| 1. |
- Anasontzis, George E, 1980, et al.
(författare)
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Constitutive homologous expression of phosphoglucomutase and transaldolase increases the metabolic flux of Fusarium oxysporum
- 2014
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Ingår i: Microbial Cell Factories. - : Springer Science and Business Media LLC. - 1475-2859. ; 13:1
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Tidskriftsartikel (refereegranskat)abstract
- Background: Fusarium oxysporum is among the few filamentous fungi that have been reported of being able to directly ferment biomass to ethanol in a consolidated bioprocess. Understanding its metabolic pathways and their limitations can provide some insights on the genetic modifications required to enhance its growth and subsequent fermentation capability. In this study, we investigated the hypothesis reported previously that phosphoglucomutase and transaldolase are metabolic bottlenecks in the glycolysis and pentose phosphate pathway of the F. oxysporum metabolism.Results: Both enzymes were homologously overexpressed in F. oxysporum F3 using the gpdA promoter of Aspergillus nidulans for constitutive expression. Transformants were screened for their phosphoglucomutase and transaldolase genes expression levels with northern blot. The selected transformant exhibited high mRNA levels for both genes, as well as higher specific activities of the corresponding enzymes, compared to the wild type. It also displayed more than 20 and 15% higher specific growth rate upon aerobic growth on glucose and xylose, respectively, as carbon sources and 30% higher biomass to xylose yield. The determination of the relative intracellular amino and non-amino organic acid concentrations at the end of growth on glucose revealed higher abundance of most determined metabolites between 1.5- and 3-times in the recombinant strain compared to the wild type. Lower abundance of the determined metabolites of the Krebs cycle and an 68-fold more glutamate were observed at the end of the cultivation, when xylose was used as carbon source.Conclusions: Homologous overexpression of phosphoglucomutase and transaldolase in F. oxysporum was shown to enhance the growth characteristics of the strain in both xylose and glucose in aerobic conditions. The intracellular metabolites profile indicated how the changes in the metabolome could have resulted in the observed growth characteristics. © 2014 Anasontzis et al.; licensee BioMed Central Ltd.
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| 2. |
- Cheilas, T, et al.
(författare)
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Hemicellulolytic activity of Fusarium oxysporum grown on sugar beet pulp. Production of extracellular arabinanase
- 2000
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Ingår i: Process Biochemistry. - 1359-5113 .- 1873-3298. ; 35:6, s. 557-561
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Tidskriftsartikel (refereegranskat)abstract
- Fusarium oxysporum F3 exhibited hemicellulolytic enzymic activity when grown on sugar beet pulp, a by-product of the sugar industry. The growth medium was specifically optimised for enhanced production of extracellular arabinanase. The optimum medium contained sugar beet pulp (4%, w/v) and corn steep liquor (6%, v/v) as carbon and nitrogen sources, respectively. Arabinanase activity as high as 0.25 U/ml of culture was obtained, which compared favourably to those reported for other microorganisms. Optimal arabinanase activity was observed at pH 6-7 and 50 °C. Investigation of the degradation of the main components of sugar beet pulp showed that arabinose containing polysaccharides and pectin were first degraded, followed by the glucose-containing polysaccharides.
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| 3. |
- Hatzinikolaou, D.G, et al.
(författare)
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Comparative growth studies of the extreme thermophile Sulfolobus acidocaldarius in submerged and solidified substrate cultures
- 2001
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Ingår i: World Journal of Microbiology & Biotechnology. - 0959-3993 .- 1573-0972. ; 17:3, s. 229-234
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Tidskriftsartikel (refereegranskat)abstract
- An attempt was made, for the first time, to exploit cultures on solidified substrates (SSC) as an alternative to submerged cultures (SmC) for growing extremophilic micro-organisms. The extreme thermophilic archaebacterium Sulfolobus acidocaldarius was grown on a number of carbon sources and, in all experiments, biomass yields and growth rates were always higher in SSC than in the corresponding SmC. Inoculum age significantly affected growth characteristics on both types of fermentation. Heavy growth of the micro-organism in SSC was observed on low-cost carbon sources such as starch. Wheat bran significantly enhanced growth characteristics when used to supplement starch media. The results of this work show that cultures on solid surfaces could be a promising alternative method for growing extreme thermophiles.
