Search

Solid-state fermentation (SSF) is characterized by its complexity and heterogeneity. Use of agro-industrial residues as substrate avoids accurate measurement of biomass and substrates during the SSF process. Exhaust gas analysis has been used to indirectly estimate the biomass growth; however, these devices don't allow simultaneous measurements from different experimental units or bioreactors and they don't allow accurate simultaneous measurement of CO2, O2, and air-flow rate. A respirometry system based on CO2, O2, and air-flow measurement detectors fed by a system of 15 solenoid valves controlled by a programmable logic controller and a data logger was developed and evaluated during the growth of Rhizomucor pusillus in SSF. The respirometry system was compared to a classical chromatographic respirometer. Accurate measurements of CO2, O2, and air-flow rate allow precise and instantaneous estimation of some kinetic parameters associated with the respiration of the culture such as the specific CO2 production rate and the respiratory quotient. The respirometry system herein described allows online measurements of the microbial process allowing control procedures to be set in SSF processes.

Fe&ndash, Al intermetallic compounds have been considered excellent candidates as alternative alloys for various applications in corrosive environments compared to other Fe-based alloys. Their excellent corrosion resistance is due to the development of an Al-based passive layer. The performance of the passive layer can be improved by adding a third alloy element. Therefore, in this study the electrochemical performance of the Fe40Al intermetallic alloy modified by the addition of a third alloy element (Cr, Ti, Co, Ni) is evaluated. The corrosion resistance of intermetallic alloys has been evaluated by electrochemical tests (potentiodynamic polarization curves, and measurements of open circuit potential, linear polarization and electrochemical impedance) in artificial saliva. The performance of intermetallic alloys was compared with that of Ti. The results obtained showed that the addition of Ni and Ti substantially improves the corrosion resistance of the base intermetallic. The corrosion resistance shown is comparable or greater than that shown by Ti. However, the addition of Co reduces the corrosion resistance of the base intermetallic.

The highest enzymatic extraction of covalent linked chlorogenic (36.1%) and caffeic (CA) (33%) acids from coffee pulp (CP) was achieved by solid-state fermentation with a mixture of three enzymatic extracts produced by Aspergillus tamarii, Rhizomucor pusillus, and Trametes sp. Enzyme extracts were produced in a practical inexpensive way. Synergistic effects on the extraction yield were observed when more than one enzyme extract was used. In addition, biotransformation of chlorogenic acid (ChA) by Aspergillus niger C23308 was studied. Equimolar transformation of ChA into CA and quinic acids (QA) was observed during the first 36 h in submerged culture. Subsequently, after 36 h, equimolar transformation of CA into protocatechuic acid was observed; this pathway is being reported for the first time for A. niger. QA was used as a carbon source by A. niger C23308. This study presents the potential of using CP to produce enzymes and compounds such as ChA with biological activities.

The modification of the third order nonlinear optical response exhibited by vertically aligned carbon nanotubes in two-wave mixing interactions was analyzed. All-optical switching effects were explored by using a vectorial optical Kerr gate with nanosecond pulses at 532 nm wavelength of excitation. The samples were prepared by a spray pyrolysis method. Morphological and structural characterization of the samples was conducted by Scanning Electron Microscopy, Transmission Electron Microscopy and Raman Spectroscopy studies. Important structural changes dependent on the temperature employed for the preparation of the carbon nanotubes were observed. It was highlighted a remarkable influence of nonlinear energy transference in spatially-resolved optical processes for designing ultrafast low-dimensional devices.

