FUTURE DIRECTIONS FOR THE SUGAR INDUSTRY
by Mary An Godshall
Sugar Processing Research Institute, Inc., New Orleans, Louisiana, USA
Summary
Current low sugar prices is certainly forcing the issue of exploring possible opportunities on adding value to the product. One avenue is through the conversion of sucrose to a fine chemical or food product. This paper reviews high valve products derived from sucrose on the market or with commercial potential. Sucrose esters are especially promising. Microbial production of natural biodegradable plastics, using sucrose as the carbohydrate source is an exciting new area. It is envisioned that the sugar factory of the future will be an integrated producer of a range of low to high value products, whose manufacture is scaled up or down as needed.
Introduction
The sugar industry is faced with dual challenges of oversupply and low prices. Aside from innovations in processing and a few low-value products, what avenues are available to the sugar industry for expansion? What are some ways to make more use of sucrose and the feedstocks available from the cane and beet sugar industry?
The sugar industry is in need, not only of innovative ideas (because there are many of those around), but also of the vision and will to implement new ways of thinking and doing. We need an integrated approach to new high-value products, new uses and new concepts in sugar manufacturing.
Value is added when a bulk commodity, typically very inexpensive, is converted to a fine chemical with desirable properties. Table 1 shows the increase in value from commodities to fine chemicals. Among bulk carbohydrate commodities, sucrose is second only to cellulose and far exceeds in output all other commercial carbohydrates combined, as shown in Table 2. It is estimated that only 1.7% of annual sucrose production goes to non-food uses. Sucrose and its co-products lend themselves to possibilities in many areas:
Looking at this list, it is possible to imagine the sugar factory of the future being an integrated producer, not only of sucrose, but of important high-value products, whose manufacture could be scaled up or down, as circumstances, economics and demand dictate.
The sucrose molecule is very reactive
Sucrose is both chemically and enzymatically reactive. It has 8 hydroxyl groups available for reaction (see Figure 1), both a benefit and a hindrance; a hindrance because it is difficult to control the reactivity of so many hydroxyl groups, so there are potentially many different products; a benefit, for the same reason. Sucrose is also an exceptional molecule for enzymatic synthesis, being hydrolyzed by enzymes as well as acting as a donor molecule for transfer reactions, leading to new products, such as polymers, oligosaccharides and non-caloric sweeteners (Vogel, 2000).
High value food products from sucrose
Sucralose
Sucralose was discovered in 1976 by Tate & Lyle researchers when they added 3 chlorine atoms to the sucrose molecule and realized they had created a substance 600 times sweeter than sucrose, with the same taste as sucrose but which did not break down in the body. Testing showed the compound to be safe for human consumption. In 1991, Canada became the first country to approve its use in foods. In 1998, sucralose was approved by the FDA for use in the United States; it is now used in at least 28 countries. McNeil Specialty Products Company, New Brunswick, New Jersey, sells sucralose under the brand name Splenda. At least 120 products sold in the U.S. use sucralose as a sweetener. The value of sucralose is US $200/lb.
Olestra
Olestra is a sucrose-based fat substitute, developed by Proctor and Gambel in the early 1970s. It was approved for food use by the FDA in January 1996 after years of testing. To make it, sucrose is reacted with fatty acids to produce a liquid sucrose polyester. Olestra is sold by P&G under the brand name Olean. Olestra has properties similar to liquid vegetable oil but without the calories. Currently, it is used to make savory snacks, specifically potato chips, in a partnership between Frito-Lay and P&G. The product created a US$400 million market the first year, and is expected to become a billion dollar market soon.
Fructo-oligosaccharides
Fructo-oligosaccharides represent an interesting case study in the development of a new product falling somewhere between the category of food additive and nutraceutical. Also known as FOS, and commercially known as Neosugar and Meijioligo, FOS are a new health food made by fermentation or enzymatic transformation of sucrose. It is extremely popular in Japan, and has also garnered interest in Europe and North America. FOS are said to be good for "abdominal health" in that they promote the growth of Bifidobacteria in the gut, which are supposed to confer many benefits to the body. It is nondigestible to partially digestible, with sweetness ranging between a third to abut 80 percent that of sucrose, depending on composition. It is sold as a syrup or a powder, usually containing some proportion of sucrose, along with three fructose-based oligosaccharides - kestose, nystose, and fructofuranosyl nystose. A fungal enzyme , fructosyl-transferase, forms oligosaccharides from sucrose syrup. It is in commercial production by at least two companies, Meiji Seika in Japan and Taiwan Sugar. It has received GRAS status (generally recognized as safe) from the FDA and is worth about US$200/kg retail. The market volume in Japan is estimated at more than 4000 metric tons per annum. Among some of its promising non-food uses are protecting swine from E. coli infection and controlling swine odor (1995 National Pork Board Report).
