Location: Commodity Utilization Research
2015 Annual Report
Objectives
The overall objective of this project is to enhance the value of sugarcane, sweet sorghum, and energy beets, and their major commercial products sugar, biofuel and bioproducts, by improving postharvest quality and processing. Specific objectives are:
1. Develop commercially-viable technologies that reduce or eliminate undesirable effects of starch and color on sugar processing/refining efficiency and end-product quality.
2. Develop commercially-viable technologies that reduce or eliminate undesirable effects of high viscosity on sugar processing/refining efficiency and end-product quality.
3. Develop commercially-viable technologies to increase the stability and lengthen storage of sugar feedstocks for the manufacture of sugars, advanced biofuels, and bioproducts.
4. Develop commercially-viable technologies for the biorefining of sugar crop feedstocks into advanced biofuels and bioproducts.
5. Identify and characterize field sugar crop quality traits that affect sugar crop refining/biorefining efficiency and end-product quality, and collaborate with plant breeders in the development of new cultivars/hybrids to optimize desirable quality traits.
6. Develop, in collaboration with commercial partners, technologies to improve the efficiency and profitability of U.S. sugar manufacturing and enable the commercial production of marketable products from residues (e.g, bagasse, trash) and by-product streams (e.g., low purity juices) associated with postharvest sugar crop processing.
Please see Project Plan for all listed Sub-objectives.
Approach
There are currently two major trends in the U.S. with respect to sugar crops: (1) the manufacture of higher quality raw sugar for supply to sugar refineries, and (2) the production of biofuels and bioproducts at new, flexible biorefineries. In recent years, mostly because of the increased harvesting of green sugarcane with leaves and tops, higher concentrations of starches and color have tended to occur. Some U.S. sugar refiners have placed a penalty for high starch concentrations in raw sugar. The occurrence of larger concentrations of insoluble starch in downstream factory products have exacerbated viscosity problems and reduced the efficiency of amylase enzymes to control starch. In close collaboration with industrial partners ARS scientists will develop new enzyme systems and other commercially viable technologies to control starch, viscosity, and color in factory and refinery streams, while also developing a method for measuring both insoluble and soluble starch in sugar products at the factory and refinery. Stable, storable, easily transportable, and available year-round supplies of sugar crop feedstocks, including sweet sorghum and energy beets, are needed for the conversion of sugars into substitute biofuels and bioproducts normally manufactured from fossil products. In close collaboration with industrial partners, ARS scientists will develop commercially-viable technologies for the extraction, stabilization, concentration, and fermentation of juices and syrups from sweet sorghum and energy beet feedstocks that will enable the deployment, growth, and profitability of new commercial biorefineries. Commercially-viable technologies will also be developed that are crucial to mitigate cultivar, seasonal, and environmental quality variations on feedstock performance.
Progress Report
In recent years, starch impurity concentrations in sugarcane have been increasing in the United States. ARS scientists at the Southern Regional Research Center in New Orleans, Louisiana, showed that the increases in insoluble starch concentrations are causing the greatest problems in sugarcane factories and refineries. ARS scientists have developed a rapid, precise, and accurate research method, using microwave-assisted sound waves, to measure total, insoluble and soluble starch. The method was validated for use in a diverse array of industrial products including fibrous waste, juices, syrups, and crystalline sugars. By using this method, the amounts of insoluble starch in raw sugars manufactured by sugarcane factories were shown to be extremely underestimated by current industrial starch methods used in the U.S. industry. Insoluble starch in white, refined sugars was shown often not to be detected by current methods. This new research method is now being used to find commercially-viable solutions to reducing or eliminating profound detrimental effects on insoluble starch. Factory and refinery staff have also requested for an industrial method that will be based on this research method.
There has been increased world-wide concern over residual (carry-over) activity of mostly high temperature (HT) and very high temperature (VHT) stable amylases in white, refined sugars from refineries to various food and end-user industries. HT and VHT stable amylases were developed for much larger markets than the sugar industry with harsher processing conditions. There is an urgent need in the sugar industry to be able to remove or inactivate residual, active amylases either in factory or refinery streams or both. The use of activated carbons to remove residual amylase activity was investigated for the sugar industry to remove measure residual amylase in syrups. Ability to remove residual amylase protein was dependent on the surface area of the powdered activated carbons as well as mixing (retention) time. The activated carbon had the additional benefits of removing color and insoluble starch. This is the first technology developed to remove undesirable insoluble starch.
