CA1141377A - Recovery process to improve viscosity in xanthan gum - Google Patents

Abstract

TITLE OF THE INVENTION:
Recovery Process to Improve Viscosity in Xanthan Gum.
ABSTRACT OF THE INVENTION:
Xanthan gum is recovered by precipitation from fermentation beer, using alcohol solvents at a temperature below 90°C, generally 70-90°F. The xanthan gum thereby produced has improved solubility especially in high salt solutions. As a result, the modified xanthan gum can be used in many instant dry food mix compositions, which are improved by use of a more quickly soluble xanthan gum; or in certain explosive mixtures having high levels of ammonium nitrate.

Description

`` 1141377 TITLE OF THE INVENTION:
Recovery Process to Improve Viscosity in Xanthan Gum.
RELATIONSHIP TO PRIOR ART:
Xanthan gum beer is prepared by fermenting the organism Xanthomonas campestris under a variety of fermentation conditions, or it can be obtained in ordinary commercial channels. Representative patents teaching preparation of xanthan gum beer 10 solutions and the precipitated gum itself are e.g., U.S. 3,232,929; U.S. 3,433,708; and U.S. 4,119,546.
The gum had been isolated in lower alkanols, or a suitable alkanol-water azeotrope. Most con-veniently, the precipitation had been carried out lS at relatively elevated temperatures, generally 100-110F.

1i41~7

- 2 - K-2006 SUMM~RY OF Th-E INVENTION
It has now been found, most surprisingly, that lowering the temperature at which the pre-cipitation process takes place to between about 5 70-g0F, and preferably to between about 75-85F, results in a modified, rapidly soluble, novel form of xanthan gum.
PREFERRED EMBODIMENTS OF THE INVENTION
Normally, just before precipitation, the beer has been pasteurized (treated to about 210F). For the purpose of the invention, the beer is cooled to about 70-80F, by circulating cooled water.
The alcohol precipitant can be any of those alcohols or alcohol-water mixtures normally employed to precipitate xanthan gum from the beer. Preferably, lower alkanols of 1-4 carbon atoms, or water-lower alkanol azeotropes are used. Most preferably, a isopropanol-water azeotrope having a constant boiling point of 100-110F is used. This azeotrope contains 83-85% isopropanol on a volume basis. In this invention, the alcohol is used during the precipitation step at a temperture of about 70-80F.
Following the usual procedure, the alcohol is used at about 2-3 times the volume of the volume of beer, preferably 2.5-2.6X.
The beer and the alcohol are pumped together in an impeller driven coil, at the ra'e of about 15 gallons per minute. The precipitated xanthan gum is recovered from the hardening coil.

~ ., 11413~77

- 3 - K-2006 As fermentation is generally done in batches, the precipitation step is also described as a batch operation, although it could easily be adapted to a continuous precipitation process if S that were desirable.
As indicated above, production of the xanthan gum, the starting material in the practice of the present invention, by Xanthomonas campestris, NRRL B-1459, under a variety of fermentation con-ditions is well known. The inventive feature ofthis application relates to the use of a lower temperature alcohol to precipitate the xanthan gum in the fermentation broth (the mixture of unpre-cipitated xanthan gum and fermentation broth is called beer), which is independent of the bio-synthetic pathway of the Xanthomonas organism in its production of xanthan gum. It would be apparent therefore to one skilled in the art that the invention is operative using either NRRL B-1459 or a proprietary mutant strain of Xanthomonas campestris known by applicant's assignee to produce xanthan gum in somewhat higher yields than does NRRL
B-1459. Since the function of the organism is merely to produce the starting material, the avail-ability of this mutant strain is not significant tothe practice of this invention. In addition, beer can also be commercially obtained.
This invention is further illustrated by the following examples.

....

-~1~13~7

- 4 - K-2006 A 1200 gallon batch (containing about 1100 gallons liquid xanthan gum) fermentation beer was pasteurized to 210F by pumping through a pas-s teurizing coil. It was then pumped through a cooling section until the cool beer temperature was 75F. (Pump rates for the entire system was 3.74 gallons per minute). An isopropanol:water azeotrope, containinq about 85% alcohol by volume, and a constant boiling point of about llOF, is added at the mix pump. The temperature of the isopropanol solution was 74F, and was added at the rate of about 13 gallons per minute. The mixture of beer and alcohol was then passed through a 30 gallon hardening coil with discharge into a press throat. Press discharge (crude precipitated xanthan gum) was dried through a single rotary dryer, set at 165F, milled and screened to pass 40 mesh. (The final product was made in batches and blended together in the dry powder state.) The spent liquid was monitered; it contained about 62%
isopropanol (volume) and was 78F.
For the purposes of comparison, an identically fermented batch was prepared. The beer is treated as usual, i.e., cooled to 110F; the alcohol solu-tion is at 97F.

11~1379~

~ 5 ~ R-2006 A sample of the dry xanthan gum prepared as in Example l was evaluated in a standard NH4NO3 solution assay. The purpose of this assay is to

5 determine the rate of viscosity development (and solubility) of the xanthan gum in concentrated NH4NO3 solutions, which are representative of commercial explosive mixtures.
Solutions are made as follows: an aqueous lO solution of NH4NO3 was prepared containing 76.8%
NH4NO3 (weight basis). Dry xanthan gum was added so that final levels of xanthan gum was 0.36%
(weight basis). Test temperature was 65C.
Viscosity at one hour and at 3 hours is measured.
15 In the system used, desirable viscosities are over 350 at one hour and in the range of 700-800 cp or higher at 3 hours.

114135~7

- 6 - ~-2006 Results were obtained on samples as follows:

Viscosity Example 21 hr. 3 hrs. % Solids 5 A. control (no coolins, 97F
alcohols, rotary dried 312 684 83.3 B. one sample prepared accord-ing to Example 1, before ~lending 616 720 89.3 C. one sampleprepared accord-ing to Example 1, after blending 440 728 88.7 The figures obtained illustrate, althoughsamples can vary, that the low temperature preci-pitation step affords a quantitatively different 20 gum product, having significantly increased vis-cosities at one hour and 3 hours, at the same solids level, when compared to a control sample.
Other uses for this improved xanthan gum are in instant drink mixes, especially an orange-flavored drink mix, or other flavored ~everages,soups, shakes, milk or soy ~ilk products, cocoa mixes, salad dressings, instant desserts, instant imitation catsup, calf milk replacers, coated dry gravy-making pet food, and similar applications.

- ~1413~7 ~ 7 - K-2006 The improved xanthan gum produced by this invention is used at levels and in compositions generall~ known in the art; usually levels of xanthan gum in dry mixes is from 0.2 to 1.5~, 5 weight percent (total weight basis).
~ hen the xanthan gum is used in aqueous explosive mixtures, it is used at levels from 0.1 to 3~, weight percent. See U.S. Patent No. 3,326,733 for representative compositions.

Claims (5)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A process for preparing xanthan gum, which comprises treating xanthan gum beer at a temperature of about 70-90°F with 2-3 times its volume, of a lower alkanol or lower alkanol aqueous azeotrope, lower alkanol being 1-4 carbon atoms, at a temperature of about 70-80°F, and recovering the precipitated xanthan gum thereby produced.

2. The process of Claim 1, wherein the lower alkanol is isopropanol.

3. The process of Claim 1, wherein the lower alkanol aqueous azeotrope is isopropanol-water.

4. The process of Claim 3 in which the azeo-trope temperature is about 74°F.

5. The process of Claim 4 in which about 2-1/2 volume times the azeotrope than beer is used.