• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 413
  • 194
  • 67
  • 11
  • 11
  • 11
  • 11
  • 11
  • 11
  • 8
  • 7
  • 7
  • 7
  • 7
  • 7
  • Tagged with
  • 753
  • 104
  • 93
  • 70
  • 62
  • 59
  • 53
  • 53
  • 53
  • 52
  • 47
  • 46
  • 45
  • 44
  • 36
  • 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.
291

Avaliação da interesterificação enzimática de misturas binárias e ternárias de gordura de leite com óleos de canola e castanha-do-pará nas propriedades do produto obtido / Assessment of the enzymatic interesterification of the binary and ternary blends of milkfat with canola oil and Brazil nut oil on the properties of the products obtained

Nunes, Gisele Fátima Morais 07 October 2011 (has links)
Este trabalho teve como objetivo avaliar o efeito da interesterificação enzimática da gordura de leite com óleos de canola e castanha-do-pará nas propriedades do produto alimentício obtido, empregando lipase de Rhizopus oryzae imobilizada em sílica-álcool polivinílico (SiO2-PVA) como catalisador. Considerou-se desejável a obtenção de um produto que, ao incorporar parte dos ácidos graxos insaturados e essenciais presentes nos óleos, apresentasse boa espalhabilidade sob temperatura de refrigeração. Na primeira etapa as propriedades das matérias-primas foram determinadas aplicando técnicas oficiais de análise e verificou-se que todas apresentaram características de acordo com a legislação brasileira para uso em produtos alimentícios. Em seguida, foram testados dois métodos (adsorção física e ligação covalente) para efetuar a imobilização da lipase selecionada em SiO2-PVA e os resultados obtidos indicaram a adequação do procedimento de adsorção física. As condições otimizadas para conduzir as reações de interesterificação enzimática de blendas binárias de gordura de leite e óleo de canola, e de gordura de leite e óleo de castanha-do-pará, foram determinadas por planejamento composto central (CCD) constituído de 11 experimentos. A influência das variáveis temperatura (45-65?C) e teor de gordura no meio reacional (50-80%) foi avaliada simultaneamente, considerando como variáveis-resposta o grau de interesterificação (GI) e a consistência dos produtos. Modelos empíricos que possibilitaram a seleção de condições para obtenção de produtos interesterificados com satisfatória espalhabilidade (consistência entre 200 e 800 gf/cm²) foram compostos e confirmados para cada caso. Para a blenda gordura de leite e óleo de canola, as condições selecionadas corresponderam a um meio contendo 65% de gordura e 35% de óleo e incubado a 45°C por 12 h. Nessas condições foram obtidos produtos com consistência de 700 gf/cm². No caso da blenda gordura de leite e óleo de castanha-dopará, produtos interesterificados que atendem o parâmetro desejado (200-800 gf/cm²) foram obtidos empregando-se um meio contendo 50% de gordura e 50% do óleo, incubados a 45°C por 24 h. Reações de interesterificação de blendas ternárias de gordura de leite, óleo de canola e óleo de castanha-do-pará foram também efetuadas de acordo com um planejamento de misturas, constituído de 17 experimentos visando avaliar a influência da proporção de cada componente da blenda na consistência do produto interesterificado. Na faixa de variação investigada, o uso de blendas contendo 56% de gordura de leite, 22% de óleo de canola e 22% de óleo de castanha-do-pará incubadas por 3 h a 45°C resultou em produtos interesterificados com satisfatória consistência e plasticidade (634 gf/cm²). O desempenho das reações enzimáticas conduzidas sob aquecimento convencional e não convencional (irradiação de micro-ondas) foi ainda avaliado para as blendas