Protein enrichment of Opuntia ficus-indica using Kluyveromyces marxianus in solid-state fermentation

Opuntia ficus-indica is used in animal feed but has a low protein content (above 4%) in comparison to high-quality forage (above 16%). It is necessary to develop technologies that improve the nutrimental value of Opuntia ficus-indica through the process of solid-state fermentation (SSF). Therefore, the objective of this study was to evaluate the changes in the chemical composition of Opuntia ficus-indica during the SSF with the yeast Kluyveromyces marxianus ITD00262. Kluyveromyces marxianus ITD00262 was grown in glucose, peptone, yeast (GPY) broth, at 28 °C and pH 4.8 for 12 h. Opuntia ficusindica was incubated in SSF at 28 °C without inoculation (T1) or inoculated with K. marxianus ITD00262 (T2). Fermented samples of Opuntia ficus-indica were dried, and the dry matter (DM), crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), lignin (LIGN) and in vitro dry matter digestibility (IVDMD) contents were ascertained. Data were analyzed with a completely randomized design with a factorial arrangement of 2×6. A decrease of 11% in DM was observed for T1 compared with T2 at 48 h of fermentation. A 300% increase in PC content was observed for T2 at 120 h of fermentation. The DMIVD was increased by 3%, whereas the values of NDF and ADF decreased by 18% in T2. According to our results, it is confirmed that the use of K. marxianus in the SSF of Opuntia ficus-indica has a positive effect and improves the nutrimental quality of this forage.Opuntia ficus-indica es utilizado en la alimentación animal, a pesar de su bajo contenido de proteínas (4%) comparado con forrajes de alta calidad (16%). Es necesario desarrollar tecnologías que permitan incrementar el valor nutrimental de O. ficus-indica, mediante procesos como la fermentación en estado sólido (FES). Por lo que el objetivo de este trabajo fue evaluar los cambios en la composición química de O. ficus-indica durante la FES al ser inoculado con K. marxianus ITD00262, para esto la cepa se activó en caldo de Glucosa peptona, extracto de levadura (GPY), a 28°C y pH de 4.8, el proceso de fermentación consistió de dos tratamientos, el primero sin inoculación de K. marxianus (T1), el segundo inoculando K marxianus (T2). Las muestras de O. ficus-indica fermentadas fueron secadas, y se les determinó los contenidos de materia seca (MS), proteína cruda (PC), fibra detergente neutra (FDN), fibra acido detergente (FDA), lignina (LIGN), digestibilidad in vitro de materia seca (IVDMD). Los datos fueron analizados con un arreglo factorial de 2×6. Se observó una disminución en la MS, el cual fue 11% menor para T1 comparado con T2 a las 48 h de fermentación. El contenido de PC, se incrementó 300% en T2 a las 120 h de fermentación. La DIVMS aumentó 3% mientras que los valores de FDN y FDA disminuyeron 18% en T2. De acuerdo con nuestros resultados, se confirma que el uso de K. marxianus en la FES de O. ficusindica, tiene un efecto positivo porque incrementa la calidad nutritiva de este forraje

Physiological characterization of two native yeasts in pure and mixed culture using fermentations of agave juice

