RESUMEN
Aims: The aim of this study is optimization of the concentrations of carbon and nitrogen sources for lipase production by Rhizopus arrhizus using response surface methodology. Study Design: For this work optimal 22 composite design was used for studying the optimal concentrations of corn starch and tryptone for lipase production by submerged fermentation. A series of planned experiments in three replications was carried out and a mathematical model was developed which was used to describe the process. Optimal levels of studied independent variables were calculated by using the model and the conversion rate. Place and Duration of Study: This study is a part of PhD dissertation developed in University of Food Technologies, Bulgaria, Department of Biochemistry and Molecular Biology. Methodology: Maximum lipase activity was achieved by an optimization of some components of the fermentation medium. Corn starch (in concentrations 5.0, 10.0, 15.0 g.dm-3) and tryptone (2.0, 5.0, 8.0 g.dm-3) as independent variables were chosen. Lipase activity was determined by a spectrophotometric assay using synthetic substrate p-nitrophenyl palmitate. Results: A planned mathematical experiment was carried out and a regression model was developed. The value of R2 was 95.65% which showed that the model had high correlation with the experimental results. The effects of every independent variable had an optimal value while the interaction effects led toenhancement of lipolytical activity. In this case the enzyme activity increased rapidly to 1100 U.dm-3. For lipase activity above that value, large enhancements of the corn starch and tryptone concentrations were needed. In order to use the medium substrates properly there the conversion rate was calculated and it was also considered for the optimization. Conclusion: By carrying out an optimal composite design a mathematical model was derived, with the aid of which, optimum values of tryptone (6.6 g.dm-3) and corn starch (10.5 g.dm-3) were determined, when the conversion rate and the first derivative of enzyme activity were considered. Those results were confirmed by triplicate experiments at the optimal concentrations. Lipase activity of Ȳ=1340.74 U.dm-3 was achieved, which was very close to the predicted one Ŷ=1235.26 U.dm-3.
RESUMEN
Fungi in the class of zygomycetes usually produce serious infections in diabetics and immunocompromised hosts. Cutaneous zygomycosis is a less common form, with an unpredictable extent of anatomical involvement and clinical course. Here, we report two cases of primary cutaneous zygomycosis as postoperative complications in otherwise healthy females. Zygomycosis was suspected and specimens from the surgical debridement were examined by microbiological and histopathological studies for confirming the clinical diagnosis. Rapid diagnosis, liposomal amphotericin B, and proper debridement of affected tissue are necessary to avoid a fatal outcome.
RESUMEN
The physiological mutant of Rhizopus arrhizus was obtained in the pyrene resistance gradient test. Comparative studies were carried out about the behavior of the germination process and the radial growth of the mutant and wild strains of R. arrhizus UCP 402. Sabouraud Sucrose and Yeast Malt Broth cultures containing pyrene (10 mg/L) induced the germination process of the sporangiospores of the wild and mutant strains of R. arrhizus. The radial growth of the strains was inversely proportional to the pyrene concentration in the culture medium. The results showed an adaptation of R. arrhizus UCP 402x (mutant) in the pyrene (50mg/L) and suggested a higher ability of application in the removal of pyrene from the contaminated areas.
O mutante fisiológico de Rhizopus arrhizus foi obtido pelo teste do gradiente de resistência ao pireno. Estudos comparativos conduzidos sobre o comportamento do processo de germinação e o crescimento radial foram realizados entre as amostras selvagem e mutante de R. arrhizus UCP 402. Os meios Sabouraud Sacarose e Caldo de Levedura e Malte contendo pireno (10 mg/L) induziram ao processo de germinação de esporangiosporos das amostras selvagem e mutante de R. arrhizus. O crescimento radial das amostras foi inversamente proporcional à concentração de pireno no meio de cultura. Os resultados demonstraram uma excelente adaptação da amostra mutante de R. arrhizus UCP 402x na concentração de pireno (50 mg/L), sugerindo uma alta habilidade e possibilidade de aplicação na remoção de pireno em áreas contaminadas.
RESUMEN
Mucormycosis occurs primarily in patients with severe underlying illness, especially leukemia, lymphoma, and uncontrolled diabetes mellitus. Cutaneous mucormycosis is somewhat less frequently associated with systemic illness than other forms of mucormycosis. It develops where a break in the integrity of the skin has occurred as a result of surgery, burn, or other forms of trauma. We report herein a case of primary cutaneous mucormycosis due to Rhizopus arrhizus in a 24-year-old healthy man without systemic illness, who developed recurrent, prograssively extending, weeping and tender swollen ulcerative patches at the artificial trauma site on the right side of his face since 9 years of age. It was successfully treated with amphotericin B ointment combined with oral itraconazole and ketoconazole.