Bio-based routes for succinic acid
Succinic acid is a valuable four-carbon molecule that serves as a viable replacement for its petroleum-derived cousin, maleic anhydride. It is commonly used in the plastics, textiles and pharmaceutical industries and is recognized as a versatile intermediate for production of solvents, chemicals and materials that can displace current petrochemical feedstocks.
Till recently, succinic acid was mainly produced by chemical processes, via hydrogenation of maleic anhydride to succinic anhydride, followed by hydration to succinic acid.
However, due to the environmental concerns and the concepts of sustainability, research has been directed towards the production of succinic acid by microbial fermentation using bacteria that can ferment sugars or sugars derived from wood wastes and plant crop residues.
Fermentative production of succinic acid has many advantages over chemical processes owing to its simplicity and environmentally friendly nature. In addition to the energy savings that accrue by substituting biomass for petroleum, carbon dioxide is “fixed” in the fermentation process, providing the potential to reduce greenhouse gas emissions during its production.
If succinic acid could be produced cheaply from biomass, the competitively-priced succinic acid could then be used directly or as a precursor for many industrial chemicals, and thus contribute to a significant reduction in use of petroleum resources.
Petrochemical routes to succinic acid
The production of non-captive succinic acid as a final product is small. It is purchased mostly by the food and pharmaceutical industries, where it is used as an acidulant and a salt-forming compound for specific formulations.
However, succinic acid is an intermediate occurring in a number of industrial processes that use maleic anhydride as starting material. Maleic anhydride, in turn, is made preferably from butane, which in turn is isolated from natural gas or obtained from petroleum cracking.
Maleic anhydride is first converted to succinic acid (or, in some processes, the dimethyl ester). A number of well-established, high-volume processes produce the solvent tetrahydrofuran (THF); the diol 1,4-butanediol (1,4-BDO); and another intermediate, gamma-butyrolactone (GBL). The chemical processes used require hydrogen and operate at high temperatures and pressures, but the conditions can be adjusted to yield any of the three products out of the same process.
THF can be opened and partially polymerized to give low-molecular weight polymers of polytetramethylene glycol (PTMEG), while GBL can be taken on to another solvent, N-methyl pyrrolidone (NMP).
Further, BDO can be used with PTMEG and (captive) succinic acid to make polyesters, which in turn, are used in polyurethane materials. Invista (a subsidiary of DuPont) markets PTMEG as Terathane glycol, the key intermediate for both Lycra elastane and high-value polyurethanes.
Petrochemical route to succinic acid & its common derivatives
Polyesters from succinic acid
Current markets for succinic acid
Succinic acid is a useful molecule and, currently, a moderately high-value chemical. It is a key compound in producing more than 30 commercially important product such as 1,4-BDO, THF, adipic acid and GBL.
It has industrial application in industries such as food, pharmaceuticals, resins, polymer, paints, cosmetics and inks etc. It is also used as surfactant, detergent extender, antifoam and ion-chelator.
World demand for succinic acid is currently around 40,000-tons annually.
Potential markets for bio-based succinic acid
If succinic acid could be produced cheaply from biomass, the lower cost would allow it to compete with chemicals currently produced from petroleum-based feedstocks. The competitively-priced succinic acid could be used directly or as a precursor for many industrial chemicals.
Three major potential markets for bio-based succinic acid have been identified:
Replacement for maleic anhydride
A primary use of succinic acid is as replacement of maleic anhydride for selective reduction to give the well-known 1,4-BDO, THF and GBL family of products. The replacement of maleic anhydride could alone represent a global market of about 2-mt for succinic acid.
1,4-BDO is widely used in a range of applications including production of engineering plastics, Lycra (spandex) fibres and solvents with estimated annual production of around 1.40-mt currently.
The hydrogenation/reduction chemistry for the conversion of succinic acid to these products is well known and is similar to the conversion of maleic anhydride to the same family of compounds. The only real technical consideration is the development of catalysts that would not be affected by impurities in the fermentation.
BDO derivatives and their applications
Combining 1,4-BDO and succinic acid also opens up the possibility of greener bio-polymers, such as polybutyl succinate (PBS), which is used in biodegradable packaging films and disposable cutlery.
The market for PBS is currently small – just 10,000 to 15,000 tons a year – but could swell with a 100% bio-based product.
Another potential market is in polyester polyols and polyurethanes, currently dominated by the use of adipic acid as precursor. Companies are looking at replacing the six-carbon adipic acid with four-carbon succinic acid, providing the costs become comparable, because adipic acid production is a messy process that produces a lot of carbon dioxide.
