Banca de DEFESA: VITOR TROCCOLI RIBEIRO

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : VITOR TROCCOLI RIBEIRO
DATE: 09/12/2022
TIME: 09:00
LOCAL: Via Google Meet
TITLE:

Influence of Tween 80 on pretreatment by steam and alkaline explosion, enzymatic hydrolysis and fermentation for ethanol production from green coconut fiber

KEY WORDS:
PAGES: 142
BIG AREA: Engenharias
AREA: Engenharia Química
SUBÁREA: Processos Industriais de Engenharia Química
SPECIALTY: Processos Bioquímicos
SUMMARY:

 

The green coconut fiber has been pointed out as an interesting alternative for the production of bioethanol, as Brazil has one of the largest global productions of the fruit and its inadequate disposal causes environmental problems. However, the high recalcitrance of green coconut makes it difficult to convert it into large volumes of bioethanol. Pretreatments are necessary to destroy the crystalline structure of cellulose and increase the efficiency of enzymatic hydrolysis. Steam explosion pretreatment has a low environmental impact and whose main consequence is the removal of hemicellulose. Furthermore, the addition of non-ionic surfactants in the bioethanol production process has been studied as a strategy to increase its production and yield. Among these, Tween 80 stands out because it has a lower cost than other additives. The goal of this study was to evaluate the ethanol production from green coconut fiber using a combined steam explosion and alkaline pretreatment, comparing the simultaneous saccharification and fermentation (SSF) and semi-simultaneous saccharification and fermentation (SSSF) strategies. The use of Tween 80 in the pretreatment, enzymatic hydrolysis, and fermentation steps was also investigated. Initially, the influence of the temperature and humidity in the steam explosion pretreatment were evaluated in the glucose production. As there was no delignification after steam explosion, and to increase enzymatic digestibility, an alkaline pretreatment with sodium hydroxide was carried out in sequence. The combination of steam explosion pretreatment and alkaline pretreatment of green coconut fiber led to cellulose contents above 47.22 ± 1.06% (w/w), which initially were 30.68 ± 0.52% (w/w), and maximum glucose yield equal to 54.74%. Surfactant did not increase delignification in the steam explosion pretreatment, however it increased the conversion to glucose when compared to experiments without Tween 80. The use of surfactant in enzymatic hydrolysis increased glucose production reaching a maximum value of 20.31 ± 0.48 g/L with combined pretreated biomass when 1.0% (w/v) surfactant was added. In the absence of surfactant in any steps, the SSSF strategy stood out over the SSF. SSSF increased the yield and ethanol production and the strain that obtained the best production was Saccharomyces cerevisiae PE2, reaching a maximum ethanol production equal to 24.88 ± 1.04 g/L under 15% (w/v) solids. Different effects of Tween 80 were observed during fermentation. The use of 2.0% (w/v) Tween 80 reduced cell viability as well as reduced ethanol production in simulated medium, in SSF and SSSF. On the other hand, the use of 1.0% (w/v) Tween 80 increased the average ethanol production, although not enough to be statistically significant. To increase ethanol production under 30% (w/v) solids loading, SSSF variations were performed, including batch addition of biomass, batch addition of enzymes and temperature variation every 6 h. SSSF with non-isothermal batch feeding and gradual addition of enzymes stood out, reaching a maximum ethanol produced of 48.21 ± 1.13 g/L in the presence of 1.0% (w/v) Tween 80. Therefore, the results show that the use of the combined pretreatment generated a biomass with high cellulosic content that has a great potential for cellulosic ethanol production when fermentation strategies with Tween 80 were evaluated.

COMMITTEE MEMBERS:
Presidente - 1346198 - EVERALDO SILVINO DOS SANTOS
Interno - 3304882 - CARLOS EDUARDO DE ARAÚJO PADILHA
Interna - 3214434 - NATHALIA SARAIVA RIOS
Externo ao Programa - 3652554 - FRANCISCO CANINDE DE SOUSA JUNIOR - UFRNExterno à Instituição - PEDRO FERREIRA DE SOUZA FILHO - UFPE
Externo à Instituição - SÉRGIO DANTAS DE OLIVEIRA JÚNIOR - INPA