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| 2. |
- Vassilev, N., et al.
(författare)
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Indole-3-acetic acid production by gel-entrapped bacillus thuringiensis in the presence of rock phosphate ore
- 2007
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Ingår i: Chemical Engineering Communications. - : Informa UK Limited. - 0098-6445 .- 1563-5201. ; 194:4, s. 441-445
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Tidskriftsartikel (refereegranskat)abstract
- Bacillus thuringiensis in entrapped in k-carrageenan was capable of producing indole-3-acetic acid (IAA) in the presence of rock phosphate ore (RPO). After five repeated batch fermentation experiments, an average of 6.9 mg/L IAA was recorded in the presence of 1.5 g/L RPO and 4.7 mg/L IAA in the RPO-free control. The bacterium simultaneously solubilized phosphates with a maximum soluble P of 115 mg/L and 150 mg/L after the fourth batch cycle in 1.5 and 3.0 g/L RPO amendment, respectively. Addition of tryptophan to the media increased IAA production to 13.9 and 20.7 mg/L per batch on RPO-free and 1.5 g/L RPO-supplemented media with poor bacterial growth and RPO solubilization.
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| 3. |
- Vassilev, N., et al.
(författare)
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Simultaneous P-solubilizing and biocontrol activity of microorganisms : Potentials and future trends
- 2006
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Ingår i: Applied Microbiology and Biotechnology. - : Springer Science and Business Media LLC. - 0175-7598 .- 1432-0614. ; 71:2, s. 137-144
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Tidskriftsartikel (refereegranskat)abstract
- Phosphate (P)-solubilizing microorganisms as a group form an important part of the microorganisms, which benefit plant growth and development. Growth promotion and increased uptake of phosphate are not the only mechanisms by which these microorganisms exert a positive effect on plants. Microbially mediated solubilization of insoluble phosphates through release of organic acids is often combined with production of other metabolites, which take part in biological control against soilborne phytopathogens. In vitro studies show the potential of P-solubilizing microorganisms for the simultaneous synthesis and release of pathogen-suppressing metabolites, mainly siderophores, phytohormones, and lytic enzymes. Further trends in this field are discussed, suggesting a number of biotechnological approaches through physiological and biochemical studies using various microorganisms.
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| 4. |
- Vassilev, N., et al.
(författare)
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Simultaneous phytase production and rock phosphate solubilization by Aspergillus niger grown on dry olive wastes
- 2007
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Ingår i: Industrial crops and products (Print). - : Elsevier BV. - 0926-6690 .- 1872-633X. ; 26:3, s. 332-336
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Tidskriftsartikel (refereegranskat)abstract
- Dry olive waste (DOW), an agro-industrial material derived from the two-phase-manufacture of olive oil, was used as a substrate for phytase production by Aspergillus niger. A series of experiments were performed in conditions of solid-state fermentation in the presence of rock phosphate. Both enzyme production and phosphate solubilization depended on water medium content, type of nitrogen source, inoculum size and the presence and initial concentration of phosphate in the medium. It was found that at optimized process conditions (moisture 70%; corn steep liquor as a nitrogen source; inoculum size of 3-4 ml; presence of slow release phosphate), the filamentous fungal culture was able to produce 58 U phytase/g dry substrate and 31 mg soluble phosphate per flask.
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| 5. |
- Vassileva, Maria, et al.
(författare)
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Multifunctional properties of phosphate-solubilizing microorganisms grown on agro-industrial wastes in fermentation and soil conditions
- 2010
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Ingår i: Applied Microbiology and Biotechnology. - : Springer Science and Business Media LLC. - 0175-7598 .- 1432-0614. ; 85:5, s. 1287-1299
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Forskningsöversikt (refereegranskat)abstract
- One of the most studied approaches in solubilization of insoluble phosphates is the biological treatment of rock phosphates. In recent years, various techniques for rock phosphate solubilization have been proposed, with increasing emphasis on application of P-solubilizing microorganisms. The P-solubilizing activity is determined by the microbial biochemical ability to produce and release metabolites with metal-chelating functions. In a number of studies, we have shown that agro-industrial wastes can be efficiently used as substrates in solubilization of phosphate rocks. These processes were carried out employing various technologies including solid-state and submerged fermentations including immobilized cells. The review paper deals critically with several novel trends in exploring various properties of the above microbial/agro-wastes/rock phosphate systems. The major idea is to describe how a single P-solubilizing microorganism manifests wide range of metabolic abilities in different environments. In fermentation conditions, P-solubilizing microorganisms were found to produce various enzymes, siderophores, and plant hormones. Further introduction of the resulting biotechnological products into soil-plant systems resulted in significantly higher plant growth, enhanced soil properties, and biological (including biocontrol) activity. Application of these bio-products in bioremediation of disturbed (heavy metal contaminated and desertified) soils is based on another important part of their multifunctional properties.
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