Xanthan Biopolymer Research Articles

Dynamical behavior of xanthan polysaccharide in solution

AbstractDilute‐solution hydrodynamic data for xanthan biopolymer in water suggest a rodlike molecule of dimensions 15,000 × 20 Å, and molecular weight 2.2 × 106 g/mol. Upon addition of NaCl to this system, the xanthan molecules self‐associate to form stable aggregates. The native xanthan conformation can be thermally denatured to a disordered coil which can be stabilized at room temperature in 4M urea. The transition to semidilute solutions is manifested by discrete changes in the concentration dependence of diffusion coefficient and zero‐shear viscosity at c ≈ 2.0 × 10−4 g/mL. At higher concentrations c ≥ 1.0 × 10−3 g/mL, the light‐scattering and shear‐viscosity data are qualitatively but not quantitatively consistent with predictions of the dynamical theory of Doi and Edwards for an isotropic entangled solution of rigid‐rod molecules. Measurements of latex sphere diffusion in xanthan‐water solution show a sudden retardation at c ≈ 1.0 × 10−3 g/mL, consistent with the cooperative formation of a motionally restricted network of long, thin, rigid fibers. At high shear rates, flow birefringence experiments indicate enhanced ordering of the xanthan chains in the semidilute regime.

Xanthan Biopolymer Semipilot Fermentation

Abstract Using standard microbiological techniques in a semipilot plant-scalable fermenter, xanthan-specific culture techniques developed by the U.S. Dept of Agriculture's Northern Regional Research Laboratory (NRRL) were used at Marathon Oil Co.'s Denver Research Center (DRC) to obtain improved and reproducible high conversions and yields of xanthan biopolymer broth. Practical nutrients and fermenter parameters were studied to define and improve the viscosity performance and economics of xanthan broth production for thickening water in the Maraflood™ enhanced oil recovery process.

Continuous fermentation to produce xanthan biopolymer: Effect of dilution rate

AbstractSingle‐stage continuous fermentations to produce xanthan gum have been run at dilution rates (D) from 0.023 to 0.196 hr−1. Xanthan production rate (XPR) was a function of D. XPR increased from 0.34 g/hr/kg at D = 0.023 hr−1 to the maximum 0.84 g/hr/kg at D = ca. 0.15 hr−1. At D > 0.15 hr−1 XPR decreased and at the highest D studied (0.196 hr−1) was 0.69 g/hr/kg. Yield of xanthan from glucose consumed was 81–89%. Steady states ended between 6.5 and 8.7 turnovers when a variant strain occurred.

Xanthan biopolymer production at increase concentration by pH control

AbstractEfficient production of xanthan gum by fermentation with Xanthomonas campestris NRRL B‐1459 can be accomplished at concentrations of xanthan in the fermented broth > 3%. This level of more than twice that previously attained by us results from continuously controlling the fermentation pH with alkali. Only a slight decrease in fermentation rate and yield occurs. When ammonia is used for pH control, cell production more than doubles and fermentation time is shortened. However, xanthan yield is decreased by the diversion of additional sugar to growth.

Continuous fermentation to produce xanthan biopolymer: Laboratory investigation

AbstractXanthan biopolymer has been produced by single‐stage continuous fermentation with Xanthomonas campestris NRRL B‐1459 in a medium of glucose, minerals, distillers' solubles, and urea for as long as 20 days. At the highest dilution rate studied (D = 0.0285 hr−1), the steady state rate of xanthan production was 0.36 g/kg/hr and the steady state yield, basis glucose consumed, was 68%. Observations indicate that xanthan production rate is a function of pH and D.