Controle analítico das perdas ligno(hemi)celulósicas durante a derivatização química do bagaço de cana

Abstract

The cane sugar bagasse from the sugarcane mills has been used to generate electricity by burning and steam generation, and in the near future it will also be directed to the production of cellulosic ethanol. The bagasse is main composed of cellulose (50%), hemicellulose (30%) and lignin (20 %). In order to apply this byproduct for other purposes such as the removal of environmental contaminants, it is proposed a comparative partial derivatization of the bagasse in order to obtain a dipolysaccharide-aromatic ether-linked complex with epichlorohydrin ("cross-linked cane bagasse " - CLCB). The target in the native substrate are the alcoholic or phenolic groups plenty available and this reaction is carried out in a strongly alkaline medium. Except for a tiny fraction, cellulose is insoluble in alkali while the lignin is largely and hemicellulose (heteroxylan) is the almost completely, depending on the reaction kinetics (alkali concentration, temperature and time). Thus, loss of native bagasse are unavoidable but can be minimized. The goal of this work was then monitor such losses by determination of total carbohydrates and alkali- soluble lignin fraction being solubilized under the drastic alkaline conditions, and monitoring of resistance to enzymatic hydrolysis. Exploring factorial design with respect to the volume and concentration of alkali, temperature, bagasse grammature and reaction time, we were able selecting the most important factors influencing these procedural losses and the variables and the more appropriate conditions for both the preliminary step of mercerization as well as the subsequent one derivatization of the mercerized bagasse with covalently linking agent, epichlorohydrin. The results indicated that for the mercerization step, the NaOH concentration was the most significant variable for increased procedural losses and less resistance to enzymatic hydrolysis. As for the step of cross-linking with epichlorohydrin, the temperature was most significant for the reduction of procedural losses and increased resistance to enzymatic hydrolysis variable, indicating that in temperatures between 20 and 40 °C the desired reaction of cross-linking must have occurred with greater intensity. Although well explored the use of bagasse for similar applications in the literature, the issue of procedural losses explored here is not reported, assuming such authors work with full bagasse when in fact they should refer to residual cellulose.