binárias nas condições preditas pelo planejamento composto central, não sendo observada interferência das micro-ondas na atuação da enzima, obtendo-se produtos interesterificados com valores similares de consistência. Os dados obtidos sugerem que o processo de interesterificação enzimática catalisado pela lipase de Rhizopus oryzae imobilizada em SiO2-PVA foi eficaz para a modulação das características de plasticidade dos produtos obtidos empregando tanto misturas binárias como ternárias. / The objective of this work was to assess the effect of the enzymatic interesterification of milkfat with canola oil and Brazil nut oil on the properties of the resulting food product, using Rhizopus oryzae lipase immobilized on silica-polyvinyl alcohol (SiO2-PVA) as catalyst. The work was carried out considering as desirable to obtain a more spreadable product under domestic refrigerated conditions as well as enriched with unsaturated and essential fatty acids. Firstly, the properties of the raw materials were determined by applying official analysis techniques and results indicated that all raw materials were in agreement with the Brazilian legislation to food products. Then, two methodologies (physical adsorption and covalent binding) were tested for immobilizing the selected lipase on SiO2-PVA and physical adsorption was found to be the most suitable procedure. The optimized conditions to perform the enzymatic interesterification reactions of binary blends (milkfat and canola oil and milkfat and Brazil nut oil) were determined by central composite design (CCD), leading to a set of 11 runs. The influence of the variables, temperature (45-65°C) and the content of milk fat in the reaction medium (50-80%), was assessed simultaneously, taking the interesterification degree (ID) and consistency (10°C) as response variables. Empiric models were composed and confirmed for each case to establish conditions at which products with satisfactory spreadability (consistency in the range from 200 and 800 gf/cm²) can be obtained. For the milkfat and canola oil blend, the established conditions corresponded to a medium containing 65% of milk fat and 35% of oil, and lipase incubated at 45°C for 12 h. In these conditions, products with consistency of 700 gf/cm² were obtained. In the case of milkfat and Brazil nut oil blend, interesterified products with desirable parameter (200 and 800 gf/cm²) were obtained from reactions carried out with medium containing 50% of milk fat and 50% of oil, and lipase incubated at 45°C for 24 h. Interesterification reactions of ternary blends of milkfat, canola oil and Brazil nut oil were also carried out according to a mixture design with 17 runs to assess the influence of the mass proportion of each compound in the blend on the consistency of the interesterified products. In the range studied, the use of blends with 56% of milkfat, 22% of canola oil and 22% of Brazil nut oil and incubation at 45°C for 3 h resulted in products with satisfactory consistency and plasticity (634 gf/cm²). The performance of enzymatic reactions carried out under conventional and non-conventional (microwave irradiation) heating was also assessed for binary blends under the conditions predicted by the central composite design, and no interference of the microwave in the enzyme action was observed, resulting in interesterified products with similar values of consistency. The results obtained suggested that the process of enzymatic interesterification catalyzed by Rhizopus oryzae immobilized on SiO2-PVA was effective in modulating the plasticity properties of the products obtained using both binary and ternary blends.
292

