Secretomas fúngicos como pretratamiento biológico sobre biomasa lignocelulósica de panicum prionitis

Debido a la inminente necesidad de producir y utilizar fuentes de energía renovables, ciertos pastizales naturales como Panicum prionitis, ricos en polisacáridos y con baja eficiencia forrajera, representan una fuente de azúcares fermentables muy interesante para la producción de bioetanol de segunda generación. Sin embargo, la presencia de lignina en sus hojas hace que el proceso de producción requiera de un pretratamiento previo a la sacarificación. Los hongos de la podredumbre blanca de la madera son capaces de degradar los materiales lignocelulósicos, secretando al medio extracelular diversas enzimas involucradas en tal proceso. En base a este criterio, se evaluó la eficiencia de los secretomas de dos especies fúngicas (Pycnoporus sanguineus y Ganoderma applanatum) como agentes de pretratamiento sobre la biomasa de P. prionitis. Los resultados demuestran que el pretratamiento con secretomas fúngicos resulta más eficiente que los tradicionales (pretratamiento químico y con enzimas ligninolíticas comerciales), permitiendo hidrolizar hasta un 47,5% de la celulosa en el caso de G. applanatum. Ensayos de cromatografía líquida acoplada a espectrometría de masas permitieron la identificación de una gran cantidad de proteínas en los secretomas, revelando que el 34% y el 42% de ellas se encuentran involucradas en los procesos de degradación de la biomasa lignocelulósica para G. applanatum y P. sanguineus, respectivamenteFil: Gauna, Albertina . Universidad Nacional de RosarioFil: Feldman, Susana R.. Universidad Nacional de RosarioFil: Larran, Alvaro S.. Universidad Nacional de RosarioFil: Permingeat, Hugo R.. Universidad Nacional de RosarioFil: Perotti, Valeria E.. Universidad Nacional de Rosari

OsttaSBEIII expression alters granule size and increases starch levels and its degradability in Arabidopsis

The physicochemical properties of starches from different botanical origin, such as viscosity, gelatinization temperature, solubility and degradability depend on the amylose/amylopectin ratio and the length and frequency of the α-1,6-glycosidic bonds in amylopectin. These branches depend on the action of the starch branching enzymes (SBEs), which are highly structurally conserved in plants. We recently identified a novel gene from Ostreococcus tauri (OsttaSBEIII) which codes for a protein showing starch branching activity (OsttaSBEIII) and with a different structure than other known SBEs from plants, containing two in-tandem carbohydrate binding modules (CBM41-CBM48) at its N-terminus. OsttaSBEIII overexpression in A. thaliana plants resulted in a higher starch content and smaller granules with an increased degradability. OEOsttaSBE lines showed also an increase in the expression and activity of starch degradative enzymes and a higher content of glucose and inorganic phosphate, which suggests a remodeling of the granule structure in response to the expression of OsttaSBEIII. These results allow us to propose the use of OsttaSBEIII as a new strategy to obtain starches with greater degradability that would be useful for different biotechnological applications

Streptomyces thermoautotrophicus does not fix nitrogen

Streptomyces thermoautotrophicus UBT1 has been described as a moderately thermophilic chemolithoautotroph with a novel nitrogenase enzyme that is oxygen-insensitive. We have cultured the UBT1 strain, and have isolated two new strains (H1 and P1-2) of very similar phenotypic and genetic characters. These strains show minimal growth on ammonium-free media, and fail to incorporate isotopically labeled N2 gas into biomass in multiple independent assays. The sdn genes previously published as the putative nitrogenase of S. thermoautotrophicus have little similarity to anything found in draft genome sequences, published here, for strains H1 and UBT1, but share >99% nucleotide identity with genes from Hydrogenibacillus schlegelii, a draft genome for which is also presented here. H. schlegelii similarly lacks nitrogenase genes and is a non-diazotroph. We propose reclassification of the species containing strains UBT1, H1, and P1-2 as a non-Streptomycete, non-diazotrophic, facultative chemolithoautotroph and conclude that the existence of the previously proposed oxygen-tolerant nitrogenase is extremely unlikely