|993-3||Oxalic acid fiber expansion (OAFEX) of sugar cane bagasse and bioconversion of hemicellulosic hydrolysate into ethanol by Candida shehatae UFMG 52.2, novel yeast from Brazilian biodiversity|
|Autores:||Anuj Kumar Chandel (EEL - USP - Escola de Engenharia de Lorena) ; Felipe Antonio Fernandes Antunes (EEL - USP - Escola de Engenharia de Lorena) ; Juliana Regina Galvão Reis (EEL - USP - Escola de Engenharia de Lorena) ; Thaís Suzane Santos Milessi (EEL - USP - Escola de Engenharia de Lorena) ; Wagner Luiz da Costa Freitas (EEL - USP - Escola de Engenharia de Lorena) ; Carlos Augusto Rosa (UFMG - Universidade Federal de Minas Gerais) ; Silvio Silvério da Silva (EEL - USP - Escola de Engenharia de Lorena) |
Sugarcane bagasse (SB) is an abundantly available feedstock in Brazil which could be considered as a potential raw material for the second generation ethanol production. However, biomass recalcitrance and efficient bioconversion hinder the commercialization of cellulosic ethanol. This study aims to hemicellulose depolymerisation by oxalic acid mediated pretreatment and the ethanol production from resultant sugar solution by Candida shehatae UFMG 52.2 under batch fermentation conditions. Oxalic acid pretreatment of SB (3.5% w/v, 160 0C, 20 min, solid: liquid=1:10) produced sugars (9.51 g/l xylose, 1.35 g/l glucose and 0.70 g/l arabinose) and inhibitors (1.47 g/L acetic acid, 2.50 g/L of total phenolics). It was detoxified by calcium hydroxide overliming prior to fermentation to eliminate the fermentation inhibitors from hydrolysate. A maximum of ethanol production (3.2 g/l, yield 0.34 g/g) was obtained after 24 hrs of incubation at 30 0C and 200 rpm. Inoculum (0.5 g/l d.wt cells) was transferred aseptically prior to fermentation of detoxified oxalic acid hydrolysate. Cells production (3.57 g/l) was found continuously increased with the incubation time (72 h). These results show that Candida shehatae utilizes ethanol as carbon source for biomass growth after the exhaustion of carbon source. After 24 hrs of incubation, only 0.56 g/l remaining sugars present in the fermentation medium however biomass was regularly increasing until the end of fermentation reaction. Scanning electron microscope (SEM) analysis was also done to observe the structural changes in bagasse surface after OAFEX. This study demonstrates that oxalic acid catalyses the hemicellulose depolymerisation and the potential of new pentose fermenting yeast, Candida shehatae UFMG 52.2 for ethanol production.
Acknowledgments: FAPESP-BIOEN, CAPES and CNPq
Palavras-chave: Oxalic acid, fiber expansion (OAFEX), sugar cane bagasse, Candida shehatae UFMG 52.2, bioethanol