A modulação da lipase de triacilglicerol do adipócito (ATGL) e da perilipina 1 contribui para o aumento da lipólise em pacientes caquéticos. / Modulation of adipose triglyceride lipase (ATGL) and perilipin 1 contributes to increased lipolysis in cachectic patients.

Silvério, Renata 03 February 2012 (has links)
A depleção de tecido adiposo é um marcador da caquexia. Neste contexto, o aumento na lipólise decorrente do aumento na expressão da lipase hormônio-sensível (LHS) parece ser o fator-chave. Entretanto, a contribuição das novas proteínas relacionadas à lipólise [adipose triglyceride lipase (ATGL), comparative gene identification 58 (CGI-58) e perilipina] ainda é controversa. Caracterizamos a expressão destas proteínas e de adipocinas na caquexia. Pacientes com câncer caquéticos foram investigados. Um modelo experimental foi também estudado utilizando animais portadores de tumor sacrificados no 7º (TB7) e no 14º dia (TB14) após a inoculação tumoral e controles. Foram analisados no tecido adiposo os aspectos morfológicos, morfométricos e moleculares. Verificamos nos pacientes um aumento na expressão de LHS e ATGL, concomitantemente à redução da perilipina. Nos animais TB7 verificou-se um desequilíbrio na secreção de fatores anti e pró-inflamatórios e no grupo TB14 houve redução na expressão das proteínas analisadas sugerindo comprometimento da função celular. / Loss of fat mass is a hallmark of cachexia. It seems that an increase in lipolysis due to increased expression of hormone-sensitive lipase (HSL) is the key factor behind this effect. However, the contribution of novel proteins related to lipolysis [adipose triglyceride lipase (ATGL), comparative gene identification - 58 (CGI-58) and perilipin 1] is still controversial. We characterized the expression of those proteins and adipokines in cachexia. Subcutaneous adipose tissue from cachetic cancer patients and epidydimal pad from tumour-bearing rats was analysed. Morphological, morphometric and molecular aspects were examined. We found an increased HSL and ATGL expression and reduction in perilipin 1 content in cachectic patients. In rats, at the intermediate stage of the syndrome, there was an imbalance in the secretion of pro and anti-inflammatory factors. In terminal cachexia the expression of almost all proteins analysed was reduced in the animals, suggesting impairment of cellular function.
293

Lipase-Catalyzed Syntheses of Telechelic Polyesters

Eriksson, Magnus January 2010 (has links)
Telechelic polyesters have successfully been synthesized with lipase-catalyzed polymerization. The produced telechelics had a high degree of di­functionalization, high purity (requiring little or no workup) and controlled degree of polymerization. The syntheses were performed in one-pot one-step reaction systems. The use of protection/deprotection chemistry was not necessary, since the lipase selectivity was utilized in the syntheses. Two different types of lipase-catalyzed polymerizations were applied – ring-opening polymerization and polycondensation. In ring-opening polymerization telechelics were produced by a combination of initiation, α-functionalization, and linking through termination, w-func­tionalization. In polycondensation different types of end-cappers were used to synthesize telechelics. Several exampels of functional groups were used for end-functionalization - epoxide, methacrylate and tetraallyls. Enzyme kinetic schemes describing the different functionalization met­hods of polyesters are presented and discussed. Stoichiometry and different reaction conditions have been studied to understand the effects these functions have on the final structure of the synthesized telechelics. Polyesters are classified as biodegradable, and can also be synthesized from materials that can be extracted or fermented from renewable sources like plants. Lipase-catalysts have several beneficial attributes, like high selectivity, they are renewable and biodegradable, are non-toxic and metal-free and can operate under mild reaction conditions. The focus of this thesis has been on lipase-catalyzed syntheses and characterization of the produced telechelics, in addition some materials have been produced. Some uses of telechelics are surface modification, materials for block co-polymers, functional films and biomedical applications. / QC20100726
294

Carboxylic ester hydrolase in acute pancreatitis : a clinical and experimental study

