Solid-State Fermentation of Chestnut Shells and Effect of Explanatory Variables in Predictive Saccharification Models.

In this study, chestnut shells (CNS), a recalcitrant and low-value agro-industrial waste obtained during the peeling of Castanea sativa fruits, were subjected to solid-state fermentation by six white-rot fungal strains (Irpex lacteus, Ganoderma resinaceum, Phlebia rufa, Bjerkandera adusta and two Trametes isolates). After being fermented, CNS was subjected to hydrolysis by a commercial enzymatic mix to evaluate the effect of fermentation in saccharification yield. After 48 h hydrolysis with 10 CMCase U mL−1 enzymatic mix, CNS fermented with both Trametes strains was recorded with higher saccharification yield (around 253 mg g−1 fermented CNS), representing 25% w/w increase in reducing sugars as compared to non-fermented controls.

Removal pattern of vinasse phenolics by Phlebia rufa, characterization of an induced laccase and inhibition kinetics modeling.

Vinasse from the distillation of winemaking residues is a wastewater characterized by high levels of aromatic compounds. Batch cultures of Phlebia rufa showed a significant (p < 0.05) correlation between laccase activity and initial vinasse concentration.

Pretreatment of Grape Stalks by Fungi: Effect on Bioactive Compounds, Fiber Composition, Saccharification Kinetics and Monosaccharides Ratio.

Grape stalks, an inedible lignocellulosic residue from winemaking and agro-industrial grape juice production, can be valorized as a source of bioactive compounds and as feedstock for the saccharification and bioconversion of soluble sugars. Solid-state fermentation (SSF) by six white-rot fungi was applied as pretreatment. Fiber composition, free radical scavenging activity, four ligninolytic, and three hydrolytic enzyme activities were determined.

A Kinetic Process to Determine the Interaction Type Between Two Compounds, One of Which Is a Reaction Product, Using Alkaline Phosphatase Inhibition as a Case Study.

This study describes the development of a new methodology based on a new integrated equation which allows the determination of the kinetic parameters for two mutually non-exclusive inhibitors when one of which is produced during the time-course reaction. Alkaline phosphatase simultaneously inhibited by phosphate and urea is used to illustrate this methodology, including the evaluation of interaction effects between them. Data analyses were carried out using two integrated velocity equations: exclusive linear mixed inhibition (EMI) and non-exclusive linear mixed inhibition (NEMI).

Fungal biodegradation and multi-level toxicity assessment of vinasse from distillation of winemaking by-products.

The wastewaters from distilleries of winemaking by-products, a scarcely studied type of vinasse, were treated by white-rot fungal strains from species Irpex lacteus, Ganoderma resinaceum, Trametes versicolor, Phlebia rufa and Bjerkandera adusta. The main objectives of this study were to evaluate fungal performance during vinasse biodegradation, their enzyme patterns and ecotoxicity evolution throughout treatment. Despite all strains were able to promote strong (>80%) dephenolization and reduction of total organic carbon (TOC), P.

Mediterranean forested wetlands are yeast hotspots for bioremediation: a case study using azo dyes.

Forested wetlands are interfaces between terrestrial and aquatic environments. These ecosystems play an important role in the hydrology, chemistry and biodiversity maintenance. Despite their high microbial diversity, there has been a lack of attention to the potential of their yeast communities.

Enzyme inhibition studies by integrated Michaelis-Menten equation considering simultaneous presence of two inhibitors when one of them is a reaction product.

To determine initial velocities of enzyme catalyzed reactions without theoretical errors it is necessary to consider the use of the integrated Michaelis-Menten equation. When the reaction product is an inhibitor, this approach is particularly important. Nevertheless, kinetic studies usually involved the evaluation of other inhibitors beyond the reaction product.

Winery wastewater treatment by combination of Cryptococcus laurentii and Fenton's reagent.

Winery wastewaters (WW) have high levels of organic matter, resulting in high COD and BOD and suspended solids. This paper studies the combination of biological and chemical processes in WW treatment. Among 10 yeast isolates, Filobasidium sp.

Utilization of integrated Michaelis-Menten equations for enzyme inhibition diagnosis and determination of kinetic constants using Solver supplement of Microsoft Office Excel.

Enzyme kinetic parameters are usually determined from initial rates nevertheless, laboratory instruments only measure substrate or product concentration versus reaction time (progress curves). To overcome this problem we present a methodology which uses integrated models based on Michaelis-Menten equation. The most severe practical limitation of progress curve analysis occurs when the enzyme shows a loss of activity under the chosen assay conditions.

Influence of ligninolytic enzymes on straw saccharification during fungal pretreatment.

