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ARS Home » Southeast Area » New Orleans, Louisiana » Southern Regional Research Center » Commodity Utilization Research » Research » Research Project #426599

Research Project: Developing Technologies that Enable Growth and Profitability in the Commercial Conversion of Sugarcane, Sweet Sorghum, and Energy Beets into Sugar, Advanced Biofuels, and Bioproducts

Location: Commodity Utilization Research

2018 Annual Report

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.

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
Progress was made on all six objectives and their sub-objectives, all of which fall under National Program 306, Component 1 (Foods) and Components 2 (Non-Foods). Progress on this project focuses on Problem 1A; define, measure, and preserve/enhance/reduce attributes that impact quality and marketability; Problem 1C; new and improved food processing technologies; Problem 2B; Enable technologies for (1) expanding market applications of existing biobased products, and (2) producing new marketable non-food biobased products derived from agricultural products and byproducts, and estimate the potential economic value of the new products; and Problem 2C; collaborate with breeders and production researchers in the development of both new cultivars/hybrids and new production practices/systems that optimize the quality and production traits of crop-derived products and byproducts for conversion into non-food biobased products. In support of Objective 1, pilot studies were performed to remove residual amylase enzyme (from starch removal) and color using powdered activated carbons (PAC). The PAC removed significant amount of amylase from the sugar refinery liquor. Removal was dependent on PAC dose and retention time. PAC also removed color compounds. PAC preferentially removed natural sugar cane derived colorants better than process degradation colorants. Additional benefit from using PAC was a significant reduction of floating particles. Also in support of Objective 1, in collaboration with Colorado School of Mines in Golden, Colorado, and a sugar refinery, several chemicals were investigated for bleaching of sugars to remove color and make white sugar. Effectiveness of permanganate as a bleaching agent strongly depended on the starting sugar stream (raw sugar juice at the sugar mill or dissolved raw sugar at the sugar refinery), temperature, and the presence of coagulants. While permanganate removed over 90% color (measured at neutral pH) in raw sugar juice, no color removal was observed in dissolved raw sugar from the sugar refinery even at 20-fold higher permanganate loading. In support of Objective 2, high viscosity sugar streams were identified at the raw sugar factories. Subsequently, commercial enzymes were also identified that could possibly lower the viscosity. In support of Objective 3, storage of sweet sorghum syrups continued to investigate impact of storage (for more than a month) before fermentation to fuels and chemicals. Previous work had focused on storage of solutions with high sugar concentrations (60-80%) which showed little sugar degradation with time. The current work is focusing on lower concentration of sugars (approximately 30%) which represent a level that can be achieved at a lower cost as energy-intensive evaporation can be reduced. The syrups were monitored for stability of sugars. Also in support of Objective 3, stability of stored sweet sorghum bagasse (to be used as feed or animal bedding) continue to be monitored. While initial experiments only targeted a 30-day storage period, the materials have been continuously monitored longer than 30 days for weight loss and degradation. Only low degradation rates have been noted from these extended periods in the compressed bagasse materials. In support of Objective 4, it was shown that all the desired products (ethanol, butanol, acetoin, etc.) could be produced by microorganisms from sugar crops syrups in small scale (1 cup size) and larger scale fermenters (6 cup size). Sweet sorghum syrup from a biorefinery was transferred to a commercial collaborator that confirmed the results with their industrial microorganisms. Nutrient availability was found important in all of the fermentations and it was proven that the sweet sorghum and beet syrups contained some, but not all, necessary nutrients for the microbes. Most notably, nitrogen was lacking as a nutrient. A starchy sweet sorghum biorefinery products stream (sludge from clarification) was shown to improve fermentation yields when acetone and butanol were produced by bacteria without the addition of enzymes to break down the starch. In support of Objective 5, the sweet sorghum crop injuries during the growth season and the relationship to infestation of sugarcane aphids (small insects that attach sugarcane and sweet sorghum) were reviewed for the 2015 and 2016 seasons. Early season aphid population correlated to greater damage