Blind, Per Jonas January 1994 (has links)
Diagnosis of acute pancreatitis (AP) is erroneous in up to one third of patients when based on clinical criteria and elevated serum amylase values. Furthermore, according to autopsy reports fatal pancreatitis remains clinically undiagnosed in 22 to 86 % of hospitalised patients. Consequently, search for better methods for the diagnosis of AP seems not only justified but urgent. The pancreas secretes an nonspecific lipase, the carboxylic ester hydrolase (CEH) with molecular properties different from other pancreatic secretory enzymes. These differences may imply that sites and rates of clearances from blood of pancreatic enzymes differ. Except for the pancreas this enzyme is secreted from the lactating mammary gland with milk. A sensitive and reproducible sandwich-ELISA for quantitative determination of CEH was developed. When establishing referent values it was noted that in individuals aged 20 to 65 years serum concentrations of CEH did not depend on age, gender, the time of the day or duration from food intake to blood sampling, or use of nicotine. The mammary gland did not contribute significantly to basal serum levels of CEH; enzyme levels in lactating women or women with mammary tumours were identical to those of the reference population. Seventy percent of patients with the diagnosis AP, based on elevated serum amylase levels and abdominal pain, had elevated CEH values. Among the patients with elevated amylase alone a probable cause of pancreatitis was lacking in the majority of patients. Contrastingly, a likely cause of AP could be identified in all patients presenting with abdominal pain and elevated CEH levels alone. These findings suggested that an elevated CEH level indicated AP more reliably than an elevated amylase level. In patients with AP diagnosed by contrast enhanced computed tomography (CECT) alone, or combined with histopathological diagnosis, serum CEH levels were elevated on admission in all but one patient, and in all within the next 24 h. Furthermore, in patients with severe pancreatitis CEH levels remained at a raised level from the second to at least the 10:th day following admission, whereas a significant decrease was noted in patients with mild pancreatitis. In contrast, serum amylase values were higher in patients with mild pancreatitis during the observation period than in those with severe pancreatitis. CEH levels were higher in patients with three or more Ranson signs than in those with less than three signs from the first day after admission. CEH levels were within referent range in 164 patients without known pancreatic disease admitted due to abdominal emergency conditions, or due to planned surgery for chronic extrapancreatic gastrointestinal diseases, and 16 patients having CECT without pathological findings in the pancreas. This suggests that AP can be excluded with very high degree of probability in presence of non-elevated CEH levels. A sandwich ELISA for determination of Guinea pig CEH and a model for graded pancreatitis in the same species were developed. CEH levels showed proportional to severity of inflammation, thus confirming previous clinical observations. CEH levels in bile were proportional to inflammation, while it was absent in urine. Amylase levels in urine were identical regardless of severity of inflammation, but low in bile. These results suggested differences in sites and rates of clearance between the two enzymes. Seemingly elevated CEH levels allowed identification of clinically significant pancreatitis following ERCP, which amylase levels did not. The presented studies have shown that quantitative determination in serum of CEH by the described method is a more reliable test for the diagnosis of AP than determination of amylase activity. The differences between CEH and amylase are, at least partly, due to differences in molecular properties determining rates and routes of clearances of the two enzymes from serum. / <p>Diss. (sammanfattning) Umeå : Umeå universitet, 1994, härtill 5 uppsatser.</p> / digitalisering@umu.se
295

Lipase-catalysed lipid modifications in supercritical carbon dioxide

Gunnlaugsdottir, Helga. January 1997 (has links)
Thesis (doctoral)--Lund University, 1997. / Added t.p. with thesis statement inserted.
296

Lipase-catalysed lipid modifications in supercritical carbon dioxide

Gunnlaugsdottir, Helga. January 1997 (has links)
Thesis (doctoral)--Lund University, 1997. / Added t.p. with thesis statement inserted.
297

Resíduos de laranja como fonte direta de lipases obtenção, caracterização bioquímica e aplicações /

Francisco, Valesca Cristiane Benelli January 2017 (has links)
Orientador: Luciana Francisco Fleuri / Resumo: O processamento de suco de laranja gera grande volume residual, sendo este aproximadamente 50% do fruto. Esses resíduos contêm biomoléculas de interesse industrial tais como as lipases que são capazes de catalisar a hidrólise de glicerídeos e reações de síntese em condições micro-aquosas. A obtenção dessas enzimas diretamente de resíduos reduz os custos de produção e viabiliza diferentes aplicações. As lipases possuem características interessantes como a regioespecificidade e especificidade quanto aos tamanhos da cadeia carbônica de ácidos graxos, possibilitando a geração de produtos diferenciados. Desta forma, o presente trabalho visou, além da obtenção de lipases por meio resíduos de laranja Pera, a aplicação destas em reações capazes de promover mudanças nos substratos (lipídeos) a fim de se obter produtos diferenciados que possam apresentar atividades biológicas. Lipases foram obtidas dos resíduos de laranja Pera e caracterizadas como 1,3 específicas nas frações bagaço, casca e frit as quais apresentaram atividade lipolítica de 55,9 U/g; 58,0 U/g e 49,9 U/g, respectivamente; e da fração polpa como inespecífica com atividade de 40,4 U/g. Essas enzimas foram empregadas em reações de hidrólise e síntese com diferentes óleos vegetais e os produtos de reação analisados quanto às atividades biológicas. Foram obsevadas atividades antioxidante de até 94,87%; atividade antibacteriana sobre E. coli, L. monocytogenes, P. aureginosa, S. enteritidis e S. aureus, e influência sobre a ... (Resumo completo, clicar acesso eletrônico abaixo) / Mestre
298

