Pretreatment and enzymatic saccharification of corn fiber

Corn fiber consists of about 20% starch, 14% cellulose, and 35% hemicellulose, and has the potential to serve as a low-cost feedstock for production of fuel ethanol. Several pretreatments (hot water, alkali, and dilute, acid) and enzymatic saccharification procedures were evaluated for the conversion of corn fiber starch, cellulose, and hemicellulose to monomeric sugars. Hot water pretreatment (121°C, 1 h) facilitated the enzymatic sacch arification of starch and cellulose but not hemicellulose. Hydrolysis of corn fiber pretreated with alkali un dersimilar conditions by enzymatic means gave similar results. Hemicellulose and starch components were converted to monomeric sugars by dilute H₂SO₄ pretreatment (0.5–1.0%, v/v) at 121°C. Based on these findings, a method for pretreatment and enzymatic saccharification of corn fiber is presented. It in volves the pretreatment of corn fiber (15% solid, w/v) with dilute acid (0.5% H₂SO₄, v/v) at 121°C for 1 h, neutralization to pH 5.0, then saccharification of the pretreated corn fiber material with commercial cellulase and β-glucosidase preparations The yield of monomeric sugars from corn fiber was typically 85–100% of the theoretical yield. 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.     

Novel approach of corn fiber utilization

The corn wet milling process produces a 10% (w/w of the processed corn) byproduct called corn fiber, which is utilized worldwide as a low-value feedstock for cattle. The aim of this study was to find a higher value use of corn fiber. The main fractions of corn fiber are: 20% starch, 40% hemicellulose, 14% cellulose, and 14% protein. Extraction of the highly valuable, cholesterol-lowering corn fiber oil is not feasible owing to its low (2% w/w) concentration in the fiber. The developed technology is based on simple and inexpensive procedures, like washing with hot water, dilute acid hydrolysis at 120°C, enzymatic hydrolysis of cellulose, screening, drying, and extraction. The main fractions are sharply separated in the order of starch, hemicellulose, cellulose, lipoprotein, and lignin). The lipoprotein fraction adds up to 10% of the original dry corn fiber, and contains 45% corn fiber oil, thus yielding more oil than direct extraction of the fiber. It is concluded that the defined method makes the extraction of the corn fiber oil economically feasible. The fractionation process also significantly increases the yield of cholesterol-lowering substances (sterols and sterolesters). At the same time clear and utilizable fractions of monosaccharides, protein, and lignin are produced.     

Novel approach of corn fiber utilization

The corn wet milling process produces a 10% (w/w of the processed corn) byproduct called corn fiber, which is utilized worldwide as a low-value feedstock for cattle. The aim of this study was to find a higher value use of corn fiber. The main fractions of corn fiber are: 20% starch, 40% hemicellulose, 14% cellulose, and 14% protein. Extraction of the highly valuable, cholesterol-lowering corn fiber oil is not feasible owing to its low (2% w/w) concentration in the fiber. The developed technology is based on simple and inexpensive procedures, like washing with hot water, dilute acid hydrolysis at 120 degrees C, enzymatic hydrolysis of cellulose, screening, drying, and extraction. The main fractions are sharply separated in the order of starch, hemicellulose, cellulose, lipoprotein, and lignin). The lipoprotein fraction adds up to 10% of the original dry corn fiber, and contains 45% corn fiber oil, thus yielding more oil than direct extraction of the fiber. It is concluded that the defined method makes the extraction of the corn fiber oil economically feasible. The fractionation process also significantly increases the yield of cholesterol-lowering substances (sterols and sterolesters). At the same time clear and utilizable fractions of monosaccharides, protein, and lignin are produced.     

Preparation of starch-based biocomposites reinforced with mercerized lignocellulosic fibers: Evaluation of their thermal,morphological, mechanical,and biodegradable properties

In the present paper, starch-based biocomposites have been prepared by reinforcing corn starch matrix with mercerized Abelmoschus esculentus lignocellulosic fibers. The effect of fiber content on mechanical properties of composite was investigated and found that tensile strength, compressive strength, and flexural strength at optimum fiber content were 69.1%, 93.7% and 105.1% increased to that of cross-linked corn starch matrix, respectively. The corn starch matrix and its composites were characterized by Fourier transform infrared spectroscopy (FT-IR), Scanning electron microscopy (SEM), X-ray diffraction (XRD) and thermogravimetric (TGA) analysis. The fiber reinforced composites were found to be highly thermal stable as compared to natural corn starch and cross-linked corn starch matrix. Further, water uptake and biodegradation studies of matrix and composites have also been studied.     