Se optimizaron las condiciones de cultivo para producir las enzimas despolimerizantes por FMS de R. pusillus, utilizando diseños experimentales. Con el diseño experimental tipo PlackettBurman se identificó que la concentración de sacarosa, (NH4)2SO4, (NH4)2HPO4 y la temperatura tienen un efecto positivo sobre la producción de APec y AXil. Mientras que la concentración de sacarosa, (NH4)2SO4 y (NH4)2HPO4 tienen un efecto negativo sobre la enzima clorogenato esterasa (ClE) responsable de hidrolizar el ácido clorogénico a ácido cafeico y ácido quínico. Los perfiles de actividad enzimática de la pectinasa, xilanasa y ClE mostraron que la mayor actividad de la ClE se presentó 4 horas después de presentarse la mayor APec y AXil. A través de un diseño factorial central compuesto se determinó que los intervalos donde se presentó la zona de mayor APec y AXil fueron (g/100 g SS): 5 ≤ Sacarosa ≤ 6, 2 ≤ (NH4)2SO4 ≤ 3.3 y 2.1 ≤ (NH4)2HPO4 ≤ 2.9 y la menor actividad de la ClE fueron (g/100 g SS): 5.4 ≤ Sacarosa ≤ 7.5, 2.5 ≤ (NH4)2SO4 ≤ 4, 2.5 ≤ (NH4)2HPO4 ≤ 4. Se observó un posible efecto de represión catabólica a concentraciones mayores de sacarosa de 6 g/100 g sobre las actividades pectinolítica y xilanolítica. Mientras que la actividad de la clorogenato esterasa disminuyó conforme aumentaba el nivel de sacarosa en el medio de cultivo. Por último se evaluó la extracción del ácido clorogénico con el extracto enzimático crudo de R. pusillus producido por FMS con las condiciones optimizadas de cultivo (g/100 g SS): sacarosa, 5.5; (NH4)2SO4, 2.8 y (NH4)2HPO4, 2.6. El rendimiento de extracción del ácido clorogénico con el extracto crudo de R. pusillus fue del 69%. Este rendimiento fue similar al obtenido con las dos enzimas comerciales pectinasa y xilanasa y a la mezcla de la pectinasa comercial con los extractos crudos de R. pusillus y Trametes sp. producidos por FMS. La evidencia experimental presentada en este trabajo mostró el potencial de extraer compuestos de alto valor agregado como el ácido clorogénico esterificado a la pared celular de la pulpa de café a partir de extractos enzimáticos crudos producidos por FMS. México es un importante productor a nivel mundial de café. Los residuos como la pulpa de café, pueden ser tratados mediante procesos biotecnológicos, para evitar problemas ambientales y obtener compuestos de alto valor agregado, contribuyendo a mejorar la situación socioeconómicos de este sector agroindustrial. En esta tesis se estudió la extracción del ácido clorogénico esterificado a la pared celular de la pulpa de café mediante extractos enzimáticos producidos por fermentación en medio sólido (FMS). Los resultados están organizados en cuatro bloques: a) Desarrollo de metodología (enzimática y de respirometría), b) Pre-selección y selección de cepas, c) Estudio del efecto de las enzimas despolimerizantes sobre la obtención del ácido clorogénico y d) Optimización de la producción de extractos enzimáticos para la obtención del ácido clorogénico. Se desarrollaron y evaluaron diversas técnicas analíticas para la cuantificación de la actividad pectinasa, xilanasa y celulasa en cajas de Petri y la cuantificación de la actividad clorogenato esterasa por espectrofotometría. Se desarrolló un sistema para la medición en línea del CO2 (%) producido, O2 (%) consumido y el flujo (ml/min) durante la FMS. El sistema permitió obtener datos confiables y reproducibles. El sistema desarrollado esta en proceso de registro para patente. Se estudiaron 6 cepas de hongos filamentosos A. niger (A10 y CH4), A. tamarii, R. pusillus, Trametes sp. y Trichoderma harzianum. Los extractos enzimáticos producidos por FMS de R. pusillus y Trametes sp. presentaron la mayor capacidad para extraer el ácido clorogénico (17%) y la menor capacidad para hidrolizar el ácido clorogénico del medio. La mezcla de los extractos crudos producidos por estas dos cepas con la pectinasa comercial extrajeron el 68% del ácido clorogénico. Se determinó que la presencia de enzimas despolimerizantes, era necesaria para realizar la extracción del ácido clorogénico. Con una metodología de diseño de mezclas se determinó que la presencia de las actividades pectinolítica (APec) y xilanolítica (AXil) tiene un efecto importante en la extracción del ácido clorogénico. Los intervalos donde se presentó la zona de máxima extracción de ácido clorogénico esterificado fue (U/g PC): 60 ≤ AXil ≤ 150, 50 ≤ APec ≤ 140, 0 ≤ ACel ≤ 40. El rendimiento obtenido por las enzimas comerciales pectinasa y xilanasa (69%) fue similar al obtenido con la mezcla de los extractos crudos de R. pusillus y Trametes sp. producidos por FMS adicionando la pectinasa comercial (68%).