High value pharmaceuticals from sucrose
Sucralfate
Sucralfate, brand name, Carafate, is a sucrose aluminum hydroxide sulfate complex used as an ulcer medication for humans and animals. It is not absorbed by the body and has unique ulcer-fighting characteristics, acting like and "ulcer bandage," actively assisting in healing. Its value is between US$300 and 350/lb.
Polysucrose
Polysucrose, commercially known as Ficoll 400 (registered name of Pharmacia) and Dormacoll in Germany, is crosskinked sucrose, a copolymer of sucrose and epichlorhydrin, with a molecular weight of about 400,000. It is used to make density gradients for cell separation and as a diagnostic. Polysucrose is worth over US$400/lb. Polysucrose may also have some nutraceutical or food additive potential. A recent U.S. Patent (US 5980968) has promoted it as an ingredient in sports performance drinks, and an Iron Polysucrose food supplement is sold in India.
Specialty sucrose esters
A promising area for added sucrose use in fine chemicals production is the growing area of sucrose esters. Sucrose esters can take many forms because of the 8 hydroxyl groups in sucrose available for reaction and the many fatty acid groups, from acetate on up to larger, more bulky fats that can be reacted with sucrose. This flexibility means that many products and functionalities can be tailored, based on the fatty acid moiety used. Sucrose esters have many food and non-food uses, especially as surfactants and emulsifiers, with growing applications in pharmaceuticals, cosmetics, detergents and food because they are readily biodegradable, non-toxic and mild to the skin. A small, high value, world-wide market of about 2000 tons exists for specialty sucrose esters. A recent patent discloses a new way to make homogeneous sucrose esters (Bazin, et al., 2001).
Sucrose acetate isobutyrate
The largest volume use of a sucrose ester (~ 100,000 tons) is that of sucrose acetate isobutyrate (SAIB), used both in food and industrially. Industrial grade SAIB sells for about US$4.50/lb, and food grade for about US$7-8.00/lb. It is used in automotive paints, as a clouding and stabilizing agent in beverages, in nail polish and hair spray, among other uses, in over 40 countries. With its approval in 1999 in the U.S. for non-alcoholic beverages, its use is expected to increased greatly.
Sucrose-based detergents
Sucrose esters can be made into mild, biodegradable, non-ionic detergents, with anti-bacterial and other properties built in. This is a small, but growing market. In Argentina, Derisa Corp. markets a sucrose detergent called Sucrotex, and sucrose detergants are also manufactured in the Philippines. There is great interest in these products in Europe.
New products from sucrose
New products made from sucrose, with novel properties and promising uses, continue to appear out of research laboratories. While most of these products are not yet commercialized, they represent the potential sucrose has as a feedstock in various applications.
Sucrose thermal oligosaccharide caramel
Researchers at the University of Montana developed a sucrose thermal oligosaccharide caramel (STOC), using controlled pyrolysis of sucrose (Manley-Harris and Richards, 1993, 1995). Amorphous sucrose, heated with citric acid produces fructoglucan in 30% yield. It functions as a feeding supplement for enhancing growth of broiler chickens (Orban, et al., 1997) and may have application as a possible non-caloric food bulking agent or fat substitute. These researchers have also experimented with co-reacting other carbohydrates with sucrose to produce other products. For example, a controlled thermal reaction between sucrose and cyclodextrin produced fructosecyclodextrin compounds with the ability to enhance the solubility of inclusion complexes. These may have applications as flavor and vitamin carriers in foods.
Sucrose epoxy
Dr. Nozar Sachinvala, a research scientist at the Southern Regional Research Center of the USDA in New Orleans has discovered a series of epoxy allyl sucroses that are neither mutagenic nor cytotoxic, in contrast to the petrochemical derived diepoxide most widely usd in epoxy resins (Sachinvala, et al., 1991, 1994, 1998). He has developed several types of materials, which can form metal-to-metal, metal-to-glass and fiber-to-fiber bonds. Large markets for sugarbased adhesives are foreseen in nonwoven textiles, wallboard, home insulation and other materials of construction.
