A microalgae growing station was built with 12 photobioreactors, where several microalgae species can be grown. At the end of the project, further research involving the application of microalgae can be developed. This factor implies the emergence of new opportunities and development possibilities for future researchers and students of the Higher Institute of Engineering of Porto (ISEP).
A comprehensive review of the cultivation of the microalgae Chlorella zofingiensis was carried out to adopt the most appropriate technology to increase the production of carotenoids and lipids. The highest concentration of carotenoids and lipids occurred under stress conditions (less nitrogen source and high light intensity).
While Chlorella zofingiensis was cultivated under stress conditions to produce the desired compounds in this project (carotenoids and lipids), the concentration, harvest and extraction of these components were studied to be recovered and the residual biomass was saccharified to obtain a hydrolyzate rich in fermentable sugars.
In order to request the supply of sugarcane bagasse to be used as a feedstock, the project was presented to agroenergy sector of the Brazilian Agricultural Research Corporation (Embrapa). This contact was successfully made and will be donated by Embrapasugarcane bagasse.
From the acid hydrolysates analysis resulting from the sugarcane biomass pre-treatments, it was observed that the acid hydrolyzate obtained with H3PO4 presented a high glucose concentration and a low xylose and arabinose concentrations, this indicates that such treatment it is effective in breaking down the sugarcane biomass cellulose without need for a future enzymatic hydrolysis step to obtain fermentable sugars.
For HNO3, HCl and H2SO4, Central Composite Designs were performed and, based on the results, the conditions that maximize the achievement of total monosaccharides in the acid pre-treatment was chosen, in addition to the best acid.
In order to study the immobilization and stabilization of two commercial enzymes: Endocellulase (E-CELBA) in dextran coated iron oxide magnetic nanoparticles activated with aldehyde groups (DIOMNP) and β-glucosidase (B-GOSPC) in glyoxyl agarose (GLA) so that their immobilized derivatives could be applied in the saccharification of pretreated sugarcane bagasse. This was the first time that the pretreated sugarcane bagasse was saccharified by cascade reaction using a endocellulase immobilized on dextran coated Fe2O3 with aldehyde groups combined with a β-glucosidase immobilized on glyoxyl agarose.
During sugarcane bagasse enzymatic hydrolysis, the results obtained using soluble enzymes and immobilized derivatives were similar, approximately 0.27 g glucose/g bagasse. However, the immobilized derivatives could be used for several consecutive hydrolysis cycles, without significant loss of activity. Specifically, DIOMNP endocellulase derivative maintained more than 60% of its enzymatic activity in seven reuse cycles, and GLA b-glucosidase derivative maintained more than 58% of its enzymatic activity after 8 reuse cycles.
In order to obtain better productivity and efficiency in the production of bioethanol by submerged fermentation of the lignocellulosic hydrolyzed sugarcane biomass, obtained in the previous steps the yeast screening was performed by evaluated by their potential for fermentation of pentoses and hexoses, and how they adapt to the medium containing inhibitors formed during the pretreatment of the biomass. The strains that best consume the sugars and resist the conditions of the medium was selected for the experiment of evaluation of the ethanol production was Saccharomyces cerevisiae and Spathaspora passalidarum.
The optimization of the ethanol production process was affected due to restrictions caused by the COVID-19. With mandatory confinement by the emergency state decreed by the Portugal government, practical activities were suspended for at least 3 months. In addition, material and equipment deliveries were affected, as many of them were purchased from international companies/suppliers. Even with the end of the project, activities will be continued with a view to obtaining the results expected in the original proposal.
