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Assessment of relative importance of Process variables in Citric Acid Fermentation by Plackett-Burman design

Author Affiliations

  • 1Department of Chemical Engineering, National Institute of Technology, Warangal-506004, AP, INDIA

Res.J.chem.sci., Volume 2, Issue (9), Pages 5-8, September,18 (2012)


Citric acid fermentation process is controlled by different operating variables: Initial sucrose concentration, Initial pH, Stirrer speed, Incubation time, Fermentation temperature, O2 flow rate, moisture content, particle size, inoculum density, methanol concentration, spore age etc. The present work reports the evaluation of the parameters by Plackett-Burmandesigns, one of the factorial design methods using design expert softwareto screen the strongly influencing variables for their subsequent optimization to improve the citric acid fermentation from Sucrose using Aspergillus Niger NCIM-705. Plackett-Burman is a specialized design for 2 to 31 variables where each variable can be varied over two levels. The lower and upper limits of eleven variables stated above were identified from the literature. The variables with their operational range were processed in Plackett-Burmandesign software until a point where the design matrix evaluation for factorial main effect model was obtained. All trials were performed in triplicate and citric acid yield hs been treated as response variable. The main effect of each variable was calculated as the differencce between the average of measurements made at the high setting(+) and at the low setting(-) of that factor. The six variables; Initial sucrose concentration, initial pH, stirrer speed, incubation time, fermentation temperature and O2 flow rate were found to be the most influencing parameters on the yields of citric acid.


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