| 21. |
- Fernandes, Sheryl, et al.
(författare)
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Selective recovery of lactate dehydrogenase using affinity foam.
- 2002
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Ingår i: Biotechnology and Bioengineering. - : Wiley. - 1097-0290 .- 0006-3592. ; 79:4, s. 472-480
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Tidskriftsartikel (refereegranskat)abstract
- Selective isolation of lactate dehydrogenase (LDH) from porcine muscle extract was studied using foam generated from the vigorous stirring of a non-ionic surfactant, Triton X-114 derivatized with Cibacron blue. The cloud point of the surfactant-dye conjugate was higher than that of the native Triton X-114, and also the foam prepared from the affinity surfactant was more rigid taking a longer time to collapse. The equilibrium dissociation constant between pure LDH and surfactant-dye conjugate was 5.0 microM as compared to the value of 2.2 microM for the enzyme and free dye as measured by differential spectroscopy. The isolation procedure involved mixing of the porcine muscle extract with the affinity foam, separating and collapsing the foam, and warming the solution formed to 37 degrees C to yield the surfactant-dye phase and an aqueous phase containing the enzyme. The effect of surfactant concentration and protein load on enzyme recovery and purification was investigated. Under optimal conditions, LDH was quantitatively recovered with high purification factor in a very short time. Both recovery and purification were higher when foam prepared from an equivalent mixture of surfactant-dye conjugate and unmodified surfactant was used. The selectivity of interaction between LDH and detergent-dye conjugate was confirmed by lowered recovery when NADH was included during the binding step.
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| 22. |
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| 23. |
- Gessesse, A, et al.
(författare)
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Novel alkaline proteases from alkaliphilic bacteria grown using chicken feather.
- 2003
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Ingår i: Enzyme and Microbial Technology. - 0141-0229. ; 32:5, s. 519-524
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Tidskriftsartikel (refereegranskat)abstract
- Two alkaline protease producing alkaliphilic bacterial strains, designated as AL-20 and AL-89, were isolated from a naturally occurring alkaline habitat. The two strains were identified as Nesternkonia sp. and Bacillus pseudofirmus, respectively. Both strains grew and produced alkaline protease using feather as the sole source of carbon and nitrogen. Addition of 0.5% glucose to the feather medium increased protease production by B. pseudofirmus AL-89 and suppressed enzyme production by Nesternkonia sp. AL-20. The enzymes from both organisms were purified to electrophoretic homogeneity following ammonium sulphate precipitation, ion exchange, hydrophobic interaction, and gel filtration chromatography. The molecular weight, determined using SDS–PAGE, was 23 kDa for protease AL-20 and 24 kDa for protease AL-89. Protease AL-20 was active in a broad pH range displaying over 90% of its maximum activity between pH 7.5 and 11.5 with a peak at pH 10. The enzyme is unique in that unlike all other microbial serine proteases known so far, it did not require Ca2+ for activity and thermal stability. Its optimum temperature for activity was at 70 °C and was stable after 1 h incubation at 65 °C both in the presence and absence of Ca2+. These properties make protease AL-20 an ideal candidate for detergent application. Protease AL-89 on the other hand require Ca2+ for activity and stability at temperature values above 50 °C. Its optimum activity was at 60 and 70 °C in the absence and presence of Ca2+, respectively. It displayed a pH optimum of 11 and retained about 70% or more of its original activity between pH 6.5 and 11. B. pseudofirmus AL-89, and the protease it produce offers an interesting potential for the enzymatic and/or microbiological hydrolysis of feather to be used as animal feed supplement.
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| 24. |
- Guieysse, Benoit, et al.
