Inhibition of Lactobacillus fermentum SHY10 on the white membrane production of soaked pickled radish

The formation of white bio-membrane (shenghua) on the surface of pickle leads to uneatable and spoiled products, which has been the key problem restricting the development of Sichuan pickle industry. In this study, the 17 microorganisms in the white membrane of pickled radish were screened and identified, of which Candida parapsilosis was the main strain causing shenghua. The membrane-forming ability of Candida parapsilosis was determined by crystal violet staining to explore its adaptability to the fermentation environment concerning temperature and oxygen. It was found that Candida parapsilosis had the strongest membrane-forming capacity under the aerobic condition at 37 degrees C, with the highest OD595 nm value reached to 3.473 +/- 0.07 at 72 h post inoculation. This research identified Lactobacillus fermentum SHY10 to be the inhibitor of the membrane production of Candida parapsilosis via the Oxford cup method on a Petri dish, and via co-inoculation with Candida parapsilosis in pickles. Furthermore, this study specified that the cell-free supernatant (CFS) of L. fermentum SHY10 had the most significant inhibitory effects and likely to result from protein substances in the CFS. Proteases treated CFS had significantly reduced inhibitory effects against membrane formation, which confirmed that the active component was protein substances. Overall, this study identified a functional LAB strain with significant inhibitory effects against the white membrane formation in pickles, which provide a safe and consumer-friendly solution for the membrane problem in the fermented vegetable industry.

Automated summary

The formation of white bio-membrane (shenghua) on pickles is a key problem in the Sichuan pickle industry. This study identified Candida parapsilosis as the main strain causing shenghua and explored its membrane-forming ability in different environmental conditions. Lactobacillus fermentum SHY10 was found to inhibit the membrane production of Candida parapsilosis, with the cell-free supernatant showing the strongest inhibitory effects likely due to protein substances. This research provides a safe and consumer-friendly solution for the membrane problem in the fermented vegetable industry.