Produção de etanol 2g em reator de leito fixo e por bioprocessamento consolidado utilizando leveduras de alta performance ; 2G ethanol production in fixed bed reactor and by consolidated bioprocessing using high performance yeasts

In order to enable the industrial production of second generation (2G) ethanol, the development of processes with high productivity using hydrolysates of lignocellulosic material containing high concentration of inhibitors, with minimum enzymes concentration due to its impact on the total cost of the process, are some of the main challenges to be overcome. In this sense, researches in genetic engineering have been working towards obtaining yeast strains that are more tolerant to inhibitors present in hydrolysates and to the ethanol produced, as well as strains presenting capacity to produce and secrete enzymes, in addition to ferment pentoses and hexoses. The immobilization of cells in calcium alginate contributes to protect cells from the harmful effects of inhibitors, besides allowing the use of high cell densities, facilitating the recovery of products and the reuse of biocatalysts. Thus, the present work aimed to contribute to the development of a high productivity 2G ethanol production process using hemicellulose hydrolysates and superior recombinant yeast cells. At the first step of the research, after toxic and irreversible effects to the immobilized cells caused by the use of fermentative medium composed by concentrated hemicellulose hydrolysate during continuous fermentation were evidenced, experiments in mini-reactors unveiled the strong and synergistic effects between the high inhibitors load in fermentative medium and ethanol produced during fermentation, associated to the exposure time and the yeast strain characteristics. The results led the study to searching more robust and promising yeast strains, along with fermentative media presenting reduced inhibitors’ load. Three superior recombinant yeasts (S. cerevisae T18, HAA1 and MDS130) modified for xylose consumption, kindly donated by Prof. Johan Thevelein (KU Leuven and NovelYeast®, Belgium), were evaluated in different fermentative media formulated with concentrated crude hydrolysate (HC), detoxified hydrolysate (HD) and crude hydrolysate ...