Avaliação de pré-tratamento hidrotérmico de palha e bagaço de cana-de-açúcar para produção de xilo-oligossacarídeos e hidrolisado enzimático de glicose
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Data
2022-06-21
Autores
Dias, Lídia Manfrin
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Universidade Estadual Paulista (Unesp)
Resumo
A busca por fontes de energias renováveis e ambientalmente corretas vem aumentando nos últimos anos culminando no conceito de biorrefinaria, o qual refere-se ao aproveitamento integral da biomassa lignocelulósica através da produção de múltiplos bioprodutos de interesse comercial. Uma forma de aproveitamento dos materiais lignocelulósicos durante o processo de produção de etanol de segunda geração (etanol celulósico) é a produção de xilo-oligossacarídeos (XOS) durante o pré-tratamento da biomassa. Objetivo: O objetivo deste trabalho foi otimizar a produção de XOS através de prétratamento hidrotérmico (PTH) em bagaço (BCA) e palha (PCA) de cana-deaçúcar e hidrolisar enzimaticamente a fração celulósica obtida após o PTH para produção de etanol (etanol 2G). Metodologia: O BCA e a PCA foram pré-tratadas hidrotermicamente sob diferentes condições de temperatura, tempo e consistência (carga mássica). Essas variáveis foram incorporadas ao um delineamento composto central rotacional em resposta a produção de XOS. As frações sólidas (resíduo rico em celulose e lignina) e líquidas (hidrolisado hemicelulósico) obtidas após os diferentes PTHs foram caracterizadas quimicamente. As frações sólidas obtidas na condição otimizada (BCA e PCA) foram hidrolisadas com preparado enzimático Cellic CTec 2 com diferentes cargas mássicas e enzimáticas. Resultados: As condições de PTH para máxima produção de XOS foram de 161,9 °C por 75,3 min e 10% de consistência para o BCA e 177,2 °C por 64,8 min e 10% de consistência para a PCA. Os PTHs do BCA e da PCA nessas condições resultaram na produção de 53,3 e 96,3 mg de XOS por grama de subproduto (base seca), respectivamente. As frações sólidas do BCA e da PCA obtidas após os PTHs nas condições previamente otimizadas apresentaram conversões máximas de celulose em glicose de 70 e 94%, respectivamente. O aumento da consistência não resultou em diminuição expressiva das conversões de celulose em glicose. As concentrações de glicose nos hidrolisados oriundos do BCA e da PCA com 20% de consistência foram de 64 e 112 g.L-1, respectivamente. Desta forma, a condição de 20% de consistência foi selecionada para verificar o efeito do aumento da carga enzimática, a qual não resultou em aumento significativo das conversões de celulose em glicose, ambos BCA e PCA, com excessão a carga enzimática de 30 FPU por grama de substrato (base seca). Conclusão: Os resultados indicam que os PTHs nas condições otimizadas (BCA e PCA) foram excelentes para produção de XOS. Além disso, as frações sólidas ricas em celulose obtidas após os PTHs em condição previamente otimizada apresentaram potencial na hidrólise enzimática com preparado enzimático Cellic CTec 2, portanto, podendo ser uma estratégica para a produção de etanol de segunda geração (etanol celulósico).
