| 1. |
- Mamo, Gashaw, et al.
(författare)
-
Preface
- 2020
-
Ingår i: Alkaliphiles in Biotechnology. - 0724-6145. ; 172
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)
|
|
| 2. |
- Alkhalili, Rawana N., et al.
(författare)
-
Antimicrobial protein candidates from the thermophilic Geobacillus sp. Strain ZGt-1 : Production, proteomics, and bioinformatics analysis
- 2016
-
Ingår i: International Journal of Molecular Sciences. - : MDPI AG. - 1661-6596 .- 1422-0067. ; 17:8
-
Tidskriftsartikel (refereegranskat)abstract
- A thermophilic bacterial strain, Geobacillus sp. ZGt-1, isolated from Zara hot spring in Jordan, was capable of inhibiting the growth of the thermophilic G. stearothermophilus and the mesophilic Bacillus subtilis and Salmonella typhimurium on a solid cultivation medium. Antibacterial activity was not observed when ZGt-1 was cultivated in a liquid medium; however, immobilization of the cells in agar beads that were subjected to sequential batch cultivation in the liquid medium at 60 °C showed increasing antibacterial activity up to 14 cycles. The antibacterial activity was lost on protease treatment of the culture supernatant. Concentration of the protein fraction by ammonium sulphate precipitation followed by denaturing polyacrylamide gel electrophoresis separation and analysis of the gel for antibacterial activity against G. stearothermophilus showed a distinct inhibition zone in 15-20 kDa range, suggesting that the active molecule(s) are resistant to denaturation by SDS. Mass spectrometric analysis of the protein bands around the active region resulted in identification of 22 proteins with molecular weight in the range of interest, three of which were new and are here proposed as potential antimicrobial protein candidates by in silico analysis of their amino acid sequences. Mass spectrometric analysis also indicated the presence of partial sequences of antimicrobial enzymes, amidase, and DD-carboxypeptidase.
|
|
| 3. |
- Asliyuce Coban, Sevgi, et al.
(författare)
-
Synthesis and use of protein G imprinted cryogel as affinity matrix to purify protein G from cell lyaste.
- 2016
-
Ingår i: Journal of Chromatography. B. - : Elsevier BV. - 1873-376X .- 1570-0232. ; 1021, s. 204-212
-
Tidskriftsartikel (refereegranskat)abstract
- Monolithic macroporous cryogel imprinted with protein G was prepared using a functional co-monomer of N-methacryloyl-l-phenylalanine and 2-hydroxyethyl methacrylate. The chemical structure of the cryogel prepared was studied by FTIR-spectroscopy and its porosity was analysed using scanning electron microscopy. The cryogel was used to purify protein G from recombinant Escherichia coli cell lysate and the effect of pH, temperature, ionic strength, flow rate, etc on the adsorption of protein G to the monolithic column have been investigated. The selectivity of the imprinted cryogel was studied using protein A and myoglobin. It was possible to capture about 9mg of Protein G per g of the cryogel.
|
|
| 4. |
- Bisagni, Serena, et al.
(författare)
-
Cloning and expression of a Baeyer-Villiger monooxygenase oxidizing linear aliphatic ketones from Dietzia sp. D5
- 2014
-
Ingår i: Journal of Molecular Catalysis B: Enzymatic. - : Elsevier BV. - 1873-3158 .- 1381-1177. ; 109, s. 161-169
-
Tidskriftsartikel (refereegranskat)abstract
- A Baeyer-Villiger monooxygenase has been identified in the genome sequence of Dietzia sp. D5. Sequence similarity search revealed that the enzyme belongs to a group of BVMOs that are closely related to ethionamide monooxygenase from Mycobacterium tuberculosis (EthA). The BVMO was expressed in E. coli BL21-CodonPlus(DE3)-RP and the best expression was achieved when the E. coli cells were cultivated in terrific broth (TB) at 15 degrees C and induced with 0.1 mM of IPTG. Since the purified enzyme did not show any measurable activity, the substrate scope of the BVMO has been determined using whole-cell and crude cell extract systems. The enzyme was most active towards linear aliphatic substrates. However, it has shown a moderate degree of conversion for cyclobutanone, 2-methylcyclohexanone, bicyclo[3.2.0]hept-2-en-6-one, phenylacetone and thioanisole. There was no detectable conversion of ethionamide, cyclohexanone and acetophenone. (C) 2014 Elsevier B.V. All rights reserved.
|
|
| 5. |
- Bisagni, Serena, et al.