Isolamento e seleção de bactérias lipolíticas provenientes de água residual de abatedouro / Isolation and selection of lipolytic bacteria from wastewater slaughterhouse

Ferreira, Camila Míryan de Oliveira 26 August 2015 (has links)
Submitted by Lara Oliveira (lara@ufersa.edu.br) on 2017-01-11T16:15:33Z No. of bitstreams: 1 CamilaMOF_DISSERT.pdf: 1583672 bytes, checksum: f6ff4ec9fa18027cf6529ec82d5a0fac (MD5) / Approved for entry into archive by Vanessa Christiane (referencia@ufersa.edu.br) on 2017-01-24T14:44:38Z (GMT) No. of bitstreams: 1 CamilaMOF_DISSERT.pdf: 1583672 bytes, checksum: f6ff4ec9fa18027cf6529ec82d5a0fac (MD5) / Approved for entry into archive by Vanessa Christiane (referencia@ufersa.edu.br) on 2017-02-15T15:03:23Z (GMT) No. of bitstreams: 1 CamilaMOF_DISSERT.pdf: 1583672 bytes, checksum: f6ff4ec9fa18027cf6529ec82d5a0fac (MD5) / Made available in DSpace on 2017-03-21T14:47:57Z (GMT). No. of bitstreams: 1 CamilaMOF_DISSERT.pdf: 1583672 bytes, checksum: f6ff4ec9fa18027cf6529ec82d5a0fac (MD5) Previous issue date: 2015-08-26 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The growing interest in the production of lipases relates especially to the great biotechnological potential that these enzymes have. Lipases are enzymes that catalyze the hydrolysis of long chain triglyceride transforming them into glycerides and fatty acids. Microbial lipases have been addressed in constituting one of the most important groups of enzymes for biotechnological applications in several industrial sectors. Because of the promising potential of these enzymes and knowing that microorganisms use oils and fats as a carbon source for the production of lipases, this study aimed the isolation of lipase-producing bacteria from wastewater samples slaughterhouse through enrichment and growth in culture medium. A total of 68 morphologically distinct strains were recovered throughout the experiment. Subsequently, the lipase producing strains were selected by enzyme assay with the fluorescent dye Rhodamine B, which results in a fluorescent complex by the production of lipases in the plates. The results showed nine promising strains in the enzymatic test: ABAD01, ABAD05, ABAD07, ABAD09, ABAD12, ABAD17, ABAD20, ABAD21 and ABAD23. Likewise, reflecting the importance of studying the biotechnological potential of the microbial community associated to environments with high lipid content for the study of strains that produce lipases, with applications in the industry and in animal production / O crescente interesse na produção de lipases está especialmente relacionado ao grande potencial biotecnológico que estas enzimas apresentam. As lipases são enzimas que catalisam a hidrólise de longas cadeias de triglicerídeos transformando-os em glicerídeos e ácidos graxos. As lipases microbianas têm recebido grande atenção, constituindo um dos mais importantes grupos de enzimas para a aplicação biotecnológica nos mais variados setores industriais. Diante do potencial promissor destas enzimas e sabendo-se que micro-organismos fazem uso de óleos e gorduras como fonte de carbono para a produção de lipase, este trabalho teve como objetivo o isolamento de bactérias produtoras de lipase, a partir de amostras de águas residuais de abatedouro, por meio de enriquecimento e crescimento em meio de cultura. Foram recuperadas 68 linhagens morfologicamente distintas ao longo do experimento. Posteriormente, as linhagens produtoras de lipase foram selecionadas por meio do teste enzimático com corante fluorescente de Rodamina B, a qual resulta na produção de um complexo fluorescente pela produção de lipases nas placas. Os resultados mostraram nove linhagens promissoras no teste enzimático: ABAD01, ABAD05, ABAD07, ABAD09, ABAD12, ABAD17, ABAD20, ABAD21 e ABAD23. Os resultados obtidos refletem a importância em se estudar o potencial biotecnológico da microbiota associada aos ambientes com alto teor lipídico para a prospecção de linhagens produtoras de lipases, e suas futuras aplicações industriais e na produção animal / 2017-01-11
299