at a later growth stage. Sweet sorghum cultivars sustained less damage in 2016 planting year (compared to 2015), when higher concentrations of aconitic acid (a natural organic acid in sweet sorghum and sugarcane plants) and polyphenol (also a natural product in the sweet sorghum plant) accumulated in the stem. It is possible that these secondary (sugar being the primary) products serve as defense against aphids in the sweet sorghum plant. Advanced statistical techniques were used that could handle the large variability in the data to evaluate the information for further use. Also in support of Objective 5, methods were developed to calibrate and predict organic acids and polyphenolics in sweet sorghum juice based on light absorbance of ultraviolet and visible light. Over 24 different sweet sorghum types were included in the study with wide difference in juice composition. Of different varieties investigated, one accumulated as much as 6-fold higher aconitic acid and polyphenol-like products. Because aconitic acid is an important chemical feedstock, advanced statistical techniques were employed to predict its concentration in sweet sorghum juice, along with solids content and total sugar concentration. Non-sugar products (dissolved salts and carboxylates) accumulated in juice at the expense of fermentable sugars. Additionally, in support of Objective 5, a characterization method called cyclic voltammetry to rapidly classify sweet sorghum fermentable sugar feedstocks was investigated. The method characterizes the reactivity of the materials in a fashion that allows for types of chemicals present in the feedstocks to be identified. And these chemical types were correlated to plant health and cultivar types. For example, taller plants paralleled greater accumulation of organic carbon products, while lodged (fallen) plants had less of these products. In support of Objective 6, last tandem and crusher juice samples were collected during 2017 harvesting season from 10 Louisiana sugar cane factories. Total phenolic content was high while the sugars content was low in last tandem-crusher juice samples, suggesting that the phenolics act differently than sugar in the processing. The juices could be fermented by bacteria to produce acetone, butanol, and ethanol. Also in support of Objective 6, biochar produced by a local sugarcane mill were applied with a commercial spreader in sugarcane plots as soil amendment in 2015. Plant cane (first year) was harvested and both cane yield and sugar yield with biochar treated plots were found to be slightly greater than those for the control (no biochar treatment). First year stubble (first year after planting cane) was due to be harvested in the fall of 2017, but crop was damaged due to snow storm before harvesting. Another study was initiated to determine effects of biochar treatment in sugarcane plots with and without addition of a microbial liquid formulation produced from the fermentation of naturally occurring microorganisms. Additionally, in support of Objective 6, the fourth and final year field study was completed during 2017 harvest season. Sugar cane was grown on soils amended (single application prior to planting) with various treatments containing either biochar from bagasse, biochar from leafy residue, and fly ash (residue from factory boilers). The three soil treatments were tested either alone (just biochar or fly ash) or as mixtures of biochar with fly ash and at two application rates. All treatments were compared to controls (no treatment). It was shown that all the amendments improved the crop yield. In greenhouse studies, it was also shown that the ratooning (sprouting) ability of sugar cane improved with the addition of biochar to the soil. In support of overall project objectives and under a stakeholder agreement, sweet sorghum syrups, corn syrup, agave nectar, maple syrup, rice syrup, and other sweeteners were analyzed for protein, fat, carbohydrate, ash, mineral content, anti-oxidant activity, and other factors to determine the potential for introducing sweet sorghum syrup as a liquid sweetener and nutritional food ingredient. Sweet sorghum syrup was found to contain high levels of magnesium, potassium, and calcium. It also contained significant levels of anti-oxidant compounds.

1. Stabilization of sweet sorghum bagasse for use as animal bedding. The majority of sweet sorghum bagasse is underutilized because more is produced than can be practically reapplied to fields as a soil amendment. Unused bagasse accumulates, taking up valuable space in a processing facility. ARS researchers in New Orleans, Louisiana, tested a portable inexpensive trash compactor for compacting bagasse. With no addition of chemicals or microbes the natural conditions of the compressed bales permitted ensiling and stabilization after 30 days storage under ambient conditions. The stakeholder scaled the process up and is now selling ensiled bagasse as animal bedding to a horse breeder.

