The effects of temperature and viscosity on glucose diffusivity through saccharomyces cerevisiae biofilms

Abstract

The present study helps us to understand the effects of temperature and viscosity on bioprocesses in immobilized cell bioreactors. Glucose diffusivities through Saccharomyces cerevisiae biofilms are experimentally investigated at variable biofilm thickness, temperature, and concentration of carboxymethylcellulose (CMC) used as viscosity-raising additive. Comparing these experimental values with those for free diffusion of glucose in water shows us that biofilm strongly reduces diffusivity (about 74%), mainly due to a decrease in the effective diffusion area. Only a slight increase in diffusivity is observed when biofilm thickness is increased. In addition, the results obtained in this work demonstrate that the well-known empirical equations of Wilke and Chang, and of Guzman and Andrade can be combined to a relationship which takes into account the simultaneous effects of temperature and viscosity on the effective glucose diffusivity. This equation appears to be valid in glucose aqueous solutions whether or not biofilm is used, whereas it is not applicable when viscosity-raising additives, such as CMC, are used.Le present travail nous aide a comprendre les effets de la temperature et de la viscosite sur les processus biologiques dans les reacteurs a cellules immobilisees. Les coefficients de diffusion du glucose a travers biofilms de Succharomyces cerevisiae sont determines experimentalement a epaisseur de biofilm, temperature et concentration de carboxymethylcellulose (CMC), employe comme additif de viscosite, variables. Une comparaison de ces valeurs avec celles obtenues pour la libre diffusion du glucose en eau montre que le biofilm reduit remarquablement la diffusivite (74% environ), a cause de la diminution de la superficie effective de diffusion. Seulement une augmentation minime de la diffusivite est observee quand I'epaisseur du biofilm est augmentee. En plus, les resultats obtenus dans ce travail montrent que les bien connus modeles de Wilke et Chang et de Guzman et Andrade peuvent &tre combines dans une relation qui tient compte des effets simultanes de la temperature et de la viscosite sur la diffisivite effective du glucose. Cette equation resulte &tre valide quant a solutions aqueuses de glucose soit en presence qu'en absence de biofilm, tandis qu'elle n'est pas applicable quand additifs de viscosite, comme la CMC, sont utilises.

Simulation of biological therapies for degenerated intervertebral discs

“…Assuming the glucose consumption rate was 5 × 10 −11 mmol/cell/h, one could estimate the maximum cell density in the NP in the disc (with 9 mm thickness) being ∼15,000 cells/mm 3 for a glucose diffusivity of 5.2 × 10 −6 cm 2 /s, an average value for NP used in our study. Note that the glucose diffusivity in water at 37°C is around 9.4 × 10 −10 m 2 /s, the value of glucose diffusivity for NP used in our study reflects 55% of the value in the water, which is consistent with the values in cartilaginous tissues reported in the literature …”

Aerobic Oxidation of d-Glucose on Support-Free Nanoporous Gold

“…When the initial glucose concentration increases, the internal diffusion and adsorption rate of glucose molecules will be enhanced because of the increasing of the concentration gradient, which results in an increase of the overall reaction rate. On the other hand, increasing the glucose concentration would also lead to higher viscosity 25 which should subsequently hinder the diffusion of glucose molecules in pores. Therefore, the glucose oxidation in this system has an optimum concentration in the median range, as depicted in Figure 9.…”

Heat Transfer and Hydrodynamics in Preparative Continuous Annular Chromatography (P-CAC)

“…The pressure drop was assumed to be 0.7 bar in all calculations, which leads to a total flow rate of 37 to 66 ml/ min depending on the special operating conditions. The physical properties of the highly concentrated aqueous sucrose solution (200 g/l) and the infinitely diluted sucrose solution (properties of pure water) were taken from literature [1,5,13,14]. Additional experiments have been carried out to measure the viscosity of the concentrated sugar solution at three different temperatures.…”

“…The temperature and concentration dependence of the dynamic viscosity of the fluid l is described by the following equation [5]:…”