Jorge A. Mendoza-Pérez

Shrinkage and Deformation of Agave atrovirens Karw Tissue during Convective Drying: Influence of Structural Arrangements

The influence of structural arrangements of Agave discs cut transversally (ADCT) and longitudinally (ADCL) on moisture loss, shrinkage, and shape was evaluated during convective drying by physical and image parameters. ADCT showed lower drying and shrinkage rates than ADCL. The fractal exponent (d) relating volume and thickness of samples rose from 1.552 ± 0.126 to 2.394 ± 0.128 and from 1.662 ± 0.111 to 1.848 ± 0.070 for ADCT and ADCL, respectively, which indicates that shrinkage was nonisotropic for both cases. Parameters considered for evaluating the changes of size and shape of Agave discs at macro- and microscopic levels during drying were projected area (PA), major length (ML), shape factor (SF), and fractal dimension of contour (FDC). The values obtained for these parameters demonstrated that changes in shrinkage and shape of both samples were dependent on structural arrangements of the samples. During the drying of ADCT samples, which have short and rigid structures, pronounced creasing was observed compared to ADCL materials, which are mainly formed by long and rigid structures. Also, it was observed that orientation of fibers influenced shrinkage and deformation.

Sequential enzymatic saccharification and fermentation of ionic liquid and organosolv pretreated agave bagasse for ethanol production

Agave bagasse (AGB) has gained recognition as a drought-tolerant biofuel feedstock with high productivity in semiarid regions. A comparative analysis of ionic liquid (IL) and organosolv (OV) pretreatment technologies in AGB was performed using a sequential enzymatic saccharification and fermentation (SESF) strategy with cellulolytic enzymes and the ethanologenic Escherichia coli strain MS04. After pretreatment, 86% of xylan and 45% of lignin were removed from OV-AGB, whereas IL-AGB reduced lignin content by 28% and xylan by 50% when compared to the untreated biomass. High glucan (>90%) and xylan (>83%) conversion was obtained with both pretreated samples. During the fermentation stage (48h), 12.1 and 12.7kg of ethanol were produced per 100kg of untreated AGB for IL and OV, respectively. These comparative analyses showed the advantages of SESF using IL and OV in a biorefinery configuration where a better understanding of AGB recalcitrance is key for future applications.

Optimization of Alkaline and Dilute Acid Pretreatment of Agave Bagasse by Response Surface Methodology

Utilization of lignocellulosic materials for the production of value-added chemicals or biofuels generally requires a pretreatment process to overcome the recalcitrance of the plant biomass for further enzymatic hydrolysis and fermentation stages. Two of the most employed pretreatment processes are the ones that used dilute acid (DA) and alkaline (AL) catalyst providing specific effects on the physicochemical structure of the biomass, such as high xylan and lignin removal for DA and AL, respectively. Another important effect that need to be studied is the use of a high solids pretreatment (≥15%) since offers many advantaged over lower solids loadings, including increased sugar and ethanol concentrations (in combination with a high solids saccharification), which will be reflected in lower capital costs; however, this data is currently limited. In this study, several variables, such as catalyst loading, retention time, and solids loading, were studied using response surface methodology (RSM) based on a factorial central composite design of DA and AL pretreatment on agave bagasse using a range of solids from 3 to 30% (w/w) to obtain optimal process conditions for each pretreatment. Subsequently enzymatic hydrolysis was performed using Novozymes Cellic CTec2 and HTec2 presented as total reducing sugar (TRS) yield. Pretreated biomass was characterized by wet-chemistry techniques and selected samples were analyzed by calorimetric techniques, and scanning electron/confocal fluorescent microscopy. RSM was also used to optimize the pretreatment conditions for maximum TRS yield. The optimum conditions were determined for AL pretreatment: 1.87% NaOH concentration, 50.3 min and 13.1% solids loading, whereas DA pretreatment: 2.1% acid concentration, 33.8 min and 8.5% solids loading.