Solid state and submerged fermentations in the presence of white-rot basidiomycetes (Bjerkandera adusta, Fomes fomentarius, Ganoderma resinaceum, Irpex lacteus, Phanerochaete chrysosporium, Trametes versicolor and basidiomycete Euc-1) and the litter-decomposing basidiomycete Lepista nuda were evaluated as a pretreatment to increase enzymatic saccharification of wheat straw. Enzymatic hydrolysis of holocellulose after solid state pretreatment showed a significant (P<0.05) increase of saccharification process for T.

Cellulose hydrolysis by cellobiohydrolase Cel7A shows mixed hyperbolic product inhibition.

In order to establish which are the contribution of linear (total), hyperbolic (partial) or parabolic inhibitions by cellobiose, and also a special case of substrate inhibition, the kinetics of cellobiohydrolase Cel7A obtained from Trichoderma reesei was investigated. Values of kinetic parameters were estimated employing integrated forms of Michaelis-Menten equations through the use of non-linear regression, and criteria for selecting inhibition models are discussed. With cellobiose added at the beginning of the reaction, it was found that cellulose hydrolysis follows a kinetic model, which takes into account a mixed hyperbolic inhibition, by cellobiose with the following parameter values: K (m) 5.

Enzymatic saccharification of biologically pre-treated wheat straw with white-rot fungi.

Wheat straw was submitted to a pre-treatment by the basidiomycetous fungi Euc-1 and Irpex lacteus, aiming to improve the accessibility of cellulose towards enzymatic hydrolysis via previous selective bio-delignification. This allowed the increase of substrate saccharification nearly four and three times while applying the basidiomycetes Euc-1 and I. lacteus, respectively.

Modification of wheat straw lignin by solid state fermentation with white-rot fungi.

The potential of crude enzyme extracts, obtained from solid state cultivation of four white-rot fungi (Trametes versicolor, Bjerkandera adusta, Ganoderma applanatum and Phlebia rufa), was exploited to modify wheat straw cell wall. At different fermentation times, manganese-dependent peroxidase (MnP), lignin peroxidase (LiP), laccase, carboxymethylcellulase (CMCase), avicelase, xylanase and feruloyl esterase activities were screened and the content of lignin as well as hydroxycinnamic acids in fermented straw were determined. All fungi secreted feruloyl esterase while LiP was only detected in crude extracts from B.

Utilization of integrated Michaelis-Menten equation to determine kinetic constants.

Students of biochemistry and related biosciences are urged to solve problems where kinetic parameters are calculated from initial rates obtained at different substrate concentrations. Troubles begin when they go to the laboratory to perform kinetic experiments and realize that usual laboratory instruments do not measure initial rates but only substrate or product concentrations as a function of reaction time. To overcome this problem we present a methodology which uses the integrated form of Michaelis-Menten equation.

Simultaneous ethanol and cellobiose inhibition of cellulose hydrolysis studied with integrated equations assuming constant or variable substrate concentration.

The integrated forms of the Michaelis-Menten equation assuming variable substrate (depletion) or constant substrate concentration were used to study the effect of the simultaneous presence of two exoglucanase Cel7A inhibitors (cellobiose and ethanol) on the kinetics of cellulose hydrolysis. The kinetic parameters obtained, assuming constant substrate (K(m) = 21 mM, Kic = 0.035 mM; K(icl) = 1.

Simulaaneous ethanol and cellobiose inhibition of cellulose hydrolysis studied with integrated equations assuming constant or variable substrate concentration.

The integrated forms of the Michaelis-Menten equation assuming variable substrate (depletion) or constant substrate concentration were used to study the effect of the simultaneous presence of two exoglucanase Cel7A inhibitors (cellobiose and ethanol) on the kinetics of cellulose hydrolysis. The kinetic parameters obtained, assuming constant substrate (K =21 mM, K =0.035 mM; K =1.

Enzymatic kinetic of cellulose hydrolysis: inhibition by ethanol and cellobiose.

The ethanol effect on the Trichoderma reesei cellulases was studied to quantify and clarify this inhibition type. To determine inhibition parameters of crude cellulase and purified exoglucanase Cel7A, integrated Michaelis-Menten equations were used assuming the presence of two inhibitors: cellobiose as the reaction product and ethanol as a possible bioproduct of cellulose fermentation. It was found that hydrolysis of cellulose by crude enzyme follows a model that considers noncompetitive inhibition by ethanol, whereas Cel7A is very slightly competitively inhibited.

Discrimination among eight modified michaelis-menten kinetics models of cellulose hydrolysis with a large range of substrate/enzyme ratios: inhibition by cellobiose.

The kinetics of exoglucanase (Cel7A) from Trichoderma reesei was investigated in the presence of cellobiose and 24 different enzyme/Avicel ratios for 47 h, in order to establish which of the eight available kinetic models best explained the factors involved. The heterogeneous catalysis was studied and the kinetic parameters were estimated employing integrated forms of Michaelis-Menten equations through the use of nonlinear least squares. It was found that cellulose hydrolysis follows a model that takes into account competitive inhibition by cellobiose (final product) with the following parameters: Km = 3.