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Doctoral Thesis
DOI
https://doi.org/10.11606/T.18.2021.tde-02062021-144545
Document
Author
Full name
Franciele Pereira Camargo
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Carlos, 2021
Supervisor
Committee
Silva, Maria Bernadete Amancio Varesche (President)
Carneiro, Tânia Forster
Garboggini, Fabiana Fantinatti
Silva, Silvana de Queiroz
Zaiat, Marcelo
Title in Portuguese
Caracterização taxônomica e funcional da comunidade microbiana envolvida na obtenção de biogás e outros compostos de interesse biotecnológico a partir de resíduos do processamento de citros/laranja
Keywords in Portuguese
Acetogênese
Biomassa lignocelulósica
Caracterização metataxonômica
Limoneno
Metagenômica shotgun
Planejamento Fatorial.
Abstract in Portuguese
A recuperação de energia a partir de biomassa lignocelulósica, como os resíduos sólidos de citros (RSC), vem sendo estudada como alternativa para seu reaproveitamento. O objetivo desta pesquisa foi avaliar a utilização de RSC como substrato para a obtenção de H2 e demais bioprodutos em reatores em batelada, bem como caracterizar a comunidade microbiana envolvida neste processo. Foi possível obter um consórcio autóctone por meio da autofermentação do RSC, além de isolar uma cepa similar à Enterococcus casseliflavus (99%), e obter os parâmetros cinéticos de seu crescimento em glicose, como crescimento específico (μ = 0,35 h), tempo de geração celular (Tg = 1,98 h-1), potencial máximo de concentração de H2 (P = 9,1 mmol H2.L-1), velocidade específica máxima de obtenção de H2 (Rm = 1,99 mmol H2.L-1) e tempo de início da obtenção de H2 (λ = 4,08 h). Na etapa seguinte, foram avaliados dois diferentes pré-tratamentos, sendo que a maior concentração de H2 ocorreu nos reatores contendo RSC in natura (13,31 mmol H2.L-1), quando comparado à hidrotermólise (P = 8,19 mmol H2.L-1) e deslignificação alcalina (P = 7,27 mmol H2.L-1). Por meio do método de Plackett & Burman, foram avaliadas as variáveis pH (5,5, 7,0 e 8,5), temperatura (30, 37 e 44 °C), concentração de inóculo alóctone (1, 2 e 3 gSTV.L-1) e de RSC (5, 10 e 15 g.L-1), volume do headspace (40, 50 e 60%) e componentes do meio de cultura, como extrato de levedura (0, 0,5 e 1 g.L-1), CaCO3 (0, 2,5 e 5 g.L-1), NaCl (0, 2,5 e 5 g.L-1) e peptona (0, 2,5 e 5 g.L-1). O pH, concentração de inóculo e substrato (RSC) foram as variáveis significativas. A condição ótima estabelecida por meio de Delineamento do Composto Central Rotacional foi de 4 gSTV.L-1 de inóculo (lodo granular aplicado ao processamento termofílico de vinhaça de cana-de-açúcar), 29,8 g.L-1 de RSC e pH 8,98, com P = 48,47 mmol H2.L-1. A partir do sequenciamento shotgun, foi possível confirmar a partir da expressão gênica diferencial que as vias de degradação da celulose pela via acetogênica foram superexpressas nos reatores otimizados, sendo Clostridium e Paraclostridium os gêneros mais abundantes.
Title in English
Taxonomic and functional characterization of the microbial community involved in obtaining biogas and other compounds of biotechnological interest from citrus peel waste
Keywords in English
Shotgun metagenomics
Acetogenesis
Factorial design
Lignocellulosic biomass
Limonene
Metataxonomic characterization
Abstract in English
Energy recovery from lignocellulosic biomass, such as citrus peel waste (CPW), has been studied as an alternative to its reuse. This research aimed at evaluating the use of CPW as substrate to obtain H2 and other by-products in batch reactors, as well as characterizing the microbial community involved in this process. It was possible to obtain an autochthonous consortium through the self-fermentation of CPW, in addition to isolating a strain similar to Enterococcus casseliflavus (99%), as well as obtaining its growth kinetic parameters in glucose, namely specific growth (μ = 0.35 h), generation time (Tg = 1.98 h-1), maximum H2 concentration potential (P = 9.1 mmol H2.L-1), maximum H2 production rate (Rm = 1.99 mmol H2.h-1) and starting time of H2 production (λ = 4.08 h). The effect of hydrothermolysis (180 °C; 15 minutes) and alkaline delignification (NaOH 5 mol.L-1; 1% H2O2; 24 hours) pretreatments in CPW were evaluated, where it was observed that the H2 obtainment was higher in reactors containing fresh CPW (13.31 mmol H2.L-1) when compared to hydrothermolysis (P = 8.19 mmol H2.L-1) and alkaline delignification (P = 7.27 mmol H2.L-1). By means of applying the Plackett & Burman statistical method, the variables pH (5.5,7.0 and 8.5), temperature (30, 37 and 44 °C), inoculum (1, 2 and 3 gSTV.L-1) and CPW (5,10 and 15 g.L-1) concentrations, headspace volume (40, 50 and 60%) and components of the culture medium were evaluated, namely yeast extract (0, 0.5 and 1 g.L-1), CaCO3, NaCl and peptone (0, 2.5 and 5 g.L-1) concentrations, with pH, inoculum and CPW concentrationthe most significant variables. The optimal condition established by the Rotational Central Composite Design was 4 gSTV.L-1 of inoculum (sludge of sugarcane vinasse anaerobic treatment), 29.8 g.L-1 of CPW and pH 8.98, with maximum production of 48.47 mmol H2.L-1. After the shotgun sequencing, it was possible to confirm, from differential gene expression, that the cellulose degradation acetogenic pathways were overexpressed in the optimized reactor, with Clostridium and Paraclostridium the most abundant genera.
 
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Publishing Date
2021-06-29
 
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