Extraction and Optimization of Process Parameters for Xylitol Production using Microbes from Corncobs

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Addis Ababa University


This Research paper aimed mainly on the extraction of xylitol from corncob hydrolysate and optimization of fermentation parameters such as; fermentation period, yeast dose and initial pH. Raw corn cobs were collected from market in Addis Ababa, Ethiopia, and was hydrolyzed with 1% (w/w) dilute sulfuric acid. Hydrolysate was detoxified by activated carbon treatment and fermentation was carried out using the well-known xylitol producing Candida yeast, Candida mogii. Serial dilution method, Colony Forming Unit, was used to enumerate yeast cells present in a milliliter of inoculum. Box Behnken experimental design was employed to correlate the fermentation parameters to xylitol yield. Yeast dose was expressed in terms of percentage volume of fermentation medium on levels of 5%, 7.5% and 10% along with three levels of initial pH, 4.5, 5 and 5.5, and fermentation period of 24, 48 and 72 hours. HPLC with RI detector and Amine NH2 column was used to determine xylitol concentration. The highest xylitol yield of 23.56 gL was obtained at 5% yeast dose, 45 pH and 45.68 hours. The results showed area of xylitol peak and the presence of sugar residuals. According to the experiment design, all three parameters have significant effect on xylitol yield. The effect of fermentation period and yeast dose showed dominant effect. The combined effect of yeast dose with pH, and yeast dose with fermentation period were also observed to be significant. The adequacy of the model was tested by analysis of variance. The value of R-squared for the developed correlation is 0.9821implying 98.21 percent variation in response is attributed to the experimental variables studied. In generally, this study has shown an alternative for the chemical production of xylitol can be carried out by candida mogii with economic and environmental friendly conditions from agricultural residue as lignocellulosic material. The yield of xylitol was promising with all parameters and down-stream process.



Corncob, Candida mogii, Hydrolysate, Xylitol, Xylose