Investigation on the Protective Effects of Cranberry Against the DNA Damage Induced by Benzo[a]pyrene

There are few reports that demonstrate the antigenotoxic potential of cranberries. Although the types of berry fruits consumed worldwide are many, this paper focuses on cranberries that are commonly consumed in Mexico (Vaccinium macrocarpon species). The purpose of the present study is to determine whether cranberry ethanolic extract (CEE) can prevent the DNA damage produced by benzo[a]pyrene (B[a]P) using an in vivo mouse peripheral blood micronucleus assay. The experimental groups were organized as follows: a negative control group (without treatment), a positive group treated with B[a]P (200 mg/kg), a group administered with 800 mg/kg of CEE, and three groups treated with B[a]P and CEE (200, 400, and 800 mg/kg) respectively. The CEE and benzo[a]pyrene were administered orally for a week, on a daily basis. During this period the body weight, the feed intake, and the determination of antigenotoxic potential were quantified. At the end of this period, we continued with the same determinations for one week more (recovery period) but anymore administration of the substances. The animals treated with B[a]P showed a weight increase after the first week of administration. The same phenomenon was observed in the lots combined with B[a]P and CEE (low and medium doses). The dose of 800 mg/kg of CEE showed similar values to the control group at the end of the treatment period. In the second part of the assay, when the substances were not administered, these experimental groups regained their normal weight. The dose of CEE (800 mg/kg) was not genotoxic nor cytotoxic. On the contrary, the B[a]P increases the frequency of micronucleated normochromatic erythrocytes (MNNE) and reduces the rate of polychromatic erythrocytes (PE) at the end of the treatment period. With respect to the combined lots, a significant decrease in the MN rate was observed from the sixth to the eighth day of treatment with the two high doses applied; the highest protection (60%) was obtained with 800 mg/kg of CEE. The same dose showed an anticytotoxic effect which corresponded to an improvement of 62.5% in relation to the animals administered with the B[a]P. In the second period, all groups reached values that have been seen in the control group animals. Our results suggest that the inhibition of clastogenicity of the cranberry ethanolic extract against B[a]P is related to the antioxidant capacity of the combination of phytochemicals present in its chemical composition.

A Comparative Study of Physical and Chemical Processes for Removal of Biomass in Biofilters

After 6 months of operation a long-term biofilter was stopped for two weeks and then it was started up again for a second experimental period of almost 1.3 years, with high toluene loads and submitted to several physical and chemical treatments in order to remove excess biomass that could affect the reactor’s performance due to clogging, whose main effect is a high pressure drop. Elimination capacity and removal efficiency were determined after each treatment. The methods applied were: filling with water and draining, backwashing, and air sparging. Different flows and temperatures (20, 30, 45 and 60 °C) were applied, either with distilled water or with different chemicals in aqueous solutions. Treatments with chemicals caused a decrease of the biofilter performance, requiring periods of 1 to 2 weeks to recover previous values. The results indicate that air sparging with pure distilled water as well as with solutions of NaOH (0.01% w/v) and NaOCl (0.01% w/v) were the treatments that removed more biomass, working either at 20, 30 or 45 °C and at relatively low flow rates (below 320 L h−1), but with a high biodegradation inhibition after the treatments. Dry biomass (g VS) content was determined at three different heights of the biofilter in order to carry out each experiment under the same conditions. The same amount of dry biomass when applying a treatment was established so it could be considered that the biofilm conditions were identical. Wet biomass was used as a control of the biofilter’s water content during treatments. Several batch assays were performed to support and quantify the observed inhibitory effects of the different chemicals and temperatures applied.

Evaluation of Blueberry Juice in Mouse Azoxymethane-Induced Aberrant Crypts and Oxidative Damage

Blueberry is a plant with a number of nutritional and biomedical capabilities. In the present study we initially evaluated the capacity of its juice (BJ) to inhibit the number of aberrant crypts (AC) induced with azoxymethane (AOM) in mouse. BJ was administered daily by the oral route to three groups of animals during four weeks (1.6, 4.1, and 15.0 μL/g), respectively, while AOM (10 mg/kg) was intraperitoneally injected to the mentioned groups, twice a week, in weeks two and three of the assay. We also included two control groups of mice, one administered distilled water and the other the high dose of BJ. A significant increase of AC was observed in the AOM treated animals, and a mean protection of 75.6% was determined with the two low doses of BJ tested; however, the high dose of the juice administered together with AOM increased the number of crypts more than four times the value observed in animals administered only AOM. Furthermore, we determined the antioxidant potential of BJ with an ex vivo DPPH assay and found a dose-dependent decrease with a mean of 19.5%. We also determined the DNA oxidation/antioxidation by identifying 8-hydroxy-2′-deoxyguanosine adducts and found a mean decrease of 44.3% with the BJ administration with respect to the level induced by AOM. Our results show a complex differential effect of BJ related to the tested doses, opening the need to further evaluate a number of factors so as to determine the possibility of a cocarcinogenic potential.

