Cellulose loading and water sorption value as important parameters for the enzymatic hydrolysis of cellulose

The enzymatic hydrolysis of cotton raw cellulose (RC) samples, sieved RC samples through meshes <100 (CS1), 100–200 (C12), 200–400 (C24), mercerized RC samples (M-C), freeze-dried RC (RC-FD) samples, microcrystalline cellulose Avicel, bacterial cellulose (BC), raw sisal pulp and mercerized sisal pulp (S-M) was performed at cellulose-to-cellulase mass ratios of 1,000:1, 699:1, 400:1, 100:1 and 10:1. The index of crystallinity and water sorption values were quantified for all samples. The morphological features were analyzed by means of scanning electron microscopy (SEM). For cellulose-to-cellulase mass ratio of 100:1 and 10:1, the maximum hydrolysis extents of cellulose samples after 24 h reaction could not be correlated with their physical characteristics. However, hydrolyses of samples with large water sorption values were faster than those with lower water sorption values. The hydrolysis efficiency decreased when the cellulose-to-cellulase mass ratio was greater than 400:1; under this condition a remarkable dependence of the hydrolysis yield on the type of cellulosic sample was observed. The water sorption ability could be directly correlated with the hydrolysis extent, except for RC-FD and BC samples, which presented the lowest values. In the former, freeze-drying has led to pore collapse, with concomitant reduction of the amount of adsorbed water. For the latter sample, the densely packed structure made the water sorption slower than in all other samples. Despite of this fact, the presence of nanofibrils on the surface of BC (as detected by SEM) improved the enzyme adsorption, indicating that analysis by complementary techniques should be performed in order to predict the enzymatic hydrolysis efficiency.     

Biodiesel Production from Integration Between Reaction and Separation System: Reactive Distillation Process

Biodiesel is a clean burning fuel derived from a renewable feedstock such as vegetable oil or animal fat. It is biodegradable, non-inflammable, non-toxic, and produces lesser carbon monoxide, sulfur dioxide, and unburned hydrocarbons than petroleum-based fuel. The purpose of the present work is to present an efficient process using reactive distillation columns applied to biodiesel production. Reactive distillation is the simultaneous implementation of reaction and separation within a single unit of column. Nowadays, it is appropriately called “Intensified Process”. This combined operation is especially suited for the chemical reaction limited by equilibrium constraints, since one or more of the products of the reaction are continuously separated from the reactants. This work presents the biodiesel production from soybean oil and bioethanol by reactive distillation. Different variables affect the conventional biodiesel production process such as: catalyst concentration, reaction temperature, level of agitation, ethanol/soybean oil molar ratio, reaction time, and raw material type. In this study, the experimental design was used to optimize the following process variables: the catalyst concentration (from 0.5 wt.% to 1.5 wt.%), the ethanol/soybean oil molar ratio (from 3:1 to 9:1). The reactive column reflux rate was 83 ml/min, and the reaction time was 6 min.     

Alkane Activation over Acidic Zeolites: The First Step

The heterogeneous acid‐catalyzed activation step of alkanes leading to the reaction intermediates (carbocationic or alkoxy species) was up to now the matter of a longstanding controversy. Gas chromatography and online mass spectroscopy measurements show that H₂ and methane are formed over H‐zeolites, whereas HD and CH₃D are formed over D‐zeolites as the primary products in the reaction with isobutane. These results indicate that σ‐bond protolysis by strong acid sites is the first step for hydrocarbon activation on these catalysts at mild temperatures (473 K), in analogy to the activation path occurring in liquid superacid media.     

UV spectrophotometric determination of bioflavonoids from a semisolid pharmaceutical dosage form containing Trichilia catigua Adr. Juss and Ptychopetalum olacoides Bentham standardized extract: analytical method validation and statistical procedures

