Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acids and salts thereof
Reexamination Certificate
1999-07-09
2001-09-11
Killos, Paul J. (Department: 1623)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acids and salts thereof
C562S590000, C435S145000, C435S142000
Reexamination Certificate
active
06288275
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a novel method for separating and purifying carboxylic acids, particularly long chain dicarboxylic acids, from fermentation broths, and to improved methods for producing carboxylic acids by fermentation.
2. Background of the Related Prior Art
Carboxylic acids, particularly long chain dicarboxylic acids are commercially important products utilized in the production of polymers, adhesives, perfumes, and antibiotics. As is known, production of dicarboxylic acids on an industrial scale typically occurs by fermentation with various microorganisms, e.g., yeast, using alkanes or fatty acids as the carbon source. The broth obtained from fermentation generally contains a significant amount of impurities such as the biomass from spent microorganisms, proteins, amino acids, fatty acids, sugars, carbohydrates, etc.
Several techniques exist for separating carboxylic acids from the various impurities present in the fermentation broth. For example, U.S. Pat. No. 4,075,093, describes a process of separating citric acid and isotropic acid from fermentation broths using membranes of selective permeability composed of polysulfones modified by acid groups, or of vinyl polymers which are chemically modified by acid or basic groups, within a particular pressure range.
U.S. Pat. No. 4,904,389 describes a process for separating saturated dicarboxylic acids from their mono and di-unsaturated analogs present in a fermentation broth using a membrane filtration system at a pressure of up to 20 bar and adjusting the pH of the fermentation broth to a pH of from 4 to 11, such that the membrane is selectively impermeable to at least one of the dicarboxylic acids present in the fermentation broth.
While the aforementioned membrane filtration methods may be useful in separating carboxylic acids from fermentation broths, such methods are time-consuming and require the prior separation of microorganism cells from the aqueous portion of the fermentation broth using various techniques such as filtration, centrifugation, etc.
Carboxylic acids may also be separated from other impurities in the fermentation broth by techniques involving separation of the biomass from the fermentation broth, precipitation of the carboxylic acid from the fermentation broth, and recovery of the crystals from the broth. For example, U.S. Pat. No. 5,612,131 describes a process for recovering organic acids, particularly citric acid, from fermentation broth by removing the biomass of spent microorganism cells and treating the cell-free broth with a strong acid or salt to precipitate out the organic acid, followed by separating the crystals to recover the organic acid.
U.S. Pat. No. 4,339,536 describes the separation of long chain dicarboxylic acids from a fermentation broth by adding diatomaceous earth to the fermentation broth, filtering the broth under pressure, and then precipitating the dicarboxylic acid from the broth using a mineral acid and heating.
JP No. 176498 describes the separation of dicarboxylic acids from fermentation broth by removing the biomass from the broth, heating and treating the cell-free broth with activated carbon, regulating the pH of the broth to below 4.0 using an inorganic acid, and recovering the crystallized dicarboxylic acid from the broth.
JP No. 086443 describes the refining of dicarboxylic acids from fermentation broth, which includes separating the biomass from the fermentation broth, heating the cell-free broth at a pH above 7.0, regulating the pH to below 3.0 using an inorganic acid, and recovering the dicarboxylic acid crystals.
The aforementioned processes requiring precipitation of the carboxylic acid from the fermentation broth are inefficient in that the precipitation process itself is time-consuming and requires the prior separation of the spent microorganism cells from the broth. Further, the crystals obtained from the precipitation process yield a less purified product than is desired.
Accordingly there continues to be a need for improved methods to efficiently separate carboxylic acids, particularly dicarboxylic acids, from a fermentation broth on an industrial scale to yield a substantially pure product at high yields and at reasonably low operating costs.
SUMMARY OF THE INVENTION
The present invention is directed to a method for separating carboxylic acids from a fermentation broth. The method comprises adjusting the pH of the fermentation broth to about 2.0 or below, and heating the acidified fermentation broth to a temperature sufficient to cause formation of three immiscible phases, wherein one of the three phases is an organic phase which contains the carboxylic acids.
Another aspect of the present invention is an improved method for producing carboxylic acids by fermentation. The method comprises fermenting with a microorganism in a culture medium including a nitrogen source, an organic substrate and optionally a co substrate to provide a fermentation broth, and adjusting the pH of the fermentation broth to about 2.0 or below. The acidified fermentation broth is then heated to a temperature sufficient to cause formation of three immiscible phases, wherein one of the three phases is an organic phase which contains the carboxylic acids.
Quite advantageously, the present process for separating carboxylic acids from an impure fermentation broth does not require the prior separation of the biomass of spent cells from the liquid portion of the fermentation broth, or the precipitation of the carboxylic acid from the cell-free broth. Instead, the whole fermentation broth containing spent microorganism cells is acidified using a strong mineral acid, which results in the liberation of salts from the carboxylates formed during the fermentation process, to yield free carboxylic acids. The acidified broth, upon heating, separates into three immiscible phases, namely, an organic phase containing substantially pure, free carboxylic acids, an aqueous phase containing some spent cells, and a solid phase containing mostly spent cells. The organic phase containing substantially pure carboxylic acids can be easily separated from the other two phases to provide substantially pure carboxylic acids in high yield, i.e., yield of about 70 to about 100% by weight.
Accordingly, the presently claimed method for separating carboxylic acids from an impure fermentation broth provides a high purity product, reasonably low operating costs and an increase in productivity resulting from the reduction in the amount of time required to separate the carboxylic acids.
As used herein, the term “fermentation broth” refers to the broth obtained after completion of fermentation and/or bioconversion by a microorganism in a culture medium which includes a nitrogen source, an organic substrate, and optionally a co substrate.
As used herein, the term “carboxylic acids” refers to compounds possessing one or more carboxyl groups. The term “polycarboxylic acids” refers to compounds possessing two or more carboxyl groups.
Other than in the claims and in the operating examples, or where otherwise indicated, all numbers expressing quantities of ingredients or reaction conditions used herein are to be understood as modified in all instances by the term “about”.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The carboxylic acids to be separated from the fermentation broth may be monocarboxylic acids, or polycarboxylic acids. Preferably, the polycarboxylic acids are dicarboxylic acids. Examples of suitable dicarboxylic acids include, but are not limited to, 9-octadecenedioic acid, octadecanedioic acid, tetradecanedioic acid, dodecanedioic acid, hexadecanedioic acid, hexadecenedioic acid, heptadecanedioic acid, eicosanedioic acid and eicosenedioic acid, tridecanedioic acid, pentadecanedioic acid and combinations thereof.
Production of carboxylic acids by fermentation with various microorganisms is well known to those skilled in the art as described more fully herein below. U.S. Pat. Nos. 5,254,466, 5,648,247, and 5,620,878, the contents of each of which are inc
Chaudhry Mahreen
Deluca Peter
Drach John E.
Henkel Corporation
Hess Susan L.
LandOfFree
Separation and purification of carboxylic acids from... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Separation and purification of carboxylic acids from..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Separation and purification of carboxylic acids from... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2493202