Cultivating conditions optimization of the anaerobic digestion of corn ethanol distillery residuals using response surface methodology

This study investigated the individual and interactive effects of three factors — temperature, inoculum/substrate ratio (ISR) and inoculum typology — on the anaerobic digestion of corn ethanol distillery wastewater. Biochemical methane potential assays planned with factorial design with two independent quantitative variables on three levels (ISR: 1:1, 2:1 and 3:1; temperature: 30°C, 33.5°C, 37°C) and one independent qualitative variable (inoculum type: suspended, granular, mixed) have been performed. Response Surface Methodology has been used to study the effect of the factors with the aim of maximizing the specific methane yields (Y_CH4) obtainable with this substrate. The results show that all three investigated factors influence in a significant matter the Y_CH4, the ISR having the strongest effect on it. The temperature has significant influence on the Y_CH4 only in combination with high ISR values. The optimal conditions for the maximum Y_CH4 (551 mL CH₄ g^?1 VS_added) have been found at 37°C operating temperature, ISR=3:1 and using granular inoculum. These conditions gave rise to a 4-fold increase of Y_CH4 with respect to the worst combination of factors (Y_CH4=129 mL g^?1 VS_added for the suspended inoculum type, at 30°C and ISR=1:1). The results improve the knowledge on the digestion of this substrate, providing information for successful process up-scaling.

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Fermentation of “Quick Fiber” produced from a modified corn-milling process into ethanol and recovery of corn fiber oil

Approximately 9% of the 9.7 billion bushels of corn harvested in the United States was used for fuel ethanol production in 2002, half of which was prepared for fermentation by dry grinding. The University of Illinois has developed a modified dry grind process that allows recovery of the fiber fractions prior to fermentation. We report here on conversion of this fiber (Quick Fiber [QF]) to ethanol. QF was analyzed and found to contain 32%wt glucans and 65%wt total carbohydrates. QF was pretreated with dilute acid and converted into ethanol using either ethanologenic Escherichia coli strain FBR5 or Saccharomyces cerevisiae. For the bacterial fermentation the liquid fraction was fermented, and for the yeast fermentation both liquid and solids were fermented. For the bacterial fermentation, the final ethanol concentration was 30 g/L, a yield of 0.44 g ethanol/g of sugar(s) initially present in the hydrolysate, which is 85% of the theoretical yield. The ethanol yield with yeast was 0.096 gal/bu of processed corn assuming a QF yield of 3.04 lb/bu. The residuals from the fermentations were also evaluated as a source of corn fiber oil, which has value as a nutraceutical. Corn fiber oil yields were 8.28%wt for solids recovered following prtetreatment.     

Fermentation and costs of fuel ethanol from corn with quick-germ process

The Quick-Germ process developed at the University of Illinois at Urbana-Champaign is a way to obtain corn oil, but with lower capital costs than the traditional wet-milling process. Quick-Germ has the potential to increase the coproduct credits and profitability of the existing dry-grind fuel ethanol process, but the fermentability of the corn remaining after oil recovery has not been tested. Therefore, a series of pilot scale (50 L) fermentations was carefully controlled and monitored with unique methods for standard inoculation and automatic sampling. It was found that the concentration of suspended solids was significantly reduced in the Quick-Germ fermentations. When compared at the same concentration of fermentable sugars, the fermentation rate and yield were not statistically different from controls. When Quick-Germ was integrated into a state-of-the-art dry-grind fuel ethanol process, computer simulation and cost models indicated savings of approx $0.01/L of ethanol ($0.04/gal) with the Quick-Germ process. Additional savings associated with the lower suspended solids could not be quantified and were not included. However, the savings are sensitive to the price of corn oil. Mention of brand or firm name does not constitute an endorsement by the U.S. Department of Agriculture over others of a similar nature not mentioned.     

Fuel ethanol production from corn fiber current status and technical prospects

Corn fiber, which consists of about 20% starch, 14% cellulose, and 35% hemicellulose, has the potential to serve as a low cost feedstock for production of fuel ethanol. Currently, the use of corn fiber to produce fuel ethanol faces significant technical and economic challenges. Its success depends largely on the development of environmentally friendly pretreatment procedures, highly effective enzyme systems for conversion of pretreated corn fiber to fermentable sugars, and efficient microorganisms to convert multiple sugars to ethanol. Several promising pretreatment and enzymatic processes for conversion of corn fiber cellulose, hemicellulose, and remaining starch to fermentable sugars were evaluated. These hydrolyzates were then examined for ethanol production in bioreactors, using genetically modified bacteria and yeast. Several novel enzymes were also developed for use in pretreated corn fiber saccharification. Names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by USDA implies no approval of the product to the exclusion of others that may also be suitable.     

