Citric acid production from orange peel wastes by solid-state fermentation

Valencia orange (Citrus sinensis) peel was employed in this work as raw material for the production of citric acid (CA) by solid-state fermentation (SSF) of Aspergillus niger CECT-2090 (ATCC 9142, NRRL 599) in Erlenmeyer flasks. To investigate the effects of the main operating variables, the inoculum concentration was varied in the range 0.5À10³ to 0.7À10(8) spores/g dry orange peel, the bed loading from 1.0 to 4.8 g of dry orange peel (corresponding to 35-80 percent of the total volume), and the moisture content between 50 and 100 percent of the maximum water retention capacity (MWRC) of the material. Moreover, additional experiments were done adding methanol or water in different proportions and ways. The optimal conditions for CA production revealed to be an inoculum of 0.5À10(6) spores/g dry orange peel, a bed loading of 1.0 g of dry orange peel, and a humidification pattern of 70 percent MWRC at the beginning of the incubation with posterior addition of 0.12 mL H2O/g dry orange peel (corresponding to 3.3 percent of the MWRC) every 12 h starting from 62 h. The addition of methanol was detrimental for the CA production. Under these conditions, the SSF ensured an effective specific production of CA (193 mg CA/g dry orange peel), corresponding to yields of product on total initial and consumed sugars (glucose, fructose and sucrose) of 376 and 383 mg CA/g, respectively. These results, which demonstrate the viability of the CA production by SSF from orange peel without addition of other nutrients, could be of interest to possible, future industrial applications.

Biotechnological production of citric acid

This work provides a review about the biotechnological production of citric acid starting from the physicochemical properties and industrial applications, mainly in the food and pharmaceutical sectors. Several factors affecting citric acid fermentation are discussed, including carbon source, nitrogen and phosphate limitations, pH of culture medium, aeration, trace elements and morphology of the fungus. Special attention is paid to the fundamentals of biochemistry and accumulation of citric acid. Technologies employed at industrial scale such as surface or submerged cultures, mainly employing Aspergillus niger, and processes carried out with Yarrowia lipolytica, as well as the technology for recovering the product are also described. Finally, this review summarizes the use of orange peels and other by-products as feedstocks for the bioproduction of citric acid.

Bio-synthesis and hydrolysis of ethyl phenylacetate and ethyl 2-phenylpropionate in organic solvent by lyophilized mycelia

To select the best biocatalysts for ethanol acylations with phenylacetic and 2-phenylpropionic acids, lyophilized mycelia of Aspergillus oryzae CBS 10207, A. oryzae MIM, Rhizopus oryzae CBS 11207, R. oryzae CBS 39134, R. oryzae CBS 26028 and R. oryzae CBS 32847 were tested in this study. The carboxylesterase activities of A. oryzae MIM and R. oryzae 11207, which revealed to be the best biocatalysts, were investigated either in 0.1 M phosphate buffer or in n-heptane to catalyze the hydrolysis or the synthesis of ethyl esters of these acids, respectively. A. oryzae proved more effective than R. oryzae, probably due to more favorable microenvironment conditions and thermodynamic scenario. The results in terms of product formation and substrate consumption versus time were used to estimate the maximum conversion yields, the equilibrium constants and the times needed to reach half maximum conversion, thus providing sufficient information about these equilibria.

Micélios liofilizados de Aspergillus oryzae CBS 10207, A. oryzae MIM, Rhizopus oryzae CBS 11207, R. oryzae CBS 39134, R. oryzae CBS 26028 e R. oryzae CBS 32847 foram testados neste estudo com vista à seleção do melhor biocatalisador para efetuar a acilação de etanol com ácidos fenilacético e 2-fenilpropiônico. As atividades carboxilesterásicas de A. oryzae MIM e R. oryzae 11207, que resultaram ser os melhores biocatalisadores, foram investigadas tanto em tampão fosfato 0,1 M como em n-heptano para catalisar a hidrólise ou a síntese dos ésteres etílicos destes ácidos. A. oryzae pareceu ser mais eficaz que R. oryzae, provavelmente devido a condições micro-ambientais e a um cenário termodinâmico mais favoráveis. Os resultados obtidos em termos de formação do produto e consumo dos substratos em função do tempo foram usados para a estimativa dos rendimentos de conversão máximos, as constantes de equilíbrio e os tempos necessários para alcançar metade da conversão máxima, fornecendo desta forma suficientes informações sobre esses equilíbrios.

Homenaje al cincuentenario de la Organización Mundial de la Salud / A tribute to the 50th anniversary of World Health Organization

The justification to this special issue about WHO are given, underlining the international impact of its policies and programmes in the last 50 years

Infección chagásica en donantes de sangre de hospitales de las regiones endémicas de Chile (1982-1987): transcendencia epidemiológica del problema / Chagasic infection in blood donors from hospitals in endemic regions of Chile (1982-1987). Epidemiological transcendence of the problem

La enfermedad de Chagas, producida por el Trypanosoma cruzi y transmitida por triatominos hematófagos, existe en América desde el sur de Estados Unidos hasta Chile y Argentina. Existe en sectores rurales y periurbanos de la mitad norte de Chile, siendo su prevalencia del 16,9%. Constantes migraciones rural-urbanas han contribuído a su propagación hacia sectores urbanos. Para investigar el impacto de dichas migraciones sobre la población susceptible de donar sangre y el probable incremento del riesgo de transmisión del T. cruzi vía transfusional se efectuaron encuestas seroepidemiológicas en donantes de 22 hospitales de la mitad norte de Chile. Mediante la reacción de hemaglutinación indirecta se examinaron 16.841 donantes encontrándose un 2,7% de positividad, porcentaje que permitió estimar que habría 126.477 potenciales donantes de sangre infectados por T. cruzi en los sectores urbanos estudiados. Estos hechos refuerzan la necesidad que en bancos de sangre de las regiones endémicas del país se efectúe rutinariamente serología para enfermedad de Chagas, para adoptar o reforzar medidas preventivas pertinentes