Pyrrolidones are used to make green solvents and eco-friendly chemicals for water treatment, and have a global market of about 0.50-mt.
Reaction of GBL with various amines leads to the production of materials such as pyrrolidone and N-methylpyrrolidone (NMP).
While succinic acid is a great platform molecule, it is not used much today because of its cost.
It has historically cost $3 to $5 per kg, depending on the prevailing oil price, much higher than petroleum-derived maleic anhydride, which sells at about $1.5 per kg. The lower price explains why maleic anhydride represents a market of about 2.0-mt, eclipsing succinic acid and consigning it to niche applications.
But given the right economics, the impact of succinic acid as a C4 platform chemical could easily exceed $1-bn a year by 2015. Market research firm, Frost & Sullivan believes the market will expand to 180,000-tons by 2015, thanks largely to the introduction of bio-based succinic acid.
The U.S. Department of Energy has funded considerable research over the past 15 years to develop improved microorganisms and separations technology to reduce the overall cost of bio-based succinic acid. Advances have reduced the cost from $2 per pound in 1992 to about $0.50 per pound in 2003 for bio-based succinic acid, and further reductions in cost are anticipated.
Biochemistry of bio-based succinic acid
The biochemistry for the production of succinic acid from monomeric sugars (both pentoses and hexoses) is well known.
The consumption of both the five-carbon sugars (pentoses, xylose, and arabinose from hemicellulose) and six-carbon sugars (hexoses, of which glucose from starch and fructose from cane sugar are the chief examples) goes through a common intermediate, phosphoenol pyruvate (PEP).
Biochemical pathway to succinic acid
Fermentation technology developments
The use of fermentation technology for the production of succinic acid has been the subject of intensive development over the past 15 years. Two main approaches have been pursued:
• The isolation of rumen bacteria from natural sources; and
• The metabolic engineering of E coli.
In 1996, MBI (Lansing, MI, USA) patented a unique bacterium, dubbed Actinobacillus succinogenes, it isolated from the rumen of bovine animals for production of succinic acid from sugars.
Since then, other organisms and their mutants have been isolated that produce important amounts of succinic acid; however, significant amounts of acetic acid and other acids are also produced.
Although some wild-type microorganisms are capable of producing succinic acid at a high concentration, the strains cannot be applied directly to industrial processes, due to two principal drawbacks:
• Most, although not all, succinic acid-producing microorganisms are strict anaerobes, which require a zero oxygen concentration throughout the entirety of the process. Although anaerobic fermentation is not technically difficult, operating the entire process under strict anaerobic conditions is not an easy task, and requires additional expensive equipments.
• Secondly, succinic acid-producing microorganisms generate other acids, including lactic acid and acetic acid, during fermentation. The purification of succinic acid from a mixture of these other acids is both inefficient and costly. As a result, the overall yield of succinic acid based on glucose is generally less than 80%.
Considering these drawbacks, therefore, intensive systems approaches have been undertaken to construct microorganisms capable of efficiently producing pure succinic acid under mild environmental conditions. For the best mutant (disclosed in the U.S. Patent 5,573,931), there is the additional complication of requiring magnesium as the base for neutralization of the fermentation, as well as the expensive nutrient, biotin. Magnesium is both expensive and difficult to recycle in the process and presents an important additional cost to be considered for use of this organism in a fermentation process.
The second approach, followed by the U.S. Department of Energy, is the production of mutations of E coli. The parent organism is a K-12 E. Coli, called NZN111, and through mutation the organism AFP111 was developed. The fermentation of the AFP111 strain can be neutralized with any ordinary base and has no unusual nutritional requirements.
A two-stage fermentation process has been developed by teams of researchers in which the organism is first grown under aerobic conditions and switched over to anaerobic conditions for fermentation. This is a very unusual process as compared to other E. Coli fermentations, which are usually completely aerobic or completely anaerobic.
The AFP111 utilizes carbonate in the anaerobic fermentation resulting in a high yield (over 90% weight basis) of succinate based on glucose. In a recently finished set of studies, the AFP111 organism and a new mutant called AFP184 were shown to produce succinate utilizing a mixed glucose and xylose feedstocks. These results are very exciting in light of the interest in developing mixed sugar feedstocks.
