| 1. |
- Pawar, Sudhanshu, et al.
(författare)
-
Biofilm formation by designed co-cultures of Caldicellulosiruptor species as a means to improve hydrogen productivity
- 2015
-
Ingår i: Biotechnology for Biofuels. - : Springer Science and Business Media LLC. - 1754-6834. ; 8
-
Tidskriftsartikel (refereegranskat)abstract
- Background: Caldicellulosiruptor species have gained a reputation as being among the best microorganisms to produce hydrogen (H2) due to possession of a combination of appropriate features. However, due to their low volumetric H2 productivities (QH2), Caldicellulosiruptor species cannot be considered for any viable biohydrogen production process yet. In this study, we evaluate biofilm forming potential of pure and co-cultures of Caldicellulosiruptor saccharolyticus and Caldicellulosiruptor owensensis in continuously stirred tank reactors (CSTR) and up-flow anaerobic (UA) reactors. We also evaluate biofilms as a means to retain biomass in the reactor and its influence on QH2. Moreover, we explore the factors influencing the formation of biofilm. Results: Co-cultures of C. saccharolyticus and C. owensensis form substantially more biofilm than formed by C. owensensis alone. Biofilms improved substrate conversion in both of the reactor systems, but improved the QH2 only in the UA reactor. When grown in the presence of each other’s culture supernatant, both C. saccharolyticus and C. owensensis were positively influenced on their individual growth and H2 production. Unlike the CSTR, UA reactors allowed retention of C. saccharolyticus and C. owensensis when subjected to very high substrate loading rates. In the UA reactor, maximum QH2 (approximately 20 mmol · L−1 · h−1) was obtained only with granular sludge as the carrier material. In the CSTR, stirring negatively affected biofilm formation. Whereas, a clear correlation was observed between elevated (>40 μM) intracellular levels of the secondary messenger bis-(3′-5′)-cyclic dimeric guanosine monophosphate (c-di-GMP) and biofilm formation. Conclusions: In co-cultures C. saccharolyticus fortified the trade of biofilm formation by C. owensensis, which was mediated by elevated levels of c-di-GMP in C. owensensis. These biofilms were effective in retaining biomass of both species in the reactor and improving QH2 in a UA reactor using granular sludge as the carrier material. This concept forms a basis for further optimizing the QH2 at laboratory scale and beyond.
|
|
| 2. |
- Abouhmad, Adel, et al.
(författare)
-
Exploring the enzymatic and antibacterial activities of novel mycobacteriophage lysin b enzymes
- 2020
-
Ingår i: International Journal of Molecular Sciences. - : MDPI AG. - 1661-6596 .- 1422-0067. ; 21:9
-
Tidskriftsartikel (refereegranskat)abstract
- Mycobacteriophages possess different sets of lytic enzymes for disruption of the complex cell envelope of the mycobacteria host cells and release of the viral progeny. Lysin B (LysB) enzymes are mycolylarabinogalactan esterases that cleave the ester bond between the arabinogalactan and mycolic acids in the mycolylarabinogalactan-peptidoglycan (mAGP) complex in the cell envelope of mycobacteria. In the present study, four LysB enzymes were produced recombinantly and characterized with respect to their enzymatic and antibacterial activities. Examination of the kinetic parameters for the hydrolysis of para-nitrophenyl ester substrates, shows LysB-His6 enzymes to be active against a range of substrates (C4-C16), with a catalytic preference towards p-nitrophenyl laurate (C12). With p-nitrophenyl butyrate as substrate, LysB-His6 enzymes showed highest activity at 37◦C. LysB-His6 enzymes also hydrolyzed different Tween substrates with highest activity against Tween 20 and 80. Metal ions like Ca2+ and Mn2+ enhanced the enzymatic activity of LysB-His6 enzymes, while transition metal ions like Zn2+ and Cu2+ inhibited the enzymatic activity. The mycolylarabinogalactan esterase activity of LysB-His6 enzymes against mAGP complex was confirmed by LC-MS. LysB-His6 enzymes showed marginal antibacterial activity when tested alone against Mycobacterium smegmatis, however a synergetic activity was noticed when combined with outer membrane permealizers. These results confirm that LysB enzymes are lipolytic enzymes with potential application as antimycobacterials.
|
|
| 3. |
- Börner, Tim, et al.
