The Biochemistry and Pathology of Hypervitaminosis A

Nieman, C.; Obbink, Henk

doi:10.1016/s0083-6729(08)61009-2

Cited by 99 publications

(22 citation statements)

References 87 publications

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“…A flotação do lodo é decorrente da dificuldade de liberação de gases produzidos na digestão anaeróbia 27 . A inibição depende do tipo de microrganismo, especificamente bactérias, pois as espécies metanogênicas e gram-positivas são mais vulneráveis ao efeito de inibição dos ácidos graxos, quando comparadas com as gram-negativas 46,47 . O comprimento da cadeia carbônica e o número de insaturações presentes nos ácidos graxos também são parâmetros de inibição para os microrganismos 24,48 .…”

Section: Problemas Relacionados Aos Elevados Teores De Lipídeos No Trunclassified

Aplicação de lipases no tratamento de águas residuárias com elevados teores de lipídeos

Mendes¹,

Castro²,

Pereira³

et al. 2005

Quím. Nova

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Recebido em 12/12/03; aceito em 14/9/04; publicado na web em 4/2/05 APPLICATION OF LIPASES FOR WASTEWATER TREATMENT CONTAINING HIGH LEVELS OF LIPIDS. The process of anaerobic digestion has been greatly developed during the last decades for the treatment of wastewater from food industries as for example, wastewaters from sugar and starch manufacturing and from breweries. However, for wastewaters which contain high amounts of fats and proteins, such as those from slaughterhouses and dairies, anaerobic digestion was found to be troublesome, due to the potential of sludge flotation, the formation of scum layers of lipids at the surface of the reactor, which are not digested and the toxicity of the intermediate compounds (long chain fatty acids) generated during the anaerobic digestion of the wastewater. The addition of hydrolytic enzymes, such as lipases prior to the anaerobic digestion can minimize these problems. In this work, this strategy is reviewed and the technical issues that must be considered in determining its feasibility are discussed.Keywords: wastewater; lipids; lipase and enzymatic treatment. INTRODUÇÃOA adoção de um maior rigor nos padrões de descarte de águas residuárias tem motivado a realização de pesquisas, cujo objetivo é reduzir o impacto ambiental, especialmente em efluentes contendo elevados teores de lipídeos, como os provenientes de laticínios, matadouros e avícolas, enlatados, extração de óleos, entre outros. A Política Nacional de Recursos Hídricos, instituída pela Lei Federal n° 9.433 de 8 de janeiro de 1997 trata da cobrança pelo uso dos corpos d'água para o lançamento de despejos líquidos.Os lipídeos contidos nesses efluentes, além de representarem uma perda industrial importante, interferem negativamente nos Sistemas de Tratamento de Efluentes. Elevadas concentrações de lipídeos resultam na formação de lodos com diferentes características físicas e reduzida atividade hidrolítica devido à flotação dessa biomassa, aumento do tempo de retenção hidráulica desses efluentes nas lagoas de estabilização, redução da capacidade de aeradores e elevada demanda de produtos floculantes 1 . Dentro deste contexto, processos alternativos vêm sendo utilizados na redução da concentração de lipídeos contidos nesses efluentes por meio de ação de enzimas, particularmente lipases. Essas enzimas apresentam uma importância particular, pelo fato de hidrolisarem especificamente óleos e gorduras, o que pode ser de grande interesse para o tratamento de efluentes com alto teor de gordura. As lipases (triacilglicerol acil hidrolases, E.C.3.1.1.3) compreendem um grupo de enzimas hidrolíticas que atuam na interface orgânica-aquosa, catalisando a hidrólise de ligações éster-carboxílicas, presentes em acilgliceróis 2 . A sua utilização reduz os níveis de sólidos suspensos e lipídeos, o que possibilita melhores condições de operação no tratamento anaeróbio e desobstrui filmes de óleos em tubulações, resultando no aumento da vida útil dos equipamentos.Além disso, esse tratamento apresenta algumas vantagens, tais como a e...

