Secretome characterization of the lignocellulose-degrading fungi Pycnoporus sanguineus and Ganoderma resinaceum growing on Panicum prionitis biomass.

C4 grasses are common species in rangelands around the world and represent an attractive option for second-generation biofuel production. Although they display high polysaccharide content and reach great levels of biomass accumulation, there is a major technical issue to be addressed before they can be used for bioethanol industrial production: lignin removal. Concerning this, Pycnoporus and Ganoderma fungal genera have been highlighted due to their ability to hydrolyze lignocellulose in biological pretreatments. Our goals here were to evaluate the pretreatment efficiency using the secretome of species from Pycnoporus and Ganoderma spp. harvested from a glucose-free inductive medium (using a C4 grass) and to identify the fungal enzymatic activities responsible for the lignin degradation and glucose release. Our results show that P. sanguineus secretome exhibits a higher activity of lignocellulolytic enzymes such as cellulases, xylanases, laccases, and manganese peroxidases compared with that from G. resinaceum. Interestingly, zymograms in the presence of 2 M glucose suggest that a ß-glucosidase isoform from P. sanguineus could be glucose tolerant. The proteomic approach carried out allowed the identification of 73 and 180 different proteins in G. resinaceum and P. sanguineus secretomes, respectively, which were functionally classified in five main categories and a miscellaneous group. These results open new avenues for future experimental work that lead to a deeper comprehension and a greater application of the mechanisms underlying lignocellulosic biomass degradation.

Evaluation of biological pretreatments to increase the efficiency of the saccharification process using Spartina argentinensis as a biomass resource.

Second generation bioethanol obtained from native perennial grasses offers a promising alternative for biofuel production, avoiding land use competition for crops production. Spartina argentinensis is a native perennial C4 grass with high photosynthetic rates, well adapted to halo-hydromorphic soils, though its forage quality (palatability and digestibility) for livestock is quite low due to its high lignin content. Hence, cattle raisers burn these grasslands frequently in order to stimulate the emergence of new leaves with higher digestibility for cattle feeding. Lignin is the main barrier to overcome in order to efficiently hydrolyze the cellulose for bioethanol production. In this work, we evaluate different pretreatments (phosphoric acid, ligninolytic enzymes and fungal supernatants) aimed to remove lignin and improving cellulose hydrolysis efficiency. Results show that pretreatment with Pycnoporus sanguineus supernatant improves fermentable carbohydrates availability, compared with a conventional chemical pretreatment, and that 56.84% of cellulose can be hydrolyzed using this pretreatment.

Growth, nutrient status, and photosynthetic response to diesel-contaminated soil of a cordgrass, Spartina argentinensis.

The present study was conduced to investigate the tolerance limits of Spartina argentinensis, which occurs in inland marshes of the Chaco-Pampean regions of Argentina, to diesel-contaminated soil. A glasshouse experiment was designed to investigate the effect of diesel fuel from 0% to 3% on growth and photosynthetic apparatus of S. densiflora by measuring gas exchange and photosynthetic pigments. We also performed chemical analysis of plant samples, and determined mycorrhizal index. Tiller and root biomasses declined with increasing diesel fuel concentration, as well as photosynthetic rate (A). Reductions in A could be accounted for by non-stomatal limitations. Mycorrhizal roots of S. argentinensis were reduced by the presence of diesel fuel, but did not affect its nutritional status; in fact, most element concentrations increased with diesel contamination. Despite the negative effect of diesel-contaminated soil, S. argentinensis continued growing, which could be useful management options for phytorremediation of diesel-contaminated soils.

Accumulation and tolerance characteristics of chromium in a cordgrass Cr-hyperaccumulator, Spartina argentinensis.

The cordgrass Spartina argentinensis, which occurs in inland marshes of the Chaco-Pampean regions of Argentina, has been found to be a new chromium hyperaccumulator. A glasshouse experiment was designed to investigate the effect of Cr(6+) from 0 to 20 mmol l(-1) on growth and photosynthetic apparatus of S. argentinensis by measuring chlorophyll fluorescence parameters, gas exchange and photosynthetic pigment concentrations. Boron, calcium, chromium, copper, iron, manganese, magnesium, potassium and phosphorous concentrations were also determined. S. argentinensis showed phytotoxicity at tiller concentration of 4 mg g(-1) Cr, and symptoms of stress at tiller concentration of 1.5 mg g(-1) Cr, as well as reductions in leaf gas exchange, in chlorophyll a fluorescence parameters, in photosynthetic pigment contents and in the uptake of essential nutrients. Reductions in net photosynthetic rate could be accounted for by non-stomatal limitations. Moreover, the bioaccumulator factors exceeded greatly the critical value (1.0) for all Cr treatments, and the transport factors indicated that this species has a higher ability to transfer Cr from roots to tillers at higher Cr concentrations. These results confirmed that S. argentinensis is a chromium hyperaccumulator and that it may be useful for restoring Cr-contaminated sites.

