Study of charcoal detoxification of acid hydrolysate from corncob and its fermentation to xylitol

In the present study, adsorption isotherms, kinetics and thermodynamics of fermentation inhibitors generated during the acid hydrolysis of corncob were investigated using activated charcoal (0.5-2.0% w/v) as the adsorbent. The results indicated that lower pH and lower temperature favor the adsorption of both furans and phenolics. The adsorption kinetic regimes were found more favorable in pseudo second order kinetics than pseudo first order kinetics. The experimental values were in good correlation with the predicted values with a regression coefficient (R2) value of more than 0.99. Moreover, the negative values of enthalpy (ΔH), and free energy (ΔG) indicated that the adsorption process was spontaneous in nature and exothermic. The detoxified corncob hydrolysate on its assessment for fermentability revealed the production of 4.8 g/L and 4.3 g/L xylitol from Candida tropicalis ITCC 1830 and C. tropicalis MTCC 9038. The activated charcoal adsorption has shown differential adsorption capacity and isotherms on various inhibitors under different conditions. Hence using the optimum conditions the process efficiency can be improved to make the whole process cost competitive.