Sorghum Stalk Research Articles

Analysis of Sorghum Stalks and Fibres for Use in the Production of Low-Cost Housing Materials

Research into low-cost housing solutions, especially for low- and middle-income countries, has grown in recent years. Greater use of natural materials, both mineral and bio-based, offers opportunities for more affordable and sustainable materials and products. In the low- and middle-income countries, residential buildings are too expensive for most people due to the use of the concrete in buildings. Utilisation of agricultural wastes can serve a threefold purpose: (i) minimise the impact of construction products on the environment, (ii) reduce waste, and (iii) decrease the cost. The aim of this study was to investigate fibres and stalks from the sorghum plant as potential additives in low-cost brick production. Analysis of the sorghum fibres and stalks has included microstructural examination using a scanning electron microscope and mercury intrusion porosimetry, together with tensile strength testing of fibres. Fibres and stalks did not undergo chemical pre-treatment. Sorghum stalks and fibres were found to have comparable tensile strength to fibres currently used for brick production, and the methods used to prepare stalks were not found to adversely affect their strengths. Consequently, this research has shown that fibres produced from local agricultural wastes have potential for use in low-cost housing such as one-storey residential load-bearing structures and buildings.

Changes in pyrolysis characteristics of agricultural residues before and after water washing

Three agricultural residues (peanut straw, sorghum stalk and reed) were first pretreated by water washing, with which the pyrolysis experiments were carried out in a fixed bed reactor to investigate how the pyrolysis characteristics are changed by removing the alkali earth metals (AAEMs) and a part of fibrous components by water washing. The result shows that the water washing removes 52.7%–92.6% potassium and approximately half of neutral detergent solute (NDS) from three agricultural residues. The removal of AAEMs and NDS has a complex influence on the pyrolysis of agricultural residues, especially for peanut straw due to its higher contents of both AAEMs and NDS. However, the removal of AAEMs has an inhibitory effect on the reactions such as decarboxylation, decarbonylation, dehydrogenation and polycondensation, and the elution of NDS directly affects the yields and composition of gas and liquid products. For all three agricultural residues, overall, the water washing promotes the production of bio-oil and bio-char, but it lowers the gas yield. The bio-oils generated from the water-washed agricultural residues have higher proportions of oxygenates, especially sugars and furans, with lower proportions of hydrocarbons and nitrogenous compounds. Besides, after washing, the yields of CO2, CO and CH4 with peanut straw decrease significantly, while the proportion of long-chain fatty acids in bio oil increases.

Studying the process of extracting sugary substances from the stalks of sweet sorghum in the technology of making food syrups

The need to intensify the process of extracting sugar substances from sweet sorghum stalks in order to improve the quality and yield of the target product has been substantiated. Existing techniques of sugar substance extraction used in sweet sorghum processing technologies have been analyzed. The application of a combined technique for extracting sugary substances has been proposed implying the production of pressed and diffusion juice. The results of optimizing the press technique of juice extraction from sorghum stalks are given. The equations of material balance of products and sugars have been built, depending on such factors as the degree of pressing, the initial content of solids and sugars in the stalks. A procedure for calculating the yield of pressed juice, cake, and the content of total sugars has been devised, according to which the preliminary pressing of the stalks ensures the extraction of juice in the range of 25‒35 %, the yield of the pressed cake is 75‒65 % on average, with a sugar content exceeding 60 %. It has been experimentally established that the use of the anti-current process of extraction of sugar substances from the pressed cake ensures their complete extraction from raw materials. The rational parameters for this process have been defined. At a temperature of 66–70 °C and a duration of 20 minutes, it is possible to obtain an extract whose content of solids is 13.0 %, total sugars ‒ 11.10 %, and whose purity is 85.38 %. The research was carried out in order to intensify the extraction of sugar substances from sweet sorghum plant raw materials, to improve the technical level of the extraction process, and implement the devised method under industrial conditions. Further implementation of these results in the food industry could make it possible to establish the production of a wide range of sugar-containing products, both organically and as a natural substitute for sugar in food products.

Life cycle impact assessment of biofuels derived from sweet sorghum in the U.S.