Microorganisms for producing ethanol, butanol, and 1,4-butanediol were obtained and tested for capability to produce the stated products from pure sugar solutions. The fermentation techniques and protocols were obtained from collaborators or the literature. The technique to investigate the production of acetoin from sugar was transferred to a collaborator for testing.
The following constitutes the progress made on subordinate projects.
The microbial contamination of extracted sugarcane juice is a problem at the factory because it causes sugar losses and the formation of degradation products that interfere with processing. Although commercial biocides were added to juice in U.S. sugarcane factories to control microbial growth and contamination, their efficiency had long been questioned. Three types of biocides, based on bleach, sodium carbamate, and hops, obtained from Louisiana sugar factories were evaluated. The biocides were studied individually and in combinations at two Louisiana factories. None of the commercial biocides worked effectively in the factories whereas heat and precipitation reactions during the juice clarification process were effective. The use of biocides as surface disinfectants is now being studied at Louisiana factories.
Sweet sorghum syrup is vulnerable to surface microbial spoilage during storage because of its rich sugar medium, and this represents a major technical challenge to the commercial, large-scale manufacture of biofuels and bioproducts from this feedstock. Syrups manufactured from clarified juice are more stable than those manufactured from raw juice. Heat pasteurization of juice at different temperatures was investigated, and it was found that heating sweet sorghum juice between 60 and 70 degrees centigrade for 30 min would allow the storage of sweet sorghum juice for at least 72 hours and offer operational flexibility to sweet sorghum processers. As it had previously shown that soybean oil on the surface of syrups can stabilize and preserved sweet sorghum syrups for up to 1 year, different surface size layers of inexpensive and readily available soybean, canola, and sunflower oil on clarified sweet sorghum syrup were further investigated. Differences in oil type were found and the greater the surface layer the better the storage.
The new knowledge that there is markedly more insoluble starch than previously considered in products across both the sugarcane factory and refinery has made the control of starch by amylase enzymes more difficult. Intermediate-temperature (IT) stable amylases can break down a certain amount of both insoluble and soluble starch in clarified juice at 96 degrees centigrade for the first 10 minutes before substantial deactivation of the enzyme, without causing unwanted no carry-over (residual) amylase activity. Novel combinations and doses of IT stable amylase added simultaneously to a factory’s clarifier tank, next-to-the-last evaporator, and last evaporator at a factory, were shown to aid the control of both insoluble and soluble starch, and have been recommended to sugarcane industrialists.
Insoluble and swollen starch were shown to be the main contributors to viscosity increases from starch in both the sugarcane factory and refinery. The direct addition of amylase to a process was undisputedly shown to cause small but meaningful reductions in viscosity of syrup which has major consequences for increased sugar recovery. Different combinations of amylase applications at multiple points in a factory were shown to reduce viscosity.
Quality traits of sweet sorghum can strongly affect processing performance and yields and quality of end-products. Two commercial sweet sorghum hybrids, bred to provide abundant seed to growers and higher yields, were shown to offer similar quality and performance attributes as a popular sweet sorghum cultivar. All the sweet sorghum genotypes were very susceptible to environmental changes. The presence of side stalks dramatically reduced crop yields, and detrimentally affected quality and processing performance. Breeders now have more information on which quality traits to breed for, and processers have more knowledge on factors that strongly affect processing which will underpin development of processing tools and aids for their control.
Gold and fullerene nano-particles (less than one micron in size) are widely used by the medical, microelectronic, and catalysis industry. Both of these nano-particles are negatively charged, and therefore, expected to interact with biochar sorbents. Gold nano-particles (30nm) were created by boiling chlorauric acid solution in the presence of citric acid. Between pH 3 and 5, 300 degrees centigrade biochar rapidly and irreversibly retained the gold nano-particles. The uptake of gold nano-particles progressively decreased as a function of burning temperature up to 500 degrees centigrade, and then slightly increased for biochar produced at 700 degrees centigrade. At each pyrolysis temperature, the uptake of gold nano-particles at pH 7 was negligibly low. Strong bonding interaction involving hydrogen atom was the cause of observed interactions. Results will be used to develop precious metal-mining technology and in the contaminant risk assessment tools.
Sophisticated high-resolution nuclear magnetic resonance techniques specific to proton, carbon, and phosphorus were utilized to visualize specific chemicals responsible for desirable and undesirable functions of bioenergy feedstocks. In sugarcane and grape seed-derived antioxidants, specific redox couple was identified to cause reversible electron transfer reactions. In pecan shell and manure agricultural wastes and value-added products, five different phosphorus species were determined to be the forms of nutrients available to the food crops.
