Copper metallothionein (Cu-MT) was extracted from the induced biomass of Aspergillus niger. The crude extract (FI), obtained by cell homogenization, was partially purified by heat treatment (FII) and ultrafiltration (FIII). Further purification of the Cu-MT extract by affinity chromatography resulted in three major fractions, FIVa, FIVb and FIVc, of which fraction FIVc was considered to be the Cu-MT extract fraction. Fraction FIVc was re-chromatography on affinity chromatography and the eluted fraction showed a single peak (FIVc'). Spectrophotometric analysis of fraction FIVc' demonstrated a maximum absorption peak at 268 nm. Native and denatured electrophoretic analysis of fraction FIVc ' showed the presence of a single band with an estimated molecular weight of 9.5 and 10.0 kDa, respectively. Inhibition of mushroom tyrosinase (PPO) by the Cu-MT extracts was investigated, using selected phenolic substrates, including catechin, chlorogenic acid, catechol, 4-methylcatechol, caffeic acid, L-3,4-dihydroxyphenylalanine, 3,4-dihydroxyphenylacetic acid, 3-( p-hydroxyphenyl) propionic acid, p-hydroxyphenylpyruvic acid, p- and m-cresol. The results showed that the inhibitory effect of the Cu-MT extract increased with the degree of purification. The results revealed that the Cu-MT extracts were effective inhibitors of PPO activity and the best inhibitory effect was demonstrated with catechin as substrate; however, PPO activity was not inhibited by the Cu-MT extract when p-hydroxyphenylpyruvic acid and p- and m-cresol were used as substrates. The results also showed that the Cu-MT extracts exhibited different types of inhibition, including mixed, competitive and uncompetitive on PPO activity. In addition, the experimental findings indicated that the nature and degree of enzymatic inhibitions by the Cu-MT extracts were dependent upon the structural nature of the substrates as well as the methods including, spectrophotometer and polarograph, used for the detection of enzyme

Two natural enzymatic browning inhibitors, copper-metallothionein (Cu-MT) and polyphenol esterase (PPE), were obtained from A. niger and investigated. Reflectance measurements, expressed as L (lightness variable) and a (red to green degree of color) were used to compare, over extended periods of time, the relative inhibitory effectiveness of Cu-MT and PPE to those observed with the use of selected chemicals including ascorbic acid (AA), citric acid (CA), ethylenediaminetetraacetic acid (EDTA), sodium bisulfite (NaHSO3) and 4-hexylresorcinol (4HR), in the prevention of browning on the cut surfaces of selected food products such as apple and potato slices as well as freshly prepared apple juice. Treatment of each food product required an optimum concentration of the selected inhibitor for the inhibition of browning. (Abstract shortened by UMI.)

A crude enzyme extract (FI) of polyphenol esterase (PPE), obtained from the microbial culture of Aspergillus niger, was partially purified by ammonium sulfate precipitation. The partially purified fraction (FII) was subjected to further purification by ion-exchange chromatography, which resulted in five separated fractions, FIIIa, FIIIb, FIIIc, FIIId and FIIIe), where FIIIa showed the highest PPE activity towards chlorogenic acid, as substrate. The biocatalysis of the PPE with a wide range of mono- and diphenols, as substrates, was shown to inhibit mushroom tyrosinase (PPO) activity. Fraction FIIIa exhibited an inhibitory effect, measured spectrophotometrically, on PPO activity with the monophenols, including 4-hydroxyphenylpyruvic acid and m- and p-cresols and the diphenols, including chlorogenic acid, catechin, 3,4-dihydroxyphenylacetic acid (DHPAA), L-3,4-dihydroxyphenylalanine (L-DOPA), 4-methylcatechol, catechol and caffeic acid; however, using the polarographic method, the inhibition of PPO activity by PPE biocatalysis occurred with the diphenols but not with the monophenols. The selected enzymatic fraction FIIIa was further purified, using size-exclusion chromatography, which resulted in three fractions FIVa, FIVb and FIVc. Although fraction FIVc contained the highest PPE activity, it showed a lack of enzyme stability. Fraction FIIIa was therefore, subjected to further purification by hydrophobic interaction chromatography thereby yielding fractions FVa, FVb, FVc, FVd, FVe, FVf and FVg, where fraction FVc showed the highest PPE activity. The denatured electrophoretic analysis of fraction FVc showed the presence of one major band, with a molecular weight of 60 kDa. The successive purification of PPE resulted in a marked increase in the inactivation of PPO activity with diphenols, as demonstrated by both the lower I50 and inhibition dissociation constant (Ki) values. The purified fraction FVc was shown to exhibit, spectrophotometrically, a competitive and un