Isolamento e seleção de bactérias lipolíticas / Isolation and selection of lipolytic bacteria

Souza, Camila Michele Pereira de 25 February 2016 (has links)
Submitted by Lara Oliveira (lara@ufersa.edu.br) on 2017-01-11T16:29:41Z No. of bitstreams: 1 CarlaMPS_DISSERT.pdf: 1086600 bytes, checksum: 49317ae6809eaa5cf0c66b69c7c2370a (MD5) / Approved for entry into archive by Vanessa Christiane (referencia@ufersa.edu.br) on 2017-01-24T14:44:19Z (GMT) No. of bitstreams: 1 CarlaMPS_DISSERT.pdf: 1086600 bytes, checksum: 49317ae6809eaa5cf0c66b69c7c2370a (MD5) / Approved for entry into archive by Vanessa Christiane (referencia@ufersa.edu.br) on 2017-02-15T14:56:58Z (GMT) No. of bitstreams: 1 CarlaMPS_DISSERT.pdf: 1086600 bytes, checksum: 49317ae6809eaa5cf0c66b69c7c2370a (MD5) / Made available in DSpace on 2017-03-21T14:54:53Z (GMT). No. of bitstreams: 1 CarlaMPS_DISSERT.pdf: 1086600 bytes, checksum: 49317ae6809eaa5cf0c66b69c7c2370a (MD5) Previous issue date: 2016-02-25 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The production of enzymes by microorganisms is advantageous that the vegetable and animal origin due to the ease in obtaining and handling them. The processes catalyzed by microbial enzymes are generally faster, more efficient, less costly and environmentally sustainable than those that are made with chemical catalysts. This fact directly influences the increased use of these enzymes in industrial environment. Lipases are enzymes that catalyze the hydrolysis of long chain triglyceride transforming them into glycerides and fatty acids. Microbial lipases are part of one of the most important groups of enzymes for industrial application. Besides being involved in certain processes in the food, pharmaceutical, cosmetics, textile, paper and leather, these enzymes are also used in supplementation of animal feed that have deficiency in processing lipids. On the promising potential of these enzymes, this work had as main objective the isolation of bacteria producing lipase from samples from hot springs with temperatures ranging from 37-54 ° C. The most promising lines for lipase production were selected by testing the Rhodamine B and p-nitrophenyl palmitate (pNPP). Of the 51 isolated bacterial strains, 17 demonstrated the potential lipolytic Rhodamine test. Of these, nine were selected in the enzyme activity test (pNPP) verifying that the cultivation temperature influences the production of enzymes. The temperature of 30 ° C was the most favorable to growth and production of the enzymes. For the enzymatic activity temperature, it was found that one of the lines has greater activity at 70 ° C, thereby increasing interest in the use of same in the industrial environment the thermostable enzyme production. The results reflect the importance of studying the biotechnological potential of the microbiota associated with thermal environments for prospecting producing strains of lipases, and future agro-industrial applications / A produção de enzimas por microrganismos é mais vantajosa que as de origem vegetal e animal devido à maior facilidade na obtenção e manipulação dos mesmos. Os processos catalisados por enzimas microbianas são geralmente mais rápidos, mais eficientes, de menor custo e ambientalmente sustentáveis do que aqueles que são realizados com catalisadores químicos. Esse fato influencia diretamente no aumento da utilização dessas enzimas no ambiente industrial. As lipases são enzimas que catalisam a hidrólise de longas cadeias de triglicerídeos transformando-os em glicerídeos e ácidos graxos. As lipases microbianas fazem parte de um dos mais importantes grupos de enzimas para a aplicação industrial. Além de estar envolvida em determinados processos dos setores alimentício, farmacêutico, cosméticos, têxtil, de papel e couro, essas enzimas também são utilizadas na suplementação de ração para animais que possuem deficiência no processamento de lipídeos. Diante do potencial promissor destas enzimas, este trabalho teve como objetivo principal o isolamento de bactérias produtoras de lipase a partir de amostras provenientes de águas termais com temperaturas variando entre 37 a 54 °C. As linhagens mais promissoras para produção de lipase foram selecionadas por meio do teste da Rodamina B e do p-nitrofenil palmitato (pNPP). Das 51 linhagens bacterianas isoladas, 17 demonstraram potencial lipolítico no teste de Rodamina. Destas, nove foram selecionadas no teste de atividade enzimática (pNPP) verificando que a temperatura de cultivo influencia na produção das enzimas. A temperatura de 30 °C foi a mais favorável para crescimento e produção das enzimas. Quanto à temperatura de atividade enzimática, verificou-se que uma das linhagens possui maior atividade à 70 °C, aumentando assim, o interesse da utilização da mesma no meio industrial pela produção enzimática termoestável. Os resultados obtidos refletem a importância em se estudar o potencial biotecnológico da microbiota associada aos ambientes térmicos para a prospecção de linhagens produtoras de lipases, e suas futuras aplicações agroindustriais / 2017-01-11
300

