To Örebro University

Improving the nutritional value of commonly cultivated crops is one of the most pending problems for modern agriculture. In natural environments plants associate with a multitude of fungal microorganisms that improve plant fitness. The best described group are arbuscular mycorrhizal fungi (AMF). These fungi have been previously shown to improve the quality and yield of several common crops. In this study we tested the potential utilization of Rhizophagus irregularis in accelerating growth and increasing the content of important dietary phytochemicals in onion (Allium cepa). Our results clearly indicate that biomass production, the abundance of vitamin B1 and its analogs and organic acid concentration can be improved by inoculating the plant with AM fungi. We have shown that improved growth is accompanied with up-regulated electron transport in PSII and antioxidant enzyme activity.

Uranium-stabilizing ligands can be useful complexing agents for uranium in aqueous solution. The discovery of novel ligand candidates for selective uranium capture in artificial and natural waters could provide scope for their use in water remediation and metal recovery from low- and high grade ores. In this study we used seven fungal strains, isolated from shale waste, to monitor the uranium retention capacity from an aqueous solution. After four weeks of incubation, suspensions containing the fungal strains were filtered, and up to 100% of the total uranium inventory was removed from a 10 mg L-1 solution. Approximately 70% of the total uranium removal is attributed to complexation and/or adsorption by particles in the malt extract and some 10% is adsorbed by the fungal biomass. The additional 20% uranium removed could be related to the excretion of fungal metabolites. From 58% to 90% of the uranium is removed within ten minutes. The formation of colloidal/particulate uranium is proposed to be controlled by organic ligands in the culture medium and organic ligands excreted by the fungi where phosphorus moieties seem to be important. Membrane fouling by the hydrocarbons is also suggested to contribute to a loss of uranium from the aqueous phase.

Contamination of the environment due to mining and mineral processing is an urgent problem worldwide. It is often desirable to establish a grass cover on old mine waste since it significantly decreases the production of leachates. To obtain sustainable growth, it is often necessary to improve several properties of the waste such as water-holding capacity, nutrient status, and toxicity. This can be done by addition of organic materials such as wood residues, e. g., compost. In this study, we focus on the solution chemistry of the leachates when a substrate containing historic sulfidic mine waste mixed with 30 % (volume) bark compost is overgrown by Agrostis capillaris. The pot experiments also included other growth-promoting additives (alkaline material, mycorrhiza, and metabolizable carbon) to examine whether a more sustainable growth could be obtained. Significant changes in the plant growth and in the leachates composition were observed during 8 weeks of growth. It was concluded that in this time span, the growth of A. capillaris did not affect the composition of the leachates from the pots. Instead, the composition of the leachates was determined by interactions between the bark compost and the mine waste. Best growth of A. capillaris was obtained when alkaline material and mycorrhiza or metabolizable carbon was added to the substrate.

Uranium contamination of soils and water is a worldwide problem due to geology or anthropogenic release such as mining, or use of inorganic fertilizers. In situ remediation of low and moderately contaminated sites is a complicated procedure due to the complex chemistry of uranium. This study demonstrates that at pH 3.5, a fungal strain isolated from unprocessed uranium bearing shale creates hydrochemical conditions that immobilize 97% of a total of 10 mg L^-1 dissolved uranium in a 0.20 μm pore system. The redistribution occurred within 10 minutes and remained for five weeks and just 12% of the inventory was retrieved in the biomass. Size exclusion chromatography of the dissolved phase identified organic substances in the range of more than 60 kD down to 100 D as a response to time of incubation. Geochemical modeling indicates formation of uranium-organic complexes where ligand size, coordination chemistry and their tendency to agglomerate determine the redistribution.

In Sweden there are hundreds of sites that need to be remediated due to high release of metals such as Cu. In order to minimize costs the methods should involve cheap materials and technical solutions. This study focuses on the possibility to establish Agrostis capillaris on sulfidic mine waste, after mixing with 30 % bark compost, and the subsequent release of Cu. Ini- tially the substrate produced leachates with pH 3.5 containing approximately 1 mg/L Cu. After 4 months the pH had increased to 4.5 and up to 80 % of the Cu was retained