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Patent Issued for Process for Simultaneous Saccharification and Fermentation for Production of Ethanol

February 25, 2014



By a News Reporter-Staff News Editor at Life Science Weekly -- A patent by the inventors Hitz, William D. (Wilmington, DE); Huang, Tom (Fremont, CA); Iverson, Amanda Kathleen (Wilmington, DE); Lefebvre, Brian G. (Wilmington, DE); Mitchinson, Colin (Half Moon Bay, CA), filed on December 17, 2010, was published online on February 11, 2014, according to news reporting originating from Alexandria, Virginia, by NewsRx correspondents (see also E I du Pont de Nemours and Company).

Patent number 8647850 is assigned to E I du Pont de Nemours and Company (Wilmington, DE).

The following quote was obtained by the news editors from the background information supplied by the inventors: "Fuel ethanol produced from renewable resources is one of the long-term solutions to global fossil fuel shortages, rising energy costs, and global warming effects related to increased atmospheric carbon dioxide. Fuel ethanol from renewable resources is produced by fermentation of sugars. Currently in the United States, glucose derived from corn grain is the most abundant sugar source for ethanol production. Due to the demands for corn grain as a feed and food supply, methods of converting various types of cellulosic biomass (including hemicellulose) to fermentable sugars are being developed. Sugar derived from this biomass source is a mixture of hexoses and pentoses, primarily glucose and xylose. As a result of developments in cellulosic biomass processing, these sugars may be released in high concentrations and used in fermentation in high concentrations to produce ethanol, with reduced water consumption and higher throughput. As such, conversion of biomass to ethanol poses great possibility for improving environmental impacts by providing a potentially economically viable alternative to fossil fuels.

"Typical processes for the conversion of cellulosic biomass to ethanol comprise three steps; chemical and/or physical treatment of the biomass to reduce the lignin content of the biomass and to make polysaccharides available for enzymatic hydrolysis; saccharification or digestion or hydrolysis where polysaccharides are enzymatically converted to fermentable sugars; and fermentation where the fermentable sugars are consumed by an ethanologen for the production of ethanol. In some cases, depending on the conditions and the nature of the ethanologen, it may be energetically most efficient to combine the saccharification and fermentation steps. Optimization of each of these steps is needed for the production of high concentrations of ethanol.

"Ethanologens have typically been yeast (e.g. Saccharomyces) or bacteria (e.g. Zymomonas). Zymomonas is well suited for the production of ethanol as it is generally robust, grows in relatively high glucose concentrations, and can be engineered to utilize C5 sugars such as xylose and arabinose (common products of saccharification) for ethanol generation. However, effective utilization of Zymomonas requires improving processes for using Zymomonas as an ethanologen.

"The use of Zymomonas as an ethanologen is known (Saddler et al., Can. J. Microbiol. (1982), 28(12), 1311-19: Golias et al., J. Biotechnol., (26 Jun. 2002) (96) 2, pp. 155168; Ma et al., Renewable Energy (2009) 34:1466-1470), however Zymomonas is sensitive to high concentrations of acetate produced by many of the biomass pretreatment methods. Reduction of acetate levels can be achieved by methods such as washing pretreated biomass (Teixeira et al., Appl. Biochem. Biotechnol., (Spring, 2000) Vol. 84-86, pp. 111-127).

"The use of a xylose utilizing Zymomonas in simultaneous saccharifcation and fermentation is also known, where the biomass was treated with sodium hydroxide followed by peracetic acid and washed (Teixeira et al. Supra). Eklund et al. (Enzyme and Microbial Technology (1995), 17(3), 255-9) demonstrated simultaneous saccharification and fermentation using Zymomonas as the ethanologen where the biomass was pre-treated with steam and sulfur dioxide and washed, then fermentation was at a total insoluble solids concentration of about 10% in both flasks and fermenters with some agitation, where the production of ethanol was about 28 g/L.