Yeast cells are subjected to diverse environmental conditions during the alcoholic fermentation of agave juice, causing different kinetic behaviors. Agave juice was used as culture medium to evaluate the kinetic behavior of Saccharomyces cerevisiae ITD-00185 and Torulaspora delbrueckii ITD-00014a, as pure and mixed cultures, under different inoculum sizes (1×105, 1×106, 1×107 and 1×108 cells mL-1), and combined pH levels (3.5, 4.0 and 4.5) and temperatures (18 °C, 28 °C and 38 °C). Saccharomyces cerevisiae displayed high fermentation capacities at all inoculum concentrations assayed. However, T. delbrueckii required a high inoculum concentration (≥1×107 cells mL-1) to perform at fermentation levels similar to S. cerevisiae. Low temperatures (18 °C) slowed fermentation, while high temperatures (38 °C) adversely affected the development of the yeast strains, especially T. delbrueckii. The best temperature was 28 °C in all fermentations. The pH level had a strong effect on the performance of the coculture, since the fermentation kinetics suggested a synergistic effect at pH 4.5, while an antagonistic effect was postulated at pH 3.5. In all of the mixed culture cases, a positive effect at 28 °C, especially at pH 4.0 and 4.5, was demonstrated by greater levels of sugar consumption and ethanol production (~20%, p<0.05) compared to fermentations of the S. cerevisiae monoculture. The coculture results allow us to postulate that a complex interaction exists between the two yeasts, which could be synergistic or antagonistic, as the environmental conditions change.Las levaduras se someten a diversas condiciones ambientales durante la fermentación alcohólica de jugo de agave, causando diferentes comportamientos cinéticos. Se utilizó jugo de agave como medio de cultivo para evaluar el comportamiento cinético de Saccharomyces cerevisiae ITD-00185 y Torulaspora delbrueckii ITD-00014a, en cultivos puros y mezclados, en diferentes condiciones de tamaño de inóculo (1×105, 1×106, 1×107 y 1×108 células ml-1) y combinaciones de pH (3.5, 4.0 y 4.5) y temperatura (18 °C, 28 °C y 38 °C). Saccharomyces cerevisiae mostró alta capacidad fermentativa en todas las concentraciones de inóculo. Torulaspora delbrueckii requirió alta concentración de inóculo (≥1×107 células mL-1) para fermentar como S. cerevisiae. A 18 °C se retardó la fermentación, mientras que a 38 °C se afectó negativamente al desarrollo de las levaduras, especialmente T. delbrueckii. La fermentación fue vigorosa para ambas levaduras a 28 °C. El pH tuvo un fuerte efecto sobre el rendimiento del co-cultivo, sugiriendo un efecto sinérgico a pH 4.5 y efecto antagónico a pH 3.5. Para cultivo mixto se observó un efecto positivo a 28 °C, especialmente a pH 4.0 y 4.5, demostrando mejor consumo de azúcar y producción de etanol (~ 20%, p <0,05) comparado con el monocultivo de S. cerevisiae. Los resultados globales permiten postular una interacción compleja entre las dos levaduras, que puede ser sinérgica o antagónica, según las condiciones ambientales

Modeling of isoamyl acetate production by fermentation with Pichia fermentans in an aerated system coupled to in situ extraction

International audienceThis study deals with the production of isoamyl acetate (IAA) by fermentation of sugar cane molasses with the strain Pichia fermentans ITD00165, using L-leucine as precursor. A mathematical model that describes the experimental data from fermentation was developed for its use as a tool for further process optimization. The fermentation system was constantly aerated and coupled to liquid–liquid in situ extraction with decane as the recovery solvent. Thus, the model integrates the biological production of IAA, its partition coefficient in the two liquid phase system and the stripping effect of aeration. A productivity of 26 mg L−1 h−1 was obtained with addition of 4 g L−1 of L-leucine at 12 h of fermentation. The use of the model for process optimization was explored. According to it, the maximum theoretical productivity that can be obtained is 63 mg L−1 h−1. The model was used to determine that 1.6 g L−1 is the minimum concentration of L-leucine that can be added without significantly reducing IAA production. Also, it makes possible to propose an adequate decane/culture medium ratio, to have a desired final concentration and amount of recovered IAA. This value can be adjusted based on the needs of further purification steps and is useful to define a global economic optimum of the process

Effect of Vegetable Oils or Glycerol on the In Vitro Ruminal Production of Greenhouse Gases

The objective of this research was to evaluate the ruminal fermentation parameters and in vitro Greenhouse gas (GHG) production derived from the fermentation of a balanced sheep diet with the addition of vegetable oils (canola, corn, safflower, and sunflower) or glycerol at different proportions (0, 20, and 40 g/kg of dry matter, DM). The fermentations showed that the highest Gmax was obtained with the addition of 40 g/kg of sunflower oil and 20 g/kg of glycerol with values of 180.97 and 179.95 mL/g DM, respectively. The treatment with 40 g/kg DM of corn oil showed the lowest values in CH4 production (7.15 mL/g DM when compared to the control) and it seemed to be a potential feeding strategy for reducing GHG emissions without affecting gas production. However, the N-NH3 content for this treatment in both doses (1.90 and 1.88 mg/dL) indicated that some toxicity for the animal could be expected