甲酰胺塑化热塑性淀粉的性能研究

用甲酰胺作为塑化剂制备了热塑性淀粉 (TPS) ,扫描电镜显示甲酰胺可以使淀粉塑化 ,形成均一的连续相 ;流变性能说明在加工温度范围内 ,甲酰胺塑化淀粉 (FPTPS)的剪切应力对温度变化敏感性要小于甘油塑化淀粉 (GPTPS) ;用热重和DSC研究了热稳定性和玻璃化转变 ;FPTPS在 13%～ 2 3%的水含量时有较好的力学性能 ,水含量为 13%时 ,FPTPS有最大的断裂强度 3 9MPa ;水含量为 17%时 ,FPTPS最大的伸长率为 95 % ;与GPTPS相比 ,在RH(Relativehumidity) =0 5 0 %and 10 0 %环境下 ,FPTPS有良好的耐回生性能 ,这主要是因为甲酰胺可以和淀粉羟基形成更稳定的氢键     

Cellulose/iron oxide hybrids as multifunctional pigments in thermoplastic starch based materials

Cellulose/iron oxide hybrids were prepared by the controlled hydrolysis of FeC₂O₄ in the presence of vegetable and bacterial cellulose fibres as substrates. By varying the relative amount of FeC₂O₄ and NaOH, either hematite or magnetic iron oxides were grown at the cellulose fibres surfaces. This chemical strategy was used for the production of a number of materials, whose coloristic properties associated to their reinforcement role allowed their use as new hybrid pigments for thermoplastic starch (TPS) based products. The TPS reinforced materials were characterized by several techniques in order to evaluate: the morphology and the compatibility between the matrix and the fillers; the mechanical reinforcement effect of the cellulose/iron oxide pigments on TPS and the coloristic properties of the composites. All materials showed good dispersion and strong adhesion for the cellulose/iron oxide nanocomposites in the TPS matrix thus resulting in improved mechanical properties.     

富含纤维素类农作物秆与丙烯酸接枝共聚制备高倍率吸水树脂

用棉花秆、麦秆和玉米秆等富含纤维素类农作物秆与丙烯酸接枝共聚制备了高倍率的吸水树脂. 研究了不同水质(去离子水、自来水及雨水)对接枝产物吸水性能的影响. 采用棉花秆、麦秆、玉米秆与丙烯酸的接枝产物对去离子水的吸水倍率分别为930, 790和630 g/g, 对自来水的吸水倍率分别为670, 350和250 g/g, 用玉米秆/地瓜淀粉混合物制备的接枝产物对雨水的吸水倍率为540 g/g. 为棉花秆、 麦秆及玉米秆等富含纤维素的农作物秆的深加工与应用开辟了一条途径.     

尿素和甲酰胺塑化热塑性淀粉

用甲酰胺和尿素作为塑化剂制备了热塑性淀粉 (TPS) .扫描电镜显示甲酰胺和尿素混合物可以使淀粉塑化 ,形成均一的连续相 ;根据FT IR谱图可以确定 ,与甘油相比 ,甲酰胺可以使热塑性淀粉体系在保存时更稳定 ,各基团的化学环境变化更小 ,这是由于甲酰胺可以和淀粉羟基形成更稳定的氢键 .X ray衍射说明甲酰胺和尿素 (重量比为 10 % 2 0 % )作为混合塑化剂可以有效抑制淀粉的回生 ,同时防止尿素结晶析出 .在RH=33%的湿度环境保存 1周 ,这种热塑性淀粉有良好的拉伸强度、伸长率和断裂能 ,分别达到 4 83MPa ,10 4 6 %和 2 17N·m .水含量对热塑性淀粉的力学性能的影响也被研究 .另外 ,热失重实验和吸水实验说明这种热塑性淀粉的热稳定性和耐水性也要优于常用的甘油塑化热塑性淀粉     

Mathematical Tool from Corn Stover TGA to Determine Its Composition

Corn stover was treated by steam explosion process at four different temperatures. A fraction of the four exploded matters was extracted by water. The eight samples (four from steam explosion and four from water extraction of exploded matters) were analysed by wet chemical way to quantify the amount of cellulose, hemicellulose and lignin. Thermogravimetric analysis in air atmosphere was executed on the eight samples. A mathematical tool was developed, using TGA data, to determine the composition of corn stover in terms of cellulose, hemicellulose and lignin. It uses the biomass degradation temperature as multiple linear function of the cellulose, hemicellulose and lignin content of the biomass with interactive terms. The mathematical tool predicted cellulose, hemicellulose and lignin contents with average absolute errors of 1.69, 5.59 and 0.74?%, respectively, compared to the wet chemical method.     

