Culture medium composition is one of the most important parameters to analyze in biotechnological processes with industrial purposes. The aim of this study was to design of a culture medium for optimal growth of the bacterium Pseudoxanthomonas indica H32 allowing its production as biopesticide and biofertilizer. The influence of several carbon and nitrogen sources and their molar ratios on P. indica H32 growth was investigated. The effect of different micronutrients such as mineral salts and vitamin on P. indica H32 growth was determined as well. A mixture design based on Design-Expert 10.0 Software was performed to optimize the culture medium concentration. Finally, in the designed medium, an attribute of the biological mechanism of action of the P. indica H32 against nematodes, was evaluated: the hydrogen sulfide production. It was found that tested carbon/nitrogen ratios were not a significant influence on P. indica H32 growth. Growth of P. indica H32 was favored with use of sucrose, yeast extract and phosphate buffer without the addition of any tested micronutrients. An optimal concentration of 10 g/L sucrose and 5 g/L yeast extract were obtained at a cost of 0.10 $/L. In this concentration, the specific growth rate (µ) and maximal optical density (Xmax) were equal to 0.439 h− 1 and 8.00 respectively. It was evidenced that under the culture conditions used, P. indica H32 produced hydrogen sulfide. The designed medium led to a 1.08 $/L reduction of costs in comparison to LB medium. These results were critical to carry on with biotechnological development of P. indica H32 as a bioproduct.

La purificación de enzimas celulasas constituye un paso crítico para su producción debido a que a menudo resulta ser muy costoso. El objetivo de este estudio fue evaluar la precipitación salina de celulasas producidas por Aspergillus niger UC33 en fermentación en estado sólido, para incrementar el rendimiento y pureza de la enzima con el menor costo posible. Se empleó el programa Design-Expert 11.1.2 para el diseño experimental y la optimización de las condiciones experimentales. El sulfato de amonio se utilizó para la precipitación entre 60 y 90 % de saturación, se emplearon entre 1 y 3 h de precipitación y las temperaturas utilizadas fueron 4 y 25 °C. Las condiciones óptimas encontradas para maximizar el rendimiento y la pureza fueron 68,97 % de saturación con sulfato de amonio, tiempo de precipitación de 1,28 h y temperatura de 25 °C.  En estas condiciones los valores de rendimiento, pureza y costo, fueron: 74,81 %, 1,26 y USD $ 0,2609, respectivamente. El peso molecular de la enzima fue 38,47 kDa y la actividad celulolítica fue de 31,854 UI.

Highlights A strain of Pseudoxanthomonas indica was used in this study. Optimal fermentation conditions of P. indica H32 was found for first time. DCW of P. indica H32 was increased 1.36 after optimizing with respect to the non-optimized conditions.

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