A propagação in vitro é uma importante técnica na reprodução de orquídeas, devido às sementes serem desprovidas de endosperma e apresentarem uma baixa taxa de germinação na natureza. A sacarose é um componente importante no meio de cultura servindo como fonte de carbono e energia para as plântulas e os macronutrientes são essenciais para a nutrição e crescimento. O presente trabalho teve como objetivo avaliar o crescimento in vitro de Oncidium baueri (Orchidaceae) em diferentes concentrações de macronutrientes e sacarose. Os tratamentos consistiram em duas formulações dos macronutrientes do meio Murashige e Skoog (1962), sendo, MS completo e MS modificado com metade da concentração dos macronutrientes e de diferentes concentrações de sacarose (30 gL-1 , 40 gL-1 e 60 gL-1), com pH 5,8. O delineamento experimental foi esquema fatorial 2 x 3 (meio x concentrações de sacarose) com oito repetições, contendo 20 plântulas por parcela. Os dados foram submetidos a análise de variância complementada pelo teste de Tukey a 5% de significância. Os parâmetros avaliados após seis meses do início do experimento foram: altura da parte aérea, comprimento da maior raiz, número de raízes, número de brotos, massa fresca total e massa seca total. Constatou-se que no tratamento contendo 40 gL-1 de sacarose e a metade da concentração dos macronutrientes do meio MS, foi o mais eficiente para o desenvolvimento vegetativo e no enraizamento da orquídea Oncidium baueri.
Caulobacter crescentus (NA1000 strain) are aquatic bacteria that can live in environments of low nutritional quality and present numerous genes that encode enzymes involved in plant cell wall deconstruction, including five genes for β-xylosidases (xynB1-xynB5) and three genes for xylanases (xynA1-xynA3). The overall activity of xylanases in the presence of different agro-industrial residues was evaluated, and it was found that the residues from the processing of corn were the most efficient in inducing bacterial xylanases. The xynA1 gene (CCNA_02894) encoding a predicted xylanase of group 10 of glyco-hydrolases (GH10) that was efficiently overexpressed in Escherichia coli LMG194 using 0.02 % arabinose, after cloning into the vector pJet1.2blunt and subcloning into the expression vector pBAD/gIII, provided a fusion protein that contained carboxy-terminal His-tags, named XynA1. The characterization of pure XynA1 showed an enzymatic activity of 18.26 U mL(-1) and a specific activity of 2.22 U mg-(1) in the presence of xylan from beechwood as a substrate. XynA1 activity was inhibited by EDTA and metal ions such as Cu(2+) and Mg(2+). By contrast, β-mercaptoethanol, dithiothreitol (DTT), and Ca(2+) induced recombinant enzyme activity. Kinetic data for XynA1 revealed K M and V max values of 3.77 mg mL-(1) and 10.20 μM min-(1), respectively. Finally, the enzyme presented an optimum pH of 6 and an optimum temperature of 50 °C. In addition, 80 % of the activity of XynA1 was maintained at 50 °C for 4 h of incubation, suggesting a thermal stability for the biotechnological processes. This work is the first study concerning the cloning, overexpression, and enzymatic characterization of C. crescentus xylanase.
The production of β-Xylosidase by a new strain of Aspergillus fumigatus (PC-7S-2 M), isolated from the Brazilian Atlantic Forest, was analyzed at 28°C using modified Czapeck media supplemented with different agroindustrial residues at 1% (w/v). Conidia were inoculated for 7 days, and the best activity for β- Xylosidase was obtained in the presence of barley brewing residue after 4 days (15 U mL-1). To optimize the production of β-Xylosidase, this carbon source was used for a central composite rotational design (CCRD) to obtain a significance level of p < 0.10, which predicted an enzyme activity of 245.04 U mL-1. The model validation revealed β-Xylosidase activity was optimized at 229.06 U mL-1. Furthermore, the production of intracellular A. fumigatus β-Xylosidase increased by 1,500% (15 times) over that initially obtained, achieving 93.47% of the predicted model. This finding obtained during two years emphasizes the availability of A. fumigatus β-Xylosidase production with possible applications in biotechnological processes.
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