Hydrolysis and fermentation of sugar cane bagasse in bench scale for 2G ethanol production

O objetivo deste trabalho foi avaliar as etapas de hidrolise enzimatica e fermentacao do caldo hidrolitico do bagaco de cana-de-acucar (BCA) para producao de etanol de segunda geracao (2G). Foram realizados experimentos de hidrolise enzimatica empregando cargas de solidos de 8%, 10%, 15% e 20% (m/v). Amostras de BCA innatura e explodido a vapor foram submetidas a diferentes sequencias de pretratamentos: agua + solucao de NaOH 4%; solucao de H2SO4 1% + solucao de NaOH 4%; solucao de H2SO4 1% + solucao de NaOH 7%; solucao NaOH 7%; amonia aquosa 15%; agua. As amostras de bagaco foram caracterizadas quimica e estruturalmente (MEV). Os rendimentos em cada sequencia de pre-tratamento foram calculados. O material pre-tratado foi submetido a experimento de hidrolise enzimatica com diferentes cargas de enzimas (33, 65 e 98 FPU/g de celulose) e configuracoes (SHF Separated Hydrolysis and Fermentation, SSF Simultaneous Saccharification and Fermentation, e BA Batelada Alimentada). Nestes experimentos foi utilizado extrato enzimatico Accelerase 1500 (Genencor). Na etapa de pre-tratamento a amostra de BCA in natura pre-tratada com agua e solucao de NaOH 4% obteve a menor perda de celulose (23,9%). A remocao de hemicelulose e lignina foi de 73,7% e 79,1%, respectivamente. As demais sequencias de pretratamento obtiveram valores de remocao de hemicelulose entre 72,3% a 92,2% e de remocao de lignina entre 60,0% a 88,9%. Hidrolises realizadas com alta carga de solido (20%) apresentaram um hidrolisado mais concentrado em glicose (ca. 110 g/l), obtendo-se 64% de conversao em 34 horas. Apos a etapa de hidrolise seguiuse a etapa fermentacao. Esses experimentos foram realizados com a levedura Saccharomyces cerevisiae (liofilizado comercial) obtendo-se rendimentos na faixa de 75 a 94%. Experimento realizado na configuracao SSF atingiu 86,5% de conversao de celulose a etanol em 14 horas de experimento. Experimento na configuracao SHF obteve 63,2% de conversao de celulose a etanol em 37 horas. Experimento em BA obteve maior massa de glicose com a mesma quantidade de enzima utilizada no experimento em batelada e no mesmo tempo.The objective of this work was to evaluate the hydrolysis and alcoholic fermentation stages of the sugar cane bagasse (SCB) for second generation ethanol production (2G). Hydrolysis experiments were carried out employing 8%, 10%, 15% and 20% (m/v) solid loads. Samples of in natura SCB and steam exploded SCB were submitted to different pretreatment sequences: water + 4.0% NaOH solution; 1.0% H2SO4 solution + 4.0% NaOH 4%; 1.0% H2SO4 solution + 7.0% NaOH solution; 7.0% NaOH solution; aqueous ammonia; water. Pretreated bagasse was characterized (chemical analysis and SEM) and the mass yield of each sequence was evaluated. This material was employed in hydrolysis experiments using different enzyme loads (33, 65 and 98 FPU/g-cellulose). Three different configurations were evaluated: SHF Separated Saccharification and Fermentation, SSF Simultaneous Hydrolysis and Fermentation, and FB Fed-Batch. In these experiments it was employed Accelerase 1500 enzymatic extract (Genencor). Concerning cellulose loss, SCB pretreated with water and 4.0% of NaOH solution presented the best result (23.9%). For this case, the hemicellulose and ligning removal was 73.7% and 79.1%, respectively. For the others pretreatment sequences the hemicellulose and lignin removal range from 72.3 to 92.2%. For lignin removal the values range from 60.0 and 88.9%. Experiments employing high solid load (20%) resulting in a more concentrated hydrolyzed (ca. 110 g/L). In this experiment it was achieved 64% of cellulose to glucose conversion in 34 hour. The fermentation experiments were carried out employing Saccharomyces cerevisiae yeast (lyophilized commercial). The yield ranges from 75 to 94%. Experiment conducted in the SSF configuration achieved 86.5% of cellulose to ethanol conversion in 14 hours. Experiment carried out in SHF configuration achieved 63.2% of cellulose to ethanol conversion in 37 hours. Experiments carried out in FB configuration reached larger amount of glucose with the same enzyme load employed in batch experiment and at the same time