| Congresso Brasileiro de Microbiologia 2023 | Resumo: 1129-1 | ||||
Resumo:Eucalyptus lignin, a byproduct of the pulp and paper industry, has been studied for its conversion into industrially applicable bioproducts. Depolymerizing lignin remains a challenging process due to its high recalcitrance. However, the soluble fraction of lignin has been recognized as a potential carbon source for microorganisms, such as the oleaginous Rhodococcus opacus. This bacterium can convert lignin fragments into high-value products, including triacylglycerides (TAGs), fatty acids, and green chemicals like gallate and cis-muconate. In our study, kraft lignin from eucalyptus wood was subjected to an alkaline treatment process. The treatment was conducted using 0.5 g of lignin and 5 ml of NaOH 30% at 150 °C for 45 minutes in stainless steel cylindrical reactors immersed in a silicone oil bath. The resulting product was acidified to pH 7.0. Depolymerized fractions were recoverd after vacuum filtration or nitrogen-pressurized filtration (at a pressure of 3.5 bar) aimed at preventing the oxidation of aromatic compounds. Both methods used cellulose membranes with 0.45 µm pores. After filtration, the vacuum-filtered lignin (VF-Lig) and nitrogen-filtered lignin (NF-Lig) were characterized by UV/visible spectroscopy and their phenolic hydroxyl content were 1.14 % and 1.01 %, respectively. Our objective was to compare the growth of R. opacus CBMAI 812 in a solid medium, using native lignin (untreated) and depolymerized lignin (VF-Lig and NF-Lig) as carbon and energy sources. Additionally, we investigate the influence of supplementing the minimal M9 medium. The results showed minimal growth of R. opacus in media containing native lignin, regardless of M9 supplementation. In contrast, the use of depolymerized lignin through both filtration methods significantly promoted bacterial growth, especially in media supplemented with M9, emphasizing the importance of medium salts for the microorganism's metabolism. These results highlight the challenges faced by lignin-degrading microorganisms, like R. opacus, when utilizing native lignin as the sole carbon source. In this sense, depolymerization and filtration strategies demonstrated notable potential to make the utilization of kraft lignin in industrial processes viable. These findings contribute significantly to advancing the valorization of lignin and its sustainable utilization in converting aromatic compounds into high-value chemicals. Palavras-chave: Rhodococcus opacus, lignin, depolymerization, biovalorization, biorefinery Agência de fomento:São Paulo Research Foundation (FAPESP) - (process numbers: 2023/09410-9 e 2022/05214-8) and the Brazilian National Council for Scientific and Technological Development (CNPq) (process number: 309214/2021-1). | |||||