FOOD SCIENCE ›› 2021, Vol. 42 ›› Issue (23): 51-56.doi: 10.7506/spkx1002-6630-20210817-213

• Basic Research • Previous Articles     Next Articles

Analysis of Sites of Action of Phenyllactic Acid in Inhibiting Alternaria sp.

GUO Mingmei, KONG Yanhui, LI Xiaohe, DU Zhilei, FAN Xinguang, GONG Hansheng   

  1. (1. School of Food Engineering, Ludong University, Yantai 264025, China;2. Garden Construction and Conservation Centre of Yantai, Yantai 264000, China)
  • Online:2021-12-15 Published:2021-12-29

Abstract: The major sites of action of phenyllactic acid (PLA) against Alternaria sp. LD3.0086, isolated from naturally decayed cherries, were investigated. The minimum inhibitory concentration (MIC) was determined by spectrophotometry. The damage of PLA to the growing hyphal tip was observed by calcofluor white (CFW) staining. The ultrastructural changes of Alternaria sp. were observed by scanning electron microscope (SEM) and transmission electron microscope (TEM). The damage to the mycelial cell wall was evaluated by measuring the change of N-acetylglucosamine concentration in the culture supernatant of Alternaria sp. before and after exposure to PLA, and the damaging effect of PLA on the mycelial cell membrane was observed by the fluorescein diacetate (FDA)/propidium iodide (PI) fluorescence double staining method. The results showed that 12.5 mmol/L PLA effectively inhibited the growth of Alternaria sp. Compared with the control group treated with sterile water, PLA treatment did not cause the growing hyphal tip to deform. The concentration of N-acetylglucosamine in the culture supernatant of Alternaria sp. treated with 12.5 mmol/L PLA was basically unchanged; there was no obvious damage to the cell wall surface of Alternaria sp. treated with 12.5 mmol/L PLA for 24 h, but the intracellular structure changed obviously. After PLA treatment for a short time (4 h), the mycelial cell membrane was still relatively intact, while it was ruptured after PLA treatment for a long time (8 h). Collectively, we concluded that the major site of action of PLA against Alternaria sp. cannot be the cell wall and cell membrane of the mycelium, but inside the cells, and that PLA can enter into the cells to destroy the internal organelle structure of the hyphae or trigger a biochemical reaction, thereby inhibiting the growth and reproduction of Alternaria sp. and exerting antimicrobial activity.

Key words: phenyllactic acid (PLA); Alternaria sp.; inhibition; site of action

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