Produção, purificação e imobilização de lipases de Staphylococcus warneri EX17 produzidas em glicerol

Volpato, Giandra January 2009 (has links)
Lipases (EC 3.1.1.3) são um grupo de enzimas que catalisam a hidrólise e síntese de triacilgliceróis. Estas enzimas apresentam estabilidade em diversos solventes orgânicos, podendo ser aplicadas como biocatalisadores em vários processos anteriormente realizados apenas por catalisadores químicos. Este trabalho teve como objetivo produzir, purificar e imobilizar lipases de Staphylococcus warneri EX17, cepa capaz de utilizar glicerol como fonte de carbono. Inicialmente, as condições de cultivo para produção de lipases foram otimizadas através de duas ferramentas de planejamento experimental: delineamento Placket Burman (P-B) e delineamento composto central rotacional (DCCR). Determinou-se que as melhores condições para produção desta enzima são: temperatura de 36 °C; pH 8,1; 30 g/L de glicerol; 3,0 g/L de óleo de oliva e 2,5 g/L de óleo de soja. Também se verificou ser possível a utilização de glicerol residual, oriundo da síntese enzimática de biodiesel como fonte de carbono. O extrato enzimático mostrou-se estável em três solventes orgânicos testados (metanol, etanol e η-hexano). Ainda visando a otimização das condições de cultivo, foram realizados cultivos submersos em biorreatores a fim de estudar a influência da taxa volumétrica de transferência de oxigênio (kLa) e do controle do pH, na produção da enzima. A maior produção de lipases ocorreu quando aplicado um kLa de 38 h-1 e com o pH controlado em 7,0 ao longo do cultivo, o que permitiu aumentar a produção da enzima em 5 vezes, em relação ao obtido nas condições anteriormente empregadas. A purificação da lipase foi realizada baseando-se no mecanismo de ativação interfacial destas enzimas sobre superfícies hidrofóbicas. Duas resinas foram testadas, octil-Sepharose e butil- Toyopearl. A lipase produzida foi purificada em apenas um passo utilizando esta última resina. Foi estudada a hiperativação da lipase purificada na presença de detergentes, a atividade lipolítica foi aumentada em 2,5 vezes na presença de 0,1% de Triton X-100. A lipase purificada foi imobilizada através de três estratégias: adsorção em suporte hidrofóbico; união covalente unipontual e união covalente multipontual. A influência da imobilização na modulação das propriedades da enzima foi estudada. A lipase apresentou maior estabilidade quando imobilizada multipontualmente. A hidrólise de distintos ésteres quirais pelos diferentes biocatalisadores obtidos também foi estudada. Os ésteres utilizados foram: (±) mandelato de metila, (±)-2-O-butiril-2-fenilacético e (±)-2-hidroxi-4-fenilbutirato de etilo. A especificidade da enzima foi muito dependente do método de imobilização, sendo que a lipase imobilizada unipontualmente foi mais específica para o substrato (±)-2-hidroxi-4-fenilbutirato de etilo, enquanto que para os outros dois substratos foi a lipase adsorvida hidrofobicamente. Este estudo demonstrou que a lipase de S. warneri EX17 pode ser produzida utilizando glicerol residual como fonte de carbono, levando a diminuição do custo na produção da enzima, que apresenta propriedades bastante interessantes para sua aplicação em biocatálise. / Lipases (EC 3.1.1.3) constitute a group of enzymes that catalyze the hydrolysis and synthesis of triacylglycerols. These enzymes show stability in many organic solvents, being able to be used as biocatalysts in some processes that were once carried out only by chemical catalysys. The aim of this research was the production, purification, and immobilization of lipase by Staphylococcus warneri strain EX17 using glycerol as carbon source. Initially, the cultivation conditions for the production of lipases have been optimized through two statistical procedures, Plackett-Burman statistical design (PB) and central composite design (CCD). It was determined that the best conditions for this enzyme production are: temperature, 36 °C; pH, 8.1; glycerol, 30 g/L; olive oil, 3.0 g/L; and soybean oil, 2.5 g/L. It was also studied the use of raw glycerol from enzymatic synthesis of biodiesel as carbon source, and stability studies showed that this lipase from S. warneri EX17 was stable in methanol, ethanol and nhexane. Moreover, experiments were conducted in submerged bioreactors in order to study the influence of oxygen volumetric mass transfer rate (kLa) and the control of pH in the production of the enzyme. The higher lipase production occurred when the microorganism was submitted to a kLa of 38 h-1 and the pH controlled at 7.0 during the cultivation, which improved 5-fold the enzyme production, compared to the results obtained in shaker flasks. The lipase purification was carried out based on mechanisms of interfacial activation of these enzymes on hydrophobic surface. Two supports were tested, octyl-Sepharose and butyl-Toyopearl. The lipase produced was purified 20-fold in only one step of purification. The purified lipase was immobilized on cyanogens bromide activated agorese and its hyperactivation in the presence of detergents was studied. The lipolytic activity increased 2.5-fold in presence of 0.1% of Triton X-100. After this, lipase was immobilized by three strategies: adsorption on hydrophobic support, mild covalent attachment, and multipoint covalent attachment. The stability over thermal, organic solvent and detergent inactivation was verified, as well as the influence of the immobilization protocol in the modulation of the properties of the enzyme. The lipase showed higher stability when multipointly immobilized on glyoxyl agarose. The hydrolysis of different chiral esters by the three biocatalysts obtained was also studied. The esters used were: (±) methyl mandelate, ((±) methyl mandelate, (±)-2-O-butyryl-2-phenylacetic acid, (±)-2-hydroxy-4-phenyl-butyric acid ethyl ester. The specificity of the enzyme was highly dependent of the protocol of immobilization, and the lipase mildly immobilized on cyanogen bromide agarose was more specific to the hydrolysis of (±)-2-hydroxy-4-phenyl-butyric acid ethyl ester, while for the other two substrates was the lipase adsorbed on octyl agarose. This study demonstrated that the lipase from S. warneri EX17 can be produced using raw glycerol as carbon source, contributing to the reduction in production costs of the enzyme, and the enzyme, when immobilized on different supports, presented quite interesting properties that may be usefull as biocatalysts.

Page generated in 0.044 seconds