Mara Cea | Universidad de La Frontera (original) (raw)

Papers by Mara Cea

Bioresource Technology, 2016

Sewage sludge generated in municipal wastewater treatment plants was used as a feedstock for biod... more Sewage sludge generated in municipal wastewater treatment plants was used as a feedstock for biodiesel production via esterification/transesterification in a two-step process. In the first esterification step, greasy and secondary sludge were tested using acid and enzymatic catalysts. The results indicate that both catalysts performed the esterification of free fatty acids (FFA) simultaneously with the transesterification of triacylglycerols (TAG). Acid catalyst demonstrated better performance in FFA esterification compared to TAG transesterification, while enzymatic catalyst showed the ability to first hydrolyze TAG in FFA, which were esterified to methyl esters. In addition, FAME concentration using greasy sludge were higher (63.9% and 58.7%), compared with those of secondary sludge (11% and 16%), using acid and enzymatic catalysts, respectively. Therefore, only greasy sludge was used in the second step of alkaline transesterification. The alkaline transesterification of the previously esterified greasy sludge reached a maximum FAME concentration of 65.4% when using acid catalyst.

Chemosphere, Jun 1, 2010

Emergence of laccase-positive variant of Azospirillum lipoferum occurs via a two-step phenotypic ... more Emergence of laccase-positive variant of Azospirillum lipoferum occurs via a two-step phenotypic switching process.

Journal of Hazardous Materials, 2019

Copper nanoparticles (NCu) have been proposed as an antimicrobial agent in the agriculture. There... more Copper nanoparticles (NCu) have been proposed as an antimicrobial agent in the agriculture. Therefore, NCu may interact with numerous pollutants including pesticides. Little is known about the combined effects of NCu and pesticides in soil. This study aimed at assessing the impact on soil of NCu combined with the herbicide atrazine (ATZ). We focused on assessing the adsorption and dissipation of ATZ in presence of NCu and the changes in microbial community profiles. First, ATZ adsorption isotherms described using the Freundlich equation were evaluated. After that, soil samples were spiked with NCu (40-60 nm) at 0.05 and 0.15% w/w and ATZ (3 mg a.i kg-1) and incubated for 30 days. The results showed that ATZ adsorption is favored by the presence of NCu. On the other hand, NCu at 0.15 % w/w caused a significantly decrease in ATZ dissipation, increasing its half-life (from 6 to 37 days). Microbial community profiles (bacteria, fungi and nitrifying bacteria) remained relatively stable throughout the evaluated period. Therefore, our findings suggest that NCu can increase the persistence of ATZ in soil, which may be mostly associated to physical-chemical interaction with soil particles more than a microbial impact.

Energy Conversion and Management, 2017

A study to produce an efficient catalyst to be used for biodiesel production was carried out intr... more A study to produce an efficient catalyst to be used for biodiesel production was carried out introducing sulfonic groups in biochar using a microwave reactor. The transesterification reaction of waste cooking oils using the catalyst was also evaluated in a microwave reactor. The results showed that an increase in the temperature up to 140°C during biochar sulfonation enhanced the SO 3 H content on the catalyst surface. These results were confirmed through FT-IR and XPS analyses. A reduction in the surface area of the biochar was observed during the sulfonation. An increase of SO 3 H groups on the biochar surface was responsible for a higher FAME yield close to 90%. The catalyst could be re-used for up to six cycles by washing with hexane.

Frontiers in Microbiology

Biological synthesis of high added-value compounds like adipic acid (AA), levulinic acid (LA), or... more Biological synthesis of high added-value compounds like adipic acid (AA), levulinic acid (LA), or polyhydroxybutyrate (PHB) using pure culture has been separately reported. However, pure culture requires sterile conditions and the use of specific carbon sources resulting in high operating costs. Different alternatives based on the use of mixed microbial cultures (MMC) have been explored to resolve this problem. MMC have been widely reported for the production of PHB, but scarcely reported for LA production and never for AA synthesis. This work presents a novel strategy for the co-production of AA LA, and PHB using MMC. The strategy consists in selecting an MMC producer of AA, LA and PHB from an inoculum obtained from a wastewater treatment plant, which is then subjected to the feast and famine culture strategy in a sequential batch reactor, coupled with a batch reactor step to enhance the accumulation of AA and LA. The results showed that the MMC could produce a 16 ± 2, 23 ± 1 and 5...

Applied Microbiology and Biotechnology

Bioresource Technology

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Journal of Soil Science and Plant Nutrition, 2019

AbstractToday, metal nanoparticles are being incorporated into soil through several routes, where... more AbstractToday, metal nanoparticles are being incorporated into soil through several routes, where they could alter the sorption behavior of other contaminants such as pesticides. Therefore, a short assay was carried out through sorption isotherms to evaluate the effect of copper nanoparticles (NCu) and copper sulfate (as the bulk form) at 50, 100, and 200 mg kg−1 on the sorption capacity of two commonly applied fungicides (carbendazim and iprodione) onto two agricultural soils, contrasting in organic matter content (2% and 14%) and texture (sandy and loamy) respectively. The isotherms were well described using the Freundlich model (R2 > 0.95). Interestingly, at low organic matter, the pesticide sorption was notoriously increased in the presence of copper. However, NCu caused a minimal dose-dependent effect compared with their bulk form. Conversely, at high organic matter, the sorption was slightly altered by the presence of NCu. These findings constitute the first evidence that copper nanoparticles applied to agricultural soils can modify the sorption behavior of fungicides, which might increase their permanence in the environment. However, more detailed studies should be carried out in order to understand the interaction mechanisms between NCu/pesticides/soil and consequently their potential environmental risks. Graphical Abstracts"."

