Molecular detection of Candida krusei contamination in fruit juice using the citrate synthase gene cs1 and a potential role for this gene in the adaptive response to acetic acid

Aims: To develop a reverse transcription-polymerase chain reaction (RT-PCR) assay to detect viable Candida krusei contaminations and examine the potential role of the citrate synthase (cs1) gene in adaptation to acetic acid. Methods and Results: Fruit juice artificially contaminated with C. krusei cells was heat treated to inactivate the yeast cells, after which the improved ability of the RT-PCR over the PCR assay, through the amplification of the cs1 gene, to differentiate viable contaminations was shown. The sensitivity of the detection assay was 6 × 10⁴ CFU ml^-1. RT-PCR and densitometric analysis of the cs1 gene throughout the process of adaptation to acetic acid highlighted a potential role for the gene in the yeast's adaptive response. Conclusions: The RT-PCR assay through the targeting of the cs1 gene proved to be a specific, sensitive and direct method for the identification of a C. krusei contamination in a food environment. The cs1 gene was shown to play a potential role in the adaptation of the culture to the weak-acid preservative acetic acid. Significance and Importance of the Study: The development of a direct, sensitive and specific identification assay for C. krusei from a food environment and understanding the mechanism employed in adapting to a preservative challenge, represent important tools to the food industry in attempting to limit spoilage by this important food spoilage yeast.