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Master's Dissertation
DOI
Document
Author
Full name
Sabrina Evelin Martiniano
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
Lorena, 2013
Supervisor
Committee
Silva, Silvio Silverio da (President)
Silva, Cristiane Karina Malvezzi da
Felipe, Maria das Graças de Almeida
Title in Portuguese
Potencial fermentativo das leveduras Candida shehatae CG8-8BY e Spathaspora arborariae UFMG-HM 19.1A para a produção de etanol de segunda geração
Keywords in Portuguese
Candida shehatae
Etanol de segunda geração
Fermentacao de D-xilose
Spathaspora arborariae
Abstract in Portuguese
O etanol de segunda geracao e produzido a partir da hidrolise da biomassa vegetal, liberando os acucares presentes em sua estrutura com sua subsequente fermentacao. Entretanto, um dos desafios em sua producao e a baixa diversidade de microrganismos capazes de fermentar eficientemente a D-xilose, principal acucar no hidrolisado hemicelulosico. Este trabalho avaliou o potencial fermentativo de novas linhagens das leveduras Candida shehatae e Spathaspora arborariae para a producao de etanol a partir de hidrolisado hemicelulosico de bagaco de cana-de-acucar. Foram avaliadas quatro linhagens de C. shehatae em meio YPX (10 g/L de extrato de levedura, 20 g/L de peptona e 50 g/L de D-xilose) e, posteriormente, em hidrolisado hemicelulosico. A levedura C. shehatae CG8-8BY apresentou o melhor desempenho fermentativo em hidrolisado. Apos esta etapa, avaliou-se o efeito da suplementacao do meio na fermentacao de D-xilose por C. shehatae CG8-8BY e S. arborariae UFMG-HM19.1A. O extrato de farelo de arroz na concentracao de 20 g/L demonstrou ser uma fonte de nitrogenio eficiente e de baixo de custo para a suplementacao de hidrolisado hemicelulosico. Por ultimo, foi estudado o efeito da temperatura, agitacao e pH na fermentacao de hidrolisado hemicelulosico por meio de planejamento fatorial completo 23, com tres repeticoes no ponto central, para as duas leveduras. Todos os experimentos foram conduzidos em incubadora de bancada. De acordo com os resultados, o pH e o parametro mais relevante para a producao de etanol pelas linhagens estudadas, seguido da temperatura. Os melhores resultados foram obtidos nas condicoes de 30°C, 150 rpm e pH 5,0, referentes ao ponto central, para as duas linhagens avaliadas. Nestas condicoes, a linhagem C. shehatae CG8-8BY produziu 11,58 g/L de etanol, com fator de rendimento em etanol de 0,26 g/g, produtividade volumetrica de 0,16 g/L.h, eficiencia de fermentacao de 50,36% e consumo de D-xilose de 99,83%. A linhagem S. arborariae UFMG-HM19.1A produziu 11,6 g/L de etanol, com fator de rendimento em etanol de 0,26 g/g, produtividade volumetrica de 0,15 g/L.h, eficiencia de fermentacao de 51,1% e consumo de D-xilose de 88%. Os resultados demonstram que as leveduras estudadas apresentam potencial para producao de etanol de segunda geracao. A importancia do uso de linhagens microbianas eficazes e o aprimoramento dos metodos contribuem para um melhor desenvolvimento desta tecnologia em larga escala.
Title in English
Fermentative potential of Candida shehatae CG8-8BY and Spathaspora arborariae UFMG-HM19.1A yeasts to second generation ethanol production
Keywords in English
Candida shehatae
Dxylose fermentation
Second-generation ethanol
Spathaspora arborariae
Abstract in English
Second generation ethanol is produced from vegetal biomass, releasing sugars present into its structure with its subsequent fermentation. However, one of the challenges in its production it the low diversity of microorganisms able to ferment efficiently D-xylose, the main sugar in hemicellulosic hydrolysate. This study evaluated the fermentative potential of new yeasts strains Candida shehatae and Spathaspora arborariae UFMG-HM 19.1A to ethanol production from sugarcane hemicellulosic hydrolysate. Four strains of C. shehatae were evaluated in YPX medium (10 g/L yeast extract, 20 g/L peptone, 50 g/L D-xylose) and, subsequently, in hemicellulosic hydrolysate. C. shehatae CG8-8BY presented the best fermentative performance in hydrolysate. Then, the effect of medium supplementation in Dxylose fermentation by C. shehatae CG8-8BY e S. arborariae UFMG-HM19.1A were evaluated. Rice bran extract in a concentration of 20 g/L was presented as an efficient and inexpensive nitrogen source for hemicellulosic hydrolysate supplementation. Lastly, it were evaluated the effects of temperature, agitation and pH on hemicellulosic hydrolysate fermentation, studied by full factorial design 23, with three replications at the central point, to both yeasts. All experiments were carried out in rotatory shaker. According to results, pH is the most important parameter to ethanol production by strains studied, followed by temperature. The best results were obtained at 30 °C, 150 rpm and pH 5.0, concerning the central point, for two yeasts evaluated. Accordingly, C. shehatae CG8-8BY strain produced 11.58 g/L of ethanol, with ethanol yield equal 0.26 g/g, productivity equal 0.16 g/L.h, fermentation efficiency equal 50.36% and xylose consumption equal 99.83%. S. arborariae UFMG-HM19.1A strain produced 11.6 g/L of ethanol, with ethanol yield equal 0.26 g/g, productivity equal 0.15 g/L.h, fermentation efficiency equal 51.1% and D-xylose consumption equal 88%. Present data showed that yeasts studied have potential to second generation ethanol production. The importance of use of new effective strains and increasing of methods contributes for a better development of this technology in large scale.
 
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2016-09-14
 
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