ISSN:
0138-4988
Keywords:
Life Sciences
;
Life Sciences (general)
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Process Engineering, Biotechnology, Nutrition Technology
Notes:
The attachment, growth and product synthesis of non-flocculating Zymomonas mobilis cell, fixed in stainless steel wire spheres (WS), were investigated. The carrier surface was activated by treatment with titanium (IV) chloride (TiCl4) and γ-aminopropyltriethoxysilane (AS) in an attempt to raise the efficiency in the immobilization of the cells. System productivity for ethanol and levan production, using cells immobilized on a modified stainless steel in the batch fermentation of a sucrose medium, rose as a result of increased biomass compared to the productivity of cells fixed on untreated (control) metal surfaces. Stabilized ethanol synthesis was demonstrated in the course of four cycles (each cycle 48 h) of repeated fermentations with a stainless steel carrier treated with AS, and three cycles when TiCl4 was used. Levan synthesis decreased after three cycles with cells immobilized on a silanized surface. System productivity for ethanol and levan production after the fourth cycle in experiments with TiCl4-activated, silanized and unmodified carriers were Qeth = 1.01, 1.06 and 0.27 g/l × h; Qlev = 0.32, 0.29 and 0.12 g/l × h, respectively. However, the specific productivity of biomass for product synthesis was higher in fermentation systems with untreated stainless steel surfaces, probably due to some loss of physiological activity of cells attached to a modified carrier. Investigations of throughly washed activated stainless steel wire surfaces, by scanning electron microscopy after immobilization, showed significant attachment of cells to the carriers. A polymer layer covered the wire surface treated with TiCl4 after fermentations. This may be explained as the binding of extracellular polysaccharide, such as the fructose-polymer levan and yeast extract components, to the modified support via chelation. After four fermentations, craters and holes in the polymer layer were evident, probably as a result of CO2 formation. A small number of cells appeared on this layer. In view of the good ethanol formation during all fermentation cycles, it is probably that active Z. mobilis cells remained under the polymer layer. Wire treatment with AS resulted in the formation of long filamentous cells during fermentation and some disturbance of cellular fission. This may be partly explained by strong electrostatic interactions between the positively charged carrier surface and the predominately negatively charged surface of Z mobilis cells. However, this did not significantly affect other cellular functions. The surface of the wire treated with AG was practically without a polymer layer.
Additional Material:
6 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/abio.370180310