Organisms useful for succinic acid production
Organism Strain Sugars used
E. coli ATCC 202021 Hexoses (glucose)
Anaerobiospirillum succiniciproducens ATCC 29305 & ATCC 53488 Hexoses (glucose)
Actinobacillus succinogenes ATCC 55618 Hexoses (glucose) & pentoses (xylose and arabinose)
Downstream recovery of succinic acid
Downstream purification normally accounts for more than 60% of the total production cost in a typical fermentation process. In the case of succinic acid, separation of by-products including acetic, formic, lactic and pyruvic acids is most crucial.
Several methods for the purification have been developed.
In this process, ionized compounds are separated from non-ionized compounds by an ion exchange membrane. Succinic acid normally exists as succinate salt in the fermentation broth, while other impurities, including carbohydrates, proteins and amino acids, are mostly non-ionic.
Succinate in the fermentation broth is precipitated as calcium succinate by adding calcium hydroxide. Calcium succinate is recovered by filtration, and converted to succinic acid by sulphuric acid. The succinic acid is recovered by filtration, and further purified by acidic and basic ion exchangers. This process dramatically improved the purity of succinic acid from 44.5% in the fermentation broth to 94.2% (w/w) after purification.
Unlike the succinic acid recovery process based on electrodialysis, acidification does not completely remove proteins, mainly due to the saturation of the ion exchange sites with the succinate anion.
The reactive extraction of succinic acid with an amine-based extractant (tertiary amines such as tri-n-octylamine), is considered effective and economical because the process is operated at normal temperature and pressure.
More recently, an integrated succinic acid recovery process, composed of reactive extraction, vacuum distillation and crystallization, has been developed. It allows production of succinic acid with purity of 99.76% (w/w) and an yield of 73.09% (w/w) from the actual fermentation broth of M. succiniciproducens. This process is much simpler and more cost-effective than those mentioned above.
Simplified PFD of glucose fermentation to succinic acid
Hurdles for development
The major technical hurdles for the development of succinic acid as a building block include the development of low cost fermentation routes. There are currently two organisms under active development for the fermentation of sugars (both C6 and C5) to produce succinic acid. Based on the available information in the literature regarding these two organisms, significant improvement in the fermentation is still required to be competitive with petrochemical routes.
The major elements of improvement in the fermentation include the following:
Productivity improvements are required to reduce the capital and operating costs of the fermentation. A minimum productivity of 2.5 g/L/hr needs to be achieved in order for the process to be economically competitive.
It is essential for commercial fermentations to be run using minimal nutrients. Expensive nutrient components, such as yeast extract and biotin, must be eliminated. The nutrient requirements should be limited to the use of corn steep liquor or equivalent.
Final titer is also important when considering overall process costs. This is not a showstopper, but a high final titer will reduce overall separation and concentrating costs.
In an ideal situation the fermentation would be run at low pH, most preferably without requiring any neutralization. The cost of neutralization is not necessarily cost prohibitive, but the conversion of the salt to the free acid does add significant costs. If derivatives such as BDO, THF and GBL are going to be competitive from a cost perspective then low pH fermentation will be essential.
At least five groups are gearing up to develop commercial capacity for bio-based succinic acid. Three of them intend to bring over 140,000-tpa of capacity online by 2012.
DNP Green Technology
DNP Green Technology has set up a joint venture, called Bioamber, with agricultural research and development company, ARD (Agro-industrie Recherches et Dévelopements).
Bioamber commissioned, in December 2009, the first large scale unit for producing bio-based succinic acid in Pomacle (France), with a capacity of 2,000-tpa, at an investment of €21-mn. The process uses an E. coli strain developed specifically to produce succinic acid, with wheat-derived glucose as substrate. The purpose of the Pomacle plant is to showcase the technology. The company says it expects to have two plants – with an initial capacity of 25,000-30,000-tpa each – operational in 2012.
In Feb. 2010, in a bid to move downstream, DNP Green acquired a controlling stake in Sinoven Biopolymers Inc., a private US company, with a sales office in Philadelphia (PA, USA) and a manufacturing and formulation development facility in Shanghai (China). Sinoven Biopolymers has proprietary technology for modifying polybutylene succinate (PBS), giving it unique properties that other biodegradable polymers do not offer. These include heat resistance above 100°C, excellent strength and the ability to be processed in existing production equipment.
In March this year, DNP and GreenField Ethanol, a US-based ethanol producer, announced a partnership to build a $50-mn bio-based succinic acid refinery that will produce a new generation of environmentally friendly deicing solutions, with a negative carbon footprint and less corrosive nature as compared to traditional deicers.
In April 2010, Bioamber and Mitsui & Co. Ltd signed an agreement granting Mitsui exclusive Asian distribution rights for the bio-based succinic acid.