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Section: Problemas Relacionados Aos Elevados Teores De Lipídeos No Trunclassified

Aplicação de lipases no tratamento de águas residuárias com elevados teores de lipídeos

Mendes¹,

Castro²,

Pereira³

et al. 2005

Quím. Nova

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“…These data contrast with those of saturated fatty acids, where the most active compounds are in the range of C 8 to C 14 [1][2][3][4][5]. A dendritic structure should reduce the absorption of an amphiphile into a cell.…”

Section: Introductionmentioning

confidence: 99%

“…Saturated fatty acids have a long history as microbicides against many pathogens [1][2][3][4][5]. Measurements of inhibitory activities can be problematic because of the very low solubility of saturated fatty acids in aqueous solutions [6].…”

Section: Introductionmentioning

confidence: 99%

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Synchrotron SAX and WAX diffraction study of a hydrated very long-chain, dendritic amphiphile+DPPC mixture

Karlovská

Williams

Macri

et al. 2007

Colloids and Surfaces B: Biointerfaces

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The tri-headed anionic dendritic amphiphile, 4-(2-carboxyethyl)-4-[(icosyloxycarbonyl)amino]heptanedioic acid (3CCb20), forms solid-like gel-state mixed micelles with dipalmitoylphosphatidylcholine (DPPC) in excess water at 3CCb20 : DPPC = 0.91 : 1 molar ratio. On heating, these micelles transform into fluid bilayers stacked in the liquid crystalline lamellar L α phase at about 40 °C. This phase transition and the microstructure of 3CCb20 + DPPC aggregates were studied using smalland wide-angle synchrotron X-ray diffraction. The ability of 3CCb20 to solubilize solid-like lipid bilayers could be important in microbiocidal activities of 3CCb20, including in its anti-HIV activity.Keywords: amphiphiles; DPPC; micelles; bilayers; X-ray diffraction; phase transition 3 IntroductionSaturated fatty acids have a long history as microbicides against many pathogens [1][2][3][4][5]. Measurements of inhibitory activities can be problematic because of the very low solubility of saturated fatty acids in aqueous solutions [6]. Furthermore, as the chain length increases to C 18 and beyond, the aqueous solubility becomes immeasurable. Knowing that the compounds completely dissolve in aqueous media enables speculation about how chain length affects microbiological activity. In a homologous series of compounds, antimicrobial activity can show a cut-off effect [7]. Without knowing that the amphiphiles fully dissolve in aqueous media, we cannot conclude that the cut-off effect is due to the "intrinsic" activity of the amphiphiles or due to the decreased solubility of the amphiphile in the microbiological media. The antimicrobial data for 3CCbn show that longer chains (3CCb18-22) are more active than the shorter chains (3CCb14-16). These data contrast with those of saturated fatty acids, where the most active compounds are in the range of C 8 to C 14 [1][2][3][4][5]. A dendritic structure should reduce the absorption of an amphiphile into a cell. The highly branched structure of the head group resembles the dendritic structure of glycolipids that are anchored on the outside of cells. Branching and the triple charge might retard diffusion across membranes. Given the success of very long chain amphiphiles as antimicrobials, there might be a preference for absorption of these amphiphiles on pathogens as opposed to epithelial cells resulting in the reduced irritancy.To understand molecular mechanisms in the biological activities of these compounds, their interactions with different cell constituents must be studied. Several researchers [2,5,19] have proposed that the microbicidal mechanism of action involves fatty acids interacting with membranes. Because of the long alkyl chains, 3CCbn will likely partition into biological membranes. Upon doing so, these amphiphiles will affect the structure and dynamics of the membrane. The phospholipid bilayer comprises the structural matrix of biological membranes. Understanding how amphiphiles interact with a phopholipid bilayer will provide clues to the molecular mechanism of the biological a...

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“…A possible explanation for this paradox is that the antimicrobial effect of administered conjugated bile acids may be comediated by fatty acids (partly present as soaps) that are associated with the conjugated bile acids in mixed micelles in the proximal small intestine. Long-chain fatty acids have been known for many decades to have potent antimicrobial effects (12,13). Nonetheless, irrespective of the mechanism, these experiments provided strong evidence for a second physiological function of conjugated bile acids in the proximal small intestine: to prevent bacterial overgrowth by their antimicrobial activity.…”

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confidence: 99%