Selma da Costa Terzi

Hydrolytic enzyme production in solid-state fermentation by Aspergillus niger 3T5B8

Abstract A mixture containing polygalacturonase, cellulase, xylanase and protease enzymes was produced using Aspergillus niger 3T5B8 on different agroindustrial residues by solid-state fermentation and tested for vegetable oil extraction. The enzymic activities were evaluated using second-order empirical models from experimental data as a function of fermentation time and cellobiose concentration in the fermentation medium. The use of wheat bran as substrate without cellobiose addition and 42 h of fermentation were the most favourable conditions for producing the mixture of hydrolytic enzymes (polygalacturonase 30.75 U/ml, xylanase 30.62 U/ml, protease 5.27 U/ml). Another favourable condition was obtained when mango peel was used as substrate in the presence of 0.2% cellobiose and 24 h of fermentation (FPCAse 3.5 U/ml, xylanase 20.33 U/ml). Enzymic formulations with suitable polygalacturonase and FPCAse activities were favourable to extract oil from the pulp of tropical fruits and oleaginous seeds.

Selection of tannase-producing Aspergillus niger strains

The aim of this work was to select strains of Aspergillus niger for tannase production. Growth of colonies in plates with tannic acid-containing medium indicated their ability to synthesize tannase. Tannase activity was also measured in solid-state fermentation. A. niger 11T25A5 was the best tannase producer (67.5 U.g-1/72 hours of fermentation).

Selection of cellulolytic fungi isolated from diverse substrates

The aim of the present work was to select filamento us fungi isolated from diverse substrates to obtain the strains with potential to produce the hydrolytic enzymes. F rom a total of 215 strains, seven strains from the soils, six from the plants and one from sugarcane bagasse were sele cted and identified as belonging to the Trichoderma, Penicillium and Aspergillus genera. The best hydrolytic activities obtained by semi-solid fermentation using these strains were approximately: 35; 1; 160; 170 and 120 U/gdm (CMCase, FPase, β-glucosidase, xylanase and polygalacturonase, respectively), demonstrating the ir potential to synthesize the enzymes compared wit h the results reported in the literature.

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.