Combination of steam explosion and laccase-mediator treatments prior to Eucalyptus globulus kraft pulping

Optimization of Laccase/Mediator System (LMS) Stage Applied in Fractionation of Eucalyptus globulus

In a biorefinery framework, a laccase/mediator system treatment following autohydrolysis was carried out for eucalyptus wood prior to soda-anthraquinone pulping. The enzymatic and autohydrolysis conditions, with a view to maximizing the extraction of hemicelluloses while preserving the integrity of glucan, were optimized. Secondly, pulping of solid phase from Eucalyptus globulus wood autohydrolysis and the enzymatic process was carried out and compared with a conventional soda-anthraquinone (AQ) pulping process. The prehydrolysis and enzymatic delignification of the raw material prior to the delignification with soda- Anthraquinone (AQ) results in paper sheets with a lower kappa number and brightness and strength properties close to conventional soda-AQ paper and a liquid fraction rich in hemicellulose compounds that can be used in additional ways. The advantage of this biorefinery scheme is that it requires a lower concentration of chemical reagents, and lower operating times and temperature in the alkaline delignification stage, which represents an economic and environmental improvement over the conventional process.

Evaluation of ligninolytic enzymes, ultrasonication and liquid hot water as pretreatments for bioethanol production from cotton gin trash

Cotton gin trash (CGT) is a ubiquitous cotton-production-waste resource which can be used for ethanol production. In this research, seven combinations of three pretreatments; ultrasonication, liquid hot water and ligninolytic enzymes were evaluated on CGT to select the best pretreatments combination that increased the cellulose conversion and the ethanol yield in the saccharification and fermentation processes, respectively. The structural changes in the cellulose, hemicellulose and lignin from CGT were followed using FT-IR after each pretreatment. All the pretreatment combinations modified the CGT's structure and composition compared with the unpretreated CGT, and the majority of them improved release of sugars originally present in the CGT. The best results were achieved by the sequential combination of ultrasonication, hot water, and ligninolytic enzymes with an improvement of 10% in the ethanol yield and cellulose conversion compared to the other pretreatments. These results are a contribution to develop a feasible bioethanol production from CGT.

Effect of steam explosion and enzymatic pre-treatments on pulping and bleaching of Hesperaloe funifera

A non-wood raw material with high potential for pulp and paper applications (Hesperaloe funifera) was subjected to a steam explosion pre-treatment, and the subsequent effect of this pretreatment on biopulping and biobleaching was studied. An increase in the delignification rate, bigger than that reported for autohydrolysis and acid hydrolysis pre-treatments, and a reduction in chemical consumption were found during kraft pulping of the exploded samples. However, biopulping with the laccase-mediator system (LMS) did not lead to a reduction in the kappa number in either non-exploded or exploded unbleached pulps. On the other hand, the steam explosion pretreatment boosted the advantages of the LMS pre-treatment (decrease in kappa number and increase in brightness) favored biobleaching, with a 53.1% delignification rate and a final brightness of 67% ISO. Finally, the steam explosion pre-treatment also improved the color properties of the bleached pulp and reduced the hydrogen peroxide consumption by 24.6%.

Lignin changes after steam explosion and laccase-mediator treatment of eucalyptus wood chips

Eucalyptus globulus chips were steam exploded followed by treatment with a laccase-mediator system (LMS) under different experimental conditions. Removal of hemicelluloses and, to a lesser extent, lignin was observed. Thermogravimetic analyses of whole meal obtained from chips before and after steam explosion indicated an increase in lignin degradation temperature due to lignin condensation. In contrast, application of LMS treatment caused a reduction in lignin and polysaccharide degradation temperatures. Lignins were isolated from wood samples before and after each treatment and analyzed by 2D NMR and (13)C NMR. An increase in carboxyl and phenolic hydroxyl groups and a significant decrease in β-O-4 structures were found in steam-exploded samples. The most relevant changes observed after laccase treatment were increased secondary OH and degree of condensation.