Etanol celulósico: desarrollo de una tecnología óptima para la producción semi-continua

El bioetanol como combustible tiene una alta demanda en todo el mundo. Los principales actores en el mercado del etanol son Estados Unidos, Brasil, China, Canadá y Alemania. Sin embargo, otros países necesitan expandir su producción de etanol para reemplazar los combustibles fósiles. En este contexto, las tecnologías de etanol celulósico se enfrentan a nuevos desafíos y oportunidades. En este trabajo, reportamos la producción de etanol a partir de celulosa (bagazo de caña de azúcar) utilizando un enfoque novedoso que disminuye el tiempo de sacarificación, reduce la necesidad de enzimas y reduce los costos de producción. La cepa de levadura CLQCA-INT-005 se seleccionó entre 150 aislados de Saccharomyces cerevisae por su alta dominancia en co-cultivos y alto rendimiento de etanol. Por otro lado, la biomasa se trató previamente con hidróxido de sodio, ácido sulfúrico, ácido oxálico y ácido maleico (1% p/v) a diferentes temperaturas (130-170°C) y tiempos (10-30 minutos) en un reactor de presión. Además se realizaron pretratamientos alcalinos con irradiación con microondas y organosolvente (sulfolane-TiO2) a diferentes temperaturas y tiempos. El pretratamiento con NaOH al 1% p/v a 160°C durante 20 minutos demostró ser el más eficaz para la sacarificación enzimática. Una vez establecidos los parámetros de pretratamiento y fermentación se utilizó un sistema de fermentación y sacarificación simultánea semi-continua (SFSS) con producción de etanol cada 24 h. Una mezcla sólido: líquido en la proporción 1:3 se sometió a hidrólisis y fermentación; el proceso se produjo a lo largo de 30 días con un agotamiento casi total de la glucosa, obteniendo concentraciones de etanol que oscilaron entre 8,36 y 10,79% (v/v). Con este sistema se optimizó la cantidad de enzimas necesarias para la sacarificación, así como el tiempo de producción y la concentración de etanol, alcanzando niveles similares a los del etanol de primera generación. Todo el sistema mostró estabilidad, facilidad de gestión y control, así como la repetitividad de los resultados a lo largo de 30 días. Por lo tanto, el sistema propuesto en esta investigación podría mejorar la rentabilidad en la producción de etanol celulósico a escala industrial.Departamento de Ingeniería Agrícola y ForestalDoctorado en Ciencia e Ingeniería Agroalimentaria y de Biosistema

Cellulosic ethanol: Improving cost efficiency by coupling semi-continuous fermentation and simultaneous saccharification strategies

A novel approach to improve ethanol production from sugarcane bagasse is proposed. Biomass was pretreated with sodium hydroxide, sulfuric, oxalic, and maleic acids (1% w/v) at different temperatures (130–170 °C) and times (10–30 min). The pretreatment with NaOH at 160 °C for 20 min was found to be the most efficient for further enzymatic saccharification. A semi-continuous fermentation system coupled with a simultaneous saccharification and fermentation strategy was used, attaining fermented liquor every 24 h. The amount of enzymes needed for saccharification was optimized, as well as the production time and ethanol concentration. The process occurred with near to complete depletion of glucose, obtaining ethanol concentrations ranging from 8.36 to 10.79% (v/v). The whole system, at bench scale, showed stability over 30 days, and ease of management and control. This strategy may improve cost efficiency in the production of cellulosic ethanol at industrial scale

Assessment of the effect of nitrogen concentration on fermentation and selection of a highly competitive Saccharomyces cerevisiae strain for efficient ethanol production

The optimum nitrogen concentration for media supplementation and strain dominance are aspects of key importance to the industrial production of ethanol with a view to reducing costs and increasing yields. In this work, these two factors were investigated for four ethanologenic Saccharomyces cerevisiae strains (CLQCA-INT-001, CLQCA-INT-005, CLQCA-10-099, and UCLM 325), selected from the screening of 150 isolates, mostly from Ecuadorian yeast biodiversity. The effect of nitrogen concentration was assessed in terms of cellular growth, glucose consumption and ethanol production, and the yeast strains’ dominance was evaluated in continuous co-fermentation with cellular recycling by mitochondrial DNA analyses. Among the four selected yeast strains under study, CLQCA-INT-005 presented the highest glucose consumption at a nitrogen supplement concentration as low as 0.4 g·L−1, attaining an ethanol yield of up to 96.72% in 24 h. The same yeast strain was found to be highly competitive, showing a dominance of 80% after four cycles of fermentation in co-culture. Thus, CLQCA-INT-005 may be deemed as a very promising candidate to be used both at pilot-plant scale and at industrial scale cellulosic ethanol production

Opportunities for ivory nut residue valorization as a source of nanocellulose colloidal suspensions

