- About
-
The Global ETD Search service is a free service for researchers
to find electronic theses and dissertations. This service is
provided by the
Networked Digital Library of Theses and Dissertations.
Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
Search results
Showing 1 to 3 of 3 (0.009 seconds)| 1 |
Produção e caracterização da atividade de tirosinase no extrato bruto de Pycnoporus sanguineus CCT-4518 / Production and characterization of tyrosinase activity in Pycnoporus sanguineus CCT-4518 crude extractDUARTE, Livia Teixeira 15 July 2009 (has links)
Made available in DSpace on 2014-07-29T16:11:53Z (GMT). No. of bitstreams: 1
DISSERTACAO DEFINITIVA c ficha catalografica.pdf: 2149699 bytes, checksum: ebcbff0f45d07e12d12a9708947a59eb (MD5)
Previous issue date: 2009-07-15 / Tyrosinase (E.C.1.14.18.1) is an enzyme of industrial interest that catalyses the ohydroxylation
of monophenols (monophenolase activity) and the oxidation of o-diphenols to
reactive o-quinones (diphenolase activity), both reactions using molecular oxygen.
Pycnoporus sanguineus (L. ex Fries) Murril, is a white rot fungi capable of producing
tyrosinase and widely distributed in nature. It is found in regions of mild climate and in
tropical forest. The production and characterization of tyrosinase from P. sanguineus were
investigated. The selection of inductors, determination of the luminosity influence, biomass
and culture media in the production of tyrosinase and the effect of inhibitors on enzyme
activity were determined. The fungus produced intracellular tyrosinase and the higher activity
was observed using 0.15% L-tyrosine as inducer, in the presence of light, with inoculum of 10
mycelium discs, medium malt extract broth 2%, incubation at 30°C, and constant agitation of
150 rpm, during 2 days. 6 mmol.L-1 salicylhydroxamic acid (SHAM) and 6 mmol.L-1
phenylthiourea (PTU) inhibited 100% of the tyrosinase activity. 0.1 mmol.L-1 sodium azide
inhibited 4.15% of tyrosinase activity, while no inhibition was observed after addition of 0.1
mmol.L-1 of phenylmethanesulfonyl fluoride (PMSF). Using L-dopa as substrate, the
intracellular crude extract presented optimum pH of 6,6, optimum temperature of 45°C, low
stability at 50°C, maintaining about 50% of the activity after 15 min of incubation. The
tyrosinase production was confirmed by non-denaturing polyacrylamide gel electrophoresis,
using commercial fungal tyrosinase as positive control / A tirosinase (E.C.1.14.18.1), também conhecida como polifenoloxidase ou catecolase, é uma
enzima de interesse industrial que catalisa a o-hidroxilação de monofenóis (atividade
monofenolase) e a subseqüente oxidação do o-difenol resultante em o-quinonas reativas
(atividade difenolase), usando oxigênio molecular. O Pycnoporus sanguineus (L. ex Fries)
Murril, um fungo de decomposição branca (white rot) capaz de produzir a tirosinase, é
amplamente distribuído na natureza, sendo encontrado em regiões de clima mais ameno e em
florestas tropicais. A produção e caracterização da tirosinase produzida por P. sanguineus foi
investigada. Foi realizada seleção de indutores, determinação da influência da luminosidade,
biomassa e meios de cultura na produção de tirosinase, bem como o efeito de inibidores sobre
a atividade enzimática. O extrato bruto enzimático foi caracterizado quanto ao pH ótimo,
temperatura ótima e termoestabilidade. Os resultados obtidos demonstraram que o fungo
produziu tirosinase intracelular e a mais alta atividade ocorreu com a utilização de 0,15% de
L-tirosina como indutor, na presença de luz, com inóculo de 10 discos de micélio fúngico,
meio caldo extrato de malte 2%, incubação à 30°C e agitação de 150 rpm, durante 2 dias.
