ABSTRACT This work shows the increase in hydrolysis and acidogenesis of the organic fraction of urban solid waste (OFUSW) by the action of fungal hydrolytic enzymes obtained by solid-state fermentation (SSF) with Aspergillus niger C25B28 on citrus wastes (CW) without sterilization or the addition of nutrients. To quantify the hydrolysis and acidogenesis of the organic fraction of urban solid waste, three treatments were studied in triplicate: OFUSW plus 10 % fresh CW (RC treatment), and OFUSW plus 10 % citrus wastes pretreated by SSF (RCA treatment). The mixtures were packed into an anaerobic hydrolytic leaching bed reactor. The results showed that SSF decreased the limonene concentration by 97 %, removing 20 % of fiber and 46 % of fat from fresh CW. Pectinases (37 U/g DM [dry matter]), cellulases (33 U/g DM), xylanases (98 U/gDM), and proteases (0.2 U/gDM) were produced. Significant differences were observed between the different treatments: the greatest reduction in total solids (24 %), the highest removal efficiency of organic matter as chemical oxygen demand (COD), and the reduction of fats (23 % and 28 %, respectively), was achieved in RCA, compared to those obtained in the reactors with OFUSW and ReC without pretreatment. The production rate of volatile fatty acids (VFA) was 1.4 gVFA/Ld for RCA, 4.5 times higher than in the reactors without pretreatment.

RESUMEN Este trabajo muestra el aumento de la hidrólisis y acidogénesis de la fracción orgánica de residuos sólidos urbanos (FORSU) por la acción de enzimas hidrolíticas obtenidas mediante fermentación en medio sólido (FMS) con Aspergillus niger C25B28, sobre residuos cítricos (ReC) sin esterilización y sin adición de nutrientes. Para cuantificar la hidrólisis y acidogénesis de la FORSU se estudiaron tres tratamientos por triplicado: FORSU (R); FORSU más 10 % de ReC (RC) y tratamiento de la FORSU más 10 % de ReC pretratados por FMS (RCA). Las mezclas se empaquetaron en reactores anaerobios hidrolíticos de lecho escurrido. Los resultados muestran que la FMS disminuyó en un 97 % la concentración de limoneno y removió el 20 % de fibra más el 46 % de grasa de los ReC frescos. Se produjeron pectinasas (37 U/g materia seca [MS]), celulasas (33 U/g MS), xilanasas (98 U/g MS) y proteasas (0.2 U/g MS). Se observaron diferencias significativas entre los distintos tratamientos: en los rectores con RCA se obtuvo la mayor reducción de los sólidos totales (24 %), la mayor eficiencia de remoción de la materia orgánica como demanda química de oxígeno y la reducción de grasas (23 % y 28 %, respectivamente) en porcentajes superiores a los obtenidos en los reactores con FORSU y con ReC sin pretratar. La tasa de producción de ácidos grasos volátiles fue de 1.4 gAGV/Ld para RCA, 4.5 veces mayor que para los reactores sin pretratamiento.

The aim of this study was to compare the cellulolytic and xylanolytic activities of two strains of Trichoderma viride, one of Trichoderma reesei and one of Trichoderma harzianum grown on four different substrates. Each substrate contained 20% wheat bran and 80% agro-industrial waste (corn stover (CS), sugarcane bagasse (SCB), Yucca schidigera fiber (YS), or compost elaborated from solid waste generated in the university cafeteria (CSW)). An interaction (P < 0.01) between the substrate and strain was detected for both cellulolytic and xylanolytic enzyme activities. The highest cellulolytic activity (P < 0.01) was obtained with T. reesei grown on YS, CS, and SBC, and the lowest was from the two T. viride strains grown on most of the substrates. The highest xylanolytic activities (P < 0.01) were detected for T. harzianum with YS and SCB and T. reesei with CSW and CS, while one T. viride strain exhibited intermediate and the other showed the lowest activity. In conclusion, T. reesei CDBB356 showed the highest fibrolytic activity for most of the tested substrates, a finding that suggests it has the highest potential for fibrolytic enzyme production. There is a potential application for T. reesei CDBB356 enzymes on ruminant feed supplements to improve forage digestibility.

El objetivo de este estudio fue comparar las actividades celulolíticas y xilanolíticas de dos cepas de Trichoderma viride, una de Trichoderma reesei y una de Trichoderma harzianum cultivadas en cuatro diferentes substratos. Cada substrato contenía 20% de salvado de trigo más 80% de residuos agroindustriales (rastrojo de maíz (CS), bagazo de caña de azúcar (SCB), fibra de Yuca shidigera (YS) o composta, elaborada a partir de residuos sólidos de la cafetería universitaria (CSW)). Se detectó una interacción (P <0,01) cepa por sustrato en las actividades enzimáticas celulolíticas y xilanolíticas. La mayor actividad celulolítica (P <0,01) se obtuvo con T. reesei en YS, CS y BC y la más baja con las dos cepas de T. viride, en la mayoría de los sustratos. Las actividades xilanolíticas más altas (P <0,01) se detectaron en T. harzianum con YS y SCB y T. reesei con CSW y CS, mientras que una cepa de T. viride fue intermedia y la otra tuvo las actividades más bajas. En conclusión, T. reesei CDBB356 mostró la actividad fibrolítica más alta en la mayoría de los sustratos, confirmando el mayor potencial para producir esas enzimas. Existe una aplicación potencial de las enzimas de T. reesei CDBB356 en suplementos alimenticios para rumiantes para mejorar la digestibilidad del forraje.