2. Sweet sorghum syrup as nutrient-rich sweetener. Many sugar syrups such as corn syrup, maple syrup, etc. can be used as food sweetener but often they are low in nutritional value. ARS researchers in New Orleans, Louisiana, determined the nutritional content of a large number of commercial syrups as well as sweet sorghum syrups. It was found that sweet sorghum syrup contained twice as much protein as other syrups. It also contained high levels of potassium, magnesium, and iron; all of which are important from a nutritional standpoint. Anti-oxidant activity was also high in the sweet sorghum syrups. These results are valuable as they set the stage for the introduction of sweet sorghum syrup as a commercial liquid sweetener. The results were transferred to key stakeholders, who now use it as information to promote sweet sorghum syrup as a sweetener.

3. Using liquid permanganate to prevent degradation of sugarcane juice results in significant savings for raw sugar factories. The presence of microorganisms in sugarcane juice degrades sugar, producing gummy-like substances that interfere with processing, require additional chemical usage, and increase maintenance. ARS researchers in New Orleans, Louisiana, in collaboration with a private company and with the help of raw sugar factory staff, used liquid permanganate as a processing aid. The techniques, which were tested at full scale, resulted in lower levels of microbes, improved clarification, reduced chemicals usage, and increased sugar yield.

4. Removal of color from sugar beet extract remaining after betaine recovery. Betaine is an amino acid used as a food supplement and it is recovered from sugar beet molasses at some sugar beet refineries. Once the betaine is recovered, the remaining liquid is called beet extract and is dark in color. ARS researchers in New Orleans, Louisiana, determined the powdered active carbon dosage and operating conditions required to remove 50% of the color, as had been targeted by the stakeholder. These results are important as it allows the beet extract to be cleaned and the resulting liquid can be processed to produce additional sugar, thus improving overall sugar recovery. The results were shared with the stakeholder who will consider implementing the process.

5. Monitoring aphid population and crop injury impacting sweet sorghum. The recent outbreak of sugarcane aphids reportedly caused several billion dollars of losses in sorghum production, and several millions of dollars in additional expenses for insecticides. ARS researchers in New Orleans, Louisiana, utilized advanced statistical tools to describe the aphid population and damage timecourses (from planting to harvest), relationships between aphid population and crop damage, and influence of crop varieties and environmental factors on aphid population and damage. Developed statistical tools can be incorporated into the integrated pest management and best management practice against sugarcane aphids.

6. Pilot scale removal of impurities from sugar refinery liquor by powdered activated carbon. Sugar refineries (where they are making white granulated sugar) must remove color whether they are naturally derived or process formed. In addition, it is desired to remove the enzyme amylase that often enters the refinery in the raw sugar from a raw sugar mill. ARS researchers in New Orleans, Louisiana, used powdered active carbon to remove both color and residual amylase enzyme. Sixty four to 100% of the enzyme was removed and 55% of the colored compounds were removed, resulting in a significantly cleaner liquor. This finding is important as the sugar industry has a desire to produce ultra-pure products for special applications. The results were shared with key stakeholders at meetings and with information that would allow further scale-up.

7. Utilization of sweet sorghum biorefinery byproducts for solvent and biofuel production. In the production of sweet sorghum syrup, the juice is first cleaned by a process called clarification. The clarification uses lime and generates a low-value byproduct called mud that is rich in solids, starch, and sugars. ARS researchers in New Orleans, Louisiana, used this material to make acetone and butanol by fermentation with results twice as good when compared to processed sugars. The compounds represent important industrial solvents, can be use as biofuels, or can be used as chemical building blocks for other chemicals. The relative high product concentration will reduce the cost of recovery and may advance the technology faster.

