Leda Maria Fortes Gottschalk

Efficient production of lignocellulolytic enzymes xylanase, β-xylosidase, ferulic acid esterase and β-glucosidase by the mutant strain Aspergillus awamori 2B.361 U2/1.

The production of xylanase, β-xylosidase, ferulic acid esterase and β-glucosidase by Aspergillus awamori 2B.361 U2/1, a hyper producer of glucoamylase and pectinase, was evaluated using selected conditions regarding nitrogen nutrition. Submerged cultivations were carried out at 30 °C and 200 rpm in growth media containing 30 g wheat bran/L as main carbon source and either yeast extract, ammonium sulfate, sodium nitrate or urea, as nitrogen sources; in all cases it was used a fixed molar carbon to molar nitrogen concentration of 10.3. The use of poor nitrogen sources favored the accumulation of xylanase, β-xylosidase and ferulic acid esterase to a peak concentrations of 44,880; 640 and 118 U/L, respectively, for sodium nitrate and of 34,580, 685 and 170 U/L, respectively, for urea. However, the highest β-glucosidase accumulation of 10,470 U/L was observed when the rich organic nitrogen source yeast extract was used. The maxima accumulation of filter paper activity, xylanase, β-xylosidase, ferulic acid esterase and β-glucosidase by A. awamori 2B.361 U2/1 was compared to that produced by Trichoderma reesei Rut-C30. The level of β-glucosidase was over 17-fold higher for the Aspergillus strain, whereas the levels of xylanase and β-xylosidase were over 2-fold higher. This strain also produced ferulic acid esterase (170 U/L), which was not detected in the T. reesei culture.

COMPARAÇÃO DA ESPECIFICIDADE DE LIPASES DE DUAS CEPAS DE Aspergillus niger NA HIDRÓLISE ENZIMÁTICA DO ÓLEO DE GIRASSOL

Diversas pesquisas tem estudado a tecnologia de modificacao dos oleos e gorduras e a obtencao de concentrados de acidos graxos poli-insaturados que beneficiem a saude do ser humano. As lipases sao enzimas que catalisam a hidrolise parcial ou total destes triacilglicerois (TAGs) produzindo acidos graxos livres (AGLs), diacilglicerol (DAG), monoacilglicerol (MAG) e glicerol. Neste trabalho, as enzimas produzidas pela cepa mutante Aspergillus niger 11T53A14 e pela cepa selvagem Aspergillus niger C foram utilizadas para a hidrolise do oleo de girassol. As lipases foram caracterizadas quanto a sua espeficidade em relacao a diferentes p-nitrofenil esteres e aplicadas na hidrolise de oleo de girassol. As condicoes da hidrolise enzimatica do oleo de girassol foram: proporcao molar de agua:oleo (8:1); carga da lipase de 5 U/g de oleo; 50°C e agitacao orbital de 150 rpm. Os acidos graxos livres foram quantificados em titulador automatico com NaOH 0,05 N. Os melhores resultados de hidrolise foram obtidos com extrato bruto de A. niger C, que apresentaram 228 mM de acidos graxos livres em 5,5 horas de reacao.