Penicillium echinulatum secretome analysis reveals the fungi potential for degradation of lignocellulosic biomass

Abstract

BackgroundThe enzymatic degradation of lignocellulosic materials by fungal enzyme systems has been extensively studied due to its effectiveness in the liberation of fermentable sugars for bioethanol production. Recently, variants of the fungus Penicillium echinulatum have been described as a great producer of cellulases and considered a promising strain for the bioethanol industry.ResultsPenicillium echinulatum, wild-type 2HH and its mutant strain S1M29, were grown on four different carbon sources: cellulose, sugar cane bagasse pretreated by steam explosion (SCB), glucose, and glycerol for 120 h. Samples collected at 24, 96, and 120 h were used for enzymatic measurement, and the 96-h one was also used for secretome analysis by 1D-PAGE LC–MS/MS. A total of 165 proteins were identified, and more than one-third of these proteins belong to CAZy families. Glycosyl hydrolases (GH) are the most abundant group, being represented in larger quantities by GH3, 5, 17, 43, and 72. Cellobiohydrolases, endoglucanases, β-glycosidases, xylanases, β-xylosidases, and mannanases were found, and in minor quantities, pectinases, ligninases, and amylases were also found. Swollenin and esterases were also identified.ConclusionsOur study revealed differences in the two strains of P. echinulatum in several aspects in which the mutation improved the production of enzymes related to lignocellulosic biomass deconstruction. Considering the spectral counting analysis, the mutant strain S1M29 was more efficient in the production of enzymes involved in cellulose and hemicellulose degradation, despite having a nearly identical CAZy enzymatic repertoire. Moreover, S1M29 secretes more quantities of protein on SCB than on cellulose, relevant information when considering the production of cellulases using raw materials at low cost. Glucose, and especially glycerol, were used mainly for the production of amylases and ligninases.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-016-0476-3) contains supplementary material, which is available to authorized users.

ETHANOL PRODUCTION FROM SUGAR LIBERATED FROM Pinus SP. AND Eucalyptus SP. BIOMASS PRETREATED BY IONIC LIQUIDS

“…The most widely used microorganism for alcoholic fermentation is Saccharomyces cerevisiae (Alves Jr et al, 2014), due to its ability to hydrolyze sucrose into glucose and fructose, two easily assimilated hexoses. Other yeasts, such as Schizosaccharomyces pombe, have the additional advantage of tolerating high osmotic pressure (large amounts of salts) and high percentage of solids (Sánchez & Cardona, 2008 (Schneider et al, 2016) using S. cerevisiae and S. pombe Y-698 yeasts for alcoholic fermentation.…”

CAZyome and Sugar Transportome Unveil Singular Aspects of the Lignocellulolytic Enzyme System of Penicillium echinulatum 2HH

“…In summary, the CAZyome characterization confirms the natural potential of P. echinulatum 2HH for the production of cellulolytic mixtures. Considering that P. echinulatum 2HH is known to produce a vast range of CAZymes, primarily cellulases and xylanases, previously described by secretome analysis [7]. These results provide an important step in the molecular understanding of this microorganism, allowing strain improvements using advanced techniques and further elevating the importance of the genus Penicillium in biotechnology for biofuels.…”

“…Among the putative cellulases, only EGL1 has been cloned, characterized and heterologous expressed [24]. This characterization showed that EGL1 optimal temperature is 60°C and the optimal activity occurs over a broad pH range (5)(6)(7)(8)(9). Furthermore, the EGL1 secreted by a Pichia pastoris recombinant also showed high thermostability (84% of residual activity after 1h of pre-incubation at 70°C) and calcium exerted a strong stimulatory effect over EGL1 activity [24].…”

“…The isolation method of 2HH strain hypothesizes a potential natural adaptation for the secretion of cellulolytic enzymes, as a possible adaptation to A. punctatum larvae diet as the only growth condition available for the fungus. To date, this evolutionary hypothesis was supported only by the mixture of cellulases secreted by the 2HH strain, which provides an effective enzymatic formulation for complete saccharification of plant residues rich in cellulose and hemicellulose [7]. This hypothesis encourages the search for new insights into the uptake of carbon sources available in the environment.…”

“…P. echinulatum has been studied for about 40 years, since the isolation of the 2HH wild-type. Longterm strain improvements resulted in the S1M29 mutant that yields an expressive increase in cellulase titers and provides a better lignocellulosic biomass hydrolysis [7,8].…”