Banca de DEFESA: JOSÉ DALADIÊ BARRETO DA COSTA FILHO

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : JOSÉ DALADIÊ BARRETO DA COSTA FILHO
DATE: 18/08/2021
TIME: 09:30
LOCAL: meet.google.com/fhq-ytwh-dfm
TITLE:

Valorization of corn cob: Potential for ethanol production and application of residual lignin from enzymatic hydrolysis as cationic dye adsorbent

KEY WORDS:

Agro-industrial waste, Oxidation, Persulfate, Organsolv, Glycerol, Combined pretreatment

PAGES: 100
BIG AREA: Engenharias
AREA: Engenharia Química
SUBÁREA: Processos Industriais de Engenharia Química
SPECIALTY: Processos Bioquímicos
SUMMARY:

The conversion of lignocellulosic materials into fermentable sugars for ethanol production has been a promising alternative to increase biofuel production. However, the production of cellulosic ethanol requires an improvement in its main stages, including pretreatment, for which research has shown many possibilities. Oxidative pretreatment has gained space in the literature in the last decade, however studies with persulfate are still limited. In this context, this study aimed to investigate the effects of oxidative pretreatments with thermally activated sodium persulfate (Ox) and organosolv with acidified glycerol (Os) on corn cob, as well as to dispose of the fractions obtained after each stage. The effects on the composition after Os and Ox pretreatments were evaluated, as well as the combinations of sequential step strategies (oxidation followed by organosolv - OxOs; and organosolv followed by oxidation - OsOx) and the synergistic effect in a single step, in the presence of sulfuric acid (Oxs) or without acidification (GP). In compositional terms, the combination of techniques in two steps (OxOs and OsOx), regardless of the order of performance, and in a single step (Oxs) were responsible for the highest rates of lignin and hemicellulose removal. The recovered glycerol-based fluid phases, due to their acidic nature (pH < 1), have the potential for efficient recycling in new pre-treatment steps. The pretreated and untreated (in natura) biomass were subjected to enzymatic hydrolysis with a solids load of 5% (m/v) and an enzymatic load of 10.0 FPU/g of biomass for 48 hours. After saccharification, the hydrolyzate was separated to determine the concentration of reducing sugars and glucose. The highest concentrations were obtained with OxOs, while OsOx and Oxs showed statistically equal results, therefore, the hydrolysates of Oxs (HOxs) and OxOs (HOxOs) were applied in fermentation for 72 hours with Saccharomyces cerevisiae PE-2, while solid residues (ROxs and ROxOs) were intended for adsorption tests of the cationic dye methylene blue (AM). The hydrolyzate (HOs) and solid (ROs) of the organosolv were used as controls in the experiments in order to evaluate the role of oxidation. Rapid ethanol production in the initial 12 hours of incubation was achieved with HOxs and HOxOs (~10 g/L). The compositional characterization of ROs, ROxs and ROxOs residues indicate the presence of undigested polysaccharides during saccharification, but with a majority composition of lignin (~75%), consistent with thermogravimetric and FTIR analyses. Scanning electron microscopy (SEM) showed severe fiber digestion of corn cob in the three residual solids, as well as evidence of increased porosity in ROxs and ROxOs. The kinetic adsorption assays revealed a fast AM capture in the initial minutes, but with a slow concentration decay even after 2 hours. The kinetics that best fit the experimental data was the pseudo-second order type. The Langmuir isotherm was able to satisfactorily represent the equilibrium points analyzed after 24 hours of incubation (R² > 0.98). In both curves (kinetic and equilibrium), biomass residues submitted to oxidative pretreatment showed greater efficiency in capturing AM, a behavior corroborated by the estimation of the maximum adsorptive capacities of ROs (149.33 mg/g), ROxs (172.10 mg/g) and ROxOs (187.50 mg/g). Therefore, it can be concluded that the application of organosolv with oxidation by temperature-activated persulfate proved to be an efficient technique for cellulosic conversion in saccharification and consequently in ethanol production, as well as having positive effects on the adsorption of cationic substances.

BANKING MEMBERS:
Presidente - 1584174 - DOMINGOS FABIANO DE SANTANA SOUZA
Interno - 1346198 - EVERALDO SILVINO DOS SANTOS
Externo à Instituição - CARLOS EDUARDO DE ARAÚJO PADILHA - UFRN
Externo à Instituição - PEDRO FERREIRA DE SOUZA FILHO