RESUMEN
Pectinases catalyze the degradation of pectic substances and are used in several processes, mainly in food and textile industries. In this study, a biomimetic matrix of alginate/gelatin/calcium oxalate (AGOCa) was synthesized for the in situ immobilization via encapsulation of crude pectinase from Aspergillus niger ATCC 9642, obtaining an immobilization efficiency of about 61.7 %. To determine the performance of AGOCa matrix, this was compared to control matrices of alginate/calcium oxalate (AOxal) and alginate/water (ACa). By the evaluation of pH and temperature effects on the enzyme activity, it was observed an increase on pectinolytic activity for both three tested matrices with an increase on pH and temperature. The kinetic parameters for pectinase immobilized in the three matrices were determined using citric pectin as substrate. Values of K m of 0.003, 0.0013, and 0.0022 g mL(-1) and V max of 3.85, 4.32, and 3.17 µmol min(-1) g(-1) for AGOCa, AOxal, and ACa matrices were obtained, respectively. After 33 days of storage, the pectinase immobilized in the three different matrices kept its initial activity, but that immobilized in AGOCa presented high stability to the storage with a relative activity of about 160 %. The enzyme immobilized in AGOCa, AOxal, and ACa could be used in 10, 8, and 7 cycles, respectively, keeping 40 % of its initial activity.
Asunto(s)
Alginatos/química , Enzimas Inmovilizadas/química , Gelatina/química , Poligalacturonasa/química , Aspergillus niger/enzimología , Biomimética , Oxalato de Calcio/química , Estabilidad de Enzimas , Ácido Glucurónico/química , Ácidos Hexurónicos/química , Cinética , Temperatura , Agua/químicaRESUMEN
The hybrid alginate/gelatin/calcium oxalate (AGOCa) support was successfully synthesized through the biomimetic mineralization method for immobilization in situ of a pectinolytic extract from Aspergillus niger ATCC 9642 via entrapment technique. The efficiency of immobilization reached 72.7%. Sodium oxalate buffer (100 mM, pH 5.5) was selected as adjuvant of the immobilization process by allowing the formation of a calcified shell around the calcium alginate capsule, significantly increasing the stability to storage, thermal and recycling of the enzymatic immobilized pectinolytic extract. The pH and temperature for maximum activity were from 5.0 to 6.0 and 60 to 80 °C, respectively. The new hybrid support can be a potential alternative to obtain immobilized pectinases with properties for advantageous industrial applications.
Asunto(s)
Alginatos/química , Aspergillus niger/enzimología , Materiales Biomiméticos/síntesis química , Oxalato de Calcio/química , Proteínas Fúngicas/química , Gelatina/química , Poligalacturonasa/química , Materiales Biomiméticos/química , Enzimas Inmovilizadas/química , Ácido Glucurónico/química , Ácidos Hexurónicos/químicaRESUMEN
A sequential experimental design strategy is used to optimize the extraction of lead from slag. The slag is composed mainly of iron (= 60%) and lead (= 6%), and cannot be disposed of in conventional landfill due to its high lead content. The extraction of lead is based on the complexing properties of ethylenediaminetetra-acetic acid (EDTA), the iron being masked with fluoride ions. Atomic absorption spectroscopy (AAS) has been used for monitoring iron and lead concentrations. In a first step, Plackett-Burman PB-12 experimental design was used for screening the variables and for selecting those to be used. Two central composite designs (CCDs) were then carried out to determine the optimal conditions for lead extraction. The optimized experimental conditions were established to be: contact time with the fluoride solution 30 min; particle size of slag between 150 and 600 microm; molecular concentration of fluoride solution 2.4 x 10(-3) mol and of EDTA 5 x 10(-4) mol; pH 1.5; 8 h contact time with the EDTA solution; and temperature 60 degrees C. Under these experimental conditions the lead content was reduced by 57% compared with the raw sample.
Asunto(s)
Quelantes/química , Ácido Edético/química , Residuos Industriales , Plomo/aislamiento & purificación , Administración de Residuos/métodos , Concentración de Iones de HidrógenoRESUMEN
The pyrometallurgic process that the exhausted batteries are submitted for the recovery of metallic lead generates great amount of a by-product called slag. The slag is composed mainly of iron ( approximately 60%) and lead ( approximately 6%), and this residue cannot be disposed in conventional landfill due to the high lead content. This work presents a new methodology for the extraction of lead from slag, based on the complexing effect of EDTA, a chelating ligand that has the ability to solubilize several heavy metals. As the iron (Fe(2+)/Fe(3+)) have a formation's constant with EDTA higher than the lead and is present in high concentrations in the samples, the fluoride ion (F(-)) was employed to mask the iron ions. The tests were carried out in a qualitative way, confirming the lead extraction by the formation of a yellow precipitate of lead iodide.