Viridiana Santana Ferreira-Leitão

Structural evaluation of sugar cane bagasse steam pretreated in the presence of CO2 and SO2.

BackgroundPrevious studies on the use of SO2 and CO2 as impregnating agent for sugar cane bagasse steam treatment showed comparative and promising results concerning the cellulose enzymatic hydrolysis and the low formation of the inhibitors furfural and hydroxymethylfurfural for the use of CO2 at 205°C/15 min or SO2 at 190°C/5 min. In the present study sugar cane bagasse materials pretreated as aforementioned were analyzed by scanning and transmission electron microscopy (SEM and TEM), X-Ray Diffraction (XRD) and Infrared (FTIR spectroscopy) aiming a better understanding of the structural and chemical changes undergone by the pretreated materials.ResultsSEM and TEM data showed that the structural modifications undergone by the pretreatment with CO2 were less pronounced in comparison to that using SO2, which can be directly related to the combined severity of each pretreatment. According to XRD data, untreated bagasse showed, as expected, a lower crystallinity index (CI = 48.0%) when compared to pretreated samples with SO2 (CI = 65.5%) or CO2 (CI = 56.4%), due to the hemicellulose removal of 68.3% and 40.5%, respectively. FTIR spectroscopy supported SEM, TEM and XRD results, revealing a more extensive action of SO2.ConclusionsThe SEM, TEM, XRD and FTIR spectroscopy techniques used in this work contributed to structural and chemical analysis of the untreated and pretreated bagasse. The images from SEM and TEM can be related to the severity of SO2 pretreatment, which is almost twice higher. The crystallinity index values obtained from XRD showed that pretreated materials have higher values when compared with untreated material, due to the partial removal of hemicellulose after pretreatment. FTIR spectroscopy supported SEM, TEM and XRD results. CO2 can actually be used as impregnating agent for steam pretreatment, although the present study confirmed a more extensive action of SO2.

An approach to the utilisation of CO2 as impregnating agent in steam pretreatment of sugar cane bagasse and leaves for ethanol production

BackgroundThe conditions for steam pretreatment of sugar cane bagasse and leaves were studied using CO2 as an impregnating agent. The following conditions were investigated: time (5 to 15 min) and temperature (190 to 220°C). The pretreatment was assessed in terms of glucose and xylose yields after enzymatic hydrolysis and inhibitor formation (furfural and hydroxymethylfurfural) in the pretreatment. Results from pretreatment using SO2 as impregnating agent was used as reference.ResultsFor sugar cane bagasse, the highest glucose yield (86.6% of theoretical) was obtained after pretreatment at 205°C for 15 min. For sugar cane leaves the highest glucose yield (97.2% of theoretical) was obtained after pretreatment at 220°C for 5 min. The reference pretreatment, using impregnation with SO2 and performed at 190°C for 5 min, resulted in an overall glucose yield of 79.7% and 91.9% for bagasse and leaves, respectively.ConclusionsComparable pretreatment performance was obtained with CO2 as compared to when SO2 is used, although higher temperature and pressure were needed. The results are encouraging as some characteristics of CO2 are very attractive, such as high availability, low cost, low toxicity, low corrosivity and low occupational risk.

Amino acids interference on the quantification of reducing sugars by the 3,5-dinitrosalicylic acid assay mislead carbohydrase activity measurements

This study evaluated the interference of the amino acids tryptophan, cysteine, histidine, tyrosine, hydroxyproline, leucine, proline, serine, glycine, valine, glutamic acid, phenylalanine, and methionine on the measurement of reducing sugars using a phenol-free 3,5-dinitrosalicylic acid (DNS) reagent. It was found that in reaction mixtures containing 20mM of either tryptophan, cysteine, histidine, tyrosine, or hydroxyproline the measurement of 3.7 mM glucose was overestimated by 76%, 50%, 35%, 18%, and 10%, respectively. The amino acids valine, glutamic acid, and phenylalanine did not affect the DNS reaction, while methionine decreased the color development by 5%. The measurement of glucose, xylose, arabinose, and cellobiose at the 3.7-12.4 mM range in the presence of 20 mM cysteine resulted in an overestimated concentration of 34.8-50%. Enzymatic assays for measuring xylanolytic and filter paper activity (FPAse) were conducted in the presence of 20-60 mM cysteine, and compared to cysteine-free assays. In the presence of cysteine, the measured xylanase activity increased threefold and the FPAse activity increased twofold due to the overestimation of the reducing sugar concentrations in the assays. The interference from cysteine was reduced to a maximum of 8.6% when a DNS reagent containing phenol was used.