8. Chemical and remote sensing techniques to evaluate sweet sorghum quality. Sweet sorghum is grown for production of liquid sweeteners and generation of inexpensive sugars for biofuel and biochemical production. It is also possible that valuable co-products could be developed to support the sweet sorghum refinery. ARS researchers in New Orleans, Louisiana, evaluated 24 different sweet sorghum varieties and developed methods to calibrate and predict the concentrations of chemicals in sweet sorghum that could serve as building blocks for advance biobased chemicals. The developed chemical and remote sensing methods could replace time-consuming visual scoring in the field by breeders.

Review Publications
Klasson, K.T., Qureshi, N., Powell, R., Heckemeyer, M., Eggleston, G. 2018. Fermentation of sweet sorghum syrup to butanol in the presence of natural nutrients and inhibitors. Sugar Tech. 20(3):224-234.
Qureshi, N., Saha, B.C., Klasson, K.T., Liu, S. 2018. Butanol production from sweet sorghum bagasse with high solids content: Part I – comparison of liquid hot water pretreatment with dilute sulfuric acid. Biotechnology Progress. 34(4):960-966.
Qureshi, N., Saha, B.C., Klasson, K.T., Liu, S. 2018. High solid fed-batch butanol fermentation with simultaneous product recovery: Part II - process integration. Biotechnology Progress. 34(4):967-972.
Eggleston, G., Legendre, B., Godshall, M.A. 2017. Sugar and other sweeteners. In: Kent, J.A., editor. Handbook of Industrial Chemistry and Biotechnology. 13th edition. New York, NY: Springer International Publishing. pp. 933-978.
Lima, I.M., White Jr, P.M. 2017. Sugarcane bagasse and leaf residue biochars as soil amendment for increased sugar and cane yields. International Sugar Journal. 119(1421):382-390.
Lima, I.M., Bigner, R.L., Wright, M.S. 2017. Conversion of sweet sorghum bagasse into value-added biochar. Sugar Tech. 19:553-561.
Wright, M., Lima, I., Bigner, R. 2017. Stability and use of sweet sorghum bagasse. Sugar Tech. 19(5):451-457.
Eggleston, G., Montes, B., Heckemeyer, M., Triplett, A., Stewart, D., Lima, I., Cole, M. 2017. Problems, control, and opportunity of starch in the large scale processing of sugarcane and sweet sorghum. International Sugar Journal. 119:624-633.
Eggleston, G., Boone, S., Triplett, A., Heckemeyer, M., Powell, R., Wright, M., 2018. Preliminary study on the use of inexpensive, unsaturated vegetable oils as surface sealants in the long- and short-term storage of syrup feedstocks from sweet sorghum. Sugar Tech. 20(3):235-251.
Hass, A., Lima, I.M. 2018. Effect of feed source and pyrolysis conditions on properties and metal sorption by sugarcane biochar. Environmental Technology & Innovation. 10:16-26.
Lima, I.M., Wright, M.S. 2018. Microbial stability of worm castings and sugarcane filter mud compost blended with biochar. Cogent Food & Agriculture. 4(1):1-14.
Eggleston, G., Lima, I., Sarir, E., Thompson, J., Zatlokovicz III, J., St Cyr, E. 2017. Use of activated carbon to remove undesirable residual amylase from refinery streams. Zuckerindustrie. 142(2):96-103.
Uchimiya, M., Knoll, J.E. 2018. Prediction of carboxylic and polyphenolic chemical feedstock quantities in sweet sorghum. Energy and Fuels. 32(4):5252-5263.
Uchimiya,M., Noda, I., Orlov, A., Ramakrishnan, G. 2018. In situ and ex situ 2D infrared/fluorescence correlation monitoring of surface functionality and electron density of biochars. ACS Sustainable Chemistry & Engineering. 6(6):8055-8062.