Development of a Rapid On-Site Method for the Detection of Kazachstania servazzii and Candida sake in Kimchi Using Loop-Mediated Isothermal Amplification.

Kimchi has recently gained considerable global interest for its health benefits, including its probiotic properties and anticancer and antioxidative effects. However, in the later stages of kimchi fermentation, an increase in the number of yeast species that form a white film on the surface of kimchi, such as Kazachstania servazzii and Candida sake, takes place, which can negatively affect kimchi quality. Thus, we developed loop-mediated isothermal amplification (LAMP) assays for the on-site detection of K. servazzii and C. sake in kimchi. The internal transcribed spacer (ITS) region of 24 yeast strains were aligned to identify the specific region of the target yeasts, after which the LAMP primer for each target species was designed. The developed LAMP primer sets specifically amplified K. servazzii and C. sake and detected 0.4 and 4 pg of K. servazzii and C. sake DNA, respectively. In addition, the limits of detection were 103 CFU/ml for K. servazzii and 102 CFU/ml for C. sake, respectively. The LAMP methods were validated by applying them to fermented kimchi samples, with the LAMP reactions being completed within 35 min. Overall, we found that the developed LAMP assays had excellent potential to be used for advanced on-site detection of K. servazzii and C. sake due to their specificity, sensitivity, and rapidity.