(författare)
-
A Process Concept for High-Purity Production of Amines by Transaminase-Catalyzed Asymmetric Synthesis: Combining Enzyme Cascade and Membrane-Assisted ISPR
- 2015
-
Ingår i: Organic Process Research & Development. - : American Chemical Society (ACS). - 1083-6160 .- 1520-586X. ; 19:7, s. 793-799
-
Tidskriftsartikel (refereegranskat)abstract
- For the amine transaminase (ATA)-catalyzed synthesis of chiral amines, the choice of donor substrate is of high importance for reaction and process design. Alanine was investigated as an amine donor for the reductive amination of a poorly water-soluble ketone (4-phenyl-2-butanone) in a combined in situ product removal (ISPR) approach using liquid-membrane extraction together with an enzyme cascade. This ISPR strategy facilitates very high (>98%) product purity with an integrated enrichment step and eliminates product as well as coproduct inhibition. In the presented proof-of-concept alanine shows the following advantages over the other frequently employed amine donor isopropyl amine: (i) nonextractability of alanine affords high product purity without any additional downstream step and no losses via coextraction, (ii) higher maximum reaction rates, and (iii) broader acceptance among ATAs.
|
|
| 4. |
- Causevic, Ariana, et al.
(författare)
-
Effects of Lipase Immobilization Conditions and Support Materials for the Production of Structured Triacylglycerols
- 2023
-
Ingår i: European Journal of Lipid Science and Technology. - : Wiley. - 1438-7697 .- 1438-9312. ; 125:2
-
Tidskriftsartikel (refereegranskat)abstract
- Structured triacylglycerols (STAG) with desired properties can be synthesized by transesterification using immobilized lipases. Herein, the effect of immobilization conditions and support material on the immobilization yield, specific activity and regioselectivity of lipases from Rhizomucor miehei (RML) and Rhizopus oryzae (ROL) in the production of STAG, are evaluated. Four different support materials utilizing adsorption and one with covalent binding are investigated. Ammonium sulfate is found to significantly increase the activity-based immobilization yield (12% and 38% for RML and ROL, respectively) and specific activity on Accurel MP1000 (MP1000) when used as the immobilization buffer. Furthermore, the immobilization principle and support material influenced both the activity and regiospecificity. Immobilization by adsorption is found to result in higher catalytic activity, while covalent binding resulted in lipase inactivation. For RML, the highest specific activity of 43 µmol STAG min−1 g−1 (U) is obtained on MP1000, while ROL, which exhibited higher activities in general, results in a maximum activity of 120 U on Lifetech ECR8806. The obtained specific activites are comparable to the commercial preparations Novozym 40086 (45 U) and Lipase DF “Amano” IM (147 U) while the regiospecificity of the developed preparations is even higher, forming at least 64% less byproduct. Practical applications: There is an increasing need for lipids with specific nutritional and physical properties in health, nutrition, and food applications. In this context, STAG are highly promising products due to the possibility to tailor the composition to obtain the desired properties. Immobilized lipases are the catalyst of choice for the production of STAG, in which activity and regioselectivity are particularly important parameters for the process performance. In this study, it is shown that these parameters can be affected by the immobilization conditions and support material. Immobilized preparations with high activity and excellent regiospecificity are created on commercially available supports. This shows the possibility of STAG synthesis with high purity and beneficial properties.
|
|
| 5. |
- Elovson Grey, Carl, et al.
(författare)
-
A mass spectrometric investigation of native and oxidatively inactivated chloroperoxidase
- 2007
-
Ingår i: ChemBioChem. - : Wiley. - 1439-4227 .- 1439-7633. ; 8:9, s. 1055-1062
-
Tidskriftsartikel (refereegranskat)abstract
- The enzyme chloroperoxidase (CPO) found in Calclariomyces fumago is able to catalyze several stereoselective oxidation reaction by using a dean oxidant, usually hydrogen peroxide (H2O2), without the need for expensive cofactor generation. CPO's lack of operational stability however, is a major limitation for its commercial use. In the present study, a capillary-LC on-line trypsin- digestion system combined with reversed-phase chromatography and mass spectrometric detection was optimized for studying the primary sequence of CPO. Samples containing native CPO, CPO treated with H2O2, and CPO oxidatively inactivated by the use of indole and H2O2 were analyzed and compared. Three oxidized peptides were found in the samples treated with H2O2. Two additional oxidized peptides were found in the CPO samples that were completely inactivated, one of which contained an oxidized cysteine residue, Cys50, which is an essential amio acid due to its function as the axial ligand to the iron in the heme - the prosthetic group in CPO. In addition, the heme group was absent in the inactivated samples but was readily detected in other samples.
|
|
| 6. |
- Falck, Peter, et al.
(författare)
-
Production of arabinoxylan-oligosaccharide mixtures of varying composition from rye bran by combination of process conditions and type of xylanase.
