In siturheology of yeast biofilms

Abstract

The aim of the present work was to investigate the in situ rheological behavior of yeast biofilms growing on stainless steel under static and turbulent flow. The species used (Rhodototula mucilaginosa, Candida krusei, Candida kefyr and Candida tropicalis) were isolated from a clarified apple juice industry. The flow conditions impacted biofilm composition over time, with a predominance of C. krusei under static and turbulent flow. Likewise, structural variations occurred, with a tighter appearance under dynamic flow. Under turbulent flow there was an increase of 112 μm in biofilm thickness at 11 weeks (p < 0.001) and cell morphology was governed by hyphal structures and rounded cells. Using the in situ growth method introduced here, yeast biofilms were determined to be viscoelastic materials with a predominantly solid-like behavior, and neither this nor the G'0 values were significantly affected by the flow conditions or the growth time, and at large deformations their weak structure collapsed beyond a critical strain of about 1.5-5%. The present work could represent a starting point for developing in situ measurements of yeast rheology and contribute to a thin body of knowledge about fungal biofilm formation.

Effect of quorum sensing molecules and natamycin on biofilms of Candida tropicalis and other yeasts isolated from industrial juice filtration membranes

“…Candida tropicalis L5, a strain previously isolated from UF membranes, strongly adheres to the surface of stainless steel, forming resistant biofilms which may confer a competitive advantage over other yeasts (Brugnoni et al . ; Tarifa et al . , ).…”

“…Yeasts predominate among microbial communities as spoilage micro-organisms, particularly in acidic food products like apple juice, due to their ability to grow at low pH, high sugar concentration and low water activity conditions, and to resist inactivation by heat processing isolated from UF membranes, strongly adheres to the surface of stainless steel, forming resistant biofilms which may confer a competitive advantage over other yeasts (Brugnoni et al 2014;Tarifa et al 2013Tarifa et al , 2015. As cleaning procedures cannot easily remove yeast in such sites (Brugnoni et al 2012;Tarifa et al 2013), it was assumed that this community is able to persist over time on food production surfaces.…”

Yeast biofilm in food realms: occurrence and control

“…Brugnoni et al ( 2007 , 2011 ) found that C. krusei isolated from a large-scale apple juice processing plant was capable of rapidly colonizing and covering stainless steel surfaces. Moreover, C. krusei was found in mixed biofilms subjected to varying hydrodynamic conditions commonly found in apple juice facilities (Brugnoni et al 2014 ). Of particular significance, C. krusei biofilm was identified as potentially playing an important role in the survival and dissemination of Escherichia coli O157:H7 and Salmonella enterica in food-processing environments (Tarifa et al 2017 ).…”

The mechanical properties of microbial surfaces and biofilms

“…The mechanical properties of biofilms from Rhodotorula mucilaginosa , Candida krusei , Candida kefyr and Candida tropicalis were examined with a focus on industrial applications. Essentially, yeast biofilms of these species were determined to be viscoelastic materials with a solid-like behavior ( Brugnoni et al, 2014 , Tarifa et al, 2017 ).…”