Characterization of a Dihydromyricetin/α-Lactoalbumin Covalent Complex and Its Application in Nano-emulsions.

A dihydromyricetin (DMY)/α-lactoalbumin (α-La) covalent complex was prepared and characterized, and its application in nano-emulsions was also evaluated in this study. The results suggested that the covalent complex could be obtained using the alkaline method. The UV and IR spectra confirmed the formation of the covalent complex, and the amount of DMY added was positively correlated with the total phenol content of the complex. The complex had an outstanding 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS)-radical-scavenging ability, reducing power and α-glucosidase inhibitory activity, which were positively related to its total phenol content. The complex could be used as an emulsifier to stabilize the ß-carotene-loaded nano-emulsion. The stability and ß-carotene-protective capacity of the nano-emulsion stabilized by the complex were also positively related to the total phenol content of the complex, being higher than those of the nano-emulsion developed using α-La. Our results provide a reference for the construction of a new food delivery system and extend the applications of α-La and DMY in foods.

Paenibacillus polymyxa Antagonism towards Fusarium: Identification and Optimisation of Antibiotic Production.

An antibiotic produced by Paenibacillus polymyxa 7F1 was studied. The 7F1 strain was isolated from the rhizosphere of a wheat field. Response surface methodology was used to optimize the physicochemical parameters. The strain showed broad-spectrum activity against several plant pathogens. Identification of the strain was realized based on 16s rRNA gene and gyrB gene sequencing. The antibiotic was optimized by one-factor-at-a-time (OFAT) and response surface methodology (RSM) approaches. The suitable antibiotic production conditions were optimized using the one-factor-at-a-time method. The individual and interaction effects of three independent variables: culture temperature, initial pH, and culture time, were optimized by Box-Behnken design. The 16SrRNA gene sequence (1239 nucleotides) and gyrB gene (1111 nucleotides) were determined for strain 7F1 and shared the highest identities to those of Paenibacillus polymyxa. The results showed the optimal fermentation conditions for antibiotics produced by Paenibacillus polymyxa 7F1 were a culture temperature of 38 °C, initial pH of 8.0, and culture time of 8 h. The antibiotics produced by Paenibacillus polymyxa 7F1 include lipopeptides such as iturin A and surfactin. The results provide a theoretical basis for the development of bacteriostatic biological agents and the control of mycotoxins.

Fluxapyroxad Resistance Mechanisms in Sclerotinia sclerotiorum.

The necrotrophic pathogen Sclerotinia sclerotiorum has a global distribution and a wide host range, making it one of the most damaging and economically important of all plant pathogens. The current study found that fluxapyroxad, a typical succinate dehydrogenase inhibitor fungicide, had a strong inhibitory effect against S. sclerotiorum, with mean effective concentration for 50% inhibition (EC50) values ranging from 0.021 to 0.095 µg/ml. Further investigation of five highly resistant S. sclerotiorum mutants, with EC50 values of 12.37 to 31.36 µg/ml, found that fluxapyroxad resistance was accompanied by a certain cost to fitness. All of the mutants were found to have significantly (P < 0.05) reduced mycelial growth and altered sclerotia production in artificial culture, as well as reduced pathogenicity, compared with wild-type isolates, with one mutant completely losing the capacity to infect detached soybean leaves. Sequence analysis demonstrated that four of the mutants had point mutations leading to amino acid changes in the SsSdhB subunit of the fungicide target protein succinate dehydrogenase. In addition, two of the mutants were also found to have amino acid changes in the predicted sequence of their SsSdhD subunit, while the fifth mutant had no changes in any of its SsSdh sequences, indicating that an alternative mechanism might be responsible for the observed resistance in this mutant. No cross-resistance was found between fluxapyroxad and any of the other fungicides tested, including tebuconazole, prochloraz, dimethachlone, carbendazim, procymidone, pyraclostrobin, boscalid, fluazinam, fludioxonil, and cyprodinil, which indicates that fluxapyroxad has great potential as an alternative method of control for the Sclerotinia stem rot caused by S. sclerotiorum, and which could provide ongoing protection to the soybean fields of China.

Differential responses of eight cyanobacterial and green algal species, to carbamate insecticides.

In this study, five carbamate insecticides were subjected to 96 h acute toxicity tests to examine their effects on three cyanobacteria, Anabaena flos-aquae, Microcystis flos-aquae, and Mirocystis aeruginosa, and five green algae, Selenastrum capricornutun, Scenedesmus quadricauda, Scenedesmus obliquus, Chlorella vulgaris, and Chlorella pyrenoidosa. The average acute toxicity of the carbamate insecticides to the cyanobacteria and the green algae was in descending order carbaryl>carbofuran, propoxur, metolcarb > carbosulfan. Wide variations in response to the tested carbamate insecticides occurred among the eight individual species of cyanobacteria and green algae. The sensitivity of various species of algae exposed to carbofuran, propoxur, metolcarb, and carbaryl varied over one order of magnitude, and that of algae exposed to carbosulfan varied over two orders of magnitude. With regard to the diffrential sensitivity of cyanobacteria and green algae, the cyanobacteria were less sensitive than green algae to carbosulfan and propoxur. The pollutants may initiate a shift of algal group structure; especially, a shift from dominance by green algae to dominance by cyanobacteria, and may sustain cyanobacterial blooms at particular times. Therefore, the descending order of the ecosystem risk was carbosulfan > propoxur > carbofuran > carbaryl, metolcarb. There was a strong variance between toxicity and ecosystem risk; i.e., "low toxicity" does not imply "low ecosystem risk."

Differential sensitivity of two green algae, Scenedesmus quadricauda and Chlorella vulgaris, to 14 pesticide adjuvants.

Growth-inhibition tests for 14 pesticide adjuvants which are widely used to manufacture various pesticidal formulations in China, were performed on the green algae Scenedesmus quadricauda, and Chlorella vulgaris to compare differential sensitivity among populations of these algae to the adjuvants. The results showed that the acute toxicities of 700#, 1601#, By-140, and SOPA to S. quadricauda and C. vulgaris were the lowest among all the tested adjuvants. The acute toxicities of Tween 80, O-25, and AEO-13 phosphate to the selected two green algae were intermediate among the tested adjuvants. The acute toxicities of 602#, 500#, OT, NP-10, OP-10, and JFC were the highest. Meanwhile, the algal species vary widely in their response to those adjuvants. The results showed that there was a differential response to various adjuvants among the selected algal species and that the sensitivities of the various algal species exposed to 1601# and OT varied by nearly 1 order and to 700#, and By-140 varied by over 1 order of magnitude. In addition, the NOEC and LOEC values of the selected 14 adjuvants to S. quadricauda and C. vulgaris were tested; the result showed that NOEC < or = EC10