Ácido salicilhidroxâmico (SHAM) 6 mmol.L-1 e feniltiouréia (PTU) 6 mmol.L-1 inibiram
100% da atividade de tirosinase. Azida sódica 0,1 mmol.L-1 inibiu 4,15% da atividade de
tirosinase, enquanto nenhuma inibição foi observada após adição de fluoreto de
fenilmetanosulfonil (PMSF) 0,1 mmol.L-1. Utilizando a L-dopa como substrato, o extrato
bruto intracelular apresentou pH ótimo de 6,6, temperatura ótima de 45°C, baixa estabilidade
à temperatura de 50°C, mantendo apenas cerca de 50% de atividade após 15 minutos de
incubação. A produção da tirosinase foi comprovada através de eletroforese em gel de
poliacrilamida não desnaturante, tendo como controle positivo tirosinase fúngica comercial
|
| 2 |
Inhibition de la mélanose post-mortem chez la crevette Penaeus monodon : Étude des activités enzymatiques phénoloxydases et recherche de conservateurs alternatifs aux sulfites / Post mortem melanosis inhibition in Penaeus monodon shrimp : study of enzymatic phenoloxydase activities and research of alternative curators in sulfitesZeyer, Estelle 27 February 2018 (has links)
Le bruissement enzymatiques, appelé mélanose post mortem chez les crustacés est un phénomène enzymatique catalysé par des protéines à activités phénoloxydases (tyronase, catécholase, laccase et hémocyanine). L'utilisation de conservateurs de type sulfites (E220 à E228 et E539) reste à l'heure actuelle la solution la plus répandue pour éviter le développement de cette coloration peu attrayante pour le consommateur. Mais une partie de la population développe des réactions d'hypersensibilité en consommant des aliments sulfités. Dans l'onbjectif de rechercher une alternative à ces conservateurs, deux axes de recherche ont été développés durant ces travaux de thèse : la caractérisation biochimique des protéines responsables de la mélanose post mortem chez la crevette P. monodon, puis la recherche de molécules inhibitrices. Un fractionnement sur résine Phenyl Sepahrose™ CL-4B (HIC) suivie d'une séparation par électrophorèse SDS-PAGE ont montré la présence de trois protéines de 46, 82 et 89 kDa à activité principalement laccase. Une identification par RP-HPLC-Q/TOF a mis en évidence la présence d'hémocyanine uniquement. Un pH de 7,0 et une température comprise entre 37 et 50 °C ont mis en évidence les activités les plus importantes, en utilisant le dosage enzymatique dit "test au MBTH". Par ailleurs, un criblage à haut débit de 45 molécules potentiellement inhibitrices a été réalisé dans des conditions d'analyses standardisées grâce à l'outil de robotique de la plateforme Realcat. Une inhibition a été mise en évidence pour 23 composés, certains étant suffisamment efficaces pour être utilisés seuls. D'autres pourraient être introduits dans un cocktail de molécules inhibitrices aux fonctionnalités complémentaires. Les résultats des tests de trempage réalisés sur des crevettes entières ont montré qu'il était indispensable de compléter les études in vitro avec des essais à l'échelle de la matrice alimentaire dans son intégralité. / Enzymatic browning, called post mortem melanosis in crustaceans, is an enzymatic phenomenon catalyzed by proteins with phenoloxidase activities (tyronase, catecholase, laccase and hemocyanin). The use of sulfite preservatives (E220 to E228 and E539) remains at present the most widespread solution to avoid the development of this unattractive color towards consumers. But, a part of the population develops hypersensitivity reactions by consuming sulfited foods. With the objective to find an alternative to these conversators, two research axes have been planned : the biochemical characterization of the proteins responsible for post mortem melanosis in the P. monodon shrimp, then the search for inhibitory molecules. Fractionation on Phenyl Sepahrose™ CL-4B resin (HIC) followed by SDS-PAGE electrophoresis separation showed the presence of three proteins of 46, 82 and 89 kDa with mainly laccase activity. Identification by RP-HPLC-Q / TOF revealed the presence of hemocyanin only. A pH of 7.0 and a temperature between 37 and 50 °C showed the most important activities, using the enzymatic assay called "MBTH test". On the other hand, a high throughput screening of 45 potentially inhibitory molecules could be performed under standardized analysis conditions thanks to the robotic tools of the Realcat platform
|
| 3 |
Actions of lignocellulolytic enzymes on Abies grandis(grand fir) wood for application in biofuel productionCherdchim, Banyat 27 October 2010 (has links)
No description available.
|
Page generated in 0.0155 seconds