Biofilm formation, hyphae growth, and transcriptome characteristics of C. albicans surviving high-pressure processing

High-pressure processing (HPP) is considered effective for sterilizing minimally processed vegetable-based products. This study found that HPP could not completely inactivate the microorganisms in pickles. Candida albicans (C. albicans), an opportunistic pathogen in pickles, survived HPP exposure, while its death rate did not increase significantly with a further increase in holding time and pressure. It was striking that the biofilm formation and hyphae growth of C. albicans survived from 400 MPa HPP increased. Transcriptome analysis showed that 400 MPa affected more C. albicans genes than 300 MPa. The treatment at 300 MPa mainly facilitated transmembrane transport changes, while 400 MPa modified several metabolic processes. Furthermore, different pressure conditions caused various changes in important biofilm/hyphae-related genes, many of which were downregulated after 300 MPa treatment while upregulated after exposure to 400 MPa (NDT80, BRG1, GZF3, UME6, SET3, PES1, XOG1, RHR2, and SUN41). In addition, the GDH3, HGT9, and AAT21 genes may also play a vital role in the C. albicans tolerance of HPP. These findings emphasized the potential increased risk caused by the inability of HPP to inactive yeasts in food industry.