Sucrose hydrogels (sucrogels)
Compounds known as sucrose hydrogels or sucrogels can be made in a two step procedure. By adjusting the crosslink ratio and initial monomer concentration, the properties of the hydrogels can be manipulated over a wide range (Patil, et al., 1996; Chen & Park, 2000). The products are super-porous and fast swelling, with potential use in controlled release drug delivery. Since super porous sucrogels can be made in any size and shape and with attractive properties, they should find many industrial applications (Chen & Park, 2000).
Biodegradable plastic (bioplastic)
An area generating excitement concerning environmentally friendly "green chemistry" is the production of natural biodegradable plastics by microorganisms. Various bacterial species produce biodegradable plastics as storage polymers within their cells. Between 50-60 percent of a microorganism's body weight can be bioplastic, and in some cases, as much as 90%. Bioplastics are expensive, $10/kg (conventional plastics are less than $1/kg), but have the advantage that they can be processed on the same equipment for making conventional plastics. Research is ongoing to engineer bacteria to make novel polyhydroxyalkanoates (PHAs) and other polymers. Sucrose and molasses are a preferred carbon source (Lee, et al., 1999; Liu, et al., 1998).
Metabolix, Inc., Cambridge, Massachusetts, currently produces the only commercial bioplastic, Biopol used for medical containers and other high value applications. Research is ongoing to genetically engineer various plants to produce bioplastics in place of microorganisms.
The sugar factory of the future - Energy sufficient and diversifed
The sugar factory of the future, in strategic alliances with manufacturing, marketing and other partners, utilizing new technologies and new chemistries, will be energy sufficient and produce a range of low, medium and high value products, whose output will be tailored to the demands of the times. The sugar factory of the future already has it share of champions (Allen, et al., 1997; Kampen and Njapau, 2001; Rogers, et al., 2001), and we are seeing activity around the world. For example, pilot experiments are underway in Brazil to integrate biodegradable plastic, sugar and ethanol production into a sugar mill, along with energy production from bagasse and trash (Rosell, et al., 2001).
In Colombia, pre-feasibility studies on using the green harvest residues of sugarcane to generate electrical power have been conducted (Briceņo, et al., 2001). Long term studies on production of electricity from cane residues and gasification of bagasse are underway in Australia, Brazil and India, and other studies have been proposed or are underway in Hawaii, Thailand, Costa Rica, Jamaica, Philippines, and Cuba. An excellent review on biomass power generation utilizing sugarcane was recently published (Waldheim, et al., 2000).
Sugarcane is ideally suited for energy sufficiency, since it has the highest biomass production, and cane mills are already set up to produce most of their own energy from bagasse. Energy canes, cane hybrids developed to produce the maximum amount of biomass as a resource for making both fuel and sugar/chemical feedstocks, have been developed in Louisiana that approach the theoretical maximum fresh weight yield of sugarcane biomass: 307Mt/ha/year vs the theoretical maximum of 358 Mt/ha/yr (Legendre and Burner, 1995).
Last, but not least, is that scenario of the future, the gene expression of added value products in the sugar cane or sugar beet plant. Given the technology developing today, the imagination is the only limitation as to what products might be produced. Practical issues of recovery will be important issues.
A lot of current interest
There is a lot of current interest in exploiting agricultural biomass for new products, new energy sources and new chemistries. Using carbohydrate feedstocks creates the possibility of creating biodegradable, and thus environmentally friendly products, as well as providing a sustainable resource for the feedstock. This review has not touched on the many potential products from bagasse and molasses.
The twenty-first century should see the move from a petrochemical-based economy to a carbohydrate-based economy. The U.S. Department of Commerce has a blueprint of its renewable resources vision entitled, The Roadmap for the Future, in which the years 2020 and 2050 are seen as milepost years on the way to an energy-efficient, plant-based economy.
Many of these ideas may be ones whose time has not yet come, but there can be no doubt that the time is coming for this sort of integrated thinking, and the sugar industry should be poised to take advantage of it.
It has been stated that carbohydrates are the "sleeping giant" of biotechnology and that carbohydrates will be the next century's feedstock alternative to petroleum-based products (Yalpani, 1998). We are now at the start of that "next" century. It will be interesting to see what it holds for the sugar industry.