(författare)
-
Cloning, expression and characterization of a versatile Baeyer-Villiger monooxygenase from Dietzia sp. D5.
- 2014
-
Ingår i: AMB Express. - : Springer Science and Business Media LLC. - 2191-0855. ; 4
-
Tidskriftsartikel (refereegranskat)abstract
- A novel BVMO encoding gene was identified from a draft genome sequence of a newly isolated strain of Dietzia. Analysis of the protein sequence revealed that it belongs to a group of BVMOs whose most characterized member is cyclopentadecanone monooxygenase (CPDMO). The gene was PCR amplified, cloned and successfully expressed in E. coli. The expressed recombinant enzyme was purified using metal affinity chromatography. Characterization of the purified enzyme revealed that it has a broad substrate scope and oxidized different compounds including substituted and unsubstituted alicyclic, bicyclic-, aliphatic-ketones, ketones with an aromatic moiety, and sulfides. The highest activities were measured for 2- and 3-methylcyclohexanone, phenylacetone, bicyclo-[3.2.0]-hept-2-en-6-one and menthone. The enzyme was optimally active at pH 7.5 and 35°C, a temperature at which its half-life was about 20 hours. The stability studies have shown that this enzyme is more stable than all other reported BVMOs except the phenylacetone monooxygenase from the thermophilic organism Thermobifida fusca.
|
|
| 6. |
- Bisagni, Serena, et al.
(författare)
-
Enhancing the Activity of a Dietzia sp. D5 Baeyer-Villiger Monooxygenase towards Cyclohexanone by Saturation Mutagenesis
- 2017
-
Ingår i: ChemistrySelect. - : Wiley. - 2365-6549. ; 2:24, s. 7169-7177
-
Tidskriftsartikel (refereegranskat)abstract
- A recombinant Baeyer-Villiger monooxygenase, BVMO4 from Dietzia sp. D5 has been previously reported. The enzyme exhibited good thermostability and was active with a wide range of cyclic ketone substrates but catalysed poorly the conversion of cyclohexanone to caprolactone. The present work focuses on protein engineering of BVMO4 to improve the conversion of cyclohexanone. Thus, a structural model of BVMO4 was generated and used in combination with literature information on substrate specificity of BVMOs to identify ‘hotspots’ whose mutation would influence substrate specificity. Site saturation mutagenesis was performed on 12 selected sites and 528 mutants were screened with expected coverage of about 98 %. About one-fourth of the mutants screened exhibited more than 50 % increase in cyclohexanone oxidation activity. Compared to the wild type BVMO, the best mutants, Y499I, Y499F and Y499 L have shown about 12-fold increase for caprolactone production.
|
|
| 7. |
- Bisagni, Serena, et al.
(författare)
-
Exploring the Substrate Specificity and Enantioselectivity of a Baeyer-Villiger Monooxygenase from Dietzia sp D5: Oxidation of Sulfides and Aldehydes
- 2014
-
Ingår i: Topics in Catalysis. - : Springer Science and Business Media LLC. - 1572-9028 .- 1022-5528. ; 57:5, s. 366-375
-
Tidskriftsartikel (refereegranskat)abstract
- Baeyer-Villiger monooxygenases (BVMOs) are valuable enzymes for specific oxyfunctionalization chemistry. They catalyze the oxidation of ketones to esters, but are also capable of oxidizing other chemical functions, namely aldehydes and heteroatoms such as sulfur, nitrogen, selenium and boron. The oxidation specificity and enantioselectivity of a newly characterized BVMO (BVMO4) from a strain of Dietzia towards sulfide- and aldehyde substrates have been studied. BVMO4 could react with sulfides containing an aromatic group. The presence of a substituent on the aromatic group was tolerated when they were in the meta- and para position and the oxidations yielded predominantly the (R)-sulfoxides. Similarly, BVMO4 displayed a higher activity for aldehydes containing a phenyl group, but long aliphatic aldehydes, namely octanal and decanal, were also accepted as substrate by this enzyme. The major oxidation products of the aldehyde substrates were the respective carboxylic acids in contrast to formate ester that was obtained in most of the previous reports. The Baeyer-Villiger oxidation of the substrate 2-phenylpropionaldehyde was studied in further detail and the corresponding acid product was obtained with good regio- and enantioselectivity. This is a unique feature for BVMO4 and is of great interest for further exploration of an alternative biocatalytic process.
|
|
| 8. |
- Chávez, Georgina, et al.