Biofuels, Bioproducts and Biorefining

Bioresource Technology, 2021

• Dissolved oxygen has a greater impact on the type and amount of produced compound. • PHA produc... more • Dissolved oxygen has a greater impact on the type and amount of produced compound. • PHA production is favored at dissolve oxygen concentrations lower than 3 mg/L. • Dissolved oxygen concentrations above 3 mg/L favor the synthesize of PG and TAG. • OLR and cycle length were identified to have an impact on the accumulation of PHA.

Journal of Biobased Materials and Bioenergy, 2013

Very much attention has been focused on lipases as these enzymes can be used as biocatalysts, all... more Very much attention has been focused on lipases as these enzymes can be used as biocatalysts, allowing a cost effective and environmentally friendly method to efficiently catalyze specific reactions. However, its application at industrial scale is still limited due to several shortcomings including low stability in their native state, inhibition by organic solvents and exhaustion of enzyme activity. To overcome these problems, lipases have been immobilized by several methods onto various supports. In this context, biochar, a low-cost material derived from the pyrolysis of residual biomass, constitutes a promising immobilization support material for enzymes due its suitable physicochemical and structural properties. In this study a complete physico-chemical and mineralogical characterization of biochar derived from pyrolyzed oat hull and pine bark at 300 and 500 � C is presented. In addition, a preliminary study on the immobilization of Candida rugosa lipase using biochar derived from oat hull pyrolyzed at 300 � C is reported. The results obtained showed that the structural and chemical properties of biochar depend on the raw materials used and pyrolysis temperature. The specific surface area (BET) presented a similar trend, increasing with an increase in pyrolysis temperature. High enrichment of trace elements such as Ba, Cr, Cu, V and Zn was detected in biochar from pine bark and was discarded for lipase immobilization purposes. The binding efficiency of lipase was in the range of 40–60%, depending on biochar particle size. The higher enzymatic activity yields were associated to small particle size of oat hull biochar. However, a reduction in Candida rugosa lipase activity yield compared with the free enzyme was obtained.

Revista de la ciencia del suelo y nutrición vegetal, 2010

Atrazine, a herbicide used for the control of broadleaf weeds of different crops, was incorporate... more Atrazine, a herbicide used for the control of broadleaf weeds of different crops, was incorporated in ethylcellulose controlled release formulations (CRFs) by using the solvent evaporation technique. Allophanic clays and nanoclays were incorporated as matrix modifying agents. The formulations were characterized by scanning electron microscopy (SEM) and infrared spectroscopy (FTIR), and their behavior was determined in aqueous phase. Dissipation studies and soil columns experiments with CRFs were also carried out, and compared with commercial formulations (CFs). In addition, a short-term bioassay was performed to evaluate the effect of CRFs and CFs on the emergence and growth of field mustard (Brassica campestris L.) under greenhouse conditions. The matrix modifiers (clays and nanoclays) showed little influence on the particle morphology and atrazine encapsulation efficiency. Furthermore, these matrix modifiers had a slight effect on the atrazine release into water, its dissipation and its behavior in soil compared with the formulation without them. All CRFs increased the atrazine herbicidal activity and reduced their loss by leaching in soil. Although some similarities were found in the efficiency to reduce the seedling emergence between CRFs and CFs, a greater death of seedlings was observed in the CRFs, especially when nanoclays were added into the formulation. These facts denote an advantage of CRFs over CFs due to prolonged bio-efficiency, and longer applications intervals will be produced, minimizing the harmful impact on the environment.

Journal of Chemical Technology & Biotechnology, 2021

Catalysts

5-hydroxymethylfurfural (HMF) stands out among the chemical products derived from biomass as a bu... more 5-hydroxymethylfurfural (HMF) stands out among the chemical products derived from biomass as a building block in the chemical industry. The conventional production of HMF is usually carried out from fructose, glucose, or other monosaccharides as feedstock, but sugar beet molasses, a by-product of the sugar industry containing sucrose (45–55%), is promising. This exploratory study used three aqueous stock solutions and one biphasic system as the sources of sucrose. The dehydration of sucrose to 5-hydroxymethylfurfural was assisted by microwave heating and subcritical water conditions. The maximum yield of HMF was 27.8 mol % for the aqueous solution of synthetic sucrose at 80 min of treatment. Although HMF yield was 7.1 mol % in the aqueous sugar beet molasses solution, it increased 2-fold after clarification (15.1 mol %) and 1.6-fold in the biphasic system (11.4 mol %). These are favorable outcomes since this is an exploratory investigation. The pseudo-first-order model fitted experi...

Journal of Agronomy and Crop Science

International Journal of Biological Macromolecules