BackgroundThe objective of this study was to evaluate the environmental impact of the production of a range of liquid biofuels produced from the combination of fermenting sorghum stalk juice (bioethanol) and the pyrolysis/hydrotreatment of residual bagasse (renewable gasoline and diesel). Life cycle impact assessment (LCIA) was performed on a farm-to-wheels system that included: (i) sorghum farming, (ii) juice extraction, (iii) juice fermenting, (iv) bagasse pretreatment, (v) bagasse thermochemical treatment (pyrolysis, hydroprocessing, and steam reforming), and (vi) typical passenger vehicle operation. LCIA results were compared to those of petroleum fuels providing the equivalent functional unit—cumulative kilometers driven by spark ignition direct injection (SIDI) vehicles utilizing either renewable gasoline or ‘bioE85—a blend of bioethanol and renewable gasoline,’ and a compression ignition direct injection (CIDI) vehicle utilizing renewable diesel produced from 76 tons of harvested sweet sorghum (1 ha).ResultsSweet sorghum biofuels resulted in a 48% reduction climate change impact and a 52% reduction in fossil fuel depletion. Additionally, reduced impacts in ozone depletion and eutrophication were found (67% and 47%, respectively). Petroleum fuels had lower impacts for the categories of non-carcinogenic health impact, smog, respiratory effects, and ecotoxicity, showing tradeoffs between sorghum and petroleum fuels.ConclusionOverall, sorghum biofuels provide advantages in environmental impact categories including global warming potential, fossil fuel depletion and eutrophication, showing potential for sorghum as a promising second-generation feedstock for fuel.

Bioconversion of renewable lignocellulosic biomass into multicomponent substrate via pressurized hot water pretreatment for bioplastic polyhydroxyalkanoate accumulation

The pretreatment of lignocellulosic biomass (LB) has become an important process to reduce the cost of polyhydroxyalkanoate (PHA) production. In this study, an economical and effective pressurized hot water pretreatment was used to investigate on bioconversion of four typical LB (rubber wood, sugarcane bagasse, sorghum stalk, cassava stalk) into reducing sugar, then as feedstock to accumulate PHA by mixed microbial cultures. The results showed that pretreatment changed the surface morphology of LB and further improved saccharification efficiency. The maximum reducing sugar yield of 620.7 mg·g−1 (438.7 mg·g−1 glucose and 178.0 mg·g−1 xylose) was obtained by rubber wood. The conversion of cellulose and hemicellulose reached 83.10% and 78.22%. Moreover, PHA content reached the maximum of 773.2 mg COD·L−1 in the operation cycle of 24 h. The results demonstrated that hot water pretreatment was an effective physical process to improve the saccharification efficiency of LB for reducing the cost of PHA.

SORGHUM AS AN BIOENERGY AND FOOD SELF-SUFFICIENCY

ABSTRACT
 Sorghum is a food crop commodity that has important potential as a source of food and renewable energy for food and energy independence during the COVID-19 pandemic. Community service activities regarding processing sorghum into food and energy are very important in dealing with food dependence on rice and fuel energy from crude oil. Through extension activities and training on sorghum processing, it is hoped that it can increase public knowledge about sorghum and its processing. The method used is counseling and training on sorghum processing to the community. Extension and training activities for processing sorghum into alternative food and renewable energy in order to increase community knowledge in Blang Nibong Village, Samudera District, North Aceh Regency have been carried out and can be well received by the community. The community is very enthusiastic about participating in the service activities. The community has knowledge of the processing of sorghum into sorghum flour as an ingredient for processed food products such as steamed brownies, krispi tofu spices, cakes, and nagasari. Partners also have knowledge about other benefits of sorghum, namely as a renewable energy source. Sorghum stalks are known to contain bioethanol as fuel. Programs like this are very important to carry out, especially for people living in rural areas that have the potential for developing sorghum areas so that the program will be sustainable.

Biotransformation of hydroquinone into α-arbutin by transglucosylation activity of a metagenomic amylosucrase.

