A unique phenotypic modification of Lactococcus lactis cultivated in a couette bioreactor

Abstract

Batch cultures of Lactococcus lactis NCDO 2118 and IL 1403 were performed in a Couette bioreactor operated in the modulated wavy vortex flow and the turbulent regimes. This study provides an overall analysis taking into account both mechanical stress and mixing in a Couette bioreactor. A unique phenotypic aspect has been proved to occur only in the modulated wavy vortex flow regime for the two studied strains, namely that the cells become entrapped in a filamentous form. No change in the metabolic behavior of the cells has been observed. The polymeric matrix has been microscopically observed through FISH and fluorescent lectin binding, showing cells entrapped in a glycoconjugate matrix. All hypotheses regarding insufficient mixing as a cause of this phenotype have been discarded, leading to the conclusion that this particular phenotypic feature is essentially due a combined effect of mechanical stress and flow structure. Particle size measurement during the fermentation course indicates that formation of filamentous form results from a continuous aggregation started in the early stages of the cultivation. According to our results a minimum shear is required to induce the ability for cells to aggregate. Then, it appears that both flow structure and mechanical stress (shear) are responsible for the appearance of such a filamentous form. As far as the authors know, this is the first experimental evidence of a bio polymerization induced by the flow structure.

Heat Transport in Rotating Annular Duct: A Short Review

“…Upper Values e (m) e = 0.01 e = ∞ Microelectronics cooling device [25] Space vehicle technology, ball bearing [26] L(m) L → 0 Gas turbine discs cooling [27] L > 0 Heat recovery of burners [28] ω(rpm) ω = 50-114 ω = 30, 000 Bioreactor for culture cells [29] CO 2 turbine diffuser [4] Angle ϕ( • ) 0 ≤ ϕ < 90 Double-pipe heat exchanger [19] ϕ = 90 Vertical thermal energy storage tank [30] ∂T/∂r ( • C/m) −1 Geostrophic motion [31] +1 Most of the applications [14,15] Φ v , Φ w (−) 0.01 < Φ v < 0.1 0.006 < Φ w < 0.2 Al 2 O 3 /water Nanofluids [19] Viscoplastic type fluid [32] While important reviews have been conducted on simple annular geometry without a rotating effect for a double-pipe heat exchanger application [19,33], there are, according to our knowledge, no reviews that focus on the heat transport in rotating annular ducts. The benefits of this review are to reach triple objectives covering the theory development, the applications and the modelling aspects.…”

Application of the Direct Quadrature Method of Moments for the modelling of the enzymatic hydrolysis of cellulose: II. Case of insoluble substrate

“…Thus, the ratio of the two forces F H F p is deterministic (Coufort & Line, 2003). The hydrodynamic force F H is proportional to the particle surface and can be explicited in the case of spherical particles as (Douaire et al, 2011) :…”

Compression of pressurised elastic pockets

“…The deformation of closed spherical or elliptical shells by an applied force has been extensively studied experimentally and theoretically driven by attempts to infer the mechanical properties of biological components, such as fish eggs, sea urchins (Vlès, 1926;Cole, 1932), microcapsules (Liu et al, 1996;Carin et al, 2003) and cells (Smith et al, 1998) with earlier experiments dating back from 1891 (Pfeffer, 1891). Cells in their fluid environment are under stress that may lead to damage when under excessive compression in typical bioprocesses for example Arnaud et al (1993) and Ho et al (1995), or more recently, the studies of Douaire et al (2011) on the phenotypic modification of bacteria in a Couette bioreactor. The cell response can be modelled as a closed axisymmetric elastic shell (Smith et al, 1998).…”