Xanthomonas bipolymer for use in displacement of oil from partially depleted reservoirs

A process for preparing a deacetylated pyruvate-free xanthan-containing fermentation broth suitable for the preparation of mobility control solutions used in oil recovery which comprises

• (a) fermenting by aerobic propagation a pyruvate-free xanthan producing strain of Xanthomonas campestris in an aqueous nutrient medium whose ingredients comprise a carbohydrate, a source of assimilable nitrogen and trace elements and continuing the fermentation until at least about 100 ppm of pyruvate-free xanthan is present in the broth, and
• (b) adjusting the pH of the whole or filtered broth to at least about 9, allowing the resultant broth to stand at room temperature for at least about 10 minutes and optionally neutralizing.

A process for preparing pyruvate-free xanthan suitable for use in the recovery of oil from an oil-bearing subterranean formation by injecting a mobility control solution containing said pyruvate-free xanthan into said formation which comprises

• (a) fermenting by aerobic propagation a pyruvate-free xanthan producing strain of Xanthomonas campestris in an aqueous nutrient medium whose ingredients comprise a carbohydrate, a source of assimilable nitrogen and trace elements and continuing the fermentation until at least about 100 ppm of pyruvate-free xanthan is present in the broth, and
• (b) adding sufficient water miscible precipitating agent to cause precipitation of said pyruvate-free xanthan and separating said precipitated pyruvate-free xanthan therefrom.

A process for preparing deacetylated pyruvate-free xanthan suitable for use in the recovery of oil from an oil-bearing subterranean formation by injecting a mobility control solution containing said deacetylated pyruvate-free xanthan into said formation which comprises

• (a) fermenting by aerobic propagation a pyruvate-free xanthan producing strain of Xanthomonas campestris in an aqueous nutrient medium whose ingredients comprise a carbohydrate, a source of assimilable nitrogen and trace elements until at least about 100 ppm of pyruvate-free xanthan is present in the broth,
• (b) adjusting the pH of the whole or filtered broth to about 9, allowing the resultant broth to stand at room temperature for at least 10 minutes and optionally neutralizing, and
• (c) adding sufficient water miscible precipitating agent to cause precipitation of said deacetylated pyruvate-free xanthan and separating said precipitated deacetylated pyruvate-free xanthan therefrom.

A biologically pure culture of the microorganism Xanthomonas campestris, having the identifying characteristics of ATCC 31313, said culture being capable of producing pyruvate-free xanthan in a recoverable quantity upon fermentation in an aqueous nutrient medium containing assimilable sources of carbon, nitrogen and inorganic substances.