Arbutin is a naturally occurring glycosylated product of hydroquinone. With the ability to interrupt melanin biosynthesis in epidermal cells, it is a promising cosmetic ingredient. In this study, a novel amylosucrase, Asmet, identified from a thermal spring metagenome, has been characterized for arbutin biosynthesis. Asmet was able to catalyze transglucosylation of hydroquinone to arbutin, taking sucrose as glycosyl donor, in the temperature range of 20°C to 40°C and pH 5.0 to 6.0, with the relative activity of 80% or more. The presence of chloride salts of Li, K, and Na at 1mM concentration did not exhibit any notable effect on the enzyme's activity, unlike Cu, Ni, and Mn, which were observed to be detrimental. The hydroquinone (20mM) to sucrose ratio of 1:1 to 1:10 was appropriate for the catalytic biosynthesis of arbutin. The maximum hydroquinone to arbutin conversion of 70% was obtained in 24h of Asmet led catalysis, at 30°C and pH 6.0. Arbutin production was also demonstrated using low-cost feedstock, table sugar, muscovado, and sweet sorghum stalk extract, as a replacement for sucrose. Whole-cell catalysis of hydroquinone to arbutin transglucosylation was also established.

Production of sweet sorghum liquid sugar in the first ratoon harvest

Sorghum is a multipurpose food crop commodity. One of the benefits is by utilizing the stalks which contain sweet juice which can be processed into liquid sugar. This processed product in the form of liquid sugar from the sweet sorghum plant has the potential to meet the needs of the healthy sugar industry in the future. This study aims to determine the production of sweet sorghum plant liquid sugar in the first ratoon harvest. The research was arranged in the form of a completely randomized factorial design. The first factor consisted of two levels, namely Numbu Varieties and Super 1 Varieties. The second factor consisted of three levels, namely the storage time of sorghum stalks for 0, 3, and 6 days. The results showed that the best treatment was found in the treatment of sorghum stalks of the Numbu variety which were stored for 3 days with 35.4% yield of juice, liquid sugar with 44.01% reduced sugar content, 77.25% liquid sugar Brix content, and 3 flavor organoleptic results, taste 3.81 (like), aroma 3.50 (like), and color 3.72 (like).

Silage Fermentation on Sweet Sorghum Whole Plant for Fen-Flavor Baijiu.

The technology for producing bioethanol from sweet sorghum stalks by solid-state fermentation has developed rapidly in recent years, and has many similarities with traditional Chinese liquor production. However, the product from sweet sorghum stalks was lacking in volatile flavors, and the level of harmful contents were uncertain, therefore it could not be sold as liquor. In this study, the protein, fat, and tannin in the clusters and leaves of sweet sorghum were utilized to increase the content of flavor compounds in the ethanol product through the anaerobic fermentation of Saccharomyces cerevisiae. Meanwhile, the silage fermentation method was used to extend the preservation time of the raw materials and to further enhance the flavors of Fen-flavor liquor, with ethyl acetate as the characteristic flavor. The effects of different feedstock groups on ethyl acetate, ethyl lactate, methanol, acetaldehyde, acetal, fusel oil, total acid, and total ester were evaluated by analyzing the chemical composition of different parts of sweet sorghum and determined by gas chromatograph. The effect of different fermentation periods on the volatile flavor of sweet sorghum Baijiu was evaluated. The yield of the characteristic volatile flavor was increased by the extension of the fermentation time. Sweet sorghum Baijiu with a high ester content can be used as a flavoring liquor, blended with liquor with a shorter fermentation period to prepare the finished Fen-flavor Baijiu, conforming to the Chinese national standard for sale.

Sweet sorghum stalks extract has antimicrobial activity

Biochemicals production from the energy crop, sweet sorghum [Sorghum bicolor (L.) Moench], has attracted wide attention. However, utilization of sweet sorghum for phenolic compounds production has not yet been reported. To improve comprehensive utilization of sweet sorghum, a strategy combining acidic ethanol extraction and ion precipitation was developed to extract highly active phenolic compounds from sweet sorghum fresh stalks, which increased the final total phenolic content to 276.79 mg gallic acid equivalents/g dried extract. The sweet sorghum phenolic compounds extract was rich in gallic, gentisic, trans-ferulic, caffeic, coumaric, chlorogenic, and p-hydroxybenzoic acids, showing strong antioxidant properties. Evaluation of cell membrane integrity and biomacromolecules (protein and nucleic acid) leakage revealed that the sweet sorghum phenolic compounds extract had significant bacteriostatic activity against Staphylococcus aureus CMCC26003 and Escherichia coli CMCC44102, suggesting potential antimicrobial effects. This study provided a novel strategy for comprehensive utilization of sweet sorghum.

