[show abstract][hide abstract] ABSTRACT: Sorghum is a tropical grass grown primarily in semiarid and drier parts of the world, especially areas too dry for corn. Sorghum production also leaves about 58 million tons of by-products composed mainly of cellulose, hemicellulose, and lignin. The low lignin content of some forage sorghums such as brown midrib makes them more digestible for ethanol production. Successful use of biomass for biofuel production depends on not only pretreatment methods and efficient processing conditions but also physical and chemical properties of the biomass. In this study, four varieties of forage sorghum (stems and leaves) were characterized and evaluated as feedstock for fermentable sugar production. Fourier transform infrared spectroscopy and X-ray diffraction were used to determine changes in structure and chemical composition of forage sorghum before and after pretreatment and the enzymatic hydrolysis process. Forage sorghums with a low syringyl/guaiacyl ratio in their lignin structure were easy to hydrolyze after pretreatment despite the initial lignin content. Enzymatic hydrolysis was also more effective for forage sorghums with a low crystallinity index and easily transformed crystalline cellulose to amorphous cellulose, despite initial cellulose content. Up to 72% hexose yield and 94% pentose yield were obtained using modified steam explosion with 2% sulfuric acid at 140 degrees C for 30 min and enzymatic hydrolysis with cellulase (15 filter per unit (FPU)/g cellulose) and beta-glucosidase (50 cellobiose units (CBU)/g cellulose).
Applied biochemistry and biotechnology 09/2008; 158(1):164-79. · 1.94 Impact Factor
[show abstract][hide abstract] ABSTRACT: Soybean hulls are a potential feedstock for production of bio-ethanol due to their high carbohydrate content (≈50%) of nearly 37% cellulose. Soybean hulls could be the ideal feedstock for fuel ethanol production, because they are abundant and require no special harvesting and additional transportation costs as they are already in the plant. The objective of this research was to study the performance of dilute acid and modified steam-explosion pretreatment technologies on degradation of soybean hulls, and to identify optimum pretreatment and enzymatic hydrolysis conditions for converting soybean hulls into fermentable sugars. Effects of reaction time, temperature, acid concentration and type of acid on hydrolysis of hemicellulose in soybean hulls and total sugar yields were studied. The combination of acid (H2SO4, 2% w/v) and steam (140 °C, 30 min) efficiently solubilized the hemicellulose, giving a pentose yield of 96%. This made the material accessible to cellulase enzymes used in subsequent enzymatic hydrolysis. Combined pretreatment with enzymatic hydrolysis dramatically increased hexose yield, (23 mg/ml) corresponding to 72% of the theoretical. Maximum total sugar yield, achieved with a combination of treatment and enzymatic hydrolysis, was 80% of the theoretical.
Journal of Biobased Materials and Bioenergy 02/2008; 2(1):43-50. · 0.83 Impact Factor
[show abstract][hide abstract] ABSTRACT: The performance of soybean hulls and forage sorghum as feed stocks for ethanol production was studied. The main goal of this research was to increase fermentable sugars' yield through high-efficiency pretreatment technology. Soybean hulls are a potential feedstock for production of bio-ethanol due to their high carbohydrate content ([approximately equals]50%) of nearly 37% cellulose. Soybean hulls could be the ideal feedstock for fuel ethanol production, because they are abundant and require no special harvesting and additional transportation costs as they are already in the plant. Dilute acid and modified steam-explosion were used as pretreatment technologies to increase fermentable sugars yields. Effects of reaction time, temperature, acid concentration and type of acid on hydrolysis of hemicellulose in soybean hulls and total sugar yields were studied. Optimum pretreatment parameters and enzymatic hydrolysis conditions for converting soybean hulls into fermentable sugars were identified. The combination of acid (H[subscript]2SO[subscript]4, 2% w/v) and steam (140 °C, 30 min) efficiently solubilized the hemicellulose, giving a pentose yield of 96%. Sorghum is a tropical grass grown primarily in semiarid and dry parts of the world, especially in areas too dry for corn. The production of sorghum results in about 30 million tons of byproducts mainly composed of cellulose, hemicellulose, and lignin. Forage sorghum such as brown midrib (BMR) sorghum for ethanol production has generated much interest since this trait is characterized genetically by lower lignin concentrations in the plant compared with conventional types. Three varieties of forage sorghum and one variety of regular sorghum were characterized and evaluated as feedstock for fermentable sugar production. Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) and X-Ray diffraction were used to determine changes in structure and chemical composition of forage sorghum before and after pretreatment and enzymatic hydrolysis process. Up to 72% of hexose yield and 94% of pentose yield were obtained using "modified" steam explosion with 2% sulfuric acid at 140°C for 30 min and enzymatic hydrolysis with cellulase (15 FPU/g cellulose) and [Beta]-glucosidase (50 CBU/g cellulose). United States Department of Agriculture Doctor of Philosophy Doctoral Department of Biological & Agricultural Engineering Donghai Wang, Scott Bean
[show abstract][hide abstract] ABSTRACT: Cereal Chem. 84(1):61-66 Sorghum bran has potential to serve as a low-cost feedstock for pro- duction of fuel ethanol. Sorghum bran from a decortication process (10%) was used for this study. The approximate chemical composition of sorghum bran was 30% starch, 18% hemicellulose, 11% cellulose, 11% protein, 10% crude fat, and 3% ash. The objective of this research was to evaluate the effectiveness of selected pretreatment methods such as hot water, starch degradation, dilute acid hydrolysis, and combination of those methods on enzymatic hydrolysis of sorghum bran. Methods for pretreatment and enzymatic hydrolysis of sorghum bran involved hot water treatment (10% solid, w/v) at 130°C for 20 min, acid hydrolysis (H2SO4), starch degradation, and enzymatic hydrolysis (60 hr, 50°C, 0.9%, v/v) with commercial cellulase and hemicellulose enzymes. Total sugar yield by using enzymatic hydrolysis alone was 9%, obtained from 60 hr of enzyme hydrolysis. Hot water treatment facilitated and increased access of the enzymes to hemicellulose and cellulose, improving total sugar yield up to 34%. Using a combination of starch degradation, opti- mum hot water treatment, and optimum enzymatic hydrolysis resulted in maximum total sugar yield of up to 75%. A dramatic increase in ethanol production using the current grain starch-based technology may have resource limitations because grain production for ethanol will compete for the limited agricul- tural land needed for food and feed production (Sun and Cheng 2001). The United States needs more than 140 billion gallons (530 billion liters) of fuels per year for automobiles alone (U.S. Depart- ment of Transportation 2006). Using 100% of the 2005 corn crop (10.35 billion bushels or 260 million tons) for ethanol production would only produce 27.9 billion gallons (105 billion liters), which only meets ≈14-16% of our demands (Hamelinck et al 2005). It is obvious that other feedstocks such as agricultural residues, wood, municipal solid wastes, and wastes from pulp and paper industry are potential resources for low-cost ethanol production (Mielenz 2001). These types of "biomass" consist of primarily cellulose (35- 50%), hemicellulose (20-35%), and lignin (10-25%) (Saha and Bothast 1997). It is estimated that ≈50 billion gallons (190 billion liters) of ethanol could be produced from current biomass wastes in the United States (Saha 2004). Bran from sorghum processing such as decortication can be class- ified as cellulosic material, and it represents a renewable resource that can be used as a potential feedstock for ethanol fermentation because of its high carbohydrate content. In this study, the sorghum bran is a mixture of sorghum pericarp, some germ tissue, and resi- dual starch from the endosperm extracted during the decortication process. Sorghum structural carbohydrates, or cell-wall polysaccha- rides, primarily consist of hemicellulose and cellulose (Bailey
[show abstract][hide abstract] ABSTRACT: Pretreatment technologies have been developed to increase the bioconversion rate for both starch and cellulosic-based biomass. This study investigated the effect of decortication as a pretreatment method on ethanol production from sorghum as well as its impact on distiller's dry grains with solubles (DDGS) quality. Eight sorghum hybrids with 0, 10, and 20% of their outer layer removed were used as raw materials for ethanol production. The decorticated samples were fermented to ethanol by using Saccharomyces cerevisiae. Removal of germ and fiber prior to fermentation allowed for a higher starch loading for ethanol fermentation and resulted in increased ethanol production. The ethanol yields increased as the percentage of decortication increased. The decortication process resulted in DDGS with higher protein content and lower fiber content, which may improve the feed quality.