Producción CientíficaIvory nut seeds have been traditionally exploited in Central and South America for obtaining vegetable ivory. The residues from this industry are susceptible to valorization as a source of fatty acids (by organic extraction) and mannans (by alkaline dissolution and regeneration). Nonetheless, cellulose may also be recovered at the end of this fractionation process by acid hydrolysis and functionalization, with associated advantages over other lignocellulosic sources due to the absence of lignin in the endospermic tissue. In this work, various experimental parameters (sulfuric acid concentration, temperature, and hydrolysis time) were investigated to optimize the processing conditions for preparing stable nanocellulose suspensions after ultrasonication. The most stable nanocellulose gel (1 wt% solid content) was obtained after 4-h hydrolysis at 60 °C with 8 M H2SO4 and was characterized by using complementary tech-niques, including dynamic light scattering (DLS), transmission electron microscopy (TEM), X-ray powder diffraction (XRD), nano-fibril sulfation measurements, vibrational and solid-state nuclear magnetic resonance (CP/MAS 13C-NMR) spectroscopies, and thermal analysis. This nanocellulose hydrogel is susceptible to further utilization in various applications and fields, e.g., in agricul-ture for controlling the release of agrochemicals, in pharmaceutics for developing new dosage forms, and in the treatment of wastewater from the textile and paper industries.El proyecto fue financiado por la Pontificia Universidad Católica del Ecuador

Assessment of the effect of nitrogen concentration on fermentation and selection of a highly competitive Saccharomyces cerevisiae strain for efficient ethanol production

The optimum nitrogen concentration for media supplementation and strain dominance are aspects of key importance to the industrial production of ethanol with a view to reducing costs and increasing yields. In this work, these two factors were investigated for four ethanologenic Saccharomyces cerevisiae strains (CLQCA-INT-001, CLQCA-INT-005, CLQCA-10-099, and UCLM 325), selected from the screening of 150 isolates, mostly from Ecuadorian yeast biodiversity. The effect of nitrogen concentration was assessed in terms of cellular growth, glucose consumption and ethanol production, and the yeast strains’ dominance was evaluated in continuous co-fermentation with cellular recycling by mitochondrial DNA analyses. Among the four selected yeast strains under study, CLQCA-INT-005 presented the highest glucose consumption at a nitrogen supplement concentration as low as 0.4 g·L −1, attaining an ethanol yield of up to 96.72% in 24 h. The same yeast strain was found to be highly competitive, showing a dominance of 80% after four cycles of fermentation in co-culture. Thus, CLQCA-INT-005 may be deemed as a very promising candidate to be used both at pilot-plant scale and at industrial scale cellulosic ethanol production

Sugarcane bagasse hydrolysis enhancement by microwave-assisted sulfolane pretreatment

Sugarcane bagasse is the major by-product of the sugarcane industry and, due to its abundant availability, it has been extensively studied for lignocellulosic bioconversion in the production of bioethanol and other value-added commercial products. In the study presented herein, a combined pretreatment using sulfolane, TiO2 and alkali microwave irradiation (MW-A) was assessed for the dissolution of lignin prior to enzymatic saccharification of holocellulose. Total reducing sugars (TRS) and saccharinic acid yields were investigated. The increase in NaOH concentration up to 5% and in temperature from 120 °C to 140 °C were found to have a positive influence on both yields. While increasing the reaction time from 5 to 60 min only led to an increase in TRS yield <2%, a reaction time of 30 min almost doubled the saccharinic acids production. TRS yields and saccharinic acid production were approximately 5% and 33% higher when the sulfolane-TiO2 reaction medium was used, as compared to MW-A in water, reaching up to 64.8% and 15.24 g/L of saccharinic acids, respectively. The proposed MW-A pretreatment may hold promise for industrial applications, given the good TRS yields obtained, and the associated enzyme and time/energy savings. The use of sulfolane-TiO2 reaction medium is encouraged if saccharinic acids are to be recovered too

Determinación de la diversidad de levaduras fermentadoras de cacao (theobroma cacao) provenientes de centros de acopio de Atacames (provincia de Esmeraldas) y Mindo (provincia de Pichincha)

La Escuela Superior Politécnica del Litoral, impulsando la sociedad del conocimiento, mediante la Facultad de Ciencias de la Vida encargada de organizar las cuadragésimas XL Jornadas Nacionales de Biología, evento promocionado por la Sociedad Ecuatoriana de Biología y que se constituye como el más importante espacio para la difusión de la investigación e innovación en el área de las Ciencias de la Vida; a realizarse desde el 16 al 18 de noviembre de 2016 en el Campus Prosperina de la ESPOL, en el Auditorio del Centro de Información Bibliotecario y cuenta con la participación de investigadores nacionales e internaciones en las temáticas antes escritas, con el horario de 09h00 hasta las 18h00. Evento trascendental de actualización y fortalecimiento científico que reúne anualmente a científicos, profesionales y estudiantes del área de las ciencias biológicas y ciencias afines de todas las universidades del país en un espacio de integración, diálogo y divulgación de resultados de investigación

Ecuadorian yeast species as microbial particles for Cr(VI) biosorption

Pollution caused by heavy metals is a prime concern due to its impact on human health, animals, and ecosystems. Cr(VI), generated in a range of different industries as a liquid effluent, is one of the most frequent contaminants. In the work presented herein, the adsorption efficiency of three species of native yeasts from Ecuador (Kazachstania yasuniensis, Kodamaea transpacifica, and Saturnispora quitensis) for Cr(VI) removal from simulated wastewater was assessed, taking Saccharomyces cerevisiae as a reference. After disruption of the flocs of yeast with a cationic surfactant, adsorption capacity, kinetics, and biosorption isotherms were studied. K. transpacifica isolate was found to feature the highest efficiency among the four yeasts tested, as a result of its advantageous combination of surface charge, individual cell size (4.04 μm), and surface area (1588.27 m2/L). The performance of S. quitensis was only slightly lower. The remarkable biosorption capacities of these two isolates (476.19 and 416.67 mg of Cr(VI)/g of yeast, respectively) evidence the potential of non-conventional yeast species as sorption microbial particles for polluted water remediation