After identification of ideal gasification conditions that yield desirable attributes of biochar from poultry broiler litter, several biochar samples were generated. The samples were analyzed and tested for the following: carbon, hydrogen, oxygen, nitrogen and sulfur; proximate analysis: fixed carbon, volatile carbon, ash and moisture; quantification of elemental leaching from acid wash and rain water wash treatments, surface area, pH and copper ion adsorption. The best performing sample was identified for additional testing. In addition to supplying needed heat to condition the broiler houses, the farmer can save money on purchasing natural gas, and the gasifier can also produce a biochar as a by-product. The identified attributes of the biochar produced position it as a marketable product such as air adsorbent for waste water and air remediation, a soil amendment, or possibly a feed supplement.
Laboratory scale column adsorption studies were carried out with pure gas ammonia and nitrogen gases to determine poultry manure and plant-based carbons with the best adsorption efficiency along with the comparative studies of commercial grade carbons. Preliminary studies utilizing a chamber acid-trap system were carried out on the adsorption capacities of the carbons with relation to direct poultry manure emissions which are comprised primarily of nitrogen gases. This research represents an opportunity to not only re-use poultry manure, but also to treat the emissions from or within poultry houses. The use of activated carbon in the removal of ammonia gas in poultry houses had long been discarded primarily due to the high cost and low efficiency of the carbons. The results of the study demonstrate the potential for a cyclical waste utilization strategy in using broiler litter activated carbon to capture ammonia given off from litter.
Accomplishments
1. Evaluate the effectiveness of commercial biocides in sugarcane juice. The microbial contamination of extracted sugarcane juice is a serious problem at the factory because it causes expensive sugar losses and the formation of degradation products that interfere with processing. Although commercial biocides were added to juice in U.S. sugarcane factories to control microbial growth and contamination, their efficiency had long been questioned. ARS scientists from the Commodity Utilization Unit of the Southern Regional Research Center in New Orleans, Louisiana, evaluated three types of biocides, based on bleach, sodium carbamate, and hops, obtained from Louisiana sugar factories. The biocides were studied individually and in combinations at two Louisiana factories. None of the commercial biocides worked effectively in the factories whereas heat during the juice clarification process did. This research has already had impact with numerous U.S. sugar factories discontinuing the use of the tested commercial biocides. A conservative estimate is that, on average, each factory has saved $46,8100 per year which equates to a saving of $515,000 per year in Louisiana alone.
2. Commercialization of sweet sorghum juice clarification for large-scale syrup manufacture. The precipitation and burning of insoluble starch granules from sweet sorghum juice on heating coils prevented the large-scale manufacture of syrup at Heckemeyer Mills, Sikeston, Missouri. An ARS scientist from the Commodity Utilization Unit of the Southern Regional Research Center in New Orleans, Louisiana, showed that both starch concentration and granule size contributed to processing problems. The introduction of juice de-aeration, settling, and the USDA clarification process enabled the large-scale manufacture of syrup. Quality and processing differences due to cultivar and environmental effects were also overcome and this assured continual supply of clarified syrups to customers. This research allowed Heckemeyer Mills to become fully operational in 2015.
3. Technology to store sweet sorghum syrup. Sweet sorghum syrup is vulnerable to surface microbial spoilage during storage because of its rich sugar medium, and this represents a major technical challenge to the commercial, large-scale manufacture of biofuels and bioproducts from this feedstock. ARS scientists from the Commodity Utilization Unit of the Southern Regional Research Center in New Orleans, Louisiana, with an industrial collaborator at Heckemeyer Mill, Sikeston, Missouri, showed that adding only a 1 cm layer of soy bean oil as a surface sealant, allowed sweet sorghum syrup containing 65% dissolved solids to be stored for at least 9 months at ambient temperature. The fungal, yeast, and bacterial microorganisms responsible for syrup deterioration were identified. Handling of the syrup before storage was found to be crucial. Heckemeyer Mill will now use this novel technology to store syrup in 7,500 gal tanks.
4. Control of insoluble and soluble sugarcane starch with novel combinations of amylase. The new knowledge that there is markedly more insoluble starch than previously considered in products across both the sugarcane factory and refinery has made the control of starch by amylase enzymes much more difficult. ARS scientists from the Commodity Utilization Unit of the Southern Regional Research Center in New Orleans, Louisiana, with industrial collaborators Amano Enzyme in Japan and Alma sugarcane factory in Louisiana, showed that intermediate-temperature (IT) stable amylases can break down a certain amount of both insoluble and soluble starch in clarified juice at 96°C for the first 10 min before substantial deactivation of the enzyme, and causes no carry-over (residual) amylase activity. Novel combinations and doses of IT stable amylase added simultaneously to a factory’s clarifier tank, the next-to-last, and last evaporator at a factory were shown to aid the control of both insoluble and soluble starch and have been recommended to sugarcane industrialists. Small but meaningful reductions in viscosity of syrup were also shown to occur inside the evaporator where the amylase was directly applied. At the present time, this is the only processing tool to control insoluble starch in factories.
