A study developed at Unicamp in partnership with CTBE, CNPEM and UERJ was published in the journal Scientific Reports.
To produce second-generation ethanol (2G), enzymatic hydrolysis must be carried out, a process in which enzymes produced by microorganisms work together to degrade and convert carbohydrates from straw and sugarcane bagasse into sugars capable of undergoing fermentation.
Understanding the genetic mechanisms that regulate the control and production of these hydrolytic enzymes by these microorganisms is considered fundamental to improving technologies aimed at this purpose.
A group of researchers from Unicamp, in partnership with colleagues from the National Laboratory of Bioethanol Science and Technology (CTBE) of the National Center for Research in Engineering and Materials (CNPEM) and the State University of Rio de Janeiro (UERJ), gave a important step towards understanding different biological mechanisms behind the control and production of hydrolytic enzymes specifically by fungi.
Carried out as part of a project supported by FAPESP, the study was published in the journal Scientific Reports.
“Our findings could be useful for the development of enzymes for use in enzyme cocktails for the production of second-generation ethanol and other products,” said Anete Pereira de Souza, professor at Unicamp and project coordinator, to FAPESP Agency.
The researchers analyzed the genetic mechanisms involved in the secretion and expression of enzymes used by fungi of the species Trichoderma harzianum, Trichoderma ressei e Atroviride trichoderma to degrade sugarcane.
Found in the soil, these fungi, which grow on wood, bark and even other fungi and substrates, hydrolyze different types of carbohydrates – such as cellulose from bagasse and sugarcane straw – through enzymes present in their cell walls.
In order to evaluate whether the enzymes produced by the three species of fungi belonging to the genus Trichoderma have similarities or differences that can increase or decrease their efficiency in biomass degradation and if they act synergistically during this process, the researchers used different biotechnology and bioinformatics approaches.
Firstly, they evaluated the level of activity of the enzymes secreted by the three species of fungi during the fermentation of bagasse extracts, pure cellulose and sugarcane glucose, through the amount of proteins present in these three different substrates at the peak moment of the biodegradation process.
Using a biotechnology technique called RNA-seq, it was also possible to determine the expressed genes. Based on bioinformatics tools, the researchers compared these data and were able to identify networks of genes co-regulated by the three species of fungi that may be fundamental for the biodegradation of biomass by these microorganisms.
“We were able to identify gene coregulation networks, with a high degree of synergy, that are involved in carrying out the sugarcane biomass degradation process by the three species of fungi that encode enzymes”, said Jaire Alves Ferreira Filho, PhD student in genetics and molecular biology at Unicamp and one of the authors of the study.
High degree of synergy
A set of 80 proteins and their respective genes shared by the three species of fungi were identified. Of this total, 19 proteins were observed in all three fungal species.
These 19 proteins and their respective detected genes are involved in the production and secretion of hydrolytic enzymes and are related to different biological mechanisms of biomass biodegradation by the three different species of fungi, the researchers explain.
Elucidating the genetic relationships between these sets of genes can provide important information for the development of microorganisms of industrial interest and also contribute to the understanding of synergistic reactions between enzymes, highlight the study authors.
“The determination of these reactions should promote considerable advances and provide a solid basis for using genetic information for the production of biofuels and numerous biocompounds,” said Maria Augusta Crivelente Horta, first author of the study, who completed a postdoctoral degree with FAPESP scholarship.
THE ARTICLE
The article Network of proteins, enzymes and genes linked to biomass degradation shared by Trichoderma species (doi: 10.1038/s41598-018-19671-w), by Maria Augusta Crivelente Horta, Jaire Alves Ferreira Filho, Natália Faraj Murad, Eidy de Oliveira Santos, Clelton Aparecido dos Santos, Juliano Sales Mendes, Marcelo Mendes Brandão, Sindelia Freitas Azzoni and Anete Pereira de Souza, can be read in the magazine Scientific Reports em www.nature.com/articles/s41598-018-19671-w.
