Ruzica Tomicic

Title : Factors Affecting Adhesion Of Yeast Candida spp. And Pichia spp. To Stainless Steel Surfaces

Abstract:

Microbial adhesion and biofilm formation to surfaces is of great environmental, medical and industrial importance and consequently draws considerable attention in the last decades. The persistence of microorganisms in biofilms is a serious hygienic problem in the food industry, causing processing and post-processing cross-contamination leading to reduced product shelf life and effectiveness of sanitizing treatments as well as potentially affecting the consumer’s health. Despite the research efforts devoted on bacterial adhesion, very little information is available on the adhesion behaviors of Candida spp. and Pichia spp. onto stainless steel surfaces, although these yeasts are usually contaminants in the food industry. Hence, in this study we investigated the impact of growth medium and temperature on Candida and Pichia adherence using stainless steel (AISI 304) discs with different degrees of surface roughness (Ra = 25.20 – 961.9 nm). The adhesion of the yeast strains to stainless steel surfaces grown in Malt Extract broth (MEB) or YPD broth at three temperatures (7°C, 37°C, 43°C for Candida strains and 7°C, 27°C, 32°C for Pichia strains) was assessed by crystal violet staining. The results showed that the nutrient content of medium significantly influenced the quantity of adhered cells by the tested yeasts. Adhesion of C. albicans and C. glabrata on stainless steel surfaces were significantly higher in MEB, whereas for C. parapsilosis and C. krusei it was YPD broth. In the case with P. pijperi and P. membranifaciens, YPD broth was more effective in promoting adhesion than MEB. On the other hand, our data indicated that temperature is a very important factor which considerably affects the adhesion of these yeast. In this study, we also evaluated the antimicrobial activity of plant extracts such as Humulus lupulus, Alpinia katsumadai and Evodia rutaecarpa against C. albicans, C. glabrata and P. membranifaciens and investigated whether these plant extracts can interfere with biofilm formation as well as acting on preformed biofilms. According to the MIC values, all plant extracts were effective in inhibition of yeast strains. It was observed that biofilms of C. glabrata were more resistance to plant extracts as compared to C. albicans. However, extracts of A. katsumadai and E. rutaecarpa were promoted the growth and development of a preformed biofilm of P. membranifaciens.

Biography:

Ružica Tomičić has completed her PhD in biotechnology from Faculty of Technology, University of Novi Sad, Serbia in 2018. Currently she is employed at the Faculty of Technology, University of Novi Sad and work as a Researcher in the Laboratory of Microbiology. During doctoral studies, she had the opportunity to be involved in a research project at the Biotechnical Faculty in Ljubljana, Slovenia where she gained experience in working with pathogenic and spoilage microorganisms. As a part of her PhD thesis she studied the influence of environmental factors on microbial adhesion to biotic (such as human colon carcinoma cells HT29-MTX-E12) and abiotic (such as polystyrene, stainless steel, wood) surfaces. Antimicrobial resistance and the search for new alternative solutions such as plant extracts, essential oils and probiotics are of her special scientific interest. She is a member of Serbian Society for Microbiology and a winner of FEMS Research Grant for 2017.