Emma Johansson

Immobilization of lipase from Mucor miehei and Rhizopus oryzae into mesoporous silica—The effect of varied particle size and morphology

Immobilization of enzymes usually improves the recyclability and stability and can sometimes also improve the activity compared to enzymes free in solution. Mesoporous silica is a widely studied material as host for immobilized enzymes because of its large internal surface area and tunable pores. It has previously been shown that the pore size is critical both for the loading capacity and for the enzymatic activity; however, less focus has been given to the influence of the particle size. In this work the effect of particle size and particle morphology on the immobilization of lipase from Mucor miehei and Rhizopus oryzae have been investigated. Three kinds of mesoporous silica, all with 9 nm pores but with varying particle size (1000 nm, 300 nm and 40 nm) have been synthesized and were used as host for the lipases. The two lipases, which have the same molecular size but widely different isoelectric points, were immobilized into the silica particles at varied pH values within the interval 5-8. The 300 nm particles were proven to be the most suitable carrier with respect to specific activity for both enzymes. The lipase from M. miehei was more than four times as active when immobilized at pH 8 compared to free in solution whereas the difference was less pronounced for the R. oryzae lipase.

Rapid Synthesis of SBA-15 Rods with Variable Lengths, Widths, and Tunable Large Pores

Dispersed SBA-15 rods have been synthesized with varying lengths, widths, and pore sizes in a low-temperature synthesis in the presence of heptane and NH(4)F. The pore size of the material can systematically be varied between 11 and 17 nm using different hydrothermal treatment times and/or temperatures. The particle length (400-600 nm) and width (100-400 nm) were tuned by varying the HCl concentration. All the synthesized materials possess a large surface area of 400-600 m(2)/g and a pore volume of 1.05-1.30 cm(3). A mechanism for the effect of the HCl concentration on the particle morphology is suggested. Furthermore, it is shown that the reaction time can be decreased to 1 h, with well-retained pore size and morphology. This work has resulted in SBA-15 rods with the largest pore size reported for this morphology.

Spatial patterns of organic chlorine and chloride in Swedish forest soil.

The concentration of organic carbon, organic chlorine and chloride was determined in Swedish forest soil in the southern part of Sweden and the spatial distribution of the variables were studied. The concentration of organically bound chlorine was positively correlated to the organic carbon content, which is in line with previous studies. However, the spatial distribution patterns strongly indicate that some other variable adds structure to the spatial distribution of organic chlorine. The distribution patterns for chloride strongly resembled the distribution of organic chlorine. The spatial distribution of chloride in soil depends on the deposition pattern which in turn depends on prevailing wind-direction, amount of precipitation and the distance from the sea. This suggests that the occurrence of organic chlorine in soil is influenced by the deposition of chloride or some variable that co-varies with chloride. Two clearly confined strata were found in the area: the concentrations of organic chlorine and chloride in the western area were significantly higher than in the eastern area. No such difference among the two areas was seen regarding the carbon content.

Shape engineering vs organic modification of inorganic nanoparticles as a tool for enhancing cellular internalization

In nanomedicine, physicochemical properties of the nanocarrier affect the nanoparticles pharmacokinetics and biodistribution, which are also decisive for the passive targeting and nonspecific cellular uptake of nanoparticles. Size and surface charge are, consequently, two main determining factors in nanomedicine applications. Another important parameter which has received much less attention is the morphology (shape) of the nanocarrier. In order to investigate the morphology effect on the extent of cellular internalization, two similarly sized but differently shaped rod-like and spherical mesoporous silica nanoparticles were synthesized, characterized and functionalized to yield different surface charges. The uptake in two different cancer cell lines was investigated as a function of particle shape, coating (organic modification), surface charge and dose. According to the presented results, particle morphology is a decisive property regardless of both the different surface charges and doses tested, whereby rod-like particles internalized more efficiently in both cell lines. At lower doses whereby the shape-induced advantage is less dominant, charge-induced effects can, however, be used to fine-tune the cellular uptake as a prospective ‘secondary’ uptake regulator for tight dose control in nanoparticle-based drug formulations.

Organic and inorganic chlorine in Swedish spruce forest soil : influence of nitrogen

Concentrations of organic and inorganic chlorine were estimated in samples collected in forest soils in the southern part of Sweden, and changes were observed after the addition of nitrogen in incu ...