"Additionally McMillan et al., (Appl. Biochem. Biotechnol. (1999) Vol. 77-79:649-665.) demonstrated the use of Zymomonas in a simultaneous saccharification and fermentation process where the strain of Zymomonas was adapted to poplar hydrolysate, the biomass was pre-treated with dilute acid then MTBE extracted, the saccharification enzyme was cellulase, and where the fermentation was run in a fermenter with 11.5% insoluble solids and an agitator at 150 RPM. Using this method the authors were able to achieve production of about 35 g/L ethanol.

"The above methods demonstrate that Zymomonas may be used in processes of simultaneous saccharification and fermentation for the production of ethanol. However, the production of ethanol using these methods is low and it is clear that the processes need to be optimized to effect the production of ethanol in commercial quantities."

In addition to the background information obtained for this patent, NewsRx journalists also obtained the inventors' summary information for this patent: "The methods of the invention seek to solve the problem of optimizing the use of a prokaryotic ethanologen in simultaneous saccharification and fermentation (SSF) processes via identifying conditions that allow for the use of high input insoluble solids content in the saccharification and fermentation mixture, and that support production by the prokaryotic ethanologen such that high ethanol production is achieved. Ethanol production using the present methods may be in excess of 60 g/L.

"Accordingly the invention provides a method for the production of ethanol comprising:

"a) providing pretreated biomass comprising insoluble solids and polysaccharides;

"b) providing at least one saccharification enzyme for the conversion of polysaccharides to fermentable sugars;

"c) providing a prokaryotic ethanologen;

"d) preparing, in a bioreactor comprising an agitation means, a saccharification-fermentation mixture comprising the pretreated biomass of a), the saccharification enzyme of b), and the prokaryotic ethanologen of c); and

"e) growing the prokaryotic ethanologen in the saccharification-fermentation mixture wherein the concentration of total input insoluble solids in the saccharification-fermentation mixture is at least about 16% based on dry weight per liter, and wherein the prokaryotic ethanologen produces ethanol. In one aspect of the invention the agitation means of the invention provides no more power than about 0.2 watt/kg of total saccharification-fermentation mixture.

"In another aspect the invention provides a method for the production of ethanol comprising:

"a) providing pretreated biomass of particle size equal to or less than about 100 .mu.m or a particle size of equal to or more than about 600 .mu.m, comprising insoluble solids and polysaccharides;

"b) providing at least one saccharification enzyme for the conversion of polysaccharides to fermentable sugars;

"c) providing a prokaryotic ethanologen;

"d) preparing in a bioreactor comprising an agitation means a saccharification-fermentation mixture comprising the pretreated biomass of a), the saccharification enzyme of b), and the prokaryotic ethanologen of c); and

"e) growing the prokaryotic ethanologen in the saccharification-fermentation mixture wherein: 1) the concentration of total input insoluble solids in the saccharification-fermentation mixture is at least about 16% based on dry weight per liter; and 2) wherein the prokaryotic ethanologen produces ethanol. In another aspect the invention provides a saccharification-fermentation system comprising:

"a) a pretreated biomass comprising insoluble solids and polysaccharides;

"b) at least one saccharification enzyme for the conversion of polysaccharides to fermentable sugars; and

"c) a prokaryotic ethanologen;

"wherein the biomass of (a), enzyme of (b), and ethanologen of are combined in a saccharification-fermentation mixture, having a concentration of total input insoluble solids that is at least about 16 wt. % based on dry weight per liter."

URL and more information on this patent, see: Hitz, William D.; Huang, Tom; Iverson, Amanda Kathleen; Lefebvre, Brian G.; Mitchinson, Colin. Process for Simultaneous Saccharification and Fermentation for Production of Ethanol. U.S. Patent Number 8647850, filed December 17, 2010, and published online on February 11, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=65&u=%2Fnetahtml%2FPTO%2Fsearch-bool.html&r=3234&f=G&l=50&co1=AND&d=PTXT&s1=20140211.PD.&OS=ISD/20140211&RS=ISD/20140211

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

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Source: Life Science Weekly


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