Among the various fungal strains screened for citric acid production, Aspergillus niger is known to produce considerable amounts of citric acid and other organic acids when cultivated in carbohydrate-rich medium in solid substrate fermentation (SSF). Since A. niger on a solid substrate grows under conditions similar to the natural habitat, SSF is ideal to cultivate A. niger for the purpose of producing citric acid. / An initial optimization (study 1) was conducted in batch type fermentation experiments using peat moss supplemented with glucose to simulate an organic waste. The effects of various nutrients (glucose, (NH4)2SO 4, KH2PO4 and NaCl), fermentation parameters (moisture content, temperature, inoculum density, composition of solid substrate and particle size) and of initial level of potential stimulators (ethanol, methanol, phytate and surfactant) were evaluated with respect to citric acid production by A. niger grown on damp peat moss. In these experiments, optimization using a traditional 'one-factor-at-a-time' method was applied to determine key factor ranges for the production of citric acid. When the fermentation was carried out using the final optimal conditions. This allowed for a 50-fold increase in citric acid production compared to the production of citric acid by A. niger grown on peat moss supplemented with 100 g glucose/kg DPM. / A second set of experiments (study 2) was conducted to optimize fermentation conditions for citric acid production in a column bioreactor. A. niger NRRL 567 grown on damp peat moss was held within a column bioreactor and periodically irrigated with a glucose-rich solution simulating field conditions. Three variables including aeration, thickness of solid substrate bed and incubation temperature were optimized using a 23 full factorial design (FFD). Under optimum, the total citric acid production and yield were 120.6 g/kg DPM and 18.5% respectively. / A third experiment (study 3) compared the production of citric acid by A. niger in submerged fermentation using cheese whey, as opposed to batch and semi-continuous fermentation using peat moss. Various fermentation conditions such as nutrients (glucose, (NH4)2SO 4 and KH2PO4), stimulators (methanol, olive oil and phytate) and fermentation parameters (pH, fermentation time and inoculum density) were optimized using a central composite design (CCD). Citric acid production improved citric acid production by a factor of 13.3 when compared to the production of citric acid by A. niger NRRL 567 using whey-based medium (50 g/l) alone. / As compared to submerged and semi-continuous fermentation, Batch type SSF could take higher levels of initial glucose and produce the high concentration of citric acid within a shorter period of time. Thus, SSF may be considered to be better technique than submerged fermentation, if main disadvantage like non-homogeneous fermentation conditions could be overcome.

Proefschr. Rijksuniversiteit Groningen. / Met lit. opg.-Met samenvatting in het Nederlands.

Zugl.: Braunschweig, Techn. Univ., Diss., 2008

Thesis (MScIng)--University of Stellenbosch, 2005. / Accompanied by CD in end pocket of book. Bibliography. Also available via the Internet.