Effect of germ and fiber removal on production of ethanol from corn

Ethanol fermentations were conducted using both whole corn, and corn with 100% of the germ, and a portion (∼74%) of the fiber removed. Ethanol production increased 11% in the germ and fiber-removed corn vs the whole corn. The protein content of distiller's dried grains and solubles increased from 30 to 36%, and phosphate levels were 60% lower in corn with germ and fiber removed vs whole corn. Removal of germ and fiber prior to fermentation allows higher starch loading and results in increased ethanol production. The integration of germ and fiber removal in the dry-grind ethanol industry could increase capacity and add valuable coproducts, resulting in increased productivity and profits.     

Enzymatic hydrolysis of corn starch after extraction of corn oil with ethanol

To develop a yeast strain that is able to produce ethanol directly from starch, α-amylase cDNA (originated from mouse salivary glands) was introduced into the hyploidSaccharomyces diastiticus cells secreting glucoamylase by using a linearized integrating vector. The integrating vector contains aLEU2 gene and the inside of theLEU2 gene was cut byKpnl to make the linearized vector. One of the transformants exhibited 100% mitotic stability after 100 generations of cell multiplication. To improve its ethanol-fermentability, the haploid transformant was rare-mated with a polyploid industrial strain having no amylase activity. The resulting hybrid RH51 produced 7.5 (w/v) ethanol directly from 20% (w/v) soluble starch and its mitotic stability was 100% at the end of fermentation.     

Production of acetone butanol ethanol from degermed corn using Clostridium beijerinckii BA101

In this article we report on acetone butanol ethanol (ABE) fermentation characteristics of degermed corn when using Clostridium beijerinckii BA101. Recent economic studies suggested that recovery of germ from corn and hence corn oil would help to make the ABE fermentation process more economical. C. beijerinckii BA101 ferments corn mash efficiently to produce ABE under appropriate nutritional and environmental conditions. Corn mash contains germ/corn oil that is, possibly, ancillary to the production of butanol during the ABE fermentation process. Since the presence of corn oil is not a critical factor in solvent fermentation, it can be removed and this will allow for byproduct credit. Batch fermentation of degermed corn resulted in 8.93 g/L of total ABE production as compared with 24.80 g/L of total ABE when supplemented with P2 medium nutrients. During the course of the germ separation process, corn steeping is required prior to grinding and removing the germ. It is likely that some nutrients from the corn are leached out during the steeping process. This may reduce the rate of fermentation and impact the final concentration of butanol/ABE that can be achieved. Fermentation of degermed corn with corn steep liquor resulted in the production of 19.28 g/L of ABE.     

Thermal behavior of corn fibers and corn fiber gums prepared in fiber processing to ethanol

In this work, a thorough study of all solid products obtained in corn fiber processing to ethanol has been carried out with thermogravimetry/mass spectrometry (TG/MS) and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). The thermal behavior of corn fiber, destarched corn fiber, various alkali pretreated fibers and corn fiber gums were compared.It has been established that no significant changes occur in the thermal behavior of the feedstock material as a result of treatment with amylolytic enzymes. On one hand only the concentration of the alkali (NaOH or KOH) seems to be important in determining the chemical composition of the pretreated corn fiber samples. On the other hand, the composition of the corn fiber gums depends on the type and not the concentration of the alkali used in the pretreatment step. The presence of H₂O₂ degrades the structure and alters the composition of the corn fiber to a larger extent. The polymeric hemicellulose which is precipitated after pretreatment with NaOH + H₂O₂ contains less impurities than the corn fiber gum prepared in the absence of hydrogen peroxide.The results indicate that the applied analytical methods are suitable for studying changes in the composition of the variously treated corn fibers. The observed effects of the treatments are in good agreement with data determined with conventional analytical techniques.     

A reticuloendothelial system-activating arabinoxylan from the bark of Cinnamomum cassia

A neutral polysaccharide, named cinnaman AX, was isolated from the dried bark of Cinnamomum cassia Blume. It was homogeneous on electrophoresis and gel chromatography. It is composed of L-arabinose: D-xylose in the molar ratio of 4:3, and its molecular weight was estimated to be about 1.0 x 10(6). Methylation analysis, carbon-13 nuclear magnetic resonance and controlled Smith degradation studies enabled elucidation of its structural features. It showed remarkable reticuloendothelial system-potentiating activity in a carbon clearance test.     

