RESUMO
Lignin content, composition, distribution as well as cell wall thickness, structures, and type of tissue have a measurable effect on enzymatic hydrolysis of cellulose in lignocellulosic feedstocks. The first part of our work combined compositional analysis, pretreatment and enzyme hydrolysis for fractionated pith, rind, and leaf tissues from a hybrid stay-green corn, in order to identify the role of structural characteristics on enzyme hydrolysis of cell walls. The extent of enzyme hydrolysis follows the sequence rind < leaves < pith with 90% conversion of cellulose to glucose in 24 h in the best cases. Physical fractionation of corn stalks or other C(4) grasses into soft and hard tissue types could reduce cost of cellulose conversion by enabling reduced enzyme loadings to hydrolyze soft tissue, and directing the hard tissue to other uses such as thermal processing, combustion, or recycle to the land from which the corn was harvested.
Assuntos
Biomassa , Celulases/metabolismo , Lignina/metabolismo , Água/química , Zea mays/química , Zea mays/metabolismo , Biocombustíveis , Celulose/química , Celulose/metabolismo , Temperatura Alta , Hidrólise , Lignina/química , Componentes Aéreos da Planta/química , Componentes Aéreos da Planta/metabolismoRESUMO
In the first part of our work, we combined compositional analysis, pretreatment and enzyme hydrolysis for fractionated pith, rind, and leaf tissues from a hybrid stay-green corn, in order to identify the role of structural characteristics on enzyme hydrolysis of cell walls. Hydrolysis experiments coupled with chemical analysis of the different fractions of corn stover showed significant differences in cell wall structure before and after liquid hot water pretreatment. The extent of enzyme hydrolysis followed the sequence rind < leaves < pith with 90% conversion of cellulose to glucose in 24 h in the best cases. Since similar lignin contents remained after liquid hot water pretreatment of leaves, rind, and pith, our results indicated that the amount of lignin alone is not sufficient to explain the different enzymatic hydrolysis characteristics of the fractions. While the role of structural characteristics on enzyme hydrolysis of cell walls is measured as described in part I, the SEM images presented in this part II of our work show that sugar yields from enzymatic hydrolysis of corn fractions correlate with changes in plant cell wall structure both before and after liquid hot water pretreatment.
Assuntos
Biomassa , Celulase/metabolismo , Componentes Aéreos da Planta/ultraestrutura , Zea mays/química , Biocombustíveis , Celulose/química , Celulose/metabolismo , Etanol , Glucanos , Temperatura Alta , Microscopia Eletrônica de Varredura/métodos , Componentes Aéreos da Planta/química , Componentes Aéreos da Planta/metabolismo , Proteínas de Plantas , Água/química , Zea mays/metabolismoRESUMO
Oysters construct extensive reef communities, providing food, protection from storms, and healthy coastlines. We still do not have a clear picture of how these animals attach to surfaces. Efforts described herein provide the first examination of adhesion at the transition from free swimming larvae to initial substrate attachment, through metamorphosis, and on to adulthood. Two different bonding systems were found to coexist. Larvae use an organic, hydrated glue that persists while the animal progresses into the juvenile phase, at which point a very different adhesive emerges. Juveniles bond with an organic-inorganic composite system, positioning the organic component for maximum adhesion by residing between the animal and substrate. Beyond understanding our marine environment, these insights may aid efforts in aquaculture, reef restoration, and adhesive design.
Assuntos
Ostreidae , Adesivos , Envelhecimento , Animais , Cimentação , LarvaRESUMO
Oysters have an impressive ability to overcome difficulties of life within the stressful intertidal zone. These shellfish produce an adhesive for attaching to each other and building protective reef communities. With their reefs often exceeding kilometers in length, oysters play a major role in balancing the health of coastal marine ecosystems. Few details are available to describe oyster adhesive composition or structure. Here several characterization methods were applied to describe the nature of this material. Microscopy studies indicated that the glue is comprised of organic fiber-like and sheet-like structures surrounded by an inorganic matrix. Phospholipids, cross-linking chemistry, and conjugated organics were found to differentiate this adhesive from the shell. Symbiosis in material synthesis could also be present, with oysters incorporating bacterial polysaccharides into their adhesive. Oyster glue shows that an organic-inorganic composite material can provide adhesion, a property especially important when constructing a marine ecosystem.
Assuntos
Adesivos/química , Recifes de Corais , Ostreidae/química , Exoesqueleto/ultraestrutura , Animais , Microscopia de Fluorescência , Ostreidae/ultraestrutura , Espectrometria por Raios XRESUMO
Particle size associated with accessible surface area has a significant impact on the saccharification of plant cell walls by cellulolytic enzymes. Small particle sizes of untreated cellulosic substrate are more readily hydrolyzed than large ones because of higher specific surface area. Pretreatment enlarges accessible and susceptible surface area leading to enhanced cellulose hydrolysis. These hypotheses were tested using ground corn stover in the size ranges of 425-710 and 53-75 microm. Ultrastructural changes in these particles were imaged after treatment with cellulolytic enzymes before and after liquid hot water pretreatment. The smaller 53-75 microm corn stover particles are 1.5x more susceptible to hydrolysis than 425-710 microm corn stover particles. This difference between the two particle size ranges is eliminated when the stover is pretreated with liquid hot water pretreatment at 190 degrees C for 15 min, at pH between 4.3 and 6.2. This pretreatment causes ultrastructural changes and formation of micron-sized pores that make the cellulose more accessible to hydrolytic enzymes.
Assuntos
Celulase/farmacologia , Celulose/metabolismo , Folhas de Planta/ultraestrutura , Água , Zea mays/efeitos dos fármacos , Celulase/metabolismo , Glucose/química , Temperatura Alta , Hidrólise , Microscopia Eletrônica de Varredura , Folhas de Planta/efeitos dos fármacos , Plantas , Zea mays/anatomia & histologiaRESUMO
Detection of the foodborne pathogen Listeria monocytogenes requires that food samples be processed to remove proteins and lipids, concentrate microorganisms to a detectable concentration, and recover the concentrated cells in a small volume compatible with micron-scale biochips. Mechanistic considerations addressed in this research include the roles of membrane structure, pore size, and detergents in maximizing recovery of cells from a complex biological fluid. The fluid in this case was a food sample (hotdog extract) inoculated with L. monocytogenes. This study showed how membrane filtration using a syringe filter is able to concentrate L. monocytogenes by 95x with up to 95% recovery of living microorganisms by concentrating 50 mL of food sample into a volume of 500 microL. Tween 20 was added to the sample to prevent irreversible adsorption of the microorganism to the membrane and thereby help to ensure high recovery. Comparison of polycarbonate, mixed cellulose, nylon, and PVDF membranes with 0.2 to 0.45 microm pores showed the 0.2 microm polycarbonate membrane with straight through, mono-radial pores gives the highest recovery of living microorganisms. The mixed cellulose, nylon, and PVDF membranes have a fibrous structure whose characteristic openings are much larger than their effective pore size cut-offs of 0.22 or 0.45 microm. We define conditions for rapid membrane-based cell concentration and recovery that has the potential to supplant enrichment steps that require a day or more. This approach has the added benefit of facilitating examination of a large amount of fluid volume by reducing its volume to a range that is compatible with the microliter scales of biochip or other biosensor detection systems.