A precise, accurate, and sensitive UV spectrophotometric method was developed and validated for routine quantification of total bioflavonoids, expressed as rutin, from a topical oil-in-water pharmaceutical emulsion containing the extract of Trichilia catigua Adr. Juss and Ptychopetalum olacoides Bentham. The method was validated experimentally, and the data were treated rigorously by statistical analysis. The following analytical parameters were assessed: linearity, specificity, intra- and interrun precision measured as relative standard deviation (RSD, %), intra- and interrun accuracy (E, %), recovery (Rec., %), limit of detection (LOD, microg/mL), and limit of quantification (LOQ, microg/mL). The UV spectrophotometric method was linear (r = 0.9995) for standard rutin over the concentration range of 5.0-15.0 microg/mL with specificity for total bioflavonoids (expressed as rutin) at 361.0 nm with an absence of interferents from the complex matrix; RSD of < or = 1.79%, intrarun (E = 97.88 +/- 1.75 to 99.0 +/- 0.33%) and interrun (E = 98.38 +/- 1.12 to 100.79 +/- 1.30%) accuracy; Rec. = 98.64 +/- 0.42 to 100.74 +/- 0.41%; LOD = 0.20 microg/mL; and LOQ = 0.30 microg/mL.     

Post-irradiation time effects on the graft of poly(ethylene-alt-tetrafluoroethylene) (ETFE) films for ion exchange membrane application

Grafting of styrene followed by sulfonation onto poly(ethylene-alt-tetrafluoroethylene) (ETFE) was studied for synthesis of ion exchange membranes. Radiation-induced grafting of styrene onto ETFE films was investigated after simultaneous irradiation (in post-irradiation condition) using a ⁶⁰Co source. The ETFE films were irradiated at 20 kGy dose at room temperature and chemical changes were monitored after contact with styrene for grafting. The post-irradiation time was established at 14 days when the films were remained in styrene/toluene 1:1 v/v. After this period the grafting degree was evaluated in the samples. The grafted films were sulfonated using chlorosulfonic acid and 1, 2-dichloroethane 20:80 (v/v) at room temperature for 5 h. The membranes were analyzed by infrared spectroscopy (FTIR), differential scanning calorimeter (DSC), thermogravimetric measurements (TG) and degree of grafting (DOG). The ion exchange capacity (IEC) of membranes was determined by acid–base titration and the values for ETFE membranes were achieved higher than Nafion^® films. Preliminary single cell performance was made using pure H₂ and O₂ as reactants at a cell temperature of 80 °C and atmospheric gas pressure. The fuel cell performance of ETFE films was satisfactory when compared to state-of-art Nafion^® membranes.     

Dynamics and Control Strategies for a Butanol Fermentation Process

In this work, mathematical modeling was employed to assess the dynamic behavior of the flash fermentation process for the production of butanol. This process consists of three interconnected units as follows: fermentor, cell retention system (tangential microfiltration), and vacuum flash vessel (responsible for the continuous recovery of butanol from the broth). Based on the study of the dynamics of the process, suitable feedback control strategies [single input/single output (SISO) and multiple input/multiple output (MIMO)] were elaborated to deal with disturbances related to the process. The regulatory control consisted of keeping sugar and/or butanol concentrations in the fermentor constant in the face of disturbances in the feed substrate concentration. Another objective was the maintenance of the proper operation of the flash tank (maintenance of the thermodynamic equilibrium of the liquid and vapor phases) considering that oscillations in the temperature in the tank are expected. The servo control consisted of changes in concentration set points. The performance of an advanced controller, the dynamic matrix control, and the classical proportional-integral controller was evaluated. Both controllers were able to regulate the operating conditions in order to accommodate the perturbations with the lowest possible alterations in the process outputs. However, the performance of the PI controller was superior because it showed quicker responses without oscillations.     

Electroanalytical determination of eugenol in clove oil by voltammetry of immobilized microdroplets

Journal of Solid State Electrochemistry - The determination of eugenol employing voltammetry of immobilized microdroplets (VIM) is reported in this work. The construction of the electrode was based...     

Quality system implementation in a Brazilian university laboratory

The introduction of quality systems in laboratories at universities is a difficult task. Test services for external customers are provided to generate additional budget, and there may be a clear awareness about the need for systematic QA/QC actions. However, offering services is not of the highest priority within most university environments. The staff performance is commonly evaluated on basis of published papers and teaching activities, giving little or no weight for the test services. Therefore, implementation of a quality system is often pushed back to a lower priority leading to postponement. The efforts for creating a quality system in a laboratory from a Brazilian university are described in this paper, along with the results produced.