Methylene blue and azure B oxidation by horseradish peroxidase: a comparative evaluation of class II and class III peroxidases

We have previously shown that the oxidation of methylene blue (MB) or azure B (AB) by Phanerochaete chrysosporium lignin peroxidase (LiP) (class II) occurs via stepwise N-demethylations followed by aromatic ring cleavage under selective reaction conditions related to methylene blue:H2O2 or azure B:H2O2 stoichiometry. In this work, we compare the oxidation of the same dyes by horseradish peroxidase (HRP) of plant origin (class III) and compare LiP and HRP reactions and products. Results show HRP is able to N-demethylate both dyes, but exhibits much slower reaction kinetics than LiP and requires higher H2O2 concentrations. Product yields are also different for HRP, and contrary to LiP, HRP is unable to achieve aromatic ring cleavage. Azure C (AC), which is formed by sequential oxidation of either MB or AB, was a major reaction product in HRP-mediated reactions. Yields of AC up to 60% were obtained, suggesting a potential enzymatic route for AC production that compares quite favorably to the chemical route yield of 35%.

The Use of HRP in Decolorization of Reactive Dyes and Toxicological Evaluation of Their Products

This work studied the potential use of horseradish peroxidase (HRP) in the decolorization of the following textile dyes: Drimarene Blue X-3LR (DMBLR), Drimarene Blue X-BLN (DMBBLN), Drimarene Rubinol X-3LR (DMR), and Drimarene Blue CL-R (RBBR). Dyes were individually tested in the reaction media containing 120 mg·L−1, considering the following parameters: temperature (20–45°C), H2O2 concentration (0–4.44 mmol·L−1), and reaction time (5 minutes, 1 and 24 h). The following conditions: 35°C, 0.55 mmol·L−1, and 1h, provided the best set of results of color removal for DMBLR (99%), DMBBLN (77%), DMR (94%), and RBBR (97%). It should be mentioned that only 5 minutes of reaction was enough to obtain 96% of decolorization for DMBLR and RBBR. After the decolorization reactions of DMBLR, DMR, and RBBR, it was possible to observe the reduction of Artemia salina mortality and the no significant increase in toxicity for the products generated from DMBBLN.

Extraction and Application of Laccases from Shimeji Mushrooms (Pleurotus ostreatus) Residues in Decolourisation of Reactive Dyes and a Comparative Study Using Commercial Laccase from Aspergillus oryzae

Oxidases are able to degrade organic pollutants; however, high costs associated with biocatalysts production still hinder their use in environmental biocatalysis. Our study compared the action of a commercial laccase from Aspergillus oryzae and a rich extract from Pleurotus ostreatus cultivation residues in decolourisation of reactive dyes: Drimaren Blue X-3LR (DMBLR), Drimaren Blue X-BLN (DMBBLN), Drimaren Rubinol X-3LR (DMR), and Drimaren Blue C-R (RBBR). The colour removal was evaluated by considering dye concentration, reaction time, absence or presence of the mediator ABTS (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid), and the source of laccase. The presence of ABTS was essential for decolourisation of DMR (80–90%, 1 h) and RBBR (80–90%, 24 h) with both laccases. The use of ABTS was not necessary in reactions containing DMBLR (85–97%, 1 h) and DMBBLN (63–84%, 24 h). The decolourisation of DMBBLN by commercial laccase showed levels near 60% while the crude extract presented 80% in 24 h.