Preparation and Characterisation of Thermoplastic Starches from Cassava Starch,Cassava Root and Cassava Bagasse

Summary: Thermoplastic starches (TPS) based on cassava starch have been produced by extrusion at 120 °C, using glycerol as plasticizer. Three forms of cassava starch were employed, viz: cassava root (CR), cassava bagasse (CB) and purified cassava starch (PCS). The main differences between these are the presence of sugars and a few fibres in CR and high fibre concentration in CB. Conditions of processing and characteristics such as amylose and fibre content, crystallinity, water absorption and mechanical behaviour in the tension x deformation test were evaluated. The results demonstrated that the PCS and CR had amylose contents consistent with literature values (14–18%) and that CB is a material constituted mainly by amylopectin. It was found that fibres in high proportions (as in the bagasse) can confer reinforcement properties and are thus able to generate natural composites of TPS with cellulose fibre. The sugars naturally found in the root reduce the elongation of the TPS under tension. The PCS and CR TPS were stable with respect to indices of crystallinity after processing; and during a period of 90 d in a relative humidity of 53%, while the CB TPS tended to vary its crystallinity, probably because its amylose chain had low degree of polymerization.     

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.     

Injection molded hybrid composites based on corn fibers and poly(vinyl alcohol)

Ongoing research cooperation between USDA and the University of Pisa, Italy has yielded several composite blends of poly(vinyl alcohol) (PVA) and corn fibers (CF). The USA is the largest producer of ethanol from cereal grains. Composites based on natural fibers alone are extremely sensitive to water. Their mechanical properties deteriorated upon the absorption of water, thus suggesting a limited usefulness of such formulations in practical applications. In this study, corn-fibers produced during the wet milling process of corn for fuel ethanol were used to prepare composites. CF and PVA were processed in variable amounts in the presence of both dry/fluid plasticizers, such as glycerol and pentaerythritol. Composites prepared from CF in combination with PVA showed little change in their mechanical properties even after conditioning at variable relative humidities, as well as complete soaking in water. Composites tested after storage for one year under 50% relative humidity and 23°C exhibited mechanical properties similar to those of freshly prepared composites. Cornstarch was introduced in the formulation for the purpose of reducing the cost of the final product and to further increase the composition of natural components in the composites. Addition of starch moderately reduced the mechanical properties of the composites.     

Characterization and performance of immobilized amylase and cellulase

The performance of cellulase and amylase immobilized on siliceous supports was investigated. Enzyme uptake onto the support depended on the enzyme source and immobilization conditions. For amylase, the uptake ranged between 20 and 60%, and for cellulase, 7–10%. Immobilized amylase performance was assessed by batch kinetics in 100–300 g/L of corn flour at 65°C. Depending on the substrate and enzyme loading, between 40 and 60% starch conversion was obtained. Immobilized amylase was more stable than soluble amylase. Enzyme samples were preincubated in a water bath at various temperatures, then tested for activity. At 105°C, soluble amylase lost ∼55% of its activity, compared with ∼30% loss for immobilized amylase. The performance of immobilized cellulase was evaluated from batch kinetics in 10 g/L of substrate (shredded wastepaper) at 55°C. Significant hydrolysis of the wastepaper was also observed, indicating that immobilization does not preclude access to and hydrolysis of insoluble cellulose.     

Production of 2,3- butanediol from pretreated corn cob byKlebsiella oxytoca in the presence of fungal cellulase

A simple and effective method of treatment of lignocellulosic material was used for the preparation of corn cob for the production of 2,3-butanediol byKlebsiella oxytoca ATCC 8724 in a simultaneous saccharification and fermentation process. During the treatment, lignin, and alkaline extractives were solubilized and separated from cellulose and hemicellulose fractions by dilute ammonia (10%) steeping. Hemicellulose was then hydrolyzed by dilute hydrochloric acid (1%, wJv) hydrolysis at 100°C at atmospheric pressure and separated from cellulose fraction. The remaining solid, with 90% of cellulose, was then used as the substrate. A butanediol concentration of 25 g/L and an ethanol concentration of 7 g/L were produced byK. oxytoca from 80 g/L of corn cob cellulose with a cellulase dosage of 8.5 IFPU/g corn cob cellulose after 72 h of SSF. With only dilute acid hydrolysis, a butanediol production rate of 0.21 g/L/h was obtained that is much lower than the case in which corn cob was treated with ammonia steeping prior to acid hydrolysis. The butanediol production rate for the latter was 0.36 g/L/h.     

Coupled acid and enzyme mediated production of microcrystalline cellulose from corn cob and cotton gin waste

Microcrystalline cellulose has applications in food, pharmaceuticals, and other industries. Most microcrystalline cellulose (MCC) is produced from dissolving pulp using concentrated acids. We investigated steam explosion treatment of corn cobs and cotton gin waste for the production of microcrystalline cellulose. The corn cob was converted into a coarse brown powder after steam explosion and the lignin and residual hemicellulose fractions were extracted respectively with sodium hydroxide solution and water. The residual cellulose was readily bleached with hydrogen peroxide and converted to microcrystalline cellulose using hydrochloric acid, sulfuric acid and cellulase enzyme preparation. The resulting microcrystalline cellulose samples had properties that were similar to commercial microcrystalline cellulose. Similarly, cotton gin waste was steam exploded and converted into microcrystalline cellulose, but this material was more difficult to bleach using hydrogen peroxide. The degree of polymerization for the MCC samples ranged from 188.6 to 549.8 compared to 427.4 for Avicel PH101 MCC.     

