Abstract
Saccharum officinarum bagasse (common name: sugarcane bagasse) and Pennisetum purpureum (also known as Napier grass) are among the most promising feedstocks for bioethanol production in Argentina and Brazil. In this study, both biomasses were assessed before and after acid pretreatment and following hydrolysis with Nasutitermes aquilinus and Cortaritermes fulviceps termite gut digestome. The chemical composition analysis of the biomasses after diluted acid pretreatment showed that the hemicellulose fraction was partially removed. The (hemi) cellulolytic activities were evaluated in bacterial culture supernatants of termite gut homogenates grown in treated and untreated biomasses. In all cases, we detected significantly higher endoglucanase and xylanase activities using pretreated biomasses compared to untreated biomasses, carboxymethylcellulose and xylan. Several protein bands with (hemi) cellulolytic activity were detected in zymograms and two-dimensional gel electrophoresis. Some proteins of these bands or spots were identified as xylanolytic peptides by mass spectrometry. Finally, the diversity of cultured cellulolytic bacterial endosymbionts associated to both Argentinean native termite species was analyzed. This study describes, for the first time, bacterial endosymbionts and endogenous (hemi) cellulases of two Argentinean native termites as well as their potential application in degradation of lignocellulosic biomass for bioethanol production.
Highlights
The interest in lignocellulosic ethanol has been increasing over the last years, mainly due to the global warming concerns and the uncertainty in the cost of petroleum
The enrichment in cellulose was a direct consequence of the removal of hemicellulose (Table 1). This finding indicates that the diluted acid pretreatment removed part of the hemicellulose fraction of S. officinarum bagasse and P. purpureum
These results are in agreement with those reported by Lima and coauthors [14], who used acid, alkaline, sulfite and hot water pretreatment in sugarcane bagasse and several grasses including P. purpureum
Summary
The interest in lignocellulosic ethanol has been increasing over the last years, mainly due to the global warming concerns and the uncertainty in the cost of petroleum. In this sense, the availability of environmentally friendly and sustainable biofuels is crucial. Lignocellulose is the main component of the plant cell wall. This biomass produced by photosynthesis is the most promising and abundant renewable carbon source that can contribute to solve the current problems of energy. The diluted-acid pretreatment seems to be the most appropriate method; this chemical method has been used as a pretreatment for a wide range of lignocellulosic biomasses as well [2,3,4]
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