Inactivation mechanism of phenyllactic acid against Bacillus cereus spores and its application in milk beverage.

Phenyllactic acid (PLA) as a natural phenolic acid exhibits antibacterial activity against non-spore-forming bacteria, while the inhibitory effect against bacterial spore remained unknown. Herein, this study investigated the inactivation effect of PLA against Bacillus cereus spores. The results revealed that the minimum inhibitory concentration of PLA was 1.25 mg/mL. PLA inhibited the outgrowth of germinated spores into vegetative cells rather than germination of spores. PLA disrupted the spore coat, and damaged the permeability and integrity of inner membrane. Moreover, PLA disturbed the establishment of membrane potential due to the inhibition of oxidative metabolism. SEM observations further visualized the morphological changes and structural disruption caused by PLA. Besides, PLA caused the degradation of DNA of germinated spores. Finally, PLA was applied in milk beverage, and showed promising inhibitory effect against B. cereus spores. This finding could provide scientific basis for the application of PLA against spore-forming bacteria in food industry.

Antibacterial mechanism of sucrose laurate against Bacillus cereus by attacking multiple targets and its application in milk beverage.

Sucrose laurate (SL) is a promising dual-functional additive due to its emulsification and antibacterial activity. However, the knowledge on the antibacterial action of SL against Bacillus cereus was lacking, and thus it was investigated from multiple targets. The antibacterial results demonstrated that the minimum inhibitory concentration of SL was 0.3125 mg/mL, and the time-killing curve confirmed the strong antibacterial activity of SL. The alkaline phosphatase assay suggested that SL disrupted the cell wall integrity. The flow cytometry and fluorescence spectroscopy analysis indicated that SL damaged the integrity of cell membrane and dissipated the transmembrane potential, resulting in the leakage of intracellular materials, which were further supported by scanning electron microscopy and transmission electron microscopy. iTRAQ-based proteomic analysis indicated that SL down-regulated cell wall-associated hydrolase, inhibited the synthesis of fatty acids, influenced nucleic acid synthesis, disturbed amino acid metabolism, and blocked HMP pathway and TCA cycle. Finally, the promising application of SL was evidenced in milk beverage. This investigation could provide scientific basis for the practical application of SL as a dual-functional food additive.

[Clinical observation of the γ-globulin levels when Benign paroxysmal positional vertigo is attacking].

OBJECTIVE: To observe the characteristics of serum protein in patients with benign paroxysmal positional vertigo (BPPV) during the symptomatic period. METHOD: Fifty-five patients with BPPV and 58 control subjects were enrolled in the study. All the patients underwent the Dixe-Hallpike and Roll maneuver to confirm the type of BPPV. The average time of onset was (1.0 ± 0.8)days in the group of BPPV. The clinical features and the laboratory tests of serum protein electrophoresis, blood counts, and liver and kidney function were performed in both groups. RESULT: The levels of serum albumin (Alb), α1 globulin, α2 globulin and ß globulin of BPPV group did not differ statistically in the two groups (P > 0.05); The γ-globulin levels were significantly higher in patients with BPPV than in controls (P < 0.05). CONCLUSION: The γ-globulin levels are increased when BPPV is attacking.

[Effects of rare earth elements on amino acid contents in earthworms].

Rare earth elements are wide-used in China, but a few of studies were made on whether they had toxicity to soil fauna. In this paper, the filter paper contact method was used to study the influence of two rare earth elements on the dynamics of amino acids in earthworm body. The result showed that at low concentrations, the test rare earth elements increased the amino acid contents except proline, but decreased them at high concentrations. The amino acid contents began to increase at 400 mg.L-1, while decreased with time. Both of the two rare earth elements reduced the proline content, and behaved inhibition effect at the range of 100-1,200 mg.L-1.