Comparative Secretome Analysis of Trichoderma reesei and Aspergillus niger during Growth on Sugarcane Biomass

Author(s)

Borin, Gustavo Pagotto ^[1] ; Sanchez, Camila Cristina ^[1] ; de Souza, Amanda Pereira ^[2] ; de Santana, Eliane Silva ^[1] ; de Souza, Aline Tieppo ^[1] ; Paes Leme, Adriana Franco ^[3] ; Squina, Fabio Marcio ^[1] ; Buckeridge, Marcos ^[2] ; Goldman, Gustavo Henrique ^{[1, 4]} ; de Castro Oliveira, Juliana Velasco ^[1]

Affiliation

^[1] CNPEM, Lab Nacl Ciencia & Tecnol Bioetanol CTBE, Campinas, SP - Brazil

^[2] Univ Sao Paulo, Inst Biociencias, Dept Bot, Lab Fisiol Ecol Plantas LAFIECO, Sao Paulo - Brazil

^[3] CNPEM, Lab Nacl Biociencias LNBio, Campinas, SP - Brazil

^[4] Fac Ciencias Farmaceut Ribeirao Preto, Ribeirao Preto, SP - Brazil

• Document type: Journal article
• Source: PLoS One; v. 10, n. 6 JUN 8 2015.
• Web of Science Citations: 38

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 beta-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, Aspergillus niger produced more enzymes (quantitatively and qualitatively) than Trichoderma reesei. However, the most important enzymes related to biomass degradation, including cellobiohydrolases, endoglucanases, beta-glucosidases, beta-xylosidases, endoxylanases, xyloglucanases, and alpha-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. Conclusion Our work provides a detailed qualitative and semi-quantitative secretome analysis of Aspergillus niger and Trichoderma 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. (AU)

• FAPESP's process: 13/01071-9 - Genomic studies of global genetic expression of filamentous fungus Trichoderma reesei grown in bagasse and culm of sugarcane
• Grantee: Gustavo Pagotto Borin
• Support Opportunities: Scholarships in Brazil - Master
• FAPESP's process: 13/09541-4 - Genomic studies of global gene expression of Aspergillus niger grown on sugarcane bagasse and stem
• Grantee: Camila Cristina Sanchez
• Support Opportunities: Scholarships in Brazil - Master
• FAPESP's process: 11/08945-9 - Comparative genomic studies of global gene expression in filamentous fungi grown on bagasse and sugarcane culm
• Grantee: Juliana Velasco de Castro Oliveira
• Support Opportunities: Regular Research Grants