Bioethanol production from coconuts and cactus pretreated by autohydrolysis

Fabiano Avelino Gonçalves,Héctor A Ruiz,Everaldo Silvino Dos Santos,José A Teixeira,Gorete Ribeiro De Macedo

doi:10.1016/j.indcrop.2015.06.041

Abstract

The use of coconut fiber mature, green coconut shell, mature coconut shell and cactus is an important alternative as substrates for bioethanol production, since these lignocellulosic materials (LCMs) are abundant in Brazil, mainly in the Northeast Region. The first objective of this work was to evaluate the autohydrolysis pretreatment (AP) on these LCMs and the susceptibility of the treated materials to enzymatic hydrolysis (EH). The second part of the work deals with the application of semi-simultaneous saccharification and fermentation (SSSF) and simultaneous saccharification and fermentation (SSF) using Zymomonas mobilis, Pichia stipitis, Saccharomyces cerevisiae and as substrate the green coconut shell (selected according to the results obtained in the first part of the work). The LCMs after AP using the highest severity factor (4.64) showed changes in the chemical composition in comparison to the untreated LCMs: between the LCMs the cellulose increase was 48.55%, the hemicellulose decrease was 76.77% and an increase of 62.26% was observed for lignin. The green coconut shell was characterized by SEM, X-ray and FTIR after AP and its EH conversion into glucose was 92.52%. The best results on ethanol yield (90.09%) and ethanol productivity (0.21g/(Lh)) from green coconut shell were obtained by S. cerevisiae using SSSF. Overall, an efficient process for the bioethanol production from green coconut shell was developed.

Highlights

In search to mitigate climate change and fossil fuel dependence of some countries, arise as an alternative biofuel production, especially ethanol produced from sugarcane sucrose and cornstarch
5.64 ± 0.21 9.37 ± 0.22 10.62 ± 0.26 11.47 ± 0.41 10.45 ± 0.34 11.37 ± 0.31 12.25 ± 0.72 11.30 ± 0.29 10.34 ± 0.16 11.56 ± 0.38 10.89 ± 0.76 mature the cellulose increase was 40.55%, the hemicellulose reduction was 50.16% and lignin increase 19.10%; and for mature coconut shell the cellulose increase was 48.55%, the hemicellulose decrease was 74.71% and an increase of 16.43% was observed for lignin
For all pretreated lignocellulosic materials (LCMs), a reduction in the hemicellulose content, and increase of cellulose and lignin was observed, these aspects being strategic for the fractionation of LCM, as it allows the hydrolysis of hemicellulose and enriches the material in cellulose and lignin (Ruiz et al, 2013)

Summary

Introduction

In search to mitigate climate change and fossil fuel dependence of some countries, arise as an alternative biofuel production, especially ethanol produced from sugarcane sucrose and cornstarch. Both processes have economical and environmental limitations for its productive expansion. The LCMs used for ethanol production should be from forests (extracted from vegetable or cultivated), agroindustrial and urban wastes, vegetables grown in inhospitable environments and photosynthetic aquatic biomass (Goncalves et al, 2014) In this context, this work uses agroindustrial waste (coconut fiber mature, green coconut shell and mature coconut shell), urban waste (green coconut shell) and vegetable cultivated in inhospitable environments (cactus) aiming at the bioethanol production. In 2009, the production of cactus in Brazil was 60,000 tons (IBGE, 2012)

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Conclusion