Title : Potential of yeast Candida spp. and Pichia spp. to adhere to stainless steel surfaces under various growth conditions and their control
Abstract:
Yeast adhesion followed by biofilm formation on the surface of materials commonly used in food processing, such as stainless steel, has attracted much attention because these surfaces can become a potential source of contamination that may seriously affect food safety and quality, leading to significant financial losses. With this in mind, the present study aimed to assess the ability of Candida spp. and Pichia spp. to adhere to stainless steel discs (SS, AISI 304) with different degrees of surface roughness (Ra = 25.20 – 961.9 nm) under various growth conditions like medium (Malt Extract broth (MEB) or Yeast Peptone Dextrose (YPD) broth) and temperatures (7°C, 37°C, 43°C for Candida strains and 7°C, 27°C, 32°C for Pichia strains). In this study, we also determined the antifungal and antiadhesion activity of plant extracts such as Humulus lupulus, Alpinia katsumadai and Evodia rutaecarpa against C. albicans, C. glabrata and P. membranifaciens and evaluated whether these plant extracts can interfere with biofilm formation. The adhesion was assessed by the crystal violet staining method, while the broth microdilution method CLSI M27-A3 was used to determine the minimum inhibitory concentration (MIC) of plant extracts. Our results indicated that the growth medium which resulted in a higher adhesion of C. albicans and C. glabrata was MEB, while for C. parapsilosis and C. krusei it was YPD. In the case of P. pijperi and P. membranifaciens, YPD broth was more effective in promoting adhesion than MEB. Regarding the effect of temperature, most Candida strains adhered to stainless steel surfaces in significantly higher level at 37°C, while the adherence ability of Pichia strains were highest at 27°C. Based on MIC values, all plant extracts were effective in inhibiting yeast growth, with the obtained MIC values ranged from 100 to 400 μg/mL. It was observed that biofilm of C. glabrata was more resistance to plant extracts as compared to C. albicans. However, extracts of A. katsumadai and E. rutaecarpa promoted the growth and development of the preformed biofilm of P. membranifaciens. Therefore, this study provides valuable information for a better understanding of the adhesion behavior of Candida and Pichia on stainless steel surfaces, and knowledge of how factors influence this phenomenon is of great importance in order to avoid their colonization on food contact surfaces.
