Zum Stoffübergang bei Xanthan‐Fermentationen

Herbst, Holger; Peters, Hans‐Udo; Suh, I. S.; Schumpe, Adrian; Deckwer, Wolf‐Dieter

doi:10.1002/cite.330600514

Cited by 7 publications

(3 citation statements)

References 9 publications

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“…It should be noted that the convex curvature would be even more pronounced if the effect of decreasing viscosity with increasing power input were corrected for. A very similar trend was observed in a previous study [25] where a dynamic oxygen absorption technique was used to study oxygen transfer to xanthan solutions in a stirred tank with INTERMIG impellers. None of the existing correlations describes such a trend.…”

Section: Gas/liquid Mass Transfersupporting

confidence: 71%

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Xanthan production in stirred tank fermenters: Oxygen transfer and scale‐up

Herbst¹,

Schumpe²,

Deckwer³

1992

Chem Eng & Technol

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The microbial polysaccharide xanthan was produced by cultivation of Xanthomonas campestris in four stirred tanks with volumes ranging from 0.072 to 3 m3. Many of the previously suggested correlations for the volumetric mass transfer coefficient described the present data very unsatisfactorily. When Rushton turbines were employed as stirrers, the experimental results agreed well with a correlation suggested by Kawase and Moo-Young; for the more energy-efficient INTERMIG impellers, this correlation was modified by a factor of three. Constant specific oxygen transfer rate was found to be the appropriate scaleup criterion for constant space-time yield and constant product quality, specifically, the molar mass which determines the viscosity yield.

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Section: Gas/liquid Mass Transfersupporting

confidence: 71%

“…Details of the experimental procedures were described elsewhere [4]. The molar mass distribution of the polysaccharide was studied by size exclusion chromatography [22]. The molar mass of the standards, used for the calibration, was characterized by the low-angle laser light scattering (LALLS) method.…”

Section: Methodsmentioning

confidence: 99%

Xanthan production in stirred tank fermenters: Oxygen transfer and scale‐up

Herbst¹,

Schumpe²,

Deckwer³

1992

Chem Eng & Technol

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“…Consequently, conventional xanthan gum fermentation has low xanthan concentration (usually below 3% wt/v) and low productivity (usually below 0.5 g/(L·h). There have been many attempts to increase xanthan productivity and to lower energy costs by using new agitation designs (Funahashi et al, 1987; Galindo and Nienow, 1992, 1993; Herbst et al, 1992; Nakajima et al, 1990; Nienow, 1984; Peters et al, 1992; Tecante and Choplin, 1993) and new types of bioreactors (Herbst et al, 1989; Kawase and Tsujimura, 1994; Kessler et al, 1993; Long et al, 1988; Misra and Barnett, 1987; Pons et al, 1989; Suh et al, 1991; Zaidi et al, 1991). Fermentation with water‐in‐oil emulsion (Ju and Zhao, 1993; Schumpe et al, 1991) and cell immobilization using porous Celite beads (Robinson and Wang, 1988), which reduces broth viscosity and improves aeration and oxygen transfer, have also been studied.…”

Section: Introductionmentioning

confidence: 99%

Xanthan Gum Fermentation by Xanthomonas campestris Immobilized in a Novel Centrifugal Fibrous-Bed Bioreactor

Yang

Min

1996

Biotechnol. Prog.

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Current industrial fermentations in conventional stirred-tank fermentors for production of xanthan gum and other polysaccharides are energy-intensive and costly, mainly because the high broth viscosity causes agitation and aeration to be difficult and limits the final product concentration and productivity. In this work, a novel, centrifugal, packed-bed reactor (CPBR) was developed for viscous xanthan gum fermentation. Xanthomonas campestris cells were immobilized in a rotating fibrous matrix by natural attachment to the fiber surfaces. The mixing and aeration problems were overcome by continuously pumping and circulating the medium broth through the rotating fibrous matrix to ensure intimate contact of gas and liquid with the cells and to separate the xanthan polymer from the cells. Almost all of the cells were immobilized on the fiber surfaces as was indicated by the absence of suspended cells in the fermentation broth. Thus, cell-free xanthan broth was obtained, with ∼85% xanthan yield from glucose. The bioreactor was operated in repeated batch mode to study the feasibility and performance of long-term xanthan gum production using the immobilized cells in the fibrous bed. Consistent xanthan production rate and gum quality were obtained for eight consecutive batches studied during a total operation period of over 3 weeks. The volumetric xanthan productivity achieved in the reactor was ∼1 g/(L‚h) based on the total liquid volume and ∼3 g/(L‚h) based on the fibrous-bed volume. In contrast, conventional batch fermentation in a stirred-tank reactor (STR) with free cells usually has a productivity of only 0.5 g/(L‚h) or lower. The high productivity in CPBR was attributed to the relatively high cell density, ∼7 g/L, in the reactor. The specific xanthan productivity was lower in CPBR than in STR, however. This was because of the relatively low cell viability (∼60%) and limitation in oxygen transfer in CPBR, which can be improved by increasing the medium recirculation rate and the rotational speed of the fibrous matrix.

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