(författare)
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Combined UV-biological degradation of PAHs
- 2004
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Ingår i: Chemosphere. - : Elsevier BV. - 1879-1298 .- 0045-6535. ; 55:11, s. 1493-1499
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Tidskriftsartikel (refereegranskat)abstract
- The UV-photolysis of PAHs was tested in silicone oil and tetradecane. In most cases, the degradation of a pollutant provided within a mixture was lower than when provided alone due to competitive effects. With the exception of anthracene, the larger pollutants (4- and 5-rings) were always degraded first, proving that UV-treatment preferentially acts on large PAHs and thereby provides a good complement to microbial degradation. UV-photolysis was also found to be suitable for treatment of soil extract from contaminated soils. The feasibility of UV-biological treatment was demonstrated for the removal of a mixture of phenanthrene and pyrene in silicone oil. UV-irradiation of the silicone oil led to 83% pyrene removal but no phenanthrene photodegradation. Subsequent treatment of the oil in a two-phases partitioning bioreactor (TPPB) system inoculated with Pseudomonas sp. was followed by complete phenanthrene biodegradation but no further pyrene removal. Totally, the combined process allowed 92% removal of the PAH mixture. Further work should focus on characterizing the photoproducts formed and studying the influence of the solvent on the photodegradation process.
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| 25. |
- Guieysse, Benoit, et al.
(författare)
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Influence of the initial composition of algal-bacterial microcosms on the degradation of salicylate in a fed-batch culture
- 2002
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Ingår i: Biotechnology Letters. - 1573-6776. ; 24:7, s. 531-538
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Tidskriftsartikel (refereegranskat)abstract
- The influence of the initial composition of an algal-bacterial microcosm constituted of Chlorella sorokiniana and Ralstonia basilensis was tested for the fed-batch degradation of salicylate at 5 mM. Salicylate degradation was always limited by the O-2 generation rate, which was initially proportional to the algal density, but rapidly became limited by the availability of light once the algae started to grow. The decrease of the salicylate removal rate observed at high algal densities was likely caused by mutual shading within the algal population and the increase of O-2 consumption due to algal dark respiration. With repeated salicylate amendments, all systems converged towards the same characteristics, reaching an optimum rate of salicylate degradation at 1 mmol l(-1) day.
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| 26. |
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| 27. |
- Hashim, Suhaila, et al.
(författare)
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Starch hydrolysing Bacillus halodurans isolates from a Kenyan soda lake
- 2004
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Ingår i: Biotechnology Letters. - 1573-6776. ; 26:10, s. 823-828
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Tidskriftsartikel (refereegranskat)abstract
- Fourteen obligate alkaliphilic and halotolerant bacterial isolates, exhibiting extracellular amylase activity at 55degreesC and pH 10, were isolated from hot springs around Lake Bogoria, Kenya. From 16S rDNA sequence analysis, nine isolates shared 100% identity with Bacillus halodurans strain DSM 497(T), while the rest shared 99% identity with alkaliphilic Bacillus species A-59. PCR of the intergenic spacer region between 16S and 23S rRNA genes (ISR-PCR) divided the isolates into two groups, while tDNA-PCR divided them into three groups. Bacillus halodurans DSM 497T had a different ISR pattern from the isolates, while it had a tDNA-PCR profile similar to the group that shared 99% identity with alkaliphilic Bacillus species A-59. All isolates hydrolysed soluble starch as well as amylose, amylopectin and pullulan. The amylase activity (1.2 - 1.8 U ml(-1)) in the culture broths had an optimum temperature of 55 - 65degreesC, was stimulated by 1 mM Ca2+, and was either partially (16 - 30%) or completely inhibited by 1 mM EDTA. Activity staining of the cell-free culture supernatant from the isolates revealed five alkaline active amylase bands.
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| 28. |
- Hatti-Kaul, Rajni, et al.
(författare)
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Downstream processing in biotechnology
- 2001. - 2nd
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Ingår i: Basic Biotechnology. - 0521770742 - 9780521770743 - 0521779170 - 9780521779173 ; , s. 187-211
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Bokkapitel (refereegranskat)
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| 29. |
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| 30. |
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