Yeast biofilm development and rheological properties on turbluent flow regimes

BRUGNONI, LORENA INÉS; TARIFA, MARÍA CLARA; LOZANO, JORGE E.; GENOVESE DIEGO B.

Maastricht

Congreso; 6th Congress of European Microbiologists; 2015

Background: In food processing lines or in complex equipment, microorganisms are exposed to varying hydrodynamic conditions caused by the flow of liquid food, and biofilms grown under a wide distribution of hydrodynamic strengths. Objetives: The aim of the present work was to investigate the in situ thickness, architecture, and rheological properties of yeast biofilms growing on stainless steel under turbulent flow. Methods: The yeast species used (Rhodototula mucilaginosa, Candida krusei, Candida kefyr and Candida tropicalis) were isolated from an apple juice industry. Biofilm formation in turbulent flow were performed in a Rotating Disk System (RDS) already described (Brugnoni et al., 2011). Viscoelastic properties of biofilms were determined by small deformation dynamic oscillatory measurements in a Paar Physica rheometer MCR301 (Anton Paar GmbH, Graz, Austria), using parallel plates.Conclusions: Results show yeasts biofilms formed on stainless steel at Reynolds (Re) numbers ranging from 294,000 to 1.2 × 106. These growth phases transform adherent blastospores to well-defined cellular communities. Biofilm formation increases with Re and time. Flow conditions impacted biofilm composition, with a predominance of C. krusei. Under turbulent flow in biofilm thickness increased >100 μm and cell morphology was governed by hyphal structures and rounded cells. Biofilms resulted viscoelastic materials with a solid-like behavior. Rheological values were not significantly affected by flow conditions or growth time. At large deformations their weak structure collapsed beyond a critical strain.