5. Insoluble starch detrimentally affects refinery processes. It was previously considered in the sugarcane industry that soluble starch was solely responsible for filtration problems associated with the carbonatation clarification process at a refinery. ARS scientists from the Commodity Utilization Unit of the Southern Regional Research Center in New Orleans, Louisiana, with three refinery collaborators from New Orleans, Louisiana, Gramercy, Louisiana, and Savannah, Georgia, showed that insoluble starch also negatively affects carbonatation refining. Specifically, the total starch concentration and the ratio of soluble and insoluble starch are implicated. The majority of raw sugars entering the refinery contain 35-65% insoluble starch which can persist across the whole refinery and into refined sugars. Soluble starch negatively affects carbonatation reactions by limiting the production of calcium carbonate crystal, an internal filter-aid needed to remove impurities from the dissolved raw sugar. Insoluble starch decreases carbonation efficiency similarly to soluble starch but also clogs and coats the press filter membrane, both of which are detrimental to energy and processing costs at the refinery. The effects of different starch forms in raw sugars are complicated and may be exacerbated by other raw sugar impurities. This work provides strong evidence that refiners need to measure insoluble starch as well as soluble starch in their raw materials.
6. Quality of stored sugarcane bagasse for energy production. Large amounts of excess sugarcane bagasse are piled and stored from year to year outside sugarcane factories. ARS scientists from the Commodity Utilization Unit of the Southern Regional Research Center in New Orleans, Louisiana, in collaboration with three Louisiana sugarcane factories, determined the microbial and physical/chemical properties of covered and uncovered piles of sugarcane bagasse stored for 9 months. Due to lower moisture content, covered bagasse prevented the sugarcane bagasse from deteriorating and maintained the fuel value of the bagasse much better than uncovered bagasse. This has major implications for factories and processers, who need the stored bagasse to burn in boilers and provide energy and steam to start-up the next processing season.
7. Ethanol fermentation of sugars and clarified sweet sorghum juice. Multiple U.S. stakeholders want to maintain ethanol in their portfolio of biofuels manufactured from sugar crops. ARS scientists in the Commodity Utilization Research Unit in New Orleans, Louisiana, showed that sugars in diluted, clarified sweet sorghum syrup were excellent raw materials for the production of ethanol from a commercial yeast strain. The sweet sorghum syrup had an acid buffering effect, allowing the fermentation to progress more rapidly than expected at optimal conditions. Although organic acids are present in some sugar crop juices, only acetic acid had a major, detrimental impact on the fermentation. These results will allow stakeholders to consider clarified sweet sorghum sugar solutions (with anticipated amount of organic acids) to be fermentable to bioethanol by commercial yeast strains.
8. Methods for breeders and industrialists to characterize quality traits of sweet sorghum. Methods to rapidly, simply and inexpensively measure quality traits in the new sweet sorghum feedstocks for the manufacture of biofuels and bioproducts are urgently needed. Breeders need them to develop better hybrids and cultivars and industrialists need them to measure feedstock quality and for grower payment systems. An ARS scientist from the Commodity Utilization Unit in New Orleans, Louisiana, developed methods to measure the redox reactivity, antioxidant activity, and the degree of aromaticity (UV/visible and fluorescence spectral features) of sweet sorghum juices and seeds. A quantitative correlation was observed between these parameters and the amount of condensed tannins and flavonoids, which are related to color, in seeds. For sweet sorghum juice, total organic carbon/nitrogen and electrical conductivity analyses provided more accurate alternatives to traditional methods to measure total sugar and salt contents, while employing the instrumentations available at the factory. Advanced spectroscopic technique (nuclear magnetic resonance) confirmed quinone/dihydroxybenzene as the redox couple observable in the newly developed method.