In the breeding processes of fungal strains of entomopathogenic, it is necessary to know which ones they are and how the most important variables have influence on the most virulent strains. In this study an evaluation was made of a series of growth and virulence variables of a parental strain of Beauveria bassiana (Bals.) Vuill. (Hyocreales: Cordycipitaceae) (88) and derived mutants resistant to the toxic compound 2-doxy-D-glucose (2DG). 2DG is a toxic analogue of glucose, and has frequently been used to isolate a variety deregulated mutants in the metabolism of carbon in some microorganisms. Of the variables evaluated, prior to the bioassay of virulence on larvae of Tenebrio molitor (Coleoptera: Tenebrionidae), the percentage of germination of conidia (G) was best correlated with the parameters of virulence such as time of onset of death (t0) (r=-0.879; p<0.05), lethal time 50 (LT50) (r=-0.869; p<0.05) and maximum mortality M (r=0.589; p=0.1). The other variables evaluated showed a lower correlation with virulence. There is a high correlation of t0 with the LT50 (r=0.967; p<0.05), a variable determined in the early stage of infection of B. bassiana in larvae of T. molitor. The mutant strains 881.2, 882.5 and 885.5 resistant to 2DG showed improved characteristics in virulence compared with the parental strain (88). The above was confirmed through simple regression coefficients and Principal Components Analysis (PCA), used to examine the relationship among the variables of study. The analysis of the results shows the physiological characteristics with highest influence to select more virulent strains of entomopathogenic fungi.

En los procesos de mejoramiento de cepas de hongos entomopatógenos es necesario conocer cuáles son y cómo inciden las variables más importantes en las cepas más virulentas. En este estudio se evaluó una serie de variables de crecimiento y de virulencia de una cepa parental de Beauveria bassiana (Bals.) Vuill. (Hypocreales: Cordycipitaceae) (88) y mutantes derivadas resistentes al compuesto tóxico 2-desoxi-D-glucosa (2DG). La 2DG es un análogo tóxico de la glucosa, y se ha usado con frecuencia para aislar diversas mutantes de microorganismos desregulados en el metabolismo del carbono. De las variables evaluadas, previo al bioensayo de virulencia sobre larvas de Tenebrio molitor (Coleoptera: Tenebrionidae), el porcentaje de germinación de conidios (G) se correlacionó mejor con los parámetros de virulencia como el tiempo de inicio de muerte (t0) (r=-0.879; p<0.05), tiempo letal 50 (TL50) (r=-0.869; p<0.05) y mortalidad máxima M (r=0.589; p=0.1). Las demás variables evaluadas mostraron una correlación menor con la virulencia. Se destaca la alta correlación de t0 con el TL50 (r=0.967; p<0.05), variable determinada en la etapa temprana de infección de B. bassiana en larvas de T. molitor. Las cepas mutantes 881.2, 882.5 y 885.5 resistentes a 2DG mostraron características mejoradas en la virulencia comparadas con la cepa parental (88). Lo anterior se corroboró mediante coeficientes de regresión simple y Análisis de Componentes Principales (ACP), usados para examinar la relación entre las variables de estudio. El análisis de los resultados muestra las características fisiológicas con mayor influencia para seleccionar cepas más virulentas de hongos entomopatógenos.

Conidia production of entomopathogenic fungi Beauveria bassiana (Bals.-Criv.) Vuill. is performed in a solid state culture (SSC) using agricultural products and their residues, such as rice (Oryza sativa) and sugarcane (Saccharum ojjicinarum) bagasse, where CO2 can be accumulated as a product of metabolism. In this study rice (Oryza sativa var. japonica) was used as substrate using two atmospheric compositions: normal air and other enriched with CO2 (5 %), through exchanges every 12 or 24 h. The effect of these treatments was determined on the conidial production and amylase enzymes by B. bassiana, using a completely randomized design and analysis of variance using Tukey-Kramer test (p< 0.05). Maximum conidia production per g of initial dry substrate (gssi) was obtained with the normal atmosphere (1.14×10(9) conidia gssi-1), while with 5 % of CO2 the conidia production decreased up to 85 % (1.8×10(8) conidia gssi-1). However, in this latter treatment amylase activity increased three times (16.58 UI gssi-1) with respect to the normal atmosphere (5.41 UI gssi-1). These results are important for the conidia and enzymes production by fungi in SSC, with the recommendation to modify the concentration of CO2, as it is required to favor the type of product.

