News Column

Patent Issued for Control of Contaminant Microorganisms in Fermentation Processes with Peroxygen-Releasing Compounds

July 8, 2014

By a News Reporter-Staff News Editor at Life Science Weekly -- E I du Pont de Nemours and Company (Wilmington, DE) has been issued patent number 8759051, according to news reporting originating out of Alexandria, Virginia, by NewsRx editors (see also E I du Pont de Nemours and Company).

The patent's inventors are Solomon, Ethan Baruch (Wilmington, DE); Okull, Derrick Otieno (Pleasanton, CA); Tufano, Thomas Peter (Wilmington, DE).

This patent was filed on December 19, 2011 and was published online on June 24, 2014.

From the background information supplied by the inventors, news correspondents obtained the following quote: "In the last decade, the use of ethanol as a transportation fuel has increased significantly. Ethanol production in the United States rose from approximately 6.4 billion liters in the year 2000 to over 37 billion liters in 2009. The number of ethanol plants increased from 54 in 2000 to 170 in 2009. Similar increases in production and plant construction have occurred in Latin America and Europe. In 2007, the United States Congress enacted the Energy Independence and Security Act (H.R. 6), which set the renewable fuel standard at 136 billion liters of ethanol by the year 2022. If this standard is to be met, the ethanol industry will continue to grow.

"Currently both industrial ethanol (e.g., fuel) and beverage ethanol are produced on large scale from agricultural (natural) feedstocks by fermentation processes in which sugar is converted to ethanol and carbon dioxide by inoculant yeast. Many feedstocks can be used to provide the sugar for fermenting, including potentially, any starch or cellulosic material, which includes nearly all plants, as any starch or cellulose can be a precursor to sugar. Some of the common feedstocks particularly suitable for producing fuel ethanol include corn, milo, sorghum, sugar cane, sugar beets and molasses.

"The feedstocks used for ethanol production are natural products therefore, a wide variety of microorganisms such as bacteria, fungi, and yeasts are likely to be naturally present in the feedstocks. Commercial fermentation process conditions are not completely sterile, hence these 'contaminant microorganisms' will be present in the process. In commercial ethanol production, microorganisms of greatest concern are lactic acid-producing bacteria and acetic acid-producing bacteria. Such bacteria enter the process from several sources including raw materials, equipment, process water, air, and inoculant yeast, among others. Concentrations of such bacteria may increase in the process environment either through introduction with incoming materials (raw materials, water, air, yeast) or naturally proliferate as a result of conditions favorable to bacterial growth. The optimum atmosphere for yeast production is also extremely conducive to the growth of these bacteria. Organic acids produced by the bacteria inhibit the growth of yeasts and thus reduce ethanol production rate. The bacteria may also consume sugars and other nutrients intended for use by the yeast to produce desired products, rendering the entire process less economical.

"Many fermentation processes use antibiotics as antimicrobial compositions. Such use has become disfavored due to suspected development of antibiotic-resistant bacteria and accumulation of antibiotic residues in fermentation byproducts. Antibiotic-resistant bacteria are a significant concern in human health.

"Byproducts of ethanol production include solids that are collected after distillation of the ethanol product. Such solids include distillers dried grains with solubles (DDGS) and distiller's wet grains with solubles (DWGS). Many countries are considering regulatory actions that would limit or eliminate the use of antibiotics for ethanol production. DDGS and DWGS are sold as animal feed products.

"The need for antimicrobial treatments is increasing, not only because of the growth in production volume of ethanol but also the expansion in size of ethanol production facilities. Whereas a plant producing 150-200 million liters per year (MMly) was considered a large facility just a few years ago, 380 MMly (or more) facilities are today's industry standard. In fed-batch processes, the volume of individual fermentation batches has increased significantly. To accommodate this added capacity, the flow rate of feedstock (commonly known as 'mash' once it has been prepared for entry into fermentation) into a fermentation system has increased from approximately 2000-3000 liters per minute to 4500-6000 liters per minute in the largest ethanol production facilities.

"WO 2007/149450 describes the use of stabilized chlorine dioxide (SCD) to prevent bacterial contamination in ethanol production. SCD is added prior to the onset of significant bacterial growth in ethanol production, as a preventive rather than as a remedial measure. The growth of contaminant bacteria prior to and during the fermentation of sugar to alcohol is thus substantially prevented, creating conditions that enhance growth of inoculant yeast and enable inoculant yeast to produce ethanol without inhibition by organic acids produced by the bacteria.