Comparative Response and Structural Characterization of Sugarcane Bagasse, Straw and Bagasse-Straw 1:1 Mixtures Subjected To Hydrothermal Pretreatment and Enzymatic Conversion

The change of manually harvested sugarcane, after crop burning, to mechanically harvest green cane allows straw and bagasse to be available for further processing via either chemical or biochemical routes, which increases the sector’s energy efficiency. In this study, sugarcane bagasse, straw and a bagasse-straw 1:1 mixture were subjected, under comparative conditions, to hydrothermal pretreatment at 195°C for 10 minutes and to enzymatic conversion. We evaluated the individual responses of the three different materials regarding the effect of the pretreatment on hemicellulose and lignin extraction, the formation of furfural and hydroxymethylfurfural and cellulose enzymatic digestibility. The morphological, chemical and physical properties of the raw and pretreated materials were analyzed by Scanning Electron Microscopy (SEM), infrared spectroscopy (FTIR) and X-ray Diffraction (XRD). We observed a higher hemicellulose extraction from straw (93.3%) in comparison to bagasse (83.7%), and the hemicellulose extract that was obtained from straw contained a higher concentration of inhibitors. Intermediate values for hemicellulose extraction (88.5%) and inhibitor formation were observed for the bagasse-straw 1:1 mixture. The cellulose enzymatic hydrolysis yield was higher for straw (90.5%) in comparison to bagasse (68.2%), whereas an intermediate yield of 73.3% was observed for the mixture. According to the SEM images, the pretreatment altered the native biomass at the level of the structure of the cell wall, and consequently, the arrangement of the macromolecular components of the cell wall was closely related to the high degree of hemicellulose removal. FTIR data indicated chemical changes mostly in OH, OCH3 and C=O groups; these changes were most noticeable in the pretreated straw. Adjusted data for the crystallinity index suggested that the pretreated materials had decreased crystallinity. All of the results showed that straw had a lower recalcitrance.

Optimization of biohydrogen yield produced by bacterial consortia using residual glycerin from biodiesel production

The aims of this study were to simplify the fermentation medium and to optimize the conditions of dark fermentation of residual glycerin to produce biohydrogen. It was possible to remove all micronutrients of fermentation medium and improve biohydrogen production by applying residual glycerin as feedstock. After statistical analysis of the following parameters pH, glycerin concentration and volatile suspended solids, the values of 5.5; 0.5g.L(-1) and 8.7g.L(-1), respectively, were defined as optimum condition for this process. It generated 2.44molH2/molglycerin, an expressive result when compared to previous results reported in literature and considering that theoretical yield of H2 from glycerol in dark fermentation process is 3molH2/molglycerol. This study allowed the improvement of yield and productivity by 68% and 67%, respectively.

Produção de hidrogênio via fermentação anaeróbia - aspectos gerais e possibilidade de utilização de resíduos agroindustriais brasileiros

Biological production of hydrogen through anaerobic fermentation has received increasing attention and offers a great potential as an alternative process for clean fuel production in the future. Considering biological systems for H2 production, anaerobic fermentation stands out, primarily due to its higher production of H2 compared with other biological processes. In addition the possibility of using different agro-industrial wastes as substrates opens up infinite possibilities. The development and implementation of sustainable processes for converting renewable materials into different value-added products is essential for the full exploitation of Brazilian agro-industrial wastes.

Monitoring of atrazine biodegradation by Pleurotus ostreatus INCQS 40310 through the simultaneous analysis of atrazine and its derivatives by HPLC

Abstract Atrazine is a widely used herbicide on crops of major economic relevance such as corn and sugarcane. The widespread use of this herbicide could result in its accumulation in, or contamination of environmental niches. It is important to emphasize that not only atrazine but also its derivatives should be monitored. The aim of this study was to develop an appropriate methodology for simultaneous separation of atrazine (ATZ) and its derivatives, desethylatrazine (DEA), deisopropylatrazine (DIA), hydroxyatrazine (HA), desethyldeisopropylatrazine (DEDIA), desethylhydroxyatrazine (DEHA), and deisopropylhydroxyatrazine (DIHA) using high-performance liquid chromatography (HPLC). HPLC analyses were performed under gradient elution mode using a Shim-pack VP ODS C18 (250 × 4.6 mm, 4.6 μm) column, 5 mmol.L− 1 of sodium phosphate buffer (pH 7.2) and acetonitrile as the mobile phase at a flow rate of 1 mL.min− 1 and 25°C. Detection was monitored at 221 nm. Some validation parameters, such as selectivity, linearity, precision, accuracy, limit of detection and limit of quantification were evaluated for analyses of atrazine, DEA, and DEDIA. The method was successfully applied to the detection of DEA and DIA, the main degradation products observed after 15 days of incubation in the presence of Pleurotus ostreatus INCQS 40310. The formation of DEA and DIA was unequivocally confirmed by GC-MS.