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| 4. |
- Hatzinikolaou, D.G, et al.
(författare)
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Production and partial characterisation of extracellular lipase from aspergillus niger
- 1996
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Ingår i: Biotechnology letters. - 0141-5492 .- 1573-6776. ; 18:5, s. 547-552
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Tidskriftsartikel (refereegranskat)abstract
- The production and certain kinetic characteristics of extracellular lipase from Aspergillus niger were investigated. It was possible to substantially enhance the activity of excreted lipase by optimising the interaction between carbon and nitrogen sources applying a two-parameter complete experimental design and response surface analysis. The enzyme was partially purified and a number of kinetic characteristics such as optimum pH and temperature, thermal and pH stability and K(m) were determined and discussed. The elevated levels of lipase activity (40.5 U/ml) found in this work competed favourably with most of those reported for lipase hyperproducing fungi.
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| 5. |
- Kalogeris, E., et al.
(författare)
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Application of different processes for the biodegradation of 1,3-dichloro-2-propanol by the bacterium Pseudomonas putida DSM 437
- 2007
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Ingår i: Chemical and biochemical engineering quarterly. - 0352-9568 .- 1846-5153. ; 21:3, s. 297-305
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Tidskriftsartikel (refereegranskat)abstract
- 1,3-Dichloro-2-propanol (1,3-DCP), is a highly toxic compound used in many industrialprocesses. Biodegradation of 1,3-DCP, by the bacterial strain Pseudomonasputida DSM 347, was studied applying three different processes. A number of combinations,with respect to glucose and 1,3-DCP concentration were examined during batchprocess. When the initial concentration of 1,3-DCP was 600 mg L–1 in the presence of400 mg L–1 glucose, the biodegradation degree and rate were 10.8 % and 0.68 mg L–1h–1 respectively. 1,3-DCP biodegradation by the resting cells of P. putida DSM 347 wastested at mass concentrations from = 200 to 1 000 mg L–1 using biomass concentrationof 5 g dry cell mass L–1. Biodegradation of 1,3-DCP ranged from 84 to 90 %, initialbiodegradation rates ranged from r = 2.36 to 10.55 mg L–1 h–1, while dependence of bothparameters from the initial concentration of halohydrin was observed. A system of twoContinuous Stirred Tank Reactors (CSTRs) in series was developed for the biodegradationof a highly toxic stream of 1,3-DCP (2000 mg L–1). The overall biodegradationdegree of the system was 68 %, while biodegradation rates of the first and secondbioreactor were r = 2.88 and 5.21 mg L–1 h–1 respectively.
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| 6. |
- Stathopoulou, P.M., et al.
(författare)
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Assessment of the biomass hydrolysis potential in bacterial isolates from a volcanic environment: Biosynthesis of the corresponding activities
- 2012
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Ingår i: World Journal of Microbiology and Biotechnology. - : Springer Science and Business Media LLC. - 1573-0972 .- 0959-3993. ; 28:9, s. 2889-2902
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Tidskriftsartikel (refereegranskat)abstract
- The biomass degrading enzymatic potential of 101 thermophilic bacterial strains isolated from a volcanic environment (Santorini, Aegean Sea, Greece) was assessed. 80 % of the strains showed xylanolytic activity in Congo Red plates, while only eight could simultaneously hydrolyze cellulose. Fifteen isolates were selected on the basis of their increased enzyme production, the majority of which was identified as Geobacilli through 16S rDNA analysis. In addition, the enzymatic profile was evaluated in liquid cultures using various carbon sources, a procedure that revealed lack of correlation on xylanase levels between the two cultivation modes and the inability of solid CMC cultures to fully unravel the cellulose degrading potential of the isolates. Strain SP24, showing more than 99 % 16S DNA similarity with Geobacillus sp. was further studied for its unique ability to simultaneously exhibit cellulase, xylanase, β-glucosidase and β-xylosidase activities. The first two enzymes were produced mainly extracellularly, while the β-glycosidic activities were primarily detected in the cytosol. Maximum enzyme production by this strain was attained using a combination of wheat bran and xylan in the growth medium. Bioreactor cultures showed that aeration was necessary for both enhanced growth and enzyme production. Aeration had a strong positive effect on cellulase production while it negatively affected expression of β-glucosidase. Xylanase and β-xylosidase production was practically unaffected by aeration levels.
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