"Patent application CA 2,300,807 describes the use of urea hydrogen peroxide (UHP) to prevent bacterial growth in fermentation processes. UHP is available commercially in only limited quantities as this adduct has production and storage issues. UHP is added to the process prior to the introduction of yeast, thus eliminating a substantial population of bacterial contaminants, and allowing inoculant yeast to convert fermentation feedstocks into ethanol unhindered. UHP can only be utilized prior to the introduction of inoculant yeast, as the yeast is capable of metabolizing, and thus neutralizing the UHP and rendering it inactive against bacteria. UHP is also not stable during storage conditions commonly encountered in the ethanol industry.

"Although some methods are known, there remains demand for improved methods, for addressing contaminant microorganisms in the fermentation industry, both for carbohydrate-containing feedstocks and in fermentation processes. An improved method should preferably be antibiotic-free and not result in residues that accumulate in fermentation coproducts or give rise to antibiotic-resistant bacteria. The method should be efficacious at a wide variety of pH ranges and conditions encountered in the fermentation industry. The method should also use treatment that has a reasonable shelf life, prior to use. There is also a need to improve economics of today's larger volume fermentation processes. The present invention meets these needs."

Supplementing the background information on this patent, NewsRx reporters also obtained the inventors' summary information for this patent: "The present invention provides a method for controlling growth of contaminant microorganisms in a fermentation process using a nitrogen-free peroxygen-releasing compound, such as sodium percarbonate, calcium peroxide, or magnesium peroxide. The method comprises adding a nitrogen-free peroxygen-releasing compound to one or more steps of a fermentation process, wherein the fermentation process comprises (i) providing an inoculant, a fermentable sugar and process water; (ii) introducing separately, or in any combination, the inoculant, fermentable sugar and process water into a fermentation vessel to provide a fermentation broth; (iii) contacting the inoculant with the fermentable sugar in the fermentation vessel at a temperature at which the inoculant converts the fermentable sugar to ethanol. Optionally nutrients are added to one or more of the inoculant, fermentable sugar and process water. Nutrients may also be added directly to the fermentation vessel. The peroxygen-releasing compound may be added to the inoculant, fermentable sugar or process water prior to introducing each of these to the fermentation vessel. Alternatively the peroxygen-releasing compound may be added directly to the fermentation vessel.

"The peroxygen-releasing compound may be formulated with nutrients and other products that might prove beneficial to the overall operation of a fermentation process. Nutrients may be used such as urea or diammonium phosphate (to provide a nitrogen source for the inoculant yeast) or minerals such as zinc or magnesium.

"The present invention provides a method for controlling the growth of contaminant microorganisms in the reactants (defined hereinbelow) in the fermentation broth, and in the products of a fermentation process. The method also controls growth of contaminant microorganisms on surfaces of components of a fermentation system. The method consists of, consists essentially of, or comprises the step of adding a nitrogen-free peroxygen-releasing compound to a reactant or the fermentation broth, or to a surface or into a vessel of the fermentation system.

"The present invention also provides a method that can be used in cleaning-in-place (CIP) applications to treat surfaces of equipment used in fermentation processes. By 'CIP' is meant herein that surfaces can be cleaned without the need to disassemble the equipment.

"The method includes adding a nitrogen-free peroxygen-releasing compound in an amount effective to control the growth of contaminant microorganisms without detrimental effect on the inoculant used in the fermentation process. The effective amount varies, but can be determined by one skilled in the art in view of the disclosures herein. The peroxygen-releasing compound may be added at a range of concentrations, but is typically added in an amount ranging from 0.0001% to 5% based on the total weight of the fermentation broth.

"The method of the present invention further provides a method to control growth of at least one contaminant microorganism in a carbohydrate feedstock wherein the step of providing a fermentable sugar comprises providing a carbohydrate feedstock and contacting the feedstock with a nitrogen-free peroxygen-releasing compound, wherein the carbohydrate content of the feedstock is at least 1% and preferably 1 to 70%, by weight, based on the total feedstock weight wherein the peroxygen-releasing compound is added in an effective amount. Typically the nitrogen-free peroxygen-releasing compound is added in an amount of 0.0001 to 5% of the peroxygen-releasing compound, based on the total weight of the feedstock."

For the URL and additional information on this patent, see: Solomon, Ethan Baruch; Okull, Derrick Otieno; Tufano, Thomas Peter. Control of Contaminant Microorganisms in Fermentation Processes with Peroxygen-Releasing Compounds. U.S. Patent Number 8759051, filed December 19, 2011, and published online on June 24, 2014. Patent URL:

Keywords for this news article include: Alcohols, Bacteria, Nitrogen, Ethanolamines, E I du Pont de Nemours and Company.

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Source: Life Science Weekly

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