The search for renewable and environmentally correct energy sources has increased in recent years, culminating in the concept of biorefinery, which refers to the full use of lignocellulosic biomass through the production of multiple bioproducts of commercial interest. One way of using lignocellulosic materials during the production process of second-generation ethanol (cellulosic ethanol) is the production of xylo-oligosaccharides (XOS) during the pre-treatment of biomass. Objective: The objective of this work was to optimize the production of XOS through hydrothermal pretreatment (PTH) in sugarcane bagasse (BCA) and straw (PCA) and to enzymatically hydrolyze the cellulosic fraction obtained after PTH to produce ethanol (2G ethanol). Methodology: BCA and PCA were hydrothermally pretreated under different conditions of temperature, time and consistency (mass load). These variables were incorporated into a central rotational composite design in response to XOS production. The solid (cellulose and lignin-rich residue) and liquid (hemicellulose hydrolyzate) fractions obtained after the different PTHs were chemically characterized. The solid fractions obtained in the optimized condition (BCA and PCA) were hydrolyzed with Cellic CTec 2 enzymatic preparation with different mass and enzymatic loads. Results: The PTH conditions for maximum XOS production were 161.9 °C for 75.3 min and 10% consistency for BCA and 177.2 °C for 64.8 min and 10% consistency for PCA. BCA and PCA PTHs under these conditions resulted in the production of 53.3 and 96.3 mg of XOS per gram of by-product (dry basis), respectively. The solid fractions of BCA and PCA obtained after PTHs under the previously optimized conditions showed maximum cellulose conversions to glucose of 70 and 94%, respectively. The increase in consistency did not result in a significant decrease in cellulose to glucose conversions. Glucose concentrations in hydrolysates from BCA and PCA with 20% consistency were 64 and 112 g.L-1, respectively. Thus, the condition of 20% consistency was selected to verify the effect of increasing the enzymatic load, which did not result in a significant increase in cellulose to glucose conversions, both BCA and PCA, with the exception of an enzyme load of 30 FPU per gram of substrate (dry weight). Conclusion: The results indicate that PTHs under optimized conditions (BCA and PCA) were excellent for XOS production. In addition, the cellulose-rich solid fractions obtained after PTHs in a previously optimized condition showed potential in enzymatic hydrolysis with the Cellic CTec 2 enzyme preparation, therefore, it could be a strategy for the production of second-generation ethanol (cellulosic ethanol).
The search for renewable and environmentally correct energy sources has increased in recent years, culminating in the concept of biorefinery, which refers to the full use of lignocellulosic biomass through the production of multiple bioproducts of commercial interest. One way of using lignocellulosic materials during the production process of second-generation ethanol (cellulosic ethanol) is the production of xylo-oligosaccharides (XOS) during the pre-treatment of biomass. Objective: The objective of this work was to optimize the production of XOS through hydrothermal pretreatment (PTH) in sugarcane bagasse (BCA) and straw (PCA) and to enzymatically hydrolyze the cellulosic fraction obtained after PTH to produce ethanol (2G ethanol). Methodology: BCA and PCA were hydrothermally pretreated under different conditions of temperature, time and consistency (mass load). These variables were incorporated into a central rotational composite design in response to XOS production. The solid (cellulose and lignin-rich residue) and liquid (hemicellulose hydrolyzate) fractions obtained after the different PTHs were chemically characterized. The solid fractions obtained in the optimized condition (BCA and PCA) were hydrolyzed with Cellic CTec 2 enzymatic preparation with different mass and enzymatic loads. Results: The PTH conditions for maximum XOS production were 161.9 °C for 75.3 min and 10% consistency for BCA and 177.2 °C for 64.8 min and 10% consistency for PCA. BCA and PCA PTHs under these conditions resulted in the production of 53.3 and 96.3 mg of XOS per gram of by-product (dry basis), respectively. The solid fractions of BCA and PCA obtained after PTHs under the previously optimized conditions showed maximum cellulose conversions to glucose of 70 and 94%, respectively. The increase in consistency did not result in a significant decrease in cellulose to glucose conversions. Glucose concentrations in hydrolysates from BCA and PCA with 20% consistency were 64 and 112 g.L-1, respectively. Thus, the condition of 20% consistency was selected to verify the effect of increasing the enzymatic load, which did not result in a significant increase in cellulose to glucose conversions, both BCA and PCA, with the exception of an enzyme load of 30 FPU per gram of substrate (dry weight). Conclusion: The results indicate that PTHs under optimized conditions (BCA and PCA) were excellent for XOS production. In addition, the cellulose-rich solid fractions obtained after PTHs in a previously optimized condition showed potential in enzymatic hydrolysis with the Cellic CTec 2 enzyme preparation, therefore, it could be a strategy for the production of second-generation ethanol (cellulosic ethanol).
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Palavras-chave
Subprodutos de cana-de-açúcar, Pré-tratamento hidrotérmico, Delineamento Composto Central Rotacional, Metodologia de Superfície de Resposta, Xilooligossacarídeos, Hidrólise enzimática, Sugarcane by-products, Hydrothermal pre-treatment, Central Composite Rotational Design, Response Surface Methodology, Xylooligosaccharides, Enzymatic hydrolysis