title: Comparative Secretome Analysis of Trichoderma reesei and Aspergillus niger during Growth on Sugarcane Biomass.
abstract: BACKGROUND
  Our dependence on fossil fuel sources and concern about the environment has generated a worldwide interest in establishing new sources of fuel and energy. Thus, the use of ethanol as a fuel is advantageous because it is an inexhaustible energy source and has minimal environmental impact. Currently, Brazil is the world's second largest producer of ethanol, which is produced from sugarcane juice fermentation. However, several studies suggest that Brazil could double its production per hectare by using sugarcane bagasse and straw, known as second-generation (2G) bioethanol. Nevertheless, the use of this biomass presents a challenge because the plant cell wall structure, which is composed of complex sugars (cellulose and hemicelluloses), must be broken down into fermentable sugar, such as glucose and xylose. To achieve this goal, several types of hydrolytic enzymes are necessary, and these enzymes represent the majority of the cost associated with 2G bioethanol processing. Reducing the cost of the saccharification process can be achieved via a comprehensive understanding of the hydrolytic mechanisms and enzyme secretion of polysaccharide-hydrolyzing microorganisms. In many natural habitats, several microorganisms degrade lignocellulosic biomass through a set of enzymes that act synergistically. In this study, two fungal species, Aspergillus niger and Trichoderma reesei, were grown on sugarcane biomass with two levels of cell wall complexity, culm in natura and pretreated bagasse. The production of enzymes related to biomass degradation was monitored using secretome analyses after 6, 12 and 24 hours. Concurrently, we analyzed the sugars in the supernatant.
  
  
  RESULTS
  Analyzing the concentration of monosaccharides in the supernatant, we observed that both species are able to disassemble the polysaccharides of sugarcane cell walls since 6 hours post-inoculation. The sugars from the polysaccharides such as arabinoxylan and β-glucan (that compose the most external part of the cell wall in sugarcane) are likely the first to be released and assimilated by both species of fungi. At all time points tested, A. niger produced more enzymes (quantitatively and qualitatively) than T. reesei. However, the most important enzymes related to biomass degradation, including cellobiohydrolases, endoglucanases, β-glucosidases, β-xylosidases, endoxylanases, xyloglucanases, and α-arabinofuranosidases, were identified in both secretomes. We also noticed that the both fungi produce more enzymes when grown in culm as a single carbon source.
  
  
  CONCLUSIONS
  Our work provides a detailed qualitative and semi-quantitative secretome analysis of A. niger and T. reesei grown on sugarcane biomass. Our data indicate that a combination of enzymes from both fungi is an interesting option to increase saccharification efficiency. In other words, these two fungal species might be combined for their usage in industrial processes.
authors.affiliation: Laboratório Nacional de Ciência e Tecnologia do Bioetanol (CTBE), Centro Nacional de Pesquisa em Energia e Materiais (CNPEM), Campinas, São Paulo, Brazil.
authors.forename: Gustavo Pagotto
authors.initials: GP
authors.lastname: Borin
authors.affiliation: Laboratório Nacional de Ciência e Tecnologia do Bioetanol (CTBE), Centro Nacional de Pesquisa em Energia e Materiais (CNPEM), Campinas, São Paulo, Brazil.
authors.forename: Camila Cristina
authors.initials: CC
authors.lastname: Sanchez
authors.affiliation: Laboratório de Fisiologia Ecológica de Plantas (LAFIECO), Departamento de Botânica, Instituto de Biociências, Universidade de São Paulo, São Paulo, Brazil.
authors.forename: Amanda Pereira
authors.initials: AP
authors.lastname: de Souza
authors.affiliation: Laboratório Nacional de Ciência e Tecnologia do Bioetanol (CTBE), Centro Nacional de Pesquisa em Energia e Materiais (CNPEM), Campinas, São Paulo, Brazil.
authors.forename: Eliane Silva
authors.initials: ES
authors.lastname: de Santana
authors.affiliation: Laboratório Nacional de Ciência e Tecnologia do Bioetanol (CTBE), Centro Nacional de Pesquisa em Energia e Materiais (CNPEM), Campinas, São Paulo, Brazil.
authors.forename: Aline Tieppo
authors.initials: AT
authors.lastname: de Souza
authors.affiliation: Laboratório Nacional de Biociências (LNBio), Centro Nacional de Pesquisa em Energia e Materiais (CNPEM), Campinas, São Paulo, Brazil.
authors.forename: Adriana Franco
authors.initials: AF
authors.lastname: Paes Leme
authors.affiliation: Laboratório Nacional de Ciência e Tecnologia do Bioetanol (CTBE), Centro Nacional de Pesquisa em Energia e Materiais (CNPEM), Campinas, São Paulo, Brazil.
authors.forename: Fabio Marcio
authors.initials: FM
authors.lastname: Squina
authors.affiliation: Laboratório de Fisiologia Ecológica de Plantas (LAFIECO), Departamento de Botânica, Instituto de Biociências, Universidade de São Paulo, São Paulo, Brazil.
authors.forename: Marcos
authors.initials: M
authors.lastname: Buckeridge
authors.affiliation: Laboratório Nacional de Ciência e Tecnologia do Bioetanol (CTBE), Centro Nacional de Pesquisa em Energia e Materiais (CNPEM), Campinas, São Paulo, Brazil; Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Ribeirão Preto, São Paulo, Brazil.
authors.forename: Gustavo Henrique
authors.initials: GH
authors.lastname: Goldman
authors.affiliation: Laboratório Nacional de Ciência e Tecnologia do Bioetanol (CTBE), Centro Nacional de Pesquisa em Energia e Materiais (CNPEM), Campinas, São Paulo, Brazil.
authors.forename: Juliana Velasco de Castro
authors.initials: JV
authors.lastname: Oliveira
mesh_terms: D001234:Aspergillus niger / Q000254:growth & development / Q000378:metabolism*; D018533:Biomass; D005656:Fungal Proteins / Q000378:metabolism; D055442:Metabolome; D055432:Metabolomics / Q000379:methods; D009005:Monosaccharides / Q000378:metabolism; D031786:Saccharum / Q000382:microbiology*; D014242:Trichoderma / Q000254:growth & development / Q000378:metabolism*
chemical_list: D005656:Fungal Proteins; D009005:Monosaccharides