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[en] Corn stover is a common agricultural product in areas with large amounts of corn production. It consists of the leaves and stalks of maize (Zea mays ssp. mays L.) plants left in field following harvest of the cereal grain. Stover makes up about half of the yield of a crop and is similar to straw. This material can be processed as cellulosic ethanol without diverting food for fuel. Unlike grain ethanol, ethanol from stover has a positive effect on food supply and grain price. Diverting corn grain into making fuel has been blamed as one of the causes of the world-wide increase in food prices. The goal of this study was to evaluate the potential of producing cellulose ethanol from corn stover under different seeding densities. The study was an output of the research fellowship of the main author in Kansas State University (KSU), under the USDA International Borlaug Fellowship. Corn stover was collected from the experimental set up of the Agronomy Department at KSU where Manhattan Corn was planted 2X, 1.5X, 1X, 0.5X the recommended 64K plants/ha; and no competition. A randomized complete block design was used with four replications. Stover preparation for fermentation began by drying, grinding to 200 μm, mild acid pre-treatment, and enzymatic hydrolysis using the combined activity of Cellulase and Novozyme under strictly controlled laboratory conditions. Cellulose, hemicelluloses, and lignin contet were determined for each sample using NREL protocols. Glucose and Xylose released per gm of biomass after acid pre-treatment and enzymatic hydrolysis were determined using HPLC. Baker's yeast (S. cereviaccae) was introduced to the biomass following enzymatic saccharification. Fermentation carried out at 300C in a centrifuge running at 100 rpm for 48 hours. Compositional analysis of corn stover fractions was highest in plant population with no competition but remained fairly comparable across planting densities. Cellulos varied from 36 to 42%, hemicellulose, 24-27%, and Lignin, 14-16%. Saccharification efficiency (glucose released from cellulose), ranges from 26-37%. 100% conversion of cellulose to glucose was far from ideal due to presence of lignin in the biomass that restricted due to the presence of lignin in biomass that restricted the full exposure fiber for enzymatic reaction. The recommended seeding rate showed the highest yield of fermentable carbohydrates but did not differ significantly from the other seeding rates. Ethanol conversion based on the glucose released after enzymatic saccharification ranged from 81.42 to 91.67%. Given the saccharification and ethanol conversion efficiencies derived from this experiment, the mean ethanol yield per dry ton biomass of corn stover was approximately 88 L-142 L. Normal seeding density yields 5.66 tons dry corn stover/ha. (author)
[en] Highlights: • The mechanism of radiation degradation of cellulose varies with temperature. • While there are hydrogen bonds, non-chain depolymerization is realized. • The radical center transfer to nearby molecule leads to chain depolymerization. • Thermal dehydration of macroradicals provokes self-disassembly of cellulose. - Abstract: The radiation-induced degradation of cellulose is analyzed taking into account the effect of temperature on the formation and interconversion of macroradicals. Non-chain depolymerization, consisting in the random cleavage of glycosidic bonds, occurs at low and moderate temperatures. As a result, oligomeric polysaccharides are formed in which the C:O:H atomic ratio is only slightly different from the original one. When the hydrogen bonds disappear and the fragmentary radicals are thermally generated, the depolymerization can proceed via the chain mechanism. Another mechanism, which we term self-disassembly, consists in consecutive shortening the polymer chain from its end at pre-pyrolysis temperatures. It is realized via the dehydration of macroradicals and leads to the elimination of monocyclic furans.
[en] Most cellulolytic enzyme blends, either procured from a commercial vendor or isolated from a single cellulolytic microbial secretome, do not efficiently hydrolyze ammonia-pretreated (e.g., ammonia fiber expansion, AFEX) lignocellulosic agricultural crop residues like corn stover to fermentable sugars. Typically reported commercial enzyme loading (30–100 mg protein/g glucan) necessary to achieve >90% total hydrolysis yield (to monosaccharides) for AFEX-treated biomass, within a short saccharification time frame (24–48 h), is economically unviable. Unlike acid-based pretreatments, AFEX retains most of the hemicelluloses in the biomass and therefore requires a more complex suite of enzymes for efficient hydrolysis of cellulose and hemicellulose at industrially relevant high solids loadings. One strategy to reduce enzyme dosage while improving cocktail effectiveness for AFEX-treated biomass has been to use individually purified enzymes to determine optimal enzyme combinations to maximize hydrolysis yields. However, this approach is limited by the selection of heterologous enzymes available or the labor required for isolating low-abundance enzymes directly from the microbial secretomes. Here, we show that directly blending crude cellulolytic and hemicellulolytic enzymes-rich microbial secretomes can maximize specific activity on AFEX-treated biomass without having to isolate individual enzymes. Fourteen commercially available cellulolytic and hemicellulolytic enzymes were procured from leading enzyme companies (Novozymes®, Genencor®, and Biocatalysts®) and were mixed together to generate several hundred unique cocktail combinations. The mixtures were assayed for activity on AFEX-treated corn stover (AFEX-CS) using a previously established high-throughput methodology. The optimal enzyme blend combinations identified from these screening assays were enriched in various low-abundance hemicellulases and accessory enzymes typically absent in most commercial cellulases cocktails. Our simple approach of blending crude commercially available enzyme cocktails allowed a drastic fourfold reduction in total enzyme requirements (from 30 to 7.5 mg enzyme/g glucan loading) to achieve near-theoretical cellulose and hemicellulose saccharification yields for AFEX-CS.
