Banca de DEFESA: Jéssica Pinheiro Silva

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : Jéssica Pinheiro Silva
DATE: 13/04/2023
TIME: 08:30
LOCAL: Meio virtual
TITLE:

Analysis of the anaerobic degradation of lignin by ruminal bacteria

KEY WORDS:

Ruminal consortia, Kraft lignin, Anaerobic degradation of lignin, Bacterial diversity.

PAGES: 100
BIG AREA: Ciências Biológicas
AREA: Biologia Geral
SUMMARY:

Lignin is one of the main components of lignocellulose biomass corresponding to ~35% of its composition. This macromolecule is considered the main source of aromatic compounds in nature. In addition to natural lignin, this structure is generated as a residual by-product of industrial processes, such as pulping, and is normally destined for combustion for energy production. Lignin utilization as a raw material to produce products of industrial interest such as vanillin, guaiacol, and phenol could contribute to the implementation of biorefineries. Lignin needs to be deconstructed before it can be transformed into bioproducts with highadded value. White rot fungi and different genera of aerobic bacteria are known as the main degraders of lignin in nature. Bacteria are also able to deconstruct lignin anaerobically, however, the process is still poorly understood. In this sense, the present work explored the potential of bovine rumen bacteria to anaerobically deconstruct lignin. For this, rumen liquid samples were inoculated in culture media containing kraft lignin as a carbon source with or without the addition of yeast extract at 37 ºC for four days, under an anaerobic atmosphere for five passages. The consortia obtained through these passages were able to decolorize the culture media, and the maximum decolorization for the consortium cultivated with kraft lignin and yeast extract as a carbon source (KLY) was 40% and 29% for the consortium using lignin kraft (KL) as a carbon source. SEM, FTIR, and GC-MS analyses indicated changes in the lignin structure and the presence of aromatic compounds related to lignin degradation such as phenol, hydrocinnamic acid, homovanyl alcohol, and vanylmandelic acid. Diversity and taxonomy analyses based on barcoding sequencing (16S rRNA gene) indicated a decrease in bacterial diversity and enrichment of members of the genus Dickeya in the consortia KLY and KL compared to the rumen microbiota. Furthermore, a remarkable number of bacterial ASVs classified as Unknown were identified suggesting the presence of yet undescribed bacterial genera related to lignin degradation. Functional prediction analysis inferred the presence of eight metabolic pathways related to lignin metabolism in the KLY and KL consortia. Bacteria were isolated from these consortiums on solid media containing kraft lignin as a carbon source, though, they were unable to grow and discolor liquid culture media in the absence of glucose.

BANKING MEMBERS:
Externa à Instituição - Renata Henrique Santana - IFB
Externa à Instituição - DASCIANA DE SOUSA RODRIGUES - EMBRAPA
Presidente - 2222088 - ELIANE FERREIRA NORONHA
Externo à Instituição - PEDRO RICARDO VIEIRA HAMANN - USP
Externa ao Programa - 1775446 - TATIANA AMABILE DE CAMPOS