Dark Fermentation of Sweet Sorghum Stalks, Cheese Whey and Cow Manure Mixture: Effect of pH, Pretreatment and Organic Load

The aim of this study was to determine the optimal conditions for dark fermentation using agro-industrial liquid wastewaters mixed with sweet sorghum stalks (i.e., 55% sorghum, 40% cheese whey, and 5% liquid cow manure). Batch experiments were performed to investigate the effect of controlled pH (5.0, 5.5, 6.0, 6.5) on the production of bio-hydrogen and volatile fatty acids. According to the obtained results, the maximum hydrogen yield of 0.52 mol H2/mol eq. glucose was measured at pH 5.5 accompanied by the highest volatile fatty acids production, whereas similar hydrogen productivity was also observed at pH 6.0 and 6.5. The use of heat-treated anaerobic sludge as inoculum had a positive impact on bio-hydrogen production, exhibiting an increased yield of 1.09 mol H2/mol eq. glucose. On the other hand, the pretreated (ensiled) sorghum, instead of a fresh one, led to a lower hydrogen production, while the organic load decrease did not affect the process performance. In all experiments, the main fermentation end-products were volatile fatty acids (i.e., acetic, propionic, butyric), ethanol and lactic acid.

Pretreatment of sweet sorghum stalk with aqueous hydrogen peroxide for enhancing methanolysis and property of the bio-oil

Alcoholysis is a promising approach for converting biomass into fuels and/or chemicals under mild conditions. However, the effect of pretreatment on biomass alcoholysis was rarely reported. Herein, the effect of pretreatment with H2O2 on sweet sorghum stalk (SSS) methanolysis was examined. The results show that the pretreatment could markedly improve the bio-oil (BO) yield and decrease the appropriate temperature for obtaining maximum BO yield. The appropriate temperature for pretreated SSS methanolysis was determined to be 280 °C and the maximum BO yield is 44 wt%. In addition, higher heating values of the BOs were also enhanced based on elemental analysis. According to analysis with gas chromatograph/mass spectrometer, phenolic compounds, esters, and sugars are predominant in the BOs, and the yield of phenolic compounds significantly increased from 91.75 to 111.68 mg . g−1 by the pretreatment. Moreover, polar species in the BOs decreased and deoxygenation occurred during pretreated SSS methanolysis. Analyses with scanning electron microscope and N2 physisorption reveal that pretreated SSS has more grooves and higher specific surface area and anomalous porosity than SSS. According to analyses with Fourier transform infrared spectrometer and X-ray photoelectron spectrometer, oxygen functional groups mainly in the forms of CO and COO were introduced into SSS by the pretreatment. The changes of physical and chemical structures should be responsible for enhancing SSS methanolysis and property of the BO.

Curtailing citrate buffer inhibition effect on S. cerevisiae to enhance the fermentability of cellulosic hydrolysate

The current investigation emphasizes the effect of different citrate buffer strengths on cellulose conversion efficiency during the enzymatic hydrolysis of pretreated sorghum stalks, and the subsequent fermentation of enzymatic hydrolysates to achieve the industrial titer of bioethanol. A set of enzymatic hydrolysis experiments were conducted in 50 mM, 5 mM and 0.5 mM citrate buffer mediums which contain dilute sulfuric acid pretreatment derived biomass as substrate. As a result, similar cellulose conversion efficiencies such as 68.7%, 68.8% and 69% were observed during enzymatic hydrolysis of pretreated biomass at 50 mM, 5 mM and 0.5 mM citrate buffer strengths, respectively. Enzymatic hydrolysates derived from 50 mM, 5 mM and 0.5 mM citrate buffer mediums has been fermented by S. cerevisiae, which resulted in ethanol yield of 0.38 gp/gs, 0.47 gp/gs, and 0.47 gp/gs, respectively. As per the fermentation results, it has been observed that, metabolic growth of S. cerevisiae has been hindered due to the presence of high concentration of citric acid (50 mM) in the enzymatic hydrolysate.