[en] Cellulose nanofibers (CNF) is used in various pharmaceutical applications due to its unique characteristics i.e., biodegradability, mechanical and biological properties. CNF is often produced by spray drying process, knowledge of the drying kinetics in terms of mass and heat transfer on the scale of single droplet is important for process development and model validation. Acoustic levitator was used to study drying process of CNF suspension at different air temperatures and initial CNF concentrations. The unique property of acoustic levitation to hold single droplet contactless in the air, enables to study particle morphology during drying process, calculate evaporation rate and estimate particle porosity. Results show that packed particles result at lower initial concentration and temperature has a moderate influence on mean porosity of CNF dried particles. (Author)
[en] In this research, the factors that affect the fading of alpha particle tracks on cellulose nitrate films were investigated. It was found that the track density decreases as temperature and the length of time after the exposure increase. The exposed films were stored at ambient temperature (30±5 degree C), 50 ,70 and 90 degree C for 15-75 minutes and the percentage of track losses were found to be in the range of 0-2, 0-9, 11-22 and 13-30 respectively. The effect of relative humidity between 10-78% was found to be insignificant. When the exposed films were immersed for l hour in water maintained at 25-85 degree C before etching, the track density decreased by 5-59%. The amount of track fading also depends on the energy of the incident alpha particles. The percentage of track loss on films exposed to 5.49 MeV radon alpha particles was found to be lower than that of 6.29 MeV thoron alpha particles. However, the negative ions present in air and the atmospheric pressure in the range of 0.04-10 atm did not show noticeable effect on the density of alpha particle tracks on the films
[en] Poly(lactic acid) (PLA) nanocomposite films reinforced with acetylated bacterial cellulose nanoribbons were prepared by solvent casting. Acetylation of bacterial cellulose (BC) was performed by an innovative and sustainable direct solvent-free route catalyzed by citric acid. The effect of derivatization and its extent on the morphological, optical, thermal and mechanical properties of the nanocomposites was analyzed. Data collected from the above studies showed that acetylation of BC nanoribbons clearly improved the nanofibers dispersion in the PLA matrix with respect to unmodified BC, which in turn resulted in increased transparency and mechanical properties of the nanocomposites produced.
[en] Two types of digesters, continuous stirring-tank reactor (CSTR) and plug flow reactor (PFR), were integrated into a biorefining concept to generate a new cellulosic ethanol feedstock -anaerobically digested fiber (AD fiber) from dairy cow feces. Cellulose content in AD fibers was significantly increased during the anaerobic digestion. CSTR and PFR AD fibers had cellulose contents of 357 and 322 g kg-1 dried AD fiber. The AD fibers were enzymatically hydrolyzed after being pretreated by dilute sulfuric acid or dilute sodium hydroxide, and the hydrolysates were used to produce ethanol. Alkali pretreatment was concluded as a suitable pretreatment method for AD fibers. Under the optimal conditions the AD fibers processed by CSTR and PFR produced ethanol of 26 g kg-1 and 23 g kg-1 dry feces, respectively. Energy balance analysis further indicated that CSTR was a preferred digestion method to prepare AD fiber for ethanol production. -- Highlights: → Anaerobic digestion process has been discovered as a process that is not only a downstream process, but also a pretreatment method to prepare cellulosic feedstock for biorefining. → In this study the effects of two different AD reactor configurations (CSTR and PFR) on AD fiber quality and bioethanol conversion of the AD fiber have been explored. → Mass and energy balance analysis elucidated that compared to PFR, CSTR is better AD treatment to prepare AD fiber for bioethanol production.
[en] Radon emanation from the soil gas was studied using a deep red coloured cellulose nitrate LR-115 type II film. The study was carried out from March 2012 to February 2013 at Mat Bridge (23°18΄ N, 92°48΄ E) along Mat Fault in Serchhip district, Mizoram (India). Changes in radon concentrations have been observed. Effects of meteorological parameters on radon emission were also studied. The measured radon data shows a moderate positive correlation with relative humidity but no specific relation with air temperature and rainfall. Data obtained have been correlated to the earthquakes that occurred around the measuring sites. - Highlights: • This paper reports continuous radon monitoring in hilly regions of Mizoram. • The study area falls under seismic zone V. • Occurrence of high intensity earthquake in this region may be disastrous. • An attempt has been made to correlate radon anomalies with seismic events. • Long term data recording is needed to develop better radon-earthquake correlation
[en] Ninety-six bacterial isolates were isolated from the soil samples collected from MADA Rice Experimental Plot, Kedah. Many of the isolates were Gram-positive bacteria suggesting this type of bacteria makes up the majority of the culturable populations residing in the plots investigated. These isolates were studied for their abilities to hydrolyse carboxymethyl cellulose (CMC) and xylan. Ability to hydrolyse CMC was observed in 61.5% of the isolates. Whilst 62.5% of the isolates exhibiting the ability to hydrolyse xylan. Active isolates were further confirmed by the presence of the respective gene(s) via molecular approaches. These isolates were later screened by restriction fragment length polymorphism (RFLP), and sequencing of representative 16S rDNAs. Majority of identified isolates were members of common soil microbe such as members of the genera Bacillus. (Author)