Development of Saccharomyces cerevisiae strains through heterologous expression of...
| Grant number: | 16/06142-0 |
| Support type: | Program for Research on Bioenergy (BIOEN) - Regular Program Grants |
| Duration: | July 01, 2016 - December 31, 2018 |
| Field of knowledge: | Engineering - Chemical Engineering |
| Principal Investigator: | Aline Carvalho da Costa |
| Grantee: | Aline Carvalho da Costa |
| Home Institution: | Faculdade de Engenharia Química (FEQ). Universidade Estadual de Campinas (UNICAMP). Campinas , SP, Brazil |
| Assoc. researchers: | Daniele Longo Machado ; Lauren Bergmann Soares ; Thaynara Coradini Pin |
Abstract
Although the steps of the second generation ethanol (2G) production process are known and commercial plants begin to emerge in Brazil and worldwide, admittedly there are still bottlenecks that need to be improved to make ethanol 2G competitive. This project involves several theses addressing different stages of the process, always seeking to tackle the remaining bottlenecks.Pretreatment is one of the most important steps in the process, and although the pretreatments considered economical are those that do not delignify the biomass, maintaining the lignin in the solid fraction has a number of disadvantages. The use of ionic liquids, solvents considered environmentally friendly and that can be recovered and reused, may turn delignification economically viable, especially if protic ionic liquid (PILs), which are simpler and cheaper to synthesize, are used. Nevertheless, there are few studies about pretreatment with PILs and in a search prior to a patent application at the end of 2015 only 3 works that were not from our research group were found. In this project a process of production of LIPs and pretreatment of sugarcane bagasse with recovery and reuse of the LIP will be proposed based on very promising preliminary results that gave rise to the patent application.The step of pentoses fermentation is also one of the bottlenecks in the process. The use of genetically modified micro-organisms has been proposed, but the fermentation with wild strains is always easier and cheaper. Although low yields and productivities are still reported, there are not much literature works that implement strategies known in the first generation ethanol production process, such as the use of high cell concentrations, cell recycle or fed-batch operation. The authors that used cell recycle reported decrease in the performance of the recycled cells in the next cycle. Preliminary results of a project carried out in the research group show that it is possible to greatly improve the performance of the process by cell recycle, while maintaining high cell viability by the treatment of the cells between recycles. Still, recycles promote the adaptation of the yeasts, greatly enhancing its performance, with significant increase in the activity of some enzymes. In this project the pentose fermentation kinetics with S. stipitis and S. passalidarum will be realized and strategies for operation with high concentrations and cell recycle, fed-batch and variable temperatures to increase the ethanol tolerance will be proposed.In enzymatic hydrolysis the difficulty is the need to work with high solids loadings to obtain high concentrations of sugars because there is a decrease in conversion (solid effect). It is very difficult to identify among the various causes that have been attributed to the solid effect which is the most important, since the various factors involved are correlated. In this project we intend to study the various phenomena involved (adsorption, mass transfer, substrate and product inhibition, etc.) and, with the knowledge acquired, propose an operating strategy to operate the hydrolysis process with high loads and high conversions, in order to obtain glucose concentration of at least 100 g/L. Considering yields of approximately 80% ethanol, characteristic of the fermentation hydrolysis liquors containing inhibitors, this concentration allows to obtain ~ 40g/L of ethanol, which is the concentration suggested in the literature to make the distillation step economically viable.The project also involves the mathematical modeling of the production of cellulolytic enzymes by the fungus T. harzianum. The model will be used to determine an optimal feeding strategy for process operation in fed-batch and aims to improve the productivity of a process already in operation at the National Laboratory of Science and Technology of Bioethanol (CTBE). (AU)