Produção de lipases e sua aplicação na eliminação de resinas em lignocelulosicos

AUTOR(ES)
DATA DE PUBLICAÇÃO

1997

RESUMO

Lipases produced from Penicillium citrinum in the Yeast Extract Medium MEL and Ammonium Sulfate Medium MSA have mantained an optimum temperature of 30 °C and pH between 8,0 - 8,5. Their pH s were around 2,2 - 3,0 (MSA medium), and 6,5 - 7,8 (MEL medium) in the maximum production of extracellular lipolytic activity. It was observed that, mantaining the lipase in the extract partially purified at 6 °C, no alterations happened in its lipolytic activity after 60 days of storage. Polyethileneterephtalate ( dacron ) was transformed through hydrazinolysis, from its film its form into powder. Dacron - Hydrazide magnetized was obtained successfully from reactions between ferric and ferrous ions in alcaline pH. The Penicillium citrinum lipases produced in MSA medium were fixed to this support, dacron - hydrazide magnetized. The results shown that 19 mg semipurified extract (EPP) were immobilized per gramme of the support after 3 - hour incubation, showing a specific activity around 73 % of the soluble enzyme. The immobilized enzyme also mantained its optimum temperature at 37 °C and optimum pH at 8,5. However, it showed itself more thermostable than the soluble enzyme, keeping 60 % of its enzymatic activity after being incubed for 1 hour at 50 °C. Using p-nitrophenylpalmitate (pNPP) as substrate ( 37 °C, pH 7,2 ), the soluble and immobilized enzyme showed a Michaelis - Menten behaviour. The soluble lipase showed an apparent Km of 235 mM and Vmáx 0,991 IU/mg of protein, while the immobilized lipase showed a Km of 281 mM and Vmáx 0,56 IU/mg of protein. After extraction with acetone, the "pitch", a viscous and brown liquid, present in the reject, was around 9 %. All tests with pulps showed free fatty acids. However, when lipase added, there was a significant increase of total fatty acids, indicating a value of 0,357 mM of free fatty acids through enzymatic hydrolysis. Infrared spectrum from hidrophilic and lipophilic extractives present in the "pitch", have indicated that preliminary pulp washes, under agitation, liberate substances which could accumulate in the equipments. Also, there are no significant differences in the elimination of free fatty acids, when the pulps are washed with different concentrations of NaOH. Results obtained from the GC data have indicated that the majority of the compounds present in the "pitch" in study, are hydrocarbons of long chains and monosaturated acids.

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