Yeast Cell Cake Characterization in Alcohol Solution for Efficient Microfiltration

Abstract

Microfiltration is widely used to remove microbial cells from the fermentation broth in the downstream processing of biotechnological products. Because filtration behaviors are strongly affected by the characteristics of the microbial cell cake formed on the surface of the membrane, insights into the cake structure facilitate the design and operation of filter equipment and membranes. In the alcohol fermentation process using a yeast strain, the cake characteristics are considered to be complicated because yeast cells are strongly influenced by external factors such as filtration pressure and alcohol concentration. In this study, we evaluated the membrane filtration properties, in particular the cake characteristics of a yeast suspension containing alcohol. Microfiltration experiments were performed in the dead-end filtration mode using yeast suspensions with several ethanol concentrations (0–20 wt%) under constant pressure. Flux decline behaviors caused by yeast cake were put in a similar form for 0–15 wt% ethanol concentrations. In contrast, a severe flux decline was observed for the suspension with 20 wt% ethanol concentration. It was also observed that in the membrane filtration of yeast cells with 20 wt% ethanol concentration, the cake structure became denser and the filtration resistance remarkably increased because of cellular destruction. Furthermore, the yeast cake exhibited a high compressibility in the solution containing a 20 wt% ethanol concentration. Therefore, the filtration rate of the alcoholic fermentation broth is not significantly improved by increased pressure due to the increase in the cake resistance.

An Evaluation of the Relationship between Membrane Properties and the Fouling Mechanism Based on a Blocking Filtration Model

“…Although the Hilic-PVDF membrane exhibited a longer curved membrane-blocking period, the slopes of the plots after the linear cake filtration period were parallel for the Hilic-PVDF and Hbic-PVDF membranes. The fact that the slopes are the same indicates that similar cakes were formed on both the membranes [41].…”

“…The datapoints corresponding to the initial stage of filtration form a downward convex curve, while a linear curve is visible in the middle when the concentration C of SA is 100-400 mg/L. The linearity of the plot, in accordance with Equation ( 13), indicates cake formation during this period [41,42]. Therefore, the filtration mechanism shifted from membrane blocking to cake filtration, as shown in Figure 4.…”

Separation Properties of Plasmid DNA Using a Two-Stage Particle Adsorption-Microfiltration Process

“…An unstirred batch filtration cell with an effective membrane area of 19.6 cm 2 was utilized in this study. Microfiltration experiments were performed in the dead-end filtration mode under constant pressure by applying compressed nitrogen gas [ 26 ]. The filtrate was collected in a reservoir placed on an electronic balance (Shimadzu Corp., Kyoto, Japan) connected to a personal computer to collect and record mass versus time data.…”