(författare)
-
Baeyer-Villiger Oxidation of Cyclohexanone in Aqueous Medium with In Situ Generation of Peracid Catalyzed by Perhydrolase CLEA
- 2014
-
Ingår i: Topics in Catalysis. - : Springer Science and Business Media LLC. - 1572-9028 .- 1022-5528. ; 57:5, s. 349-355
-
Tidskriftsartikel (refereegranskat)abstract
- A perhydrolase, immobilized as a cross linked enzyme aggregate (CLEA), was employed to catalyze the in situ formation of peracetic acid (PAA) from ethylene glycol diacetate (EGDA) and hydrogen peroxide. The produced PAA was used for the Baeyer-Villiger oxidation of cyclohexanone, which afforded caprolactone in 63 % yield. The effect of type and amount of acyl donor, solvent, pH, temperature and ratio of cyclohexanone to hydrogen peroxide on the production of caprolactone was studied. The highest caprolactone yield was obtained with 100 mM EGDA as the acyl donor at pH 6 and room temperature using a ratio of cyclohexanone to hydrogen peroxide ratio of 1:4. Interestingly, the perhydrolase CLEA exhibited the highest activity in aqueous medium in contrast to the well studied lipase B from Candida antarctica. The perhydrolase CLEA proved to be a very efficient catalyst; the K (m) and V-max values were 118 mM and 56.3 mu mol min(-1), respectively.
|
|
| 9. |
- Chávez, Georgina, et al.
(författare)
-
Baeyer-Villiger oxidation with peracid generated in situ by CaLB-CLEA catalyzed perhydrolysis
- 2013
-
Ingår i: Journal of Molecular Catalysis B: Enzymatic. - : Elsevier BV. - 1873-3158 .- 1381-1177. ; 89, s. 67-72
-
Tidskriftsartikel (refereegranskat)abstract
- Candida antarctica lipase B, immobilized as cross linked enzyme aggregates (CLEAs) was used to mediate the Baeyer-Villiger oxidation of cyclohexanone to epsilon-caprolactone, and the reaction was compared with the one using Novozym (R) 435 as catalyst. The conversion was dependent on the initial concentration of cyclohexanone, and was about 90% after 48 h at concentrations of up to 0.25 M but was decreased at higher concentrations. Caprolactone concentrations up to 0.6 M had no effect on the reaction efficiency. Among the cyclic ketones tested, the highest degree of conversion was achieved for cyclopentanone (88%) and the lowest for cyclooctanone (about 2%). The effect of methyl substitution and position of substitution on the cycloketone was studied using methylcyclohexanone and it has shown to influence the conversion efficiency. Both hydrogen peroxide and the reaction by-product acetic acid had a deleterious effect on the stability of the biocatalyst. (C) 2012 Elsevier B.V. All rights reserved.
|
|
| 10. |
- Danesh, Abolghasem, et al.
(författare)
-
Production of haloduracin by Bacillus halodurans using solid-state fermentation.
- 2011
-
Ingår i: Biotechnology Letters. - : Springer Science and Business Media LLC. - 1573-6776 .- 0141-5492. ; 33, s. 1339-1344
-
Tidskriftsartikel (refereegranskat)abstract
- Bacillus halodurans was cultivated on wheat bran as a solid-state substrate and produced haloduracin, a bacteriocin, at about 245 AU per wheat bran. Supplementation of the bran with Lauria-Bertani broth decreased haloduracin production. However, production was stimulated by addition of Mg(2)SO(4) and K(2)HPO(4). The highest production was achieved at a wheat bran/moisture ratio of 1:1.8 and in the presence of 10% (w/w) Na(2)CO(3). Under optimum conditions, the organism produced about 3,000 AU per gram dry bran.
|
|