9. Genotype, maturity, and environmental effects on sweet sorghum quality and processing. Quality traits of sweet sorghum can strongly affect processing performance and yields and quality of end-products. By conducting two field trials, ARS scientists from the Commodity Utilization Unit of the Southern Regional Research Center in New Orleans, Louisiana, in collaboration with NexSteppe hybrid company and USDA-ARS-Houma, showed there were strong genotype and maturity effects for sweet sorghum quality and processing performance. Sweet sorghum genotypes were very susceptible to environmental changes. The presence of side stalks dramatically reduced crop yields, quality, clarification and evaporation performance of sweet sorghum. Starch was an important source of untapped fermentable sugars in sweet sorghum and it was shown that starch concentration and size in juice varied by genotype and, generally, was not affected by weather or maturity. Breeders now have more information on which quality traits to breed for, and processers have more knowledge on factors that strongly affect processing which will underpin development of processing tools and aids for their control.
10. Sugarcane bagasse and trash for value-added products. Sugarcane bagasse and leafy trash remain untapped by-product and residues, respectively, associated with harvesting and processing of sugarcane. ARS scientists from the Commodity Utilization Unit of the Southern Regional Research Center in New Orleans, Louisiana, produced biochar from these two biomass sources in a pilot plant via slow pyrolysis and applied to the field at 0, 4, and 5% rates. Besides improvements in soil health, such as mineral nutrition, carbon content, water holding capacity, significant improvements in both sugarcane crop and sugar yields were observed when using the value-added biochar. Benefits to both sugarcane growers and processors result from the production of valued by-products from pyrolysis of sugarcane trash and bagasse as well as enhancing the sugarcane industry’s role in sustainable, renewable energy markets.
Review Publications
Uchimiya, M., Hiradate, S., Antal, Jr., M.J. 2015. Influence of carbonization methods on the aromaticity of pyrogenic dissolved organic carbon. Energy and Fuels. 29(4):2503-2513.
Cole, M.R., Hobden, J.A., Warner, I.M. 2015. Recycling antibiotics into GUMBOS: A new combination strategy to combat multi-drug resistant bacteria. Molecules. (20):6466-6487.
Uchimiya, M., Hiradate, S., Antal, Jr., M.J. 2015. Dissolved phosphorus speciation of flash carbonization, slow pyrolysis, and fast pyrolysis biochars. ACS Sustainable Chemistry & Engineering. 3(7):1642-1649.
Cantrell, K.B., Hunt, P.G., Uchimiya, S.M., Novak, J.M., Ro, K.S. 2012. Impact of pyrolysis temperature and manure source on physicochemical characteristics of biochar. Bioresource Technology. 107:419-428.
Eggleston, G., Borges, E. 2015. Multiple applications of ion chromatography oligosaccharide fingerprint profiles to solve a variety of sugar and sugar-biofuel industry problems. Journal of Agricultural and Food Chemistry. 63:2841-2851.
Boue, S.M., Shih, B.Y., Burow, M., Eggleston, G., Lingle, S.E., Pan, Y., Daigle, K.W., Bhatnagar, D. 2013. Postharvest accumulation of resveratrol and piceatannol in sugarcane with enhanced antioxidant activity. Journal of Agricultural and Food Chemistry. 61:8412-8419.
Wang, M.L., Cole, M.R., Tonnis, B.D., Pinnow, D.L., Xin, Z., Davis, J., Hung, Y., Yu, J., Pederson, G.A., Eggleston, G. 2014. Comparison of stem damage and carbohydrate composition in the stem juice between sugarcane and sweet sorghum harvested before and after late fall frost. Journal of Sustainable Bioenergy Systems (JSBS). 4:161-174.
White Jr, P.M., Potter, T.L., Lima, I.M. 2015. Sugarcane and pinewood biochar effects on activity and aerobic soil dissipation of metribuzin and pendimethalin. Industrial Crops and Products. 74(2015):737-744. DOI: 10.1016/j.indcrop.2015.04.022
van Heerdan, P.D.R., Eggleston, G., Donaldson, R.A. 2014. Ripening and postharvest deterioration. Chapter 4. In: Moore, P.H., Botha, F.C., editors. Sugarcane: Physiology, Biochemistry, and Functional Biology. Hoboken, NJ:Wiley-Blackwell. p. 55-84.
Legendre, B., Eggleston, G., Birkett, H., Mrini, M., Zehuaf, M., Chabaa, S., Assarrar, M., and Mounir, H. 2014. How to manage cane in the field and factory following damaging freezes. International Sugar Journal. 116(1388):526-531.
Eggleston, G., DeLucca, A., Sklanka, S., Dalley, C., St. Cyr, E., Powell, R. 2015. Investigation of the stabilization and preservation of sweet sorghum juices. Industrial Crops and Products. 64:258-270.