Biodegradable foams based on extracted fractions from sorghum by-products

Agricultural by-products comprise abundant, renewable sources of value-added compounds for the food and packaging industries. The production of biodegradable foams can be focused on replacement of polystyrene-foam with biodegradable materials, which are regarded as environmentally friendly. In this study, biodegradable food trays were developed via thermopressing, using modified and unmodified corn starches with additional extracted fractions (celluloses, hemicelluloses, and lignin) from sorghum stalk and bran. The effect of several formulations of extracted fractions from sorghum by-products on bio-foam properties was studied. All trays presented thicknesses between 3 and 4.17 mm, density between 0.16 and 0.64 g cm−3, and moisture content between 5 and 12% (dry basis). The foam trays made from chemically modified starch had lower densities, higher tensile strength and elongation at break than unmodified starch. The increment of cellulose fraction from 2% to 5% and hemicellulose fraction from 1% to 10% had significant effect on the trays’ physical and mechanical properties. All trays exhibited no color and structural changes during storage at 25 °C and 4 °C. The formulation presenting the best properties contained 2% of cellulose and 1% of hemicellulose, had a maximal resistance of 0.77 MPa and 9.46 mJ of total work, attributes which corresponded to a compact, homogenous, and dense microstructure.

Enhanced ethanol production from lignocellulosic hydrolysates by Thermoanaerobacterium aotearoense SCUT27/ΔargR1864 with improved lignocellulose-derived inhibitors tolerance

The transcriptome data of Thermoanaerobacterium aotearoense SCUT27 (SCUT27) and Thermoanaerobacterium aotearoense SCUT27/ΔargR1864 (SCUT27/ΔargR1864) under xylose showed that ArgR1864 was the negative regulator for chaperonin synthesis. With argR1864 knockout, the mutant showed up-regulated expression of DnaK-DnaJ-GrpE system and GroEL-GroES chaperonin, which not only endowed the strain with the ability to scavenge the reactive oxygen species (ROS), but also gave the mutant the capability to maintain better cell growth, xylose consumption, acetic acid and ethanol production under the stress of various lignocellulose-derived inhibitors. Diluted acid pretreated soybean straw, sorghum stalk and wheat straw hydrolysates were used to evaluate the ethanol production of SCUT27/ΔargR1864 and results showed that the mutant definitely had advantages over SCUT27 for ethanol production under lignocellulosic hydrolysates, with the xylose consumption rate increased by 25.00%–44.83%, the ethanol production improved by 113.86%–366.36% and ethanol yield enhanced by 88.89%–208.33%.

Bioethanol Production from Stalk Residues of Chiquere and Gebabe Varieties of Sweet Sorghum.

Bioethanol produced from renewable resource has potential to solve environmental pollution and to satisfy the need of demand and supply. It favours the use of nonfood lignocellulosic materials. Ethanol produced from plant materials can sustain the economy by reducing cost of imported petroleum, emitting neutral CO2. Moreover, it enhances the economy by providing value added market opportunities for transportation and agricultural sector. Therefore, the objective of the study was to investigate bioethanol production from stalk residues of Chiquere and Gebabe varieties of sweet sorghum collected from West Arsi Zone, Ethiopia. Response surface methods with a three factor (inoculum size, pH, and dilution rate) with triplicate run by using the Box–Behnken method was referred. The experiment employed dilute acid hydrolysis, because it is an easy and productive process by treating the stalks with 4% of sulfuric acid for effective hydrolysis of substrate. Finally, the fermentation was carried out at 30°C for 72 hours on a shaker at 180 rpm by using Saccharomyces cerevisiae. The significance of the result was evaluated by using ANOVA, where P values <0.05 were considered statistically significant. In the process, maximum yield of ethanol was obtained at an inoculum size of 5% (22.40%), pH level of 4.0 (21%), and dilution rate at 10 ml (21.46%). Very low yeast inoculum size and dilution factor have positive effect on the yield of ethanol, whereas very high dilution rate produced negative impact on ethanol production. FTIR spectroscopy peaks associated with O-H, C-O, and C-H stretching vibrations confirmed the presence of ethanol obtained from sweet sorghum stalks. The results of our study indicated that, being available in bulky amounts and nonedible material, sweet sorghum stalks can serve as potential feedstock for bioethanol production in developing countries such as Ethiopia.