Ferulic, caffeic, p-coumaric and chlorogenic acids are classified as hydroxycinnamic acids, presenting anticarcinogenic, anti-inflammatory and antioxidant properties. In this work, enzymatic extraction has been studied in order to extract high value-added products like hydroxycinnamic acids from coffee pulp. A commercial pectinase and enzyme extract produced by Rhizomucor pusillus strain 23aIV in solid-state fermentation using olive oil or coffee pulp (CP) as an inducer of the feruloyl esterase activity were evaluated separately and mixed. The total content (covalently linked and free) of ferulic, caffeic, p-coumaric and chlorogenic acids was 5276 mg per kg of coffee pulp. Distribution was as follows (in %): chlorogenic acid 58.7, caffeic acid 37.6, ferulic acid 2.1 and p-coumaric acid 1.5. Most of the hydroxycinnamic acids were covalently bound to the cell wall (in %): p-coumaric acid 97.2, caffeic acid 94.4, chlorogenic acid 76.9 and ferulic acid 73.4. The content of covalently linked hydroxycinnamic acid was used to calculate the enzyme extraction yield. The maximum carbon dioxide rate for the solid-state fermentation using olive oil as an inducer was higher and it was reached in a short cultivation time. Nevertheless, the feruloyl esterase (FAE) activity (units per mg of protein) obtained in the fermentation using CP as an inducer was 31.8 % higher in comparison with that obtained in the fermentation using olive oil as the inducer. To our knowledge, this is the first report indicating the composition of both esterified and free ferulic, caffeic, p-coumaric and chlorogenic acids in coffee pulp. The highest yield of extraction of hydroxycinnamic acids was obtained by mixing the produced enzyme extract using coffee pulp as an inducer and a commercial pectinase. Extraction yields were as follows (in %): chlorogenic acid 54.4, ferulic acid 19.8, p-coumaric acid 7.2 and caffeic acid 2.3. An important increase in the added value of coffee pulp was mainly due to the extraction of chlorogenic acid., Ferulinska, kafeinska, p-kumarinska i klorogena kiselina pripadaju u hidroksicinamične kiseline, koje imaju antikarcinogena, protuupalna i antioksidativna svojstva. U radu je ispitana enzimska ekstrakcija hidroksicinamičnih kiselina iz otpada nastalog pri proizvodnji kave. Upotrijebljene su, zasebno i u smjesi, komercijalna pektinaza te enzimski esktrakt dobiven fermentacijom na čvrstoj podlozi od maslinovog ulja ili otpada nastalog pri proizvodnji kave (da bi se potaknula aktivnost feruloil esteraze), s pomoću Rhizomucor pusillus 23aIV. Ukupni je udio kovalentno vezanih i slobodnih hidroksicinamičnih kiselina bio 5276 mg/kg otpada. Od toga je bilo: 58,7 % klorogene; 37,6 % kafeinske; 2,1 % ferulinske i 1,5 % p-kumarinske kiseline. Većina je hidroksicinamičnih kiselina bila kovalentno vezana za staničnu stijenku, i to: 97,2 % p-kumarinske; 94,4 % kafeinske; 76,9 % klorogene i 73,4 % ferulinske kiseline. Pomoću udjela kovalentno vezanih hidroksicinamičnih kiselina izračunat je prinos ekstrahiranog enzima. Maksimalni je udio fermentacijom proizvedenog CO2 postignut na čvrstoj podlozi od maslinovog ulja, i to za kraće vrijeme nego na podlozi od otpada nastalog pri proizvodnje kave, iako je feruloil esteraza proizvedena primjenom ove druge podloge pokazala aktivnost veću za 31,8 %. Prema spoznajama autora ovo je prvo istraživanje u kojem su određeni udjeli vezanih i slobodnih hidroksicinamičnih kiselina u otpadu nastalom pri proizvodnji kave. Najveći je prinos ekstrakcije hidroksicinamičnih kiselina postignut primjenom komercijalne pektinaze i enzimskog ekstrakta. Pritom je izdvojeno 54,4 % klorogene; 19,8 % ferulinske; 7,2 % p-kumarinske i 2,3 % kafeinske kiseline, pa je zaključeno da je ovaj postupak dobar za ekstrakciju klorogene kiseline.