ABSTRACT
RESUMEN La arveja, una fuente económica para pequeños y medianos agricultores de la zona andina, evidencia un incipiente manejo pos-cosecha y un nulo nivel de transformación. Tras la cosecha y debido a su naturaleza temporal y perecedera, la arveja acelera su metabolismo, disminuyendo su calidad y vida útil. Una opción económica y que esté disponible para los productores y LOS comercializadores para conservar sus características es el uso de empaques y la refrigeración. El objetivo fue evaluar tipos de empaques (bolsa de polietileno de baja densidad -PE-LD-, envase plástico termoformado perforado -PE-HD- y bandeja de poliestireno -PS-) y temperaturas de almacenamiento (0°C, 4°C y 18°C) en dos variedades de arveja, Sureña y Obonuco Andina. Se utilizó un diseño irrestrictamente al azar con arreglo factorial 3x3x2, teniendo como factores temperatura, empaque y variedad y como variables de estudio, las constantes cinéticas (K) de porcentaje de brotación, firmeza, pérdida de peso e índice de color. Los resultados mostraron que, para la brotación, se presentó el valor más bajo de K en Sureña, en PE-LD, a 0°C. La temperatura afectó la firmeza de los granos, conservándose a 0°C. La menor pérdida de peso se evidenció en PE-HD, a 0°C, independiente de la variedad. Para el índice de color, la K más baja se encontró en PS, a 0°C, en Obonuco Andina. Con la ecuación de Arrhenius en la variable índice de color, se estimó tiempos de vida útil de 13; 7; 5 y 2 días a temperaturas de 0°C, 6°C, 10°C y 24°C, respectivamente.
ABSTRACT The pea, an economic source for small and medium farmers in the Andes zone, evidences an incipient postharvest handling and a null level of transformation. After the harvest and due to its temporary and perishable nature, the pea accelerates its metabolism, decreasing its quality and shelf life. An economic option that is available to producers and marketers to preserve their characteristics is the use of packaging and refrigeration. The objective was to evaluate types of packaging (low density polyethylene bag (PE-LD), perforated thermoformed plastic container (PE-HD) and polystyrene tray (PS)) and storage temperatures (0°C, 4°C and 18°C) in two pea varieties (Sureña and Obonuco Andina). An unrestricted random design with a 3x3x2 factorial arrangement was used, taking as factors temperature, packing and variety; and as study variables the kinetic constants (K) of percentage of sprouting, firmness, weight loss and color index. The results showed that, for the sprouting, the lowest value of K was shown in Sureña, in PE-LD at 0°C. The temperature affected the firmness of the grains, remaining at 0°C. The lowest weight loss was evidenced in PE-HD at 0°C, regardless of the variety. For the color index, the lowest K was found in PS at 0°C, in Obonuco Andina. With the Arrhenius equation in the variable color index, useful life times of 13; 7; 5 and 2 days were estimated at temperatures of 0°C, 6°C, 10°C and 24°C respectively.
ABSTRACT
Racemases have been applied for the synthesis of enantiomerically pure compounds through the deracemization methods. Mandelate racemase from Pseudomonas putida was the only enzyme that catalyzes the interconversion of mandelate enantiomers. Using genome mining approaches, we identified 9 mandelate racemases (MRs). A novel racemase named ArMR with higher activity and better soluble protein expression, was isolated from Agrobacterium radiobacter. ArMR displayed the optimum catalytic activity at 50 ℃, pH 7.8 in Tris-HCl buffer. The half-life of ArMR at 50, 40 and 30 ℃ was 0.17, 27.2 and 70.7 h, respectively. KM parameter of ArMR towards (R)- and (S)-mandelic acid was 1.44 and 0.81 mmol/L, respectively; the corresponding kcat value was 410 s⁻¹ and 218 s⁻¹. In addition, KM of ArMR towards (R)- and (S)-2-chloro mandelic acid was 6.48 and 6.37 mmol/L, and the corresponding kcat value 0.22 s⁻¹ and 0.23 s⁻¹, respectively. Meanwhile, Mg²⁺ and Mn²⁺ could activate the enzyme whereas Zn²⁺ inactivated the enzyme completely. Discovery of more novel MRs provides supports further research and development of these racemases.
ABSTRACT
RESUMEN El impacto ambiental generado por las aguas residuales de la explotación de carbón es significativo por la carga contaminante que estas por lo general poseen, representada en grandes concentraciones de sólidos suspendidos, metales (principalmente hierro) y otros elementos traza, además del bajo pH que suelen tener. El objetivo del presente trabajo fue evaluar la eficiencia de un sistema de tratamiento biológico a partir de microalgas de la división Chlorophyta para remover la carga contaminante de las aguas residuales de una mina de la empresa Coal North Energy S.A.S. Al final del tratamiento se obtuvieron porcentajes de remoción del 66,67% para hierro total, 46,67% para cloruros y 95,1% para DQO (Demanda Química de Oxígeno).
ABSTRACT The environmental impact caused by coal mining wastewater is significant due to the pollution load, usually represented in high concentrations of suspended solids, metals (mainly iron) and other trace elements and low pH values. The aim of this study was to evaluate the efficiency of a biological treatment system using microalgae belonging to the Chlorophyta division, for the removal of contaminants from the wastewater from a mine owned by Coal North Energy S.A.S. At the end of treatment, it was possible to remove up to 66.67% of total iron, 46.67% for chloride and 95.1% for Chemical Oxigen Demand.
ABSTRACT
b-D-Galactosidase (EC 3.2.1.23) from Lactobacillus bulgaricus (1373) was immobilized in a Polyacrylamide gel lattice in the presence of dithiothreitol, glutathione, cysteine, bovine serum albumin, casein, lactose and glucono-δ-lactone. Cysteine, bovine serum albumin, and lactose were found very effective in preserving the activity. With cysteine, bovine serum albumin and lactose, the activity yields were 61, 60 and 66% respectively, as compared to 31% without protective agents. The yield improved upto 85% when all the three protective agents, cysteine, bovine serum albumin and lactose were added during immobilization. The addition of protective agents did not have any effect on optimum pH, optimum temperature, kinetic constants and pH stability when compared with β-galactosidase immobilized without the use of protective agents; however the heat and storage stabilities were found to increase.