Analyzing life-cycle water footprint for advanced bio-liquid fuel: Crop residues and non-grain biofuels in China

Increasing the production of biofuels in some provinces of China may be affected by local water resources (WR). This study analyzed the life-cycle water footprint (WF) of second-generation and non-grain fuels in different natural and technical conditions in different provinces of China. The analysis was doing using the CROPWAT software model, comparing conversion technologies, a sensitivity analysis, uncertainty analysis, and a pressure analysis of local WR. The impact of biofuel on the WF and local water load in Northeast, Southwest, Northwest, Central, and South China were analyzed. Results show that the bio-ethanol of Bagasse and Cassava in Guangxi, Sorghum stalk in Jilin, and Paddy Rice straw and Corn cobs in Heilongjiang are the most favorable feedstocks for producing biofuel, with WFs ranging from to 152–967 m3/t. The proportions of grey WF to life-cycle WF for Sorghum straw (61.89%), Corn cob bio-ethanol (60.17%), and Rapeseed biodiesel (85.20%) in China should be reduced compared with the global average WF (less than 50%). The local WR load of Wheat straw in Henan was the highest (K = 1.13) and the local WR load of Bagasse in Guangxi was lowest (K = 0.06). Increasing the output, reducing the value fraction of the crop residue, and reducing chemical fertilizer consumption have the best effect on reducing WF. Biofuel development policies, including adopting well-designed management practices, controlling fertilizer use as much as possible, carrying out nearby bioenergy strategies, and implementing a local multi-cooperation model are proposed. These results can guide provincial decision-making to expand biofuel commercialization in China.

Open simultaneous saccharification and fermentation of l-lactic acid by complete utilization of sweet sorghum stalk: a water-saving process.

A complete and efficient utilization of sweet sorghum stalk including sweet sorghum juice (SSJ) and sweet sorghum bagasse (SSB) was achieved via the open simultaneous saccharification and fermentation (SSF) of l-lactic acid. To simplify the pretreatment process and reduce water consumption, a combined hydrolysis approach was applied and the NaOH-pretreated liquor (SL) was utilized as a partial neutralizing agent. In order to further enhance the product titer, the acid hydrolysate of SSJ (SSJAH) was fed, and MgO was used as a neutralizing agent. A product titer of 94 g L−1 was obtained with a productivity of 1.55 g L−1 h−1, and the yield reached 98.31%. Totally, 274.79 g l-lactic acid was produced from 1 kg sweet sorghum stalk, and 83.22% water was saved compared with the previous study based on alkali pretreatment of SSB. This study provides an effective process for l-lactic acid biosynthesis from lignocellulosic substrates.

Organosolv Pretreatment of Sorghum Stalks Using Glycerol.

Glycerol is a promising low-cost solvent for biomass pretreatment since a large amount of glycerol is generated as a by-product in the biodiesel industry. Pretreatment is a method of disintegration of the recalcitrant structure of biomass to enhance the accessibility of cellulose and hemicelluloses to enzymes for complete saccharification. During pretreatment, glycerol breaks the lignin carbohydrate complex and selectively solubilizes lignin. Thus, the glycerol pretreatment improves the accessibility of cellulose to cellulases leading to higher sugar yields. The glycerol pretreatment is carried out at high temperature (>190°C) to disintegrate the structure of biomass. The glycerol pretreatment in the presence of acid or base catalyst such as H2SO4 or NaOH results in lower pretreatment temperature and higher glucan hydrolysis. This chapter describes the methodology to carry out glycerol pretreatment of sorghum biomass with or without acid/alkali as catalyst and the basic calculations to determine the efficiency of the pretreatment.

Coproduction of hydrogen and volatile fatty acids via integrated two-step fermentation of sweet sorghum stalks by alkaline and enzymatic treatment

Coproduction of H2 and volatile fatty acids from sweet sorghum stalks was successfully developed via two-step fermentation process involving alkaline and enzymatic treatment of the residual slurry obtained from the first step fermentation of the raw material. The optimum treatment conditions to obtain the highest yield of the end products included 2% (w/v) alkali at 120 °C for the residual slurry and 32 FPU cellulase per gram of the alkali-treated materials. The two-step fermentation using Clostridium thermosaccharolyticum increased the end product yields of H2 (6.37 mmol/g-substrate) by 95%, acetic acid (2.33 g/L) by 97% and butyric acid (2.36 g/L) by 143% compared with those obtained in the single step fermentation without any treatment. As a result, the H2 energy recovery efficiency of the two-step fermentation process with commercially attractive butyric acid as a coproduct reached 10.54%. These results provide a promising approach for sweet sorghum biorefining.