References
Allen, C.J., Mackay, M. M. Aylward, J.H., Campbell, J.A. New technologies for sugar milling and by-product modification, In: Keating, B.a. and Wilson. J.R. (eds), Intensive Sugarcane Production: Meeting the Challenges Beyond 2000, CAB Int., Wallingford, UK, 1997, 267-286.
Bazin, H.G., Polat, T., Linhardt, R.J. Sucrose based surfactants and methods thereof, U.S. Patent 6,184,196, Feb. 6, 2001
Briceņo, C.O., Cock, J.H., Torres, J.S. Electric power from green havesting residues of sugar cane in Colombia, Sugar Cane Int., March 2001, 15-19.
Chen, J., Park, K. Synthesis of fastswelling, superporous sucrose hydrogels, Carb. Polymers, 2000, 41, 259-268.
Gerngross, T.U., Slater, S.C. How green are green plastics? Scientific American, Aug. 2000, 37-41.
Kampen, W.H., Njapau, H. The biorefinery concept. Paper presented at 31st Annual Joint Meeting of the American Society of Sugar Cane Technologists, June 2001, New Orleans, LA.
Lee, S.Y., Lee, Y. Wang, f. Chiral compounds from bacterial polyesters: Sugars to plastics to fine chemicals. Biotech. and Bioeng., 1999, 65, 363-368,
Legendre, B.L., Burner, D.M. Biomass production of sugarcane cultivars and early-generation hybrids, Biomass and Bioenergy, 1995, 8, 55-61.
Liu, F., Li, W., Ridgway, D., Gu, T., and Shen, Z. Production of poly-$-hydroxybutyrate on molasses by recombinant Escherichia coli, Biotechnology Letters, 1998, 20, 345-348.
Manley-Harris, M., Richards, G.N. A novel fructoglucan from the thermal polymerization of sucrose, Carb. Res., 1993, 240, 183-196.
Manley-Harris, M., Richards, G.N. Stereoselective thermal transfer of fructose from sucrose to cyclodextrins. Carb. Res., 1995, 168, 209-217.
Orban, J.I., Patterson, J.A., Sutton, A.L., Richards, G.N. Effect of sucrose thermal oligosaccharide caramel, dietary vitamin-mineral level, and brooding temperature on growth and intestinal bacterial populations of broiler chickens. Poultry Sci., 1997, 76, 482-490.
Patil, N.S., Dordick, J.S., Rethwisch, D.G. Macroprous poly (sucrose acrylate) hydrogel for controlled release of macromolecules, Biomaterials, 1996, 17, 2343-2350.
Rogers, R.D., Spear, S.K., Swatloski, R.P., Reichert, W.M., Godshall, M.A., Johnson, T.P., Moens, L. Non-sugar products from sugarcane for the new millennium: Green pathways to a carbohydrate economy? Proc. Sugar IndustryTechnol., Vol. 60, 2001, in press.
Rossell, C.E.V., Nonato, R.V., Mantelatto, P.E., Leal, M.R.L.V. Production of biodegradable plastic (PHB), sugar and ethanol in a sugar mill. Paper submitted for presentation at ISSCT 2001.
Sachinvala, N., Jakeway, L. Other uses of sugarcane. Annual Rpt., Experiment Station, Hawaiian Sugar Planters' Association, 1994, 37-38.
Sachinvala, N.D., Niemczura, W.P., Litt, M.H. Monomers from sucrose. Carb. Res. 1991, 218, 237-245.
Sachinvala, N.D., Winsor, D.L., Parikh, D.V., Solhjoo, H.H., Blanchard, E.J., Bertoniere, N.R. Flexible sucrose based epoxies for bonding needlepunched nonwoven cotton containing composites to dissimilar material. Proc. Beltwide Cotton Conf., 1998, Vol.1, 784
Vogel, M. Sucrose -- an exceptional molecule for enzymatic synthesis. 20th Int. Carbohydrate Symposium, Hamburg, Germany, 2000. Abstract No. D-022
Waldheim, L., Morris, M., Leal, M.R.L.V. Biomass power generation: Sugar cane bagasse and trash. paper presented at Progress in Thermochemical Biomass Conversion, 17-22 September 2000, Tyrol, Austria. Available at: http://www.tps.se/pdf/Bagasse_Tyrol_0009.pdf
Wilkinson, S.L., Nature's pantry is open for business, C&E News, Jan. 22, 2001. p.61.
Yalpani, M. Carbohydrates: The renewable resources. 19th Int'l Carbohydrate Symposium, San Diego, 1998. Abstract DK-001
