Abstract Small producers in Ecuador, who are grouped within the typology of peasant family agriculture (PFA), represent 62% of the rural population and contribute to food security by producing basic foodstuffs for the family food basket. Typically, their production system is based on family labor. Their main crops are beans and corn, using the conventional tillage system (CT). Soil erosion is the most serious environmental problem in Ecuador, affecting approximately 50% of the cultivated area. An effective agronomic practice against erosion is no-tillage (NT) complemented with crop rotation (CR). Investments in soil conservation are generally high and not profitable in the short term, so it is a challenge to generate techniques that improve yields, reduce costs and produce benefits from their implementation, in order to motivate their adoption. The objective of this study was to evaluate the bean-corn rotation, comparing NT with LC, at an early stage of its implementation through the benefit/cost ratio (B/C ratio) in the Experimental Field "La Tola" (CADET), in Tumbaco-Ecuador. The results show that the B/C ratio averages for beans were similar in both NT and LC systems; on the other hand, for corn, NT outperformed LC by an average of more than 50%, thus rejecting the hypothesis that NT would generate losses. In conclusion, NT is a profitable soil conservation alternative under the soil-climatic conditions studied.

Resumen Los pequeños productores del Ecuador, quienes se agrupan dentro de la tipología de agricultura familiar campesina (AFC), representan el 62 % de la población rural, contribuyen a la seguridad alimentaria y producen para la canasta familiar los alimentos básicos. Típicamente, su sistema productivo se basa en el trabajo familiar. Sus principales cultivos son el fréjol y maíz, utilizando el sistema de labranza convencional (LC). Por otro lado, la erosión de los suelos es el problema ambiental más serio del Ecuador que afecta, aproximadamente, al 50 % del área cultivada. Una práctica agronómica efectiva contra la erosión es la siembra directa (SD) complementada con la rotación de cultivos (RC). Las inversiones en conservación de suelos, por lo general, son altas y no rentables a corto plazo, por lo que es un reto generar técnicas que mejoren el rendimiento, reduzcan costos y produzcan beneficios desde su implementación, para que motiven su adopción. El objetivo de este estudio fue evaluar la rotación fréjol-maíz, comparando SD con LC, en una etapa temprana de su implementación a través de la relación beneficio/costo (R B/C) en el Campo Experimental “La Tola” (CADET), en Tumbaco-Ecuador. Los resultados muestran que los promedios de la R B/C para fréjol fueron similares en los dos sistemas; en cambio, para maíz, SD superó a LC, en un promedio mayor al 50 %, por lo que se rechaza la hipótesis de que la SD generaría pérdidas. En conclusión, la SD es una alternativa de conservación de suelos rentable bajo las condiciones edafo-climáticas estudiadas.

Fermentação em batelada alimentada foi realizada visando a produção da enzima dextransucrase a partir de Leuconostoc mesenteroides e o seu escalonamento foi realizado usando critérios da transferência de oxigênio. Foi determinado que em fermentador de vaso de 5L de capacidade, a melhor velocidade de agitação foi de 225 m-1 e a taxa de aeração foi de 0,15 VVM, obtendo uma atividade de dextrasucrase de 127 DSU/mL. A velocidade máxima da produção de enzimaconcide com a velocidade máxima de crescimento , entre 6-7 h de fermentação, o que confirma que a produção dextrasucrase esta associada com o crescimento microbiano. Altos rendimentos na produção da enzima foram obtidos durante o escalonamento baseado-se na taxa de transferência de oxigênio.

Fed batch fermentation was carried out for the dextransucrase enzyme production from Leuconostoc mesenteroides and the production was scale-up using oxygen transfer criteriuom. It was found that in 5 L vessel fermentation capacity, the best agitation speed was 225 min-1 and aeration rate was 0.15 vvm, obtaining dextransucrase activity of 127 DSU/mL.. The maximum enzyme production velocity coincide with the maximum growth velocity between 6 and 7 h of fermentation, which confirmed that dextransucrase production was associated with microbial growth. High enzyme yields were achieved during scale up based on oxygen transfer rate.