This Research paper aimed mainly on the extraction of xylitol from corncob hydrolysate andrnoptimization of fermentation parameters such as; fermentation period, yeast dose and initial pH. Rawrncorn cobs were collected from market in Addis Ababa, Ethiopia, and was hydrolyzed with 1% (w/w)rndilute sulfuric acid. Hydrolysate was detoxified by activated carbon treatment and fermentation wasrncarried out using the well-known xylitol producing Candida yeast, Candida mogii. Serial dilutionrnmethod, Colony Forming Unit, was used to enumerate yeast cells present in a milliliter of inoculum.rnBox Behnken experimental design was employed to correlate the fermentation parameters to xylitolrnyield. Yeast dose was expressed in terms of percentage volume of fermentation medium on levels ofrn5%, 7.5% and 10% along with three levels of initial pH, 4.5, 5 and 5.5, and fermentation period of 24,rn48 and 72 hours. HPLC with RI detector and Amine NH2 column was used to determine xylitolrnconcentration. The highest xylitol yield of 23.56 gLrnwas obtained at 5% yeast dose, 45 pH and 45.68rnhours. The results showed area of xylitol peak and the presence of sugar residuals. According to thernexperiment design, all three parameters have significant effect on xylitol yield. The effect ofrnfermentation period and yeast dose showed dominant effect. The combined effect of yeast dose withrnpH, and yeast dose with fermentation period were also observed to be significant. The adequacy ofrnthe model was tested by analysis of variance. The value of R-squared for the developed correlation isrn0.9821implying 98.21 percent variation in response is attributed to the experimental variables studied.rnIn generally, this study has shown an alternative for the chemical production of xylitol can be carriedrnout by candida mogii with economic and environmental friendly conditions from agricultural residuernas lignocellulosic material. The yield of xylitol was promising with all parameters and down-streamrnprocess.