La producción de conidios del hongo entomopatógeno Beauveria bassiana (Bals.-Criv.) Vuill. se realiza en cultivo en medio sólido (CMS) utilizando productos agrícolas y sus residuos, como arroz (Oryza sativa) y bagazo de caña (Saccharum ojjicinarum), donde el CO2 puede acumularse como producto del metabolismo. En este estudio se usó arroz (Oryza sativa var. japonica) como sustrato usando dos composiciones atmosféricas: aire normal y otra enriquecida con CO2 (5 %), a través de recambios cada 12 o 24 h. Se determinó el efecto de estos tratamientos en la producción de conidios y de enzimas amilasas por B. bassiana, mediante un diseño completamente al azar y análisis de varianza usando la prueba de Tukey-Kramer (p<0.05). La producción máxima de conidios por g de sustrato seco inicial (gssi) se obtuvo con la atmósfera normal (1.14×10(9) conidios gssi-1), mientras que con 5 % de CO2 la producción de conidios disminuyó hasta 85 % (1.8×10(8) conidios gssi-1). Sin embargo, en este último tratamiento la actividad de amilasas se incrementó tres veces (16.58 UI gssi-1) respecto a la atmósfera normal (5.41 UI gssi-1). Estos resultados son importantes para la producción de conidios y de enzimas por hongos en CMS, con la recomendación de modificar la concentración de CO2, según se requiera favorecer el tipo de producto.

The aim of the present work was to study the effect of moisture content and inoculum on the growth and conidia production by Beauveria bassiana on wheat bran (WB).The highest growth rate of B. bassiana 885.2 on WB media was obtained at a w=1.0, with no detected growth at a w < 0.97. Solid-state fermentation (SSF) using WB (66% moisture; a w=1.0) achieved a maximal yield of 1.18x10 10 conidia per gram of dry substrate (gds). This yield decreased one order of magnitude with higher moisture contents or the addition of sugarcane bagasse (SCB) as a texturiser. In SSF using WB (66% humidity),the time to obtain a yield of 1x10(10) conidia/gds, referred to as t10, could be predicted using a model considering common inoculum levels and maximal yields. For instance, t10 was 285 h with an inoculum of 1x10(6) conidia/gds; however, t10 was reduced to 232 h and 148 for inocula of 7x10(6) and 5x10(7) conidia/gds, respectively. The estimation of t10 values allowed both comparison between the cultures and prediction of harvesting times in production processes. Values for hydrophobicity were within 90 and 92%, whereas viability averages were around 70% for all the cultures

A new isolate Idriella sp. GH5608 was collected in a region of Xalapa, Veracruz, Mexico. In order to explore the existence of intracellular or extracellular antibacterial activity from this strain, culture filtrates and biomass methanolic extracts were screened by microdilution method against pathogenic species to either humans or plants. Biossays-guided fractionation of the extracellular extracts from Idriella sp. GH5608 led to the identification of 5-hydroxymethyl-2-furaldehyde and 1-n-Butyl-β-D-fructopyranoside. These structures were determined by spectroscopic methods. Both compounds showed inhibitory antibacterial activities against Xanthomonas axonopodis, Pectobacterium carotovorum, P. crhysanthemi and Erwinia amylovora (MIC = 0. 625 mg/ml).

Un nuevo aislamiento, Idriella sp. GH5608 fue colectado en la región de Xalapa, Veracruz, México. Para explorar la existencia de actividad antibacteriana intracelular o extracelular de dicha cepa, los caldos de cultivo y el extracto metanólico de la biomasa fueron evaluados por el método de microdilución en caldo en contra de especies patógenas tanto para humanos como para plantas. De la purificación de los extractos de este hongo se lograron identificar el 5-hidroximetil-2-furaldehido y el 1-n-Butil-β-D-fructopiránosido. Estas estructuras fueron determinadas por métodos espectroscópicos. Ambos compuestos mostraron actividades antibacterianas en contra de Xanthomonas axonopodis, Pectobacterium carotovorum, P. crhysanthemi y Erwinia amylovora (CMI = 0. 625 mg/ml).

Um cepa diplóide (D4) isolada por combinação parasexual entre dois Aspergillus niger, mutantes superprodutores de xylanase foi caracterizado através da produção de (607 nkat/ml) e repressão catabólica por glicose. Essa cepa aumenta a produção de xylanase em mais de 100% em comparação com uma cepa selvagem (305 nkat/ml) e 28% superior do que o melhor mutante usado para induzir o ciclo parasexual. A cepa diplóide D4 foi também menos sensível a repressão catabólica pela glicose, sendo que a atividade xylanolitica foi detectada sob condições normalmente de produção repressiva pela cepa selvagem. Não foi observado um decréscimo na produção máxima de xylanase em presença de glicose para o diplóide D4.

A diploid strain (D4) isolated via parasexual recombination between two Aspergillus niger xylanase overproducing mutants was characterised in terms of enzyme production and catabolite repression by glucose. This strain increased xylanase production (607 nkat/ml), which was nearly 100% higher than titers achieved by the wild type strain (305 nkat/ml) and 28% higher than the best mutant used to induce parasexual cycle. Diploid D4 was also less sensitive to carbon catabolite repression by glucose, since xylanolytic activity was detected under conditions normally repressing production by the wild type strain. No decrease in maximal xylanase levels was observed in the presence of glucose for diploid D4.