Enzyme production by industrially relevant fungi cultured on coproduct from corn dry grind ethanol plants

Distillers dried grain with solubles (DDGS) is the major coproduct produced at a dry grind ethanol facility. Currently, it is sold primarily as a ruminant animal feed. DDGS is low cost and relatively high in protein and fiber contents. In this study, DDGS was investigated as carbon source for extracellular hydrolytic enzyme production. Two filamentous fungi, noted for their high cellulolytic and hemicellulolytic enzyme titers, were grown on DDGS: Trichoderma reesei Rut C-30 and Asper gillus niger NRRL 2001. DDGS was either used as delivered from the plant (untreated) or after being pretreated with hot water. Both microorganisms secreted a broad range of enzymes when grown on DDGS. Higher xylanase titers were obtained when cultured on hot water DDGS compared with growth on untreated DDGS. Maximum xylanase titers were produced in 4 d for A. niger and 8 d for T. reesei in shake flask cultures. Larger amounts of enzymes were produced in bioreactors (5 L) either equipped with Rushton (for T. reesei) or updraft marine impellers (A. niger). Initial production titers were lower for bioreactor than for flask cultures, especially for T. reesei cultures. Improvement of enzyme titers were obtained using fed-batch feeding schemes.     

SO2-catalyzed steam explosion of corn fiber for ethanol production

Corn fiber, a by-product of the corn wet-milling industry, represents a renewable resource that is readily available in significant quantities and could potentially serve as a low-cost feedstock for the production of fuel-grade alcohol. In this study, we used a batch reactor to steam explode corn fiber at various degrees of severity to evaluate the potential of using this feedstock in the bioconversion process. The results indicated that maximum sugar yields (soluble and following enzymatic hydrolysis) were recovered from corn fiber that was pretreated at 190°C for 5 min with 6% SO₂. Sequential SO₂-catalyzed steam explosion and enzymatic hydrolysis resulted in very high conversion (81%) of all polysaccharides in the corn fiber to monomeric sugars. Subsequently, Saccharomyces cerevisiae was able to convert the resultant corn fiber hydrolysates to ethanol very efficiently, yielding 90–96% of theoretical conversion during the fermentation process.     

Synthesis of δ-Lactones from Glutaraldehyde

A novel and general synthesis of δ-lactones from glutaraldehyde is described. The dialdehyde is first reacted with an alkyl or substituted alkyl Grignard reagent to afford a δ-hydroxyaldehyde in good yield. These aldehydes exist preferentially in the cyclic hemiacetal form (δ-lactols). Oxidation of the latter compounds to give δ-lactones is readily achieved with silver oxide or bromine. The δ-lactols and δ-lactones serve as intermediates for the total synthesis of steroids.     

Effect of crosslinking on porous poly(methyl methacrylate) produced by phase separation

Porous polymethyl methacrylate scaffolds were produced by phase separation during polymerisation in solution, using ethanol as solvent, with monomer/ethanol weight ratios from 80/20 up to 20/80 and different ethylenglycol dimethacrylate contents (1, 5 and 10 wt%) as crosslinker agent. For ethanol weight ratios equal to or lower than 50 wt%, the material presents a homogeneous distribution of dispersed pores. For higher ethanol contents, a highly interconnected porous structure is obtained. The transition from one type of morphology to the other can be also controlled with the amount of crosslinker added in the reactive mixture. Bulk polymethyl methacrylate samples (non-porous) with the same crosslinking densities were also synthesised as reference. The effect of crosslinker is studied by porosity measurements, scanning electron microscopy, dynamic-mechanical spectroscopy and differential scanning calorimetry.     

Multi-gradient hydrogels produced layer by layer with capillary flow and crosslinking in open microchannels

This technical note describes a new bench-top method for producing anisotropic hydrogels composed of gradient layers of soluble factors, particles, polymer concentrations or material properties. Each gradient layer was produced by a previous gradient method in which a droplet of one precursor solution was added to a thin layer of a second solution. The ensuing rapid capillary flow along the open channel generated a gradient precursor solution, which was then crosslinked to form a gradient gel. Repeating these steps allowed a layered gel to be iteratively constructed with as many gradient layers as desired. This technique renders the synthesis of multi-layered gradient gels accessible to virtually any researcher and should help simplify the production of more biologically relevant cellular microenvironments.     

Synthesis of Water-Soluble Chemically Degradable Polymers from Glutaraldehyde and N-Vinylpyrrolidone-Allylamine Copolymers

Water-soluble chemically degradable copolymers of N-vinylpyrrolidone with allylamine, containing azomethine links between the polymeric chains, were prepared. The composition and molecular-weight characteristics of the polymers were determined.     