Análisis discriminante de una comunidad halófila con distintas historias de fuego / Discriminant analysis of a halophylous community with different fire histories / Análise discriminante de uma comunidade halófila com distintas histórias de fogo

Los espartillares de Spartina argentinensis (Provincia de Santa Fe, Argentina) se encuentran en suelos salinos pobremente drenados y con frecuencia sufren incendios. En estudios previos se observó que parcelas con distintas historias de fuego se agrupaban de acuerdo a este factor en función de la abundancia-cobertura de las especies presentes. El objeto de este trabajo fue analizar a qué especies respondían estos agrupamientos, para lo cual se usó análisis discriminante. Se utilizaron los datos de abundancia-cobertura de la Reserva Federico Wildermuth (Santa Fe), en parcelas quemadas y sin quemar, la mitad de las cuales se volvieron a quemar en agosto de 1999, con datos de tres años: 1998: A (quemada en 1996) y D (nunca quemada); 1999 y 2000: A; B (quemada en 1996 y 1999); C (quemada solo en 1999) y D. En 1998, la función discriminante incluyó a 13 de las 38 especies presentes, siendo Melilotus alba, Iresine difusa, Distichlis spicata y S. argentinensis las de mayor peso. Las variables que quedaron en la función en 1999, 16 sobre un total de 57, fueron S. argentinensis, Heliotroppium curassavicum, M. alba, Chloris cicliata, C. gayana, Apium leptophillum, y Pluchea saggitalis, mientras que en el 2000, 16 dentro de 68 especies incluyeron a I. difusa, Salicornia ambigua, Phyla canescens, Pluchea saggitalis y M. alba. A relativo corto plazo, el sistema tiende a igualarse al original sin perturbación por fuego.

The "espartillares" of Spartina argentinensis (Santa Fe province, Argentina) thrive on saline poorly drained soils with frequent natural or man-made fires. Previous data showed that plots with different fire histories were clustered according to fire and the cover-abundance of the species of the community. Our aim was to analyze which species were responsible of the clustering using discriminant analysis of cover-abundance data of burnt and non burnt plots of the Federico Wildermuth Reserve: (A) burned in July 1996, (B) burned in July 1996 and August 1999, (C) burned in August 1999, and (D) never burned. In 1998, the discriminant function included 13 out of 38 species, being Melilotus alba, Iresine difusa, Distichlis spicata y S. argentinensis the most important. S. argentinensis, Heliotroppium curassavicum, M. alba, Chloris cicliata, C. gayana, Apium leptophillum, and Pluchea saggitalis were the most important variables (16 out of 57 species) in 1999 while in 2000 I. difusa, Salicornia ambigua, Phyla canescens, Pluchea saggitalis and M. alba were considered by the function (16 out of 68 species). The effect of fire on the "espartillar" was not long-lasting and burned and non-burned plots are much alike a few years after.

Os prados de capim marinho Spartina argentinensis (província de Santa Fe, Argentina) se encontram em solos salinos pobremente drenados e com frequência sofrem incêndios. Em estudos prévios foi observado que parcelas com distintas histórias de fogo se agrupavam de acordo a este fator em função da abundância-cobertura das espécies presentes. O objeto de este trabalho foi analisar quais as espécies a que respondiam estes agrupamentos, para o qual foi usada a análise discriminante. Utilizaram-se os dados de abundância-cobertura da Reserva Federico Wildermuth (Santa Fe), em parcelas queimadas e sem queimar, a metade das quais se voltaram a ser queimadas em agosto de 1999, com dados de três anos: 1998: A (queimada em 1996) e D (nunca queimada); 1999 e 2000: A; B (queimada em 1996 e 1999); C (queimada somente em 1999) e D. Em 1998, a função discriminante incluiu 13 das 38 espécies presentes, sendo Melilotus alba, Iresine difusa, Distichlis spicata e S. argentinensis as de maior peso. As variáveis que ficaram na função em 1999, 16 de um total de 57, foram S. argentinensis, Heliotroppium curassavicum, M. alba, Chloris cicliata, C. gayana, Apium leptophillum, e Pluchea saggitalis, enquanto que em 2000, 16 de 68 espécies incluiram a I. difusa, Salicornia ambigua, Phyla canescens, Pluchea saggitalis e M. alba. Em relativo curto prazo, o sistema tende a se igualar ao original sem perturbação por fogo.