Avaliação do potencial da microalga Chlamydomonas sp. cultivada em sistema aberto como fonte de metabólitos de alto valor agregado com aplicações integradas ao setor de biocombustíveis, visando uma perspectiva biorrefinária

Abstract

In the context of biorefinery, how microalgae are being described as raw material with potential to be exploited, making it an economically viable microalgal biomass production. In this study, a microalga Chlamydomonas sp. was cultivated for 2 days in photosynthetic ponds and submitted to nutrient absence for 3 days, being an influence of nutritional stress evaluated compared to the control group (CTG). Subsequently, an extraction efficiency of crude hexane lipid fraction (CHF), using mechanical agitation associated with the ultrasound technique, was evaluated at two different times (2 and 4 hours). In addition, as biomass before the extractive process (BBE), as well residual biomass from hexane fraction (RBHF2h and RBHF4h) were monitored by SEM and thermogravimetric analysis (TGA). The crude protein values and the upper calorific potential (HHV) were estimated as a function of the elemental composition of the RBHF2h and RBHF4h biomasses. The crude chloroform fraction (CCF) was obtained from RBHF4h (extraction with chloroform). The hydroesterified CCF and CHF fractions were characterized by TGA, FTIR and CG/MS. The micrographs of the biomass surfaces before and after the extraction process show significant fragmentation only for RBFH4h. TG curves show pronounced mass loss in the characteristic lipid temperature range, results consistent with the significant difference in material extracted at 2 h (2.95± 0.28)% and 4 h (10.54±0,46)%. The total lipid fraction was approximately 29%, representing a 58% increase over CTG. RB revealed estimated HHV and crude protein values of 18 MJ kg-1 and 56% respectively. TGA data for CCF extract reveals a material consisting mainly of saponifiable fractions, unlike CHF which is predominantly unsaponifiable. Therefore, the TGA curve ratified a better conversion rate for CCF (approximately 89%), consistent with the value shown by GC/MS (about 86%). The fatty profile for the saponifiable fractions of both extracts shows that the major fatty acids are C16:0 and C18:3 (ω-3 and ω-6). Additionally, residual biomass previously fractionated by n-hexane and chloroform (CTG) and their crude methanolic extract (CEM) were studied in order to investigate potentialities that could be integrated into biofuel production. In this context, different cell lines were treated with CEM to evaluate their cytotoxicity and their immunomodulatory potential against macrophages. The results show significant cell viability (400 µg mL-1) for all strains tested, relevant antiproliferative action against B16- F10 strain and inhibitory action on nitric oxide production (about 75%) for RAW 264.7 macrophage strain. pointing promising anti-inflammatory action. GC/MS analyzes revealed the presence of 22 substances, including phytol and campesterol, among the major phytoconstituents. Additionally, the HHV value (17.98 MJ kg-1) indicates that biomass exhibits good calorific potential, being similar to the lignocellulosic materials that are commonly used in thermal energy production.