The present invention is related a high viscosity xanthan and processes for producing said high viscosity xanthan. In particular, the invention relates to a process for increasing the viscosity of xanthan comprising the steps of: (i) diluting xanthan in a fermentation broth with more than 30 percent by volume of a diluent to said fermentation broth volume; and (ii) pasteurizing said diluted xanthan fermentation broth. A particularly preferred pasteurization process is to utilize steam from a direct steam injection system. Xanthans with increased viscosities have improved product functionality for a number of different commercial applications are produced using the processes of the present invention.

An aqueous solution of a heteropolysaccharide comprising glucose, galactose, pyruvic and succinic acid, is prepared by mixing a concentrate of said heteropolysaccharide with a saline aqueous medium containing from 12 to 30% w of at least one salt, and by shearing the mixture obtained.

Enzymatic treatment, in aqueous dispersion, of a xanthan gum containing bacteria cell residues and microgels, as impurities, by means of Basidiomycete cellulase, the aqueous dispersion having a pH from 3 to 7 and containing at least 0.1 equivalent/liter of at least one salt of alkali or alkaline-earth metal, said treatment being conducted at a temperature from 25.degree. to 65.degree. C., improved the injectivity and filtrability thereof.

Aqueous solutions of polysaccharide biopolymers, e.g., Xanthomonas/carbohydrate fermentation worts, are treated with mutanase-containing enzymes to improve the filterability and injectability thereof, and are well adapted, e.g., for secondary and tertiary hydrocarbon (petroleum) recovery by waterflooding therewith.

An aqueous solution of a heteropolysaccharide comprising glucose, galactose, pyruvic and succinic acid, is prepared by mixing a concentrate of said heteropolysaccharide with a saline aqueous medium containing from 12 to 30% w of at least one salt, and by shearing the mixture obtained.