Laura Lidia Villalba

Obtención de azúcares fermentables a partir de aserrín de pino pretratado secuencialmente con ácido base

The use of lignocellulosic waste constitutes an abundant and inexpensive source; it also offers a solution to the problem of waste disposal. The aim of the study was to evaluate the effect of different conditions of a sequential acid-base pretreatment of pine sawdust, through the release of reducing sugars in the saccharification step. The lignocellulosic material was pretreated in two stages: acid pretreatment (PT1), using sulfuric acid and basic pretreatment (PT2), employing sodium hydroxide at three levels each one: 1, 2 and 3 % in a factorial design. Enzymatic hydrolysis was carried out at 50 oC and 150 rpm in 50 mL vials. Samples were taken at 0.15, 24, 48, 72 and 96 h. The percentage of acid soluble lignin and the concentration of reducing sugars were determined. The optimum level of each factor favoring the highest delignification corresponded to 3 % sulfuric acid and 3 % sodium hydroxide. The production of reducing sugars was not affected by the PT2, but by the PT1, achieving a maximum for level 0 thereof (2 % of sulfuric acid). The sequential acid-base pretreatment was optimized and it was found that this pretreatment improves enzymatic hydrolysis of pine sawdust respect to unpretreated samples. The amount of reducing sugars obtained was comparable to that obtained by other authors.

Screening of new secretory cellulases from different supernatants of white rot fungi from Misiones, Argentina

ABSTRACT Cellulases hydrolyse the cellulose chain into single sugars efficiently. These sugars can be fermented in the bioethanol process, a source of renewable energy. Misiones rainforest is one of the most biodiverse systems on the planet subtropical ecoregions, which is the most probable site to find new fungal strains with potential for degrading cellulose through cellulases. The aim of this work was to find an efficient cellulolytic microorganism through the exploration of native white rot fungi from Misiones. From the qualitative screening 11 fungal strains were selected. The quantitative analysis revealed that the isolated LBM 033 was the best cellulases producer, reaching 57, 226 and 387 U/l of cellobiohydrolase, β-glucosidase and endoglucanase activity, respectively. The zymograms showed that the molecular mass of most of the endoglucanases ranged from 69 to 88 kDa and the molecular mass of most of the cellobiohydrolases was 45 kDa. The search of new cellulases of secretory organisms should lead to an efficient degradation of cellulosic materials, and thus facilitating potential applications in the production of bioenergy from lignocellulosic biomass.

Assessing the ability of white-rot fungi to tolerate polychlorinated biphenyls using predictive mycology

ABSTRACT The aim of the present study was to assess the ability of different white-rot fungi to tolerate polychlorinated biphenyls (PCBs) using predictive mycology, by relating fungal growth inhibition to ligninolityc enzyme secretion. Fungal strains were grown in the presence of PCBs in solid media and their radial growth values were modelled through the Dantigny-logistic like function in order to estimate the time required by the fungal colonies to attain half their maximum diameter. The principal component analysis (PCA) revealed an inverse correlation between strain tolerance to PCBs and the laccase secretion over time, being laccase production closely associated with fungal growth capacity. Finally, a PCA was run to regroup and split between resistant and sensitive fungi. Simultaneously, a function associated with a model predicting the tolerance to PCBs was developed. Some of the assayed isolates showed a promising capacity to be applied in PCB bioremediation. Abbreviations: Polychlorinated biphenyls (PCBs), white-rot fungi (WRF)

Isolation of a laccase-coding gene from the lignin-degrading fungus Phlebia brevispora BAFC 633 and heterologous expression in Pichia pastoris

Isolate and characterize a laccase‐encoding gene (lac I) of Phlebia brevispora BAFC 633, as well as cloning and expressing cDNA of lac I in Pichia pastoris. And to obtain a purified and characterized recombinant laccase to analyse the biotechnological application potential.