese Peroxidase Participates in the Liquid-Solid-Gas Triphase Regulation on Microbial Degradation of Lignocellulose in Solid-State Fermentation

The three-phase structure of solid-state fermentation (SSF) directly affects substrate degradation and fermentation efficiency. However, the mechanism of three-phase regulation on lignocellulose utilization and microbial metabolism is still unclear. Based on comparative transcriptome analysis, a lignocellulose degrading enzyme, manganese peroxidase (GlMnP), which was significantly affected by water stress meanwhile related to triphase utilization, was screened to reveal the mechanism using Ganoderma lucidum as the reference strain. The results showed that GlMnP directly participates in lignocellulose degradation by positively regulating the activity of carboxymethylcellulase (CMCase), filter paper (FPAse), and laccase (LACase) enzymes, and indirectly participates in lignocellulose degradation by negatively regulating the redox levels in microorganisms. In addition, GlMnP can also control microbial glycolysis rate to enhance lignocellulose utilization. The results indicated that GlMnP participates in the liquid-solid-gas triphase regulation on lignocellulose degradation by G. lucidum in SSF.

Physiological, Morphological and Antioxidant Responses of Pediococcus pentosaceus R1 and Lactobacillus fermentum R6 Isolated from Harbin Dry Sausages to Oxidative Stress

As functional starter cultures and potential probiotics, the ability of lactic acid bacteria to resist oxidative stress is essential to maintain viability and functional properties. This study investigates the effects of H₂O₂ at different concentrations (0, 1, 2, and 3 mM) on the physiological, morphological, and antioxidant properties of Pediococcus pentosaceus R1 and Lactobacillus fermentum R6 isolated from Harbin dry sausages. The increase in H₂O₂ concentration induced a significant increase in reactive oxygen species and a decrease in intracellular ATP levels (p < 0.05). Based on scanning electron microscopy, transmission electron microscopy, and electric conductivity analysis, H₂O₂ stress caused cell deformation, the destruction of cell membrane integrity, partial loss of the cytoplasm, and an increase in the cell conductivity of both strains. H₂O₂ stress with 1 mM or 2 mM concentrations could effectively improve the scavenging rates of free radicals, the activities of superoxide dismutase and glutathione peroxide, and the total antioxidant capacity of both strains (p < 0.05). In conclusion, an appropriate oxidative stress contributed to the activation of the antioxidant defense system of both strains, conferred strains a better effect in inhibiting the oxidation of fermented foods, and improved the health of the host.

Effects on photosynthesis and polyphenolic compounds in crop plant mung bean (Vigna radiata) following simulated accidental exposure to hydrogen peroxide

Hydrogen peroxide (H₂O₂) is a strong oxidizer and bleaching agent included in the list of substances requiring accident preparedness by the National Chemical Information System, Korea. Although chemical accidents related to H₂O₂ frequently occur globally, few studies have evaluated its toxicity and risk to soil ecosystems. Herein, accidental exposure to H₂O₂ was simulated in a microcosm including crop plant mung bean (Vigna radiata), and its long-term effects on photosynthetic activities and polyphenolic compounds were measured. Plants were evaluated based on the concentration and amount of H₂O₂ exposure, distance from H₂O₂ source, and duration post exposure. Plants exposed to high concentrations and large amounts of H₂O₂ at a close distance were most damaged; their photosynthetic activities and polyphenolic compound levels significantly decreased compared to the controls. H₂O₂ consistently damaged plants and affected their activities, but plants with minor damage recovered their photosynthetic activities and polyphenolic compound levels. Additionally, moderate oxidative stress from H₂O₂ exposure induced the synthesis of polyphenolic antioxidants including flavonol and anthocyanin. Thus, we suggest that flavonol and anthocyanin levels are the most sensitive indicators of adverse effects of H₂O₂ exposure in V. radiata. Our results highlight the risk of H₂O₂ and serve as a reference for chemical accidents.

Induction of antroquinonol production by addition of hydrogen peroxide in the fermentation of Antrodia camphorata S-29

BACKGROUND

Antroquinonol have significantly anti-tumour effects on various cancer cells. There is still lack of reports on regulation of environmental factors on antroquinonol production by Antrodia camphorata.