Role of Kupffer cells in thioacetamide-induced cell cycle dysfunction.

It is well known that gadolinium chloride (GD) attenuates drug-induced hepatotoxicity by selectively inactivating Kupffer cells. In the present study the effect of GD in reference to cell cycle and postnecrotic liver regeneration induced by thioacetamide (TA) in rats was studied. Two months male rats, intraveously pretreated with a single dose of GD (0.1 mmol/Kg), were intraperitoneally injected with TA (6.6 mmol/Kg). Samples of blood and liver were obtained from rats at 0, 12, 24, 48, 72 and 96 h following TA intoxication. Parameters related to liver damage were determined in blood. In order to evaluate the mechanisms involved in the post-necrotic regenerative state, the levels of cyclin D and cyclin E as well as protein p27 and Proliferating Cell Nuclear Antigen (PCNA) were determined in liver extracts because of their roles in the control of cell cycle check-points. The results showed that GD significantly reduced the extent of necrosis. Noticeable changes were detected in the levels of cyclin D1, cyclin E, p27 and PCNA when compared to those induced by thioacetamide. Thus GD pre-treatment reduced TA-induced liver injury and accelerated the postnecrotic liver regeneration. These results demonstrate that Kupffer cells are involved in TA-induced liver and also in the postnecrotic proliferative liver states.

Evaluation of agave fiber delignification by means of microscopy techniques and image analysis.

Recently, the use of different types of natural fibers to produce paper and textiles from agave plants has been proposed. Agave atrovirens can be a good source of cellulose and lignin; nevertheless, the microstructural changes that happen during delignification have scarcely been studied. The aim of this work was to study the microstructural changes that occur during the delignification of agave fibers by means of microscopy techniques and image analysis. The fibers of A. atrovirens were obtained from leaves using convective drying, milling, and sieving. Fibers were processed using the Acetosolv pulping method at different concentrations of acetic acid; increasing acid concentration promoted higher levels of delignification, structural damage, and the breakdown of fiber clumps. Delignification followed by spectrometric analysis and microstructural studies were carried out by light, confocal laser scanning and scanning electron microscopy and showed that the delignification process follows three stages: initial, bulk, and residual. Microscopy techniques and image analysis were efficient tools for microstructural characterization during delignification of agave fibers, allowing quantitative evaluation of the process and the development of linear prediction models. The data obtained integrated numerical and microstructural information that could be valuable for the study of pulping of lignocellulosic materials.

Spectroscopic and Microscopic Study of Peroxyformic Pulping of Agave Waste.

The peroxyformic process is based on the action of a carboxylic acid (mainly formic acid) and the corresponding peroxyacid. The influences of processing time (60-180 min), formic acid concentration (80-95%), temperature (60-80°C), and hydrogen peroxide concentration (2-4%) on peroxyformic pulping of agave leaves were studied by surface response methodology using a face-centered factorial design. Empirical models were obtained for the prediction of yield, κ number (KN) and pulp viscosity as functions of the aforementioned variables. Mathematical optimization enabled us to select a set of operational variables that produced the best fractionation of the material with the following results: pulp yield (26.9%), KN (3.6), and pulp viscosity (777 mL/g). Furthermore, this work allowed the description and evaluation of changes to the agave fibers during the fractionation process using different microscopic and spectroscopic techniques, and provided a comprehensive and qualitative view of the phenomena occurring in the delignification of agave fibers. The use of confocal and scanning electron microscopy provided a detailed understanding of the microstructural changes to the lignin and cellulose in the fibers throughout the process, whereas Raman spectroscopy and X-ray diffraction analysis indicated that cellulose in the pulp after treatment was mainly of type I.

Fotonic and Electron Microscopy Images for Quality Evaluation of Delignification of Agave Fibers

The present work is aimed to study the microstructural changes that occurred during the delignification process of agave fibers using microscopy techniques and image analysis AI. Acetosolv kinetic was followed by chemical analysis and by light LM, confocal laser scanning CLSM, and scanning electron SEM microscopies, evaluating the micrographs by image analysis IA. Kinetic studies showed that delignification process followed three stages: initial, bulk and residual; these stages kept a relation with the microstructural changes occurring in the fibers. The data obtained integrate numerical information that could be valuable for study of pulping of lignocellulosic materials and these techniques can be used as useful non-destructive methods for the evaluation of the delignification process.