Production of Cell‐Free Xanthan Fermentation Broth by Cell Adsorption on Fibers

Abstract

Xanthan gum is a microbial polysaccharide widely used in food and oil-drilling industries. Xanthan gum produced from the current commercial fermentation process usually contains cells and cell debris, which lower the filterability of the xanthan solution and limit its applications. The production of cell-free xanthan gum fermentation broth is thus desirable. The feasibility of removing cells from the xanthan fermentation broth by cell adsorption to various woven fibrous materials was studied. It was found that both cotton and polyester fibers could be used to adsorb Xanthomonas campestris cells present in the fermentation broth either during batch fermentation or after the fermentation. Almost all cells were removed from the fermentation broth by adsorption to fibers. Cotton terry cloth had rough surfaces and was the preferred material for cell adsorption. Cell adsorption to cotton was faster than to polyester fibers. The adsorption kinetics can be modeled by a first-order rate equation. The adsorption rate constants were 30-40% higher for cotton than for polyester. Cell adsorption was not efficient in the absence of xanthan gum, suggesting that the exopolysaccharide, xanthan gum, was important for efficient cell adsorption to fibers.

Production of galacto‐oligosaccharides from lactose by Aspergillus oryzae β‐galactosidase immobilized on cotton cloth

“…Inexpensive ®brous matrices, such as cotton cloth, with high porosity (>95%), large speci®c surface area, and excellent mechanical strength, have been successfully used in cell immobilization and fermentation studies (Huang and Yang, 1998;Talabardon et al, 2000;Yang et al, , 1998. The reactor with cotton cloth packed in a loose spiral form has a low pressure drop, good¯ow rates, and little diusion limitation.…”

Surface Modifications for Controlled and Optimized Cell Immobilization by Adsorption: Applications in Fibrous Bed Bioreactors Containing Recombinant Cells

“…The viability of yeast cells present in the effluent and in the fibrous matrix was measured by using a modified staining method [2,14]. The staining solution was a Ringer salt solution containing 0.03% methylene blue (composition: NaCl, 0.9 g: KCl, 0.042 g: CaCl 2 , 0.048 g; NaHCO 3 , 0.02 g; methylene blue, 0.03 g; distilled water to 100 mL) [12]. Cell samples were diluted with Ringer salt solution to a concentration of 3.0 x 10 8 cells mL -1 and 0.1 mL of the diluted sample was mixed with 0.9 mL of the staining solution.…”

“…On untreated polyurethane (PUF), on the contrary, the adsorbed cells were only about 50% of the amount on the cotton fiber. According to Yang and Lo [12], with untreated cotton showing higher surface roughness than untreated Viscose Rayon towel, it seemed plausible to attribute the poor adsorption efficiency of polyurethane foam to the inferior roughness and may be hairless on the polymer surface.…”

“…Because cotton is more hydrophilic than polyester, other mechanisms might be present for better cell adhesion under experimental conditions. It has been proposed that surface roughness of cotton facilitates cell adhesion and prevents cell from being sheared off [8,12]. A rough surface also has a greater surface area and the depression in the roughened surface can provide more favorable sites for colonization [31].…”

“…In contrast to ceramics, wood chips and straw, fibrous matrices provide adequate supporting surfaces for cell adsorption [9,10], due to their high specific surface area, void volume, mechanical and permeability, low pressure drop, diffusion problems and toxicity, maximum loading, biodegradability and durability and low cost and high availability [11][12][13]. Their natural configuration also allows them to trap more cells than other materials [12,14,15]. Recently, we succeeded in immobilizing recombinant Saccharomyces cerevisiae C468/pGAC9 cells by adsorption in an airlift-driven fibrous-bed bioreactor (FBB) [2], for continuous production of Aspergillus awamori glucomylase.…”