Influencia de la concentración de inóculo en la producción de celulasa y xilanasa por aspergillus niger / Influence of inoculum concentration on the cellulase and xylanase production by aspergillus niger

Existe un gran interés por el uso de enzimas lignocelulolíticas en varias industrias, y en la biodegradación de biomasa para la producción de biocombustibles y otras aplicaciones. Entre las fuentes microbianas de enzimas, Aspergillus niger es uno de los microorganismos más utilizados en la producción de enzimas industriales, debido a sus niveles altos de secreción de proteína y a su condición GRAS (generally regarded as safe). El objetivo del presente estudio fue evaluar la influencia de la concentración de inóculo en la morfología y producción de celulasas y xilanasas con A. niger en cultivo sumergido. Para ello, fueron inoculados matraces de 250 mL con 40 mL de medio con 3% (v/v) de una suspensión de 104 o 108 esporas por mililitro e incubados a 28 ºC y 175 rpm durante 120 horas. Se utilizaron 10 g*L-1 de lactosa como fuente de carbono. En cada caso se determinó la cantidad de biomasa, la proteína extracelular soluble, lactosa residual, actividad celulasa total y xilanasa cada 24 horas. Aunque no hubo un efecto notorio en la morfología de crecimiento, salvo en el color y el diámetro de pellets obtenidos, sí se afectó la µmax (0,06 y 0,03 h-1 para 104 y 108 esporas*mL-1, respectivamente) y la concentración máxima de biomasa. Además, mientras que las productividades volumétricas de celulasa (ΓFPA) (8,2 y 8,0 UI.*L-1*h-1 para 104 y 108 esporas*mL-1, respectivamente) fueron similares para ambos inóculos, la productividad de xilanasa (ΓXIL) fue mayor para el inóculo más concentrado (29,7 y 33,4 UI¨*L-1*h-1 para 104 y 108 esporas*mL-1, respectivamente). Los resultados indican que la productividad de celulasas y xilanasas está estrechamente relacionada con la concentración de inóculo.

There is a great interest for the use of lignocellulolytic enzymes in several industries and in biomass degradation for production of biofuels and other applications. Among the microbial sources of enzymes, Aspergillus niger is one of the most used microorganisms in the production of industrial enzymes due to its high levels of protein secretion and its GRAS (generally regarded as safe) condition. The aim of the present study was to evaluate the influence of A. niger inoculum concentration in the morphology and production of cellulases and xylanases in submerged cultures. For this, 250 mL flasks containing 40 mL culture medium were inoculated with a 3% (v/v) of either 104 or 108 spores per milliliter suspension and incubated at 28 º C and 175 rpm during 120 hours. Lactose (10 g*L-1) was used as the carbon source. In each case, the amount of biomass, the extracellular soluble protein, residual lactose, total celullase activity and xylanase activity were determined every 24 hours. Even thought there was not a notorious effect on the growth morphology, except in color and diameter of pellets; µmax was affected (0.06 and 0.03 h-1 for 104 and 108 spores*mL-1, respectively) as well as maximum biomass concentration. In addition, while the volumetric productivity of cellulase (8.2 and 8.0 UI*L-1*h-1 for 104 and 108 spores*mL-1, respectively) were similar for both inocula, the productivity of xylanase was greater for the more concentrated inoculum (29.7 and 33.4 UI*L-1*h-1 for 104 and 108 spores*mL-1, respectively).The results show that cellulase and xylanase productivities are closely related to the inoculum concentration.

Efeito inibitório in vitro de extrato vegetal de Allium sativum sobre Aspergillus niger Tiegh / In vitro inhibitory effect of Allium sativum extract on Aspergillus niger Tiegh

O sisal (Agave sisalana Perrine ex Engelm.) é a principal fonte de extração de fibras duras vegetais do mundo. No Brasil, o cultivo ocupa extensa área de solos pobres na região semi-árida dos Estados da Bahia, Paraíba e Rio Grande do Norte, em regiões com escassa ou nenhuma alternativa para exploração de outras culturas. Tendo em vista a propriedade inibitória dos extratos vegetais sobre o desenvolvimento de fungos, avaliou-se o efeito inibitório do extrato vegetal de alho (Allium sativum L.) sobre o fungo Aspergillus niger isolados da cultura do sisal. O extrato vegetal foi incorporado ao meio BDA fundente, aproximadamente 45ºC, nas concentrações 0, 500, 1000, 2000, 50000, 10000 e 50000 mg L-1. Os resultados demonstraram que a dose de 50000 mg L-1 de alho foi eficiente na inibição do crescimento do fungo Aspergillus niger "extraídos" da cultura do sisal.

Sisal (Agave sisalana Perrine ex Engelm.) is the main source of plant hard fiber extraction in the world. In Brazil, its cultivation occupies a large area of poor soils in the semi-arid region of Bahia, Paraiba and Rio Grande do Norte States, and in regions with scarce or no alternative to explore other crops. Based on the inhibitory property of plant extracts on fungal development, the inhibitory effect of garlic (Allium sativum L.) extract was evaluated on the fungus Aspergillus niger isolated from sisal crop. The plant extract was incorporated into melting PDA medium around 45ºC, at the following concentrations: 0, 500, 1000, 2000, 50000, 10000, and 50000 mg L-1. (OBS: M. Elena, há duas doses repetidas; creio que a primeira seja 5000). The concentration 50000 mg L-1 garlic extract was effective in inhibiting the growth of the fungus Aspergillus niger extracted from sisal crop.

Estudo da atividade antimicrobiana de extrato de folha de Aristolochia gigantea Mart e Zucc / Study of the antimycrobial activity of extracts from the leaves of Aristolochia gigantea Mart and Zucc

Foram investigadas as atividades antibacteriana e antifúngica dos extratos éter de petróleo e alcaloídico de folhas de Aristolochia gigantea Mart e Zucc, pelo método de difusäo em agar. O extrato éter de petróleo mostrou atividade contra uma bactéria Gram-positiva. O extrato alcaloídico apresentou atividade contra duas bactérias Gram-positivas. Uma Gram-negativa, näo apresentando qualquer atividade antifúngica.