In July 2010, Bioamber signed a licensing agreement with DuPont Applied BioSciences, for bio-based derivatives of succinic acid. As per the agreement, DuPont has the right of first refusal to secure off-take from future commercial plants.
Photo of Bioamber plant to go here
DSM & Roquette Frères
In June 2010, Royal DSM N.V., headquartered in the Netherlands, and Roquette Frères, the global starch and starch-derivatives company headquartered in France, signed a joint venture agreement for production, commercialization and market development of bio-based succinic acid.
DSM and Roquette will each have a 50% stake in the new entity, Reverdia V.o.f., headquartered in the Netherlands.
Since early 2008 the two companies have been working together to develop the most sustainable technology to produce bio-based succinic acid. The first testing volumes were produced in a demonstration plant in Lestrem (France) that was built in 2009.
DSM is reported to be planning to scale-up to a facility capable of producing 10,000-tpa to 20,000-tpa of succinic acid by mid- to late-2011, prior to ramping up to a commercial scale at around 50,000-tpa.
The joint venture plans to focus on applications such as 1,4-BDO, polyurethane resins, and biopolymers such as PBS into applications, among others, in paints and coatings, automotive and textiles.
BASF and CSM
In September 2009, BASF SE and CSM NV announced cooperation between their respective subsidiaries BASF Future Business GmbH and Purac for development of production of bio-based succinic acid, using a BASF-developed bacterial strain (Basfi succiniproducens) and glycerine or glucose as a feedstock.
Both partners have been working on the industrial fermentation and downstream processing processes and will start production of commercial volumes in the second quarter of 2010 from a Purac facility in Spain.
The bio-based succinic acid will be applied as a monomeric building block in a variety of biopolymers, e.g. biodegradable polyesters.
Myriant Technologies LLC
Myriant Technologies LLC, a privately-held biotech developer and manufacturer of renewable biochemicals, announced in April this year that it has begun to draw funds under the US Department of Energy’s $50-mn grant for its bio-based succinic acid facility in Lake Providence (Louisiana, USA). Design engineering has commenced, aimed at a start of construction by September 2010, it said.
Myriant’s renewable succinic acid process is the result of a four year development effort and is derived from the company’s proven D-lactic acid technology, which began commercial production in June 2008. The technology is based on a proprietary platform that involves modified (non-GMO) E. coli strains to produce succinic acid using locally available sorghum as feedstock.
The plant proposed to be set up is likely to have a capacity of about 30-mn lbs per year of bio-based succinic acid to start with, and a possible scale up to 70,000-tons to 80,000-tons in 2012.
Earlier, in 2009, the company announced an alliance with Uhde Corporation of America for the engineering, procurement & construction (EPC) of succinic acid plants, after successfully piloting the process together to produce ton-sized samples for customers.
The initial marketing focus is expected to be on smaller, existing markets for succinic acid, and eventually the 1,4-BDO market, and as replacement to adipic acid in some applications.
Mitsubishi Chemical Company & PTT
Mitsubishi Chemical Corporation (Tokyo, Japan) (MCC) and PTT Public Company Ltd. (Bangkok, Thailand) announced in September 2009, that they have agreed to study the development of bio-based PBS.
MCC produces PBS under the tradename GS Pla, from petro-based succinic acid in Japan and markets it worldwide.
MCC, which has developed an original process to produce bio-based succinic acid, was formerly collaborating with Ajinomoto on the project. The company claims the alliance succeeded in its goal of advancing basic research on succinic acid and that it now owns a proprietary organism that boasts high efficiency and safety.
MCC and PTT are now aiming to complete the feasibility study for establishing a joint venture by June, 2010.
There is a significant market opportunity for development of bio-based products from the C4 building block diacids, including succinic acid. When considered in aggregate, the diacid family offers access to a wide range of products that address a number of high volume chemical markets.
But the development of bio-based succinic acid faces major challenges. In order to be competitive with petro-derived product, fermentation cost needs to around $0.25 per lb or below – a significant technical challenge that still needs to be met. This will involve further improving yields in the fermentation process and bringing efficiencies into the downstream processes for purifying the acid from the fermentation broth.
If all of the efforts now underway come to fruition, worldwide production of succinic acid could increase by as much as 500% in the next five years. If that happens, the challenge will shift to marketing all of the new capacity, from the technical challenges that technology developers are now grappling with.
Finally, there is the risk of perception – there have been few successes in the bio-production of chemicals to date!
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