Fabrication of starch blend films with different matrices and their mechanical properties

The objective of the study was to determine the effects of molecular sizes of amylose (AM) and starch granules on the mechanical properties of thermoplastic starch (TPS) blend films. Leached amylose solution from cassava (CS_ AM) and mung bean (MB_AM), and two forms of amylopectin (AP) (granular; g and non-granular; ng) of waxy cassava (WxCS) starch were used. Four types of film matrices were fabricated and all TPS blend films contained same amount of AM and glycerol. Results displayed that molecular weight profiles of starch films and presence of granule remnants significantly controlled the film matrix formation, types of crystal formation, and percent of relative crystallinity (%RC) (p < 0.05). Tensile property of TPS films was controlled by %RC and presence of granule remnants. Percent elongation at break (%E_b) of TPS films increased when the films had a large range of molecular weight distribution (from 5.5 × 10⁷ g/mol to 0.4 × 10⁵ g/mol) and contained a high weight fraction (~58%) of starch molecules with M_w~0.4 × 10⁵ g/mol.     

Profile of enzyme production by trichoderma reesei grown on corn fiber fractions

Corn fiber is the fibrous by-product of wet-mill corn processing. It typically consists of about 20% starch, 14% cellulose, and 30% hemicellulose in the form of arabinoxylan. Crude corn fiber (CCF) was fractionated into de-starched corn fiber (DSCF), corn fiber with cellulose (CFC) enriched, and corn fiber arabinoxylan (CFAX), and these fractions were evaluated as substrates for enzyme production by Trichoderma reesei. T. reesei QM9414 and Rut C-30 grew on CCF, DSCF, CFC, or CFAX and secreted a number of hydrolytic enzymes. The enzymes displayed synergism with commercial cellulases for corn fiber hydrolysis. Mention of trade names or commercial products in this article is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the U.S. Department of Agriculture.     

Effect of urea and urea–gamma treatments on cellulose degradation of Thai rice straw and corn stalk

Cellulose degradation of 20% urea treated and 20% urea–10 kGy gamma treated Thai rice straw and corn stalk showed that combination effect of urea and gamma radiation gave a higher % decrease in neutral detergent fiber (NDF), acid detergent fiber (ADF), acid detergent lignin (ADL), cellulose, hemicellulose, and lignin and cutin in comparison with urea effect only for both room temperature storage and room temperature +258 K storage. The results also indicated that cellulose degradation proceeded with time, even at 258 K. A drastic drop to less than half of the original contents in NDF, ADF, and ADL could not be obtained in this study.     

Viscoelasticity and water plasticization of polymer-cellulose composite films and paper sheets

Viscoelastic properties of cellulose microfibril—polymer composites and paper sheets were studied with dynamic mechanical analysis as a function of relative humidity in order to assess the bonding properties in cellulosic networks. The amount of associated water in the composites (equilibrium moisture content) was measured by thermogravimetry. Water plasticization was evidenced by DMA both in composite and paper samples. Polymers with high affinity to water, e.g. carboxymethyl cellulose, clearly increased the water plasticization in the composites. The plasticization behavior of paper sheet samples was also influenced by polymers. However, the effect of polymers on the plasticization was different between the composite and the paper samples. The consideration of fiber bonding domain in paper structure as a gel-like layer consisting of cellulose microfibrils, polymers, and associated water can help to unveil some of the complex mechanisms behind the strength in fibrous cellulosic materials.     

Removal of methylene blue with hemicellulose/clay hybrid hydrogels

In this study, we chose corn stover hemicellulose for the preparation of hydrogels with admirable adsorption properties under mild alkaline conditions. Clay nanosheets were introduced to this system and hemicellulose/clay hybrid hydrogels were prepared. Morphological, mechanical properties and the methylene blue adsorption behaviors of the prepared hydrogels were studied. Results suggested that the addition of clay not only improved the mechanical strength of hemicellulose-based hydrogels, but also increased the adsorption capacity on methylene blue. Moreover, the adsorptions were confirmed to follow pseudo-second order equation for both gels with and without clay. The maximum adsorption capacities on methylene blue for hemicellulose-based hydrogels with or without clay reached 148.8 and 95.6 mg/g, respectively. These results implied that hemicellulose-based hydrogels could be used as promising adsorbents for the removal of methylene blue from waste water.