Journal of Microbiology

Journal Article

Response Surface Analysis for the Production of an Enantioselective Lipase from Aspergillus niger by Solid-State Fermentation: Fabiano Jares Contesini , Vania Castriani Fernades da Silva , Rafael Ferreira Maciel , Rosemary Joana de Lima , Francisco Fábio Cavalcante Barros , Patrícia de Oliveira Carvalho; J. Microbiol. 2009;47(5):563-571. Published online October 24, 2009; DOI: https://doi.org/10.1007/s12275-008-0279-8

Abstract: The lipase produced by the Aspergillus niger strain AC-54 has been widely studied due to its enantioselectivity for racemic mixtures. This study aimed to optimize the production of this enzyme using statistical methodology. Initially a Plackett-Burman (PB) design was used to evaluate the effects of the culture medium components and the culture conditions. Twelve factors were screened: water content, glucose, yeast extract, peptone, olive oil, temperature, NaH2PO4, KH2PO4, MgSO4․7H2O, CaCl2, NaCl, and MnSO4. The screening showed that the significant factors were water content, glucose, yeast extract, peptone, NaH2PO4, and KH2PO4, which were optimized using response surface methodology (RSM) and a mathematical model obtained to explain the behavioral process. The best lipase activity was attained using the following conditions: water content (20%), glucose (4.8%), yeast extract (4.0%), and NaH2PO4 (4.0%). The predicted lipase activity was 33.03 U/ml and the experimental data confirmed the validity of the model. The enzymatic activity was expressed as µmoles of oleic acid released per minute of reaction (µmol/min).

Research Support, Non-U.S. Gov't

Impact of Some Environmental Factors on Growth and Production of Ochratoxin A of/by Aspergillus tubingensis, A. niger, and A. carbonarius Isolated from Moroccan Grapes: Atar Selouane , Driss Bouya , Ahmed Lebrihi , C. Decock , Amina Bouseta; J. Microbiol. 2009;47(4):411-419. Published online September 9, 2009; DOI: https://doi.org/10.1007/s12275-008-0236-6

Abstract: The effects of temperature, water activity (aw), incubation time, and their combinations on radial growth and ochratoxin A (OTA) production of/by eight Aspergillus niger aggregate strains (six A. tubingensis and two A. niger) and four A. carbonarius isolated from Moroccan grapes were studied. Optimal conditions for the growth of most studied strains were shown to be at 25°C and 0.95 aw. No growth was observed at 10°C regardless of the water activity and isolates. The optimal temperature for OTA production was in the range of 25°C~30°C for A. carbonarius and 30°C~37°C for A. niger aggregate. The optimal aw for toxin production was 0.95~0.99 for A. carbonarius and 0.90~0.95 for A. niger aggregate. Mean OTA concentration produced by all the isolates of A. niger aggregate tested at all sampling times shows that maximum amount of OTA (0.24 µg/g) was produced at 37°C and 0.90 aw. However, for A. carbonarius, mean maximum amounts of OTA (0.22 µg/g) were observed at 25°C and 0.99 aw. Analysis of variance showed that the effects of all single factors (aw, isolate, temperature and incubation time) and their interactions on growth and OTA production were highly significant.

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