RESULTS

An effective submerged fermentation method was employed to induce antroquinonol with adding H₂ O₂ . The production of antroquinonol was 57.81 mg L^-1 after fermentation for 10 days when adding 25 mmol L^-1 H₂ O₂ at day 4 of the fermentation process. Then, antroquinonol was further increased to 80.10 mg L^-1 with cell productivity of 14.94 mg g^-1 dry mycelium when the feeding rate of H₂ O₂ was adjusted to 0.2 mmol L^-1 h^-1 in the 7 L fermentation bioreactor. After inhibiting the generation of reactive oxygen species with the inhibitor diphenyleneiodoium, the synthesis of antroquinonol from A. camphorata was significantly reduced, and the yield was only 3.3 mg L^-1 .

CONCLUSION

The results demonstrated that addition of H₂ O₂ was a very effective strategy to induce and regulate the synthesis of antroquinonol in submerged fermentation. Reactive oxygen species generated by H₂ O₂ during fermentation caused oxidative stress, which induced the synthesis of antroquinonol and other chemical compounds. Moreover, it is very beneficial process to improve production and diversity of the active compounds during liquid fermentation of A. camphorata mycelium. © 2016 Society of Chemical Industry.

Genome analysis of Daldinia eschscholtzii strains UM 1400 and UM 1020, wood-decaying fungi isolated from human hosts

BACKGROUND

Daldinia eschscholtzii is a wood-inhabiting fungus that causes wood decay under certain conditions. It has a broad host range and produces a large repertoire of potentially bioactive compounds. However, there is no extensive genome analysis on this fungal species.

RESULTS

Two fungal isolates (UM 1400 and UM 1020) from human specimens were identified as Daldinia eschscholtzii by morphological features and ITS-based phylogenetic analysis. Both genomes were similar in size with 10,822 predicted genes in UM 1400 (35.8 Mb) and 11,120 predicted genes in UM 1020 (35.5 Mb). A total of 751 gene families were shared among both UM isolates, including gene families associated with fungus-host interactions. In the CAZyme comparative analysis, both genomes were found to contain arrays of CAZyme related to plant cell wall degradation. Genes encoding secreted peptidases were found in the genomes, which encode for the peptidases involved in the degradation of structural proteins in plant cell wall. In addition, arrays of secondary metabolite backbone genes were identified in both genomes, indicating of their potential to produce bioactive secondary metabolites. Both genomes also contained an abundance of gene encoding signaling components, with three proposed MAPK cascades involved in cell wall integrity, osmoregulation, and mating/filamentation. Besides genomic evidence for degrading capability, both isolates also harbored an array of genes encoding stress response proteins that are potentially significant for adaptation to living in the hostile environments.

CONCLUSIONS

Our genomic studies provide further information for the biological understanding of the D. eschscholtzii and suggest that these wood-decaying fungi are also equipped for adaptation to adverse environments in the human host.

Response of ligninolytic macrofungi to the herbicide atrazine: dose-response bioassays

The effect of atrazine concentrations on mycelial growth and ligninolytic enzyme activities of eight native ligninolytic macrofungi isolated in Veracruz, México, were evaluated in a semi-solid culture medium. Inhibition of mycelial growth and growth rates were significantly affected (p=0.05) by atrazine concentrations (468, 937, 1875, and 3750 mg/l). In accordance with the median effective concentration (EC50), Pleurotus sp. strain 1 proved to be the most tolerant isolate to atrazine (EC50=2281.0 mg/l), although its enzyme activity was not the highest. Pycnoporus sanguineus strain 2, Daedalea elegans and Trametes maxima showed high laccase activity (62.7, 31.9, 29.3 U mg/protein, respectively) without atrazine (control); however, this activity significantly increased (p<0.05) (to 191.1, 83.5 and 120.6 U mg/protein, respectively) owing to the effect of atrazine (937 mg/l) in the culture medium. Pleurotus sp. strain 2 and Cymatoderma elegans significantly increased (p<0.05) their manganese peroxidase (MnP) activities under atrazine stress at 468 mg/l. The isolates with high EC50 (Pleurotus sp. strain 1) and high enzymatic activity (P. sanguineus strain 2 and T. maxima) could be considered for future studies on atrazine mycodegradation. Furthermore, this study confirms that atrazine can increase laccase and MnP activities in ligninolytic macrofungi.