Chlorination and biodegradation of lignin

Abstract Recent research has shown that large amounts of high-molecular weight organic chlorine of unknown origin are present in the terrestrial environment. There are indications that an underlying process may be microorganisms which produce reactive chlorine that chemically degrades organic matter and facilitates degradation of recalcitrant organic matter on one hand, and on the other hand causes a formation of organic chlorine. Our aim was to test one part of this hypothesis by investigating whether reactive chlorine facilitates microbial degradation of lignin. Different concentrations of chlorine dioxide were added to the autoclaved lignin suspension. Mycelium of the white-rot fungus P. chrysosporium was used to inoculate flasks with the lignin solutions. The evolution of CO 2 was followed during 8 d of continuous measurement. At the end of the experiment the solutions were analyzed for organic chlorine. The amount of CO 2 evolved was variable, but the results were repeatedable; addition of chlorine dioxide to the lignin solutions caused an increase in the mineralization by P. chrysosporium that increased with increasing additions of chlorine dioxide. This suggests that exposure of lignin to reactive chlorine enhance its biodegradability. The most likely cause of the observed effect is that the addition of chlorine dioxide initiated a fragmentation and oxidation of the lignin, thus rendering a more easily degraded substrate. However, the results may also be interpreted as if an additional cause to the observed effect is that the chlorination in itself somehow enhanced degradation. The amount of organically-bound chlorine decreased during the incubation, and the decrease was more pronounced with the chlorination of lignin, whereas no change at all was observable in the control batches. This makes it tempting to suggest that P. chrysosporium rather than having an enzyme system just capable of handling the chlorinated compounds, actually has a system that preferentially degrades such compounds.

Organic chlorine in deciduous and coniferous forest soils in southern Sweden

The concentration of organic chlorine (Clorg) was determined in soil samples collected in the O-horizon in forest soils in southern Sweden to describe differences among stand types and elucidate the influence of chloride (Clinorg), pH, and organic carbon. The samples were collected within the Swedish National Survey of Forest Soils and Vegetation, with moraine as the dominating soil type and with granite and gneiss as bedrock. The concentration of organic chlorine (Clorg) found in the deciduous forest soils was significantly lower than that in the coniferous forest soils. The Clorg increased with Clinorg, organic carbon content, and decreasing pH but was most strongly correlated to Clinorg. Crosswise comparisons among the variables showed that the influence of Clinorg overrode the influence of pH and organic carbon. We concluded that the major driving force in the formation of Clorg in soils is deposition of Clinorg and that the difference among deciduous and coniferous stands is due primarily to a higher input of Clinorg in the canopy of coniferous trees as a result of a larger wet and dry deposition in coniferous compared with deciduous forests. The concentration of Clorg decreased significantly from June to August. This follows the pattern of chloride deposition in the region and gives further evidence that Clinorg is a driving force in the formation of Clorg in soil. The results of the present study gives further evidence that the turnover of Clorg is closely related to the turnover of Clinorg and that it is necessary to include Clorg in the assessment of the biogeochemical cycling of chlorine in the environment.

On the Formation of Discoidal versus Threadlike Micelles in Dilute Aqueous Surfactant/Lipid Systems

In a recent study, we showed that the surfactant 1,2-distearoyl-sn-glycero-3-phosphatidylethanolamine-N-[methoxy(polyethylene glycol)-2000 (DSPE-PEG2000) induced mixed micelles of either threadlike or discoidal shape when mixed with different types of lipids. In this study, we have exchanged the PEG-lipid for the more conventional surfactants octaethylene glycol monododecyl ether (C12E8), hexadecyltrimethylammonium bromide (CTAB), and sodium dodecyl sulfate (SDS). Cryo-TEM investigations show that also these surfactants are able to induce the formation of long-lived discoidal micelles. Generally, the preference for either discoidal or threadlike micelles can be tuned by the choice of lipids and environmental conditions in much the same way as observed for the lipid/PEG-lipid system. Our investigation showed, furthermore, that the choice of surfactant may influence the type of mixed micelles formed. It is argued that the formation of discoidal rather than threadlike micelles may be rationalized as an effect of increasing bending rigidity. Our detailed theoretical model calculations show that the bending rigidity becomes significantly raised for aggregates formed by an ionic rather than a nonionic surfactant.

Production of organically bound halogens by the litter-degrading fungus Lepista nuda

The ability of Lepista nuda to produce organically bound halogens was tested both in a laboratory study of a pure culture and in a field study. It was found that L. nuda caused an increase in the t ...