- 2014
-
Ingår i: Bioresource Technology. - : Elsevier BV. - 1873-2976 .- 0960-8524. ; 174, s. 118-125
-
Tidskriftsartikel (refereegranskat)abstract
- The aim was to study arabinoxylan-oligosaccharide production from rye bran using heat pretreatment and enzymatic hydrolysis. Due to the potential application in foods, the purity of arabinoxylan was also assessed. Rye bran was heat pretreated to improve xylanase-catalyzed hydrolysis of arabinoxylan into arabinoxylan-oligosaccharides. Enzymatic removal of starch and proteins before or after heat pretreatment increased the purity, although at lower yield. The most attractive process resulted in 62% (w/w) arabinoxylan content after ethanol precipitation. Using xylanases from two glycoside hydrolase families (RmXyn10A from GH10 and Pentopan Mono BG from GH11), different mixtures of unsubstituted and arabinose-substituted xylooligosaccharides were produced. GH10 gave a higher yield of short oligosaccharides (60% w/w) with xylobiose as the main product; xylobiose and xylotriose were the main products with GH11 (40% w/w). Thus, heat pretreatment combined with enzymatic hydrolysis can be used to produce arabinoxylan-oligosaccharides from rye bran that are potentially useful in functional foods.
|
|
| 7. |
- Grey, Carl, et al.
(författare)
-
Ability of antioxidants to prevent oxidative mutations in Salmonella typhimurium TA102
- 2003
-
Ingår i: Mutation Research - Fundamental and Molecular Mechanisms of Mutagenesis. - 1879-2871. ; 527:1-2, s. 27-36
-
Tidskriftsartikel (refereegranskat)abstract
- An assay for the ability of antioxidants to prevent mutations induced by various oxidants in Salmonella typhimurium TA102 cells was developed. Protection against hydrogen-peroxide-induced mutagenicity was observed for quercetin, caffeic acid, ascorbic acid and dimethyl sulfoxide (used as a solvent for water-insoluble antioxidants). No protective effect was observed for green tea extract (weakly pro-oxidative), catechin, rutin, sinigrin, ferulic acid and -tocopherol. Mutagenicity caused by tert-butyl hydroperoxide (tBOOH) was prevented most effectively by quercetin and ascorbic acid, whereas weaker effects were observed for green tea extract and for rutin, and no effect being observed for the other antioxidants tested. The results for hydrogen peroxide indicate iron chelation to be the most important protective mechanism. Radical scavenging appeared to be effective only with dimethyl sulfoxide and ascorbic acid, which are effective scavengers of hydroxyl radicals and were used here in high concentrations. It is proposed that the hydrogen-peroxide-induced mutations in the Salmonella cells are caused by hydroxyl radicals generated by iron ions closely associated with DNA. Protection against mutagenicity caused by tert-butyl hydroperoxide appears to occur mainly through the scavenging of alkoxyl and possibly of alkyl radicals.
|
|
| 8. |
- Grey, Carl, et al.
(författare)
-
Development of a high performance anion exchange chromatography analysis for mapping of oligosaccharides
- 2009
-
Ingår i: Journal of chromatography. B. - : Elsevier BV. - 1570-0232 .- 1873-376X. ; 877:20-21, s. 1827-1832
-
Tidskriftsartikel (refereegranskat)abstract
- In the present study a HPAEC-PAD method is described that was developed for monitoring the consistency of N-glycosylation during the production and purification of recombinant proteins and monoclonal antibodies. The method successfully separated 18 neutral and sialylated oligosaccharides. Results obtained were compared with MALDI-TOF MS and it was shown that both methods gave similar results. in addition, a method validation was performed showing that the HPAEC-PAD analysis was well suited for the mapping and characterization of oligosaccharides. The method was found to be robust and additionally the precision was significantly better compared to the MALDI-TOF MS method.
|
|
| 9. |
- Grey, Carl, et al.
(författare)
-
Improved operational stability of chloroperoxidase through use of antioxidants.
- 2008
-
Ingår i: Journal of Biotechnology. - : Elsevier BV. - 1873-4863 .- 0168-1656. ; 135:2, s. 196-201
-
Tidskriftsartikel (refereegranskat)abstract
- Chloroperoxidase (CPO) from Caldariomyces fumago is a potentially very useful enzyme due to its ability to catalyze a large variety of stereoselective oxidation reactions, but poor operational stability is a main limitation for commercial use. In the present study, the possibility of increasing the operational stability by use of antioxidants was investigated using the oxidation of indole as model reaction. Caffeic acid was the antioxidant showing the strongest positive effects, reaching a total turnover number (TTN) of 135,000 at pH 4 and 4mM hydrogen peroxide, compared to 28,700 in the absence of antioxidant. Portion-wise addition of hydrogen peroxide in the presence of caffeic acid caused a further increase in TTN to 171,000. An alternative way to reach high TTN was to use tert-butyl hydroperoxide as oxidant instead of hydrogen peroxide: a TTN of 600,000 was achieved although the reaction was quite slow. In this case, antioxidants did not have any positive effect. Possible mechanisms for the observed inactivation of CPO are discussed.
|
|
| 10. |
|
|
