Wet Oxidation Pretreatment of Tobacco Stalks and Orange Waste for Bioethanol Production. Preliminary results

Wet oxidation (WO) was used as a pretreatment method prior to enzymatic hydrolysis of tobacco stalks and orange waste. The pretreatment, performed at 195 degrees C and an oxygen pressure of 1.2 MPa, for 15 min, in the presence of Na2CO3, increased the cellulose content of the materials and gave cellulose recoveries of approximately 90%.

The pretreatment enhanced the susceptibility of cellulose to enzymatic hydrolysis. The highest enzymatic convertibility, that of 64.9%, was achieved for pretreated tobacco stalks. The ethanolic fermentation of the WO filtrates, using Saccharomyces cerevisiae, was inhibited compared to the fermentation of a reference glucose solution.

Inhibition was more intense for the filtrate of tobacco stalks than for that of orange waste. The inhibition degree of the volumetric productivity of ethanol was higher (79.1-86.8%) than that of the ethanol yield (7.1-9.5%).