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Microbial fermentation can be responsible for flavor production and increasing the nutritional quality of fermented fish foods. The study aimed to isolate non-halophilic bacteria possessing proteolysis and lipolysis properties as starter cultures for low-salt content fermentation of coarse fish. The strains with high enzyme activities were screened and multiple growth characteristics were analyzed. The content of amino acid nitrogen and trichloroacetic acid (TCA)-soluble peptides in fermented fish was also investigated under different fermentation conditions. Nuclear magnetic resonance (NMR) metabolomics analysis was utilized to monitor the metabolite profile of fermented fish paste. The isolate was identified as Bacillus velezensis DZ11. The strain DZ11 exhibited obvious hydrolysis properties of lipids and proteins. During the fermentation of fish paste, a total of 40 differential metabolites were identified, of which multiple metabolites changed significantly, including nutrient-related substances and flavor precursors. Salt concentration and strain DZ11 had important effects on the differential metabolites. B. velezensis DZ11 under longer fermentation time promoted the formation of flavor precursors and potentially increased the nutritional substances of low-salt fermented fish.

In order to research the working status of the field-modulated asynchronous magnetic coupling under loading condition, the electromagnetism characteristics such as the distributions of induced current, torque and loss were obtained by using the ANSOFT software to carry on the transient analysis. The results show that the induced current in the whole of magnetic coupling is not evenly distributed. The induced current of copper is maximum, followed by the ferromagnetic pole-pieces. The highest induced current density is in the outside boundary of the copper layer so that the skin effect of current is verified. The current density and loss increases with increasing of the workload, while the torque increases firstly and then decreases with increasing of the workload. When the slip ratio exceeds 12%, the coupling appear skid phenomenon because the loads is greater than the maximum load which the coupling can bear.