Optimization of SO2-catalyzed steam pretreatment of corn fiber for ethanol production

A batch reactor was employed to steam explode corn fiber at various degrees of severity to evaluate the potential of using this feedstock as part of an enzymatically mediated cellulose-to-ethanol process. Severity was controlled by altering temperature (150–230°C), residence time (1–9 min), and SO₂ concentration (0–6% [w/w] dry matter). The effects of varying the different parameters were assessed by response surface modeling. The results indicated that maximum sugar yields (hemicellulose-derived water soluble, and cellulose-derived following enzymatic hydrolysis) were recovered from corn fiber pretreated at 190°C for 5 minutes after exposure to 3% SO₂. Sequential SO₂-catalyzed steam explosion and enzymatic hydrolysis resulted in a conversion efficiency of 81% of the combined original hemicellulose and cellulose in the corn fiber to monomeric sugars. An additional posthydrolysis step performed on water soluble hemicellulose stream increased the concentration of sugars available for fermentation by 10%, resulting in the high conversion efficiency of 91%. Saccharomyces cerevisiae was able to ferment the resultant corn fiber hydrolysates, perhydrolysate, and liquid fraction from the posthydrolysis steps to 89, 94, and 85% of theoretical ethanol conversion, respectively. It was apparent that all of the parameters investigated during the steam explosion pretreatment had a significant effect on sugar recovery, inhibitory formation, enzymatic conversion efficiency, and fermentation capacity of the yeast.     

Optimization of steam pretreatment of SO2-impregnated corn stover for fuel ethanol production

In this study, corn stover with a dry matter content of 20% was impregnated with SO₂ and then steam pretreated for various times at various temperatures. The pretreatment was evaluated by enzymatic hydrolysis of the solid material and analysis of the sugar content in the liquid. The maximum overall yield of glucose, 89% of the theoretical based on the glucan in the raw material, was achieved when the corn stover was pretreated at 200°C for 10 min. The maximum overall yield of xylose, 78%, was obtained with pretreatment at 190°C for 5 min.     

Solubility and IR studies of gamma-irradiated arabinoxylan

The structural and solubility changes of a water-insoluble arabinoxylan with a low degree of branching was studied after -irradiation by IR spectroscopy and chemical analysis of the polysaccharide and its polymeric fractions.     

二苯乙烯对秸秆纤维素超临界乙醇裂解转化液化产物的影响

以1,1-二苯乙烯(DPE)为阻聚剂,采用高压反应釜对玉米秸秆纤维素进行超临界乙醇液化,探究DPE浓度(用量)和反应温度对纤维素裂解碎片转化成液化产物的影响。结果表明,DPE浓度增加,挥发分收率降低了25.4%,生物油收率增加了19.9%,收率最高达39.8%,纤维素转化率有所下降;反应温度升高,纤维素转化率迅速增加到85.5%,挥发分也急剧升高,生物油收率最高为34.6%。GC-MS结果显示,生物油主要包括酮类、酯类、烃类等平台化合物以及较多的联苯化合物。DPE浓度过高,结合大量的纤维素裂解片段(乙基、羟基、甲基、氢等)形成联苯类化合物产生较强的空间位阻效应,使得纤维素裂解及活性片段转化成平台化合物的反应受到抑制,两者之间是一个竞争过程;温度升高,乙醇自由基活性增强,其对纤维素裂解的促进作用逐渐超过DPE对纤维素裂解的抑制作用,平台化合物收率有所升高。     

Industrial scale-up of pH-controlled liquid hot water pretreatment of corn fiber for fuel ethanol production

The pretreatment of cellulose in corn fiber by liquid hot water at 160°C and a pH above 4.0 dissolved 50% of the fiber in 20 min. The pretreatment also enabled the subsequent complete enzymatic hydrolysis of the remaining polysaccharides to monosaccharides. The carbohydrates dissolved by the pretreatment were 80% soluble oligosaccharides and 20% monosaccharides with o1% of the carbohydrates lost to degradation products. Only a minimal amount of protein was dissolved, thus enriching the protein content of the un dissolved material. Replication of laboratory results in an industrial trial at 43 gallons per minute (163 L/min) of fiber slurry with a residence time of 20 min illustrates the utility and practicality of this approach for pretreating corn fiber. The added costs owing to pretreatment, fiber, and hydrolysis are equivalent to less than $0.84/gal of ethanol produced from the fiber. Minimizing monosaccharide formation during pretreatment minimized the formation of degradation products; hence, the resulting sugars were readily fermentable to ethanol by the recombinant hexose and by pentose-fermenting Saccharomyces cerevisiae 424A (LNH-ST) and ethanologenic Escherichia coli at yields >90% of theoretical based on the starting fiber. this cooperative effort and first successful trial opens the door for examining the robustness of the pretreatment system under extended run conditions as well as pretreatment of other cellulose-containing materials using water at controlled pH.