Abstract
In search to increase the offer of liquid, clean, renewable and sustainable energy in the world energy matrix, the use of lignocellulosic materials (LCMs) for bioethanol production arises as a valuable alternative. The objective of this work was to analyze and compare the performance of Saccharomyces cerevisiae, Pichia stipitis and Zymomonas mobilis in the production of bioethanol from coconut fibre mature (CFM) using different strategies: simultaneous saccharification and fermentation (SSF) and semi-simultaneous saccharification and fermentation (SSSF). The CFM was pretreated by hydrothermal pretreatment catalyzed with sodium hydroxide (HPCSH). The pretreated CFM was characterized by X-ray diffractometry and SEM, and the lignin recovered in the liquid phase by FTIR and TGA. After the HPCSH pretreatment (2.5% (v/v) sodium hydroxide at 180 °C for 30 min), the cellulose content was 56.44%, while the hemicellulose and lignin were reduced 69.04% and 89.13%, respectively. Following pretreatment, the obtained cellulosic fraction was submitted to SSF and SSSF. Pichia stipitis allowed for the highest ethanol yield – 90.18% – in SSSF, 91.17% and 91.03% were obtained with Saccharomyces cerevisiae and Zymomonas mobilis, respectively. It may be concluded that the selection of the most efficient microorganism for the obtention of high bioethanol production yields from cellulose pretreated by HPCSH depends on the operational strategy used and this pretreatment is an interesting alternative for add value of coconut fibre mature compounds (lignin, phenolics) being in accordance with the biorefinery concept.
Highlights
The emerging need to obtain clean, low cost and renewable energy in support of a sustainable energy matrix, demands for the development of biotechnology processes, as is the case of the production of biofuels, that will contribute to the energetic selfsufficiency worldwide
Gonçalves et al [15] carried out an autohydrolysis pretreatment (200 C for 50 min) in coconut fibre mature (CFM), that resulted in a solid yield of 76.89%, cellulose increase of 40.55%, hemicellulose reduction of 50.16% and lignin increase of 19.10%
Results of analysis of variance (ANOVA) listed in Equation (6) revealed that the second-order polynomial models adequately represent the responses of cellulose yield with coefficients of determination R2, which indicates that 95.66% of the variability of response might be explained by the model
Summary
The emerging need to obtain clean, low cost and renewable energy in support of a sustainable energy matrix, demands for the development of biotechnology processes, as is the case of the production of biofuels, that will contribute to the energetic selfsufficiency worldwide. Being a step toward energetic sustainability, the matrix becomes more “green”, but does not fully satisfy the socio-environmental issues and global geographic distribution. In this regard, an alternative solution is the bioethanol production from LCMs and other non-food source of carbohydrates, available according to the location, making possible a global production of this biofuel. Some barriers are present in the production of cellulosic ethanol at commercial scale, especially the stages of pretreatment, enzymatic hydrolysis processing, fermentation (hexose and pentose) and the integral use of the raw material. There is a need to select raw materials, according to the regions, that can be employed as substrate to produce bioethanol
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