Zugl.: Braunschweig, Techn. Univ., Diss., 2007

Made available in DSpace on 2015-03-03T11:52:37Z (GMT). No. of bitstreams: 0 Previous issue date: 2014-07-25Bitstream added on 2015-03-03T12:06:21Z : No. of bitstreams: 1 000806886_20160725.pdf: 581026 bytes, checksum: 4c55faecb6d2b9cbebcf0fed8076771a (MD5) Bitstreams deleted on 2016-07-25T13:17:27Z: 000806886_20160725.pdf,. Added 1 bitstream(s) on 2016-07-25T13:18:38Z : No. of bitstreams: 1 000806886.pdf: 2412685 bytes, checksum: 76a763d7dfe3317535d6f9ec19a7cd78 (MD5) / As endoglicanases EC 3.2.1.4 são enzimas capazes de hidrolisar as ligações glicosídicas ?-1,4 da celulose, resultando na liberação de glicose, celobiose e celo-oligossacarídeos. Empregadas mundialmente em diversos processos industriais, por exemplo, como amaciante de tecidos de algodão e bioestonagem de jeans, na extração de sucos de frutas, na adição em detergentes comerciais, na fabricação de cerveja, e na produção de papel e de etanol. Atualmente, há um grande interesse em enzimas que hidrolisem biomassa lignocelulósica para obtenção de etanol de segunda geração. A imobilização de enzimas em matrizes sólidas oferece muitas vantagens, entre as quais, reuso da enzima, a fácil separação do produto e o aumento da estabilidade operacional. Os objetivos deste trabalho foram: produzir CMCases secretadas por Aspergillus niger e Humicola grisea var. thermoidea em cultivo sólido e submerso; imobilizar CMCases em suporte agarose com diferentes ativações químicas; determinar a estabilidade térmica e as propriedades cinéticas dos derivados obtidos, comparando-os com as enzimas livres; avaliar a capacidade de reuso dos derivados ativos e estáveis e analisar qualitativamente o produto de hidrólise dos substratos celulósicos. O fungo A. niger secretou grandes quantidades de CMCases, 34,1 U.mg-1, em meio Vogel, utilizando pó de bagaço de cana-de-açúcar como fonte de carbono. O pH 5 foi determinado como o ótimo para a enzima, apresentando instabilidade ao pH 10. Com a utilização de aditivos estabilizante, a trealose a 10% (m/v), manteve, em pH 10, 80% de atividade residual, por 25 horas. Em relação à temperatura, apresentou uma faixa ampla de atividade entre 45°C a 75°C, tendo como temperatura ótima 65°C. O derivado enzimático que ofereceu melhor estabilidade foi aquele em que a imobilização foi conduzida juntamente com o substrato carboximeticelulose (CMC 1%), em... / The endoglucanases EC 3.2.1.4 are enzymes that hydrolyze the ?-1, 4 glycosidic linkages of the cellulose producing glucose, cellobiose and cello-oligosaccharides. Used worldwide in many industrial processes such as fabric softener and bioestonagem cotton jeans, extraction of fruit juices, in the addition of commercial detergents, in brewing, and the production of paper and ethanol. Currently, there is great interest in enzymes that hydrolyze lignocellulosic biomass to obtain second-generation ethanol. The immobilization of enzymes on solid arrays provides many advantages as the enzyme reuse, easy separation of the product and increased operational stability. The aims of this study were to produce secreted: CMCases produce secreted by Aspergillus niger and Humicola grisea var. thermoidea in solid and submerged cultivation; CMCases immobilized on agarose support with different chemical activations; determine the thermal stability and kinetic properties of the derivatives obtained comparing them with the free enzyme; evaluate the reuse capacity assets and stable derivatives and qualitatively analyze the product of hydrolysis of cellulosic substrates. The fungus A. niger secreted large amounts of CMCases, 34.1 U.mg-1 amid Vogel, using powdered sugarcane bagasse as a carbon source. The pH of 5 was determined as the optimum for the enzyme, presenting instability to pH 10. With the use of stabilizing additives, the 10% trehalose (w / v), kept at pH10, 80% residual activity for 25 hours. Regarding temperature there was a broad activity range from 45 °C to 75 °C and the optimum temperature as 65 °C. The enzyme derivative which offered better stability was one in which immobilization was conducted with the carboxymethycellulose substrate (1% CMC) in agarose support Glutaraldehyde (70% of reactive groups), preserving catalytic activity of 35% at 60 °C for 250 hours. Through qualitative TLC analysis, it...

Trezentos pacientes portadores de colonização intracavitária pulmonar (pelos exames soro lógico e/ou tecidual) foram investigados num período de 10 anos. Os casos foram classificados como: Aspergillus fumigatus (246 casos); Ao niger (21 casos); A. flavus (7 casos); Pseudallescheria boydii (1 caso); colonização fúngica não especificada (21 casos) e colonização actinomicética (4 casos). os grupos A. niger (çasos)e A. fumigatus (controles) foram comparados a respeito de variáveis clínicas e laboratoriais, por serem os mais freqUentes e pela pobreza da literatura sobre A. niger. Esta análise mostrou associações estatisticamente significativas com o A. niger para;sexo masculino (Razão de Chances = 3,28; p <0,05); infecção nosocomial, ocorrendo em hospitais de conservação precária (RC = 150,8; p< 0,001); tuberculose ativa (RC = 8,03; P <0,001); diabete mélito tipo 11 (RC = 10,67; p<O,OOl); e êxito letal (RC = 3,1; p<0,02). Por outro lado, cristais de oxalato de cálcio no escarro e oxalose sitêmica só ocorreram no grupo A.niger. As implicações etiológicas e diagnósticas destes achados sao discutidas, enfatizando o papel do ambiente externo, da oxalose, do acúmulo de ácidos e da tuberculose ativa na etiopatogenia do A. niger. / Three hundred patients with intracavitary pulmonary colonization (by serologic and/or tissue examinations) were analysed during a ten years period. The cases were classified as: Aspergillus fumigatus (246 cases); A. niger (21 cases); A. flavus (7cases); Pseudallescheria boydii (1 case); fungal colonization not especified (21 cases) and actinomycetic colonization (4 cases). Due to their frequency and the scarcity of literature about A. niger, the groups A. niger (cases) and A. fumigatus (controls) were compared with respect to clinical and laboratorial variables. This analysis showed statistically significant associations with A. niger for: male sex (Odds Ratio = 3,28; p< 0,05); nosocomial infection, which occurred.in hospitaIs in poor state of repair (aR = 150.8; p<O,ooU; active tuberculosis (aR = 8,03; p<O,OOl); type 11 diabete mellitus (aR = 10,67; p<O,ooU; and lethal outcome (aR = 3, 1; p < o, 02). On the other hand, calcium oxalate crystals in the sputum and sistemic oxalosis occured only in A. niger group. The etiologic and diagnostic implications of these findings are discussed, with emphasis on the role of the externa 1 environernent, oxalosis, acid acurnulation and ative tuberculosis in the etiopathogenesis of A. niger.