RESUMO
Immobilized biocatalysts design has the potential to efficiently produce valuable bioproducts from lignocellulosic biomass. Among them, the carrier-free immobilization through the cross-linked enzyme aggregates technology is a simple and low-cost alternative. A two steps statistical approach was utilized to evaluate the synthesis of a cross-linked enzyme aggregate from a xylanolytic preparation, which was produced by Cohnella sp. AR92 grown in a peptone-based culture medium. The resulting immobilized biocatalyst, Xyl-CLEA, was significate more stable (25 to 45%) towards temperatures up to 50°C with respect to the free enzyme, and retained over 50% of its initial activity after 5 consecutive cycles of reuse. By means of infrared spectroscopy and electron microscopy, the Xyl-CLEA showed architectural features described as signature of type I and type II of protein aggregates. These, were the result of the simultaneous aggregation of a multiplicity of proteins from the crude enzymatic extract. The enzymatic activity was assessed using alkali pretreated sugar cane bagasse as substrate. Whereas the free enzymatic preparation released xylose as the main product, the immobilized xylanase produced xylooligosaccharides, thus showing that the immobilization procedure modified the potential application of the extracellular xylanase from Conhella sp. AR92.
Assuntos
Suplementos Nutricionais , Endo-1,4-beta-Xilanases/química , Enzimas Imobilizadas/química , Resíduos Industriais , Biomassa , Celulose/química , Química Agrícola , Reagentes de Ligações Cruzadas/química , Fermentação , Hidrólise , Agregados Proteicos/efeitos dos fármacos , Saccharum/química , Temperatura , XilanosRESUMO
AIMS: Recombinant Aspergillus nidulans sVAL040, capable of synthesizing and secreting glucose oxidase derived from Aspergillus niger was used to study the influence of pH and carbon source on enzyme production. METHODS AND RESULTS: Glucose oxidase gene (goxC) was expressed under transcriptional regulation by using the promoter of A. nidulans xlnB gene (encoding an acidic xylanase). A maximum specific glucose oxidase activity of approx. 10 U mg(-1) protein and a maximum volumetric productivity of 29.9 U l(-1) h(-1) were obtained at pH 5.5, after 80 h of growth by using xylose as inducer. Enzyme volumetric productivity increased when xylans were used instead of xylose; however, specific glucose oxidase activity did not differ significantly. CONCLUSIONS: Specific GOX activity obtained at pH 5.5 are two to three times more than those previously described for goxC multicopy transformants of A. nidulans. Xylans were a more powerful inducer than xylose although fungal growth was lower when the polymers were used. SIGNIFICANCE AND IMPACT OF THE STUDY: The obtained results by using xlnB promoter in A. nidulans could be useful in improving heterologous enzyme production by using genetic- and process-engineering strategies.
Assuntos
Aspergillus nidulans/enzimologia , Glucose Oxidase/biossíntese , Divisão Celular , Meios de Cultura , Frutose/metabolismo , Concentração de Íons de Hidrogênio , Xilanos/metabolismo , Xilose/metabolismoRESUMO
Lactic acid purification was directly done from fermentation utilizing a fluidized bed column refilled with a strong anionic exchange resin. The purpose of this work was to study the influence of two important design parameters, bed-diameter (D) and bed-height (H), in the lactic acid binding and elution capacity of the matrix. By changing the settled bed height from 2.5 to 5 cm for each diameter of column analyzed it was possible to obtain an 50% increase in the binding capacity of the resin in all experiments. This fact was attributed to a higher contact time between the culture broth and the anionic resin produced by the increase of back mixing and lactic acid residence time.
Assuntos
Reatores Biológicos , Ácido Láctico/metabolismo , Adsorção , Algoritmos , Resinas de Troca Aniônica , Técnicas Bacteriológicas , Meios de Cultura , Fermentação , Ácido Láctico/isolamento & purificação , Lacticaseibacillus casei/metabolismo , Resinas SintéticasRESUMO
Lactic acid fermentation process with L. casei CRL 686 was performed. The static adsorption isotherm over a strong anionic exchange resin, Amberlite IRA-400 was measured, and the static binding capacity parameters were quantified. Early recovery of lactic acid from this lactate producer from unclarified culture broth was performed in a liquid solid fluidized bed, with the resin as the solid adsorbent, and the dynamic adsorption capacity was calculated. Good agreement was found between static and dynamic binding capacity values. The fluidized bed height was twice the settled bed height and the overall process was controlled by the liquid solid mass transfer. This operation was also simulated by continuously well stirred tanks arranged in series and superficial solid deactivation as in a gas solid catalytic reactor. The deactivation process takes into account liquid channeling and agglomerations of solid induced by the viscosity of the broth and also by the cells during the adsorption. These patterns were also verified by experimental observations, and are in agreement with the results found in the literature. The breakthrough data together with others from previous works were satisfactorily fitted until the 90% dimensionless concentration was reached for both culture broths. The model could be used in future studies on predictions about the liquid solid fluidized bed behavior and other different operating conditions.
Assuntos
Microbiologia Industrial/métodos , Resinas de Troca Iônica , Ácido Láctico/isolamento & purificação , Adsorção , Meios de Cultura , Fermentação , Lacticaseibacillus casei/metabolismo , Modelos Teóricos , PolímerosRESUMO
The measurement of the colony radial growth rate (Kr) on solid medium of colonies of Sclerotium rolfsii Proimi F-6656 for the evaluation of scleroglucan production medium and other different media, incubation temperature and tolerance to diverse concentrations of sucrose and NaCl were studied. The optimum growth temperature observed was 30 degrees C. The Kr value reached on the Production Medium used (0.66 mm.h-1) showed no differences compared with those of the other media tested, indicating that all the requirements for growth were provided. Poor growth was only observed on Soil Extract Agar. The fungus tolerated concentrations of sucrose from 0.15 to 1.17 M, on both Czapek and production medium. Growth was limited by the highest concentrations of sucrose tested (0.88 and 1.17 M), as indicated by a slower increase in colony size. Addition of 0.86 M NaCl to the production medium and YM agar did not inhibit growth completely, but decreased the radial growth rate considerably (80 and 70% respectively).