Repositório do LNEG
Repositório Científico do Laboratório Nacional de Energia e Geologia
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Nanobubble-enhanced oxygen transfer in bacterial nanocellulose production: Comparative evaluation with static and airlift systems
Publication . Rodrigues, Ana Cristina; Martins, Daniela; Carvalho, Ricardo; Marques, Susana; Belo, Isabel; Espina, Begona; Dourado, Fernando; Gama, Miguel
ABSTRACT: Despite the unique properties of bacterial nanocellulose (BNC), oxygen limitation during large-scale production impairs microbial metabolism and cellulose synthesis, leading to high production costs and limited commercial success. Static fermentation can achieve high titers, but industrially it is operationally challenging. Agitated systems like airlift (AL) bioreactors, allow faster production but typically yield lower titers. This study pioneered the use of an agitated bioreactor equipped with a nanobubble (NB) generator, and its performance was compared with that of static and AL systems, employing a newly isolated Komagataeibacter sp. strain from kombucha cultivated in Eucalyptus bark hydrolysate and corn steep liquor. Key monitored parameters included dissolved oxygen, cell density, pH, sugar and lactic acid contents, and BNC production. The obtained BNC was characterized for its crystallinity, thermal stability, degree of polymerization, morphology and fiber size. The AL-and NB-derived BNC exhibited a denser network structure, lower crystallinity index, and lower polymerization degrees than that from static culture. NB technology generated stable nanobubbles (size: 95.8 f 12.9 nm; zeta potential:-14.2 f 8.6 mV). At 1 L. min-1 airflow, compared to AL, the NB bioreactor achieved a 6-fold higher volumetric mass transfer coefficient (kLa 35.9 f 1.2 h-1) and oxygen transfer rate (OTR: 309.7 f 10.2 mg.L-1.h-1). It supported greater cell density but maintained a similar BNC volumetric productivity to that of the AL (0.023 g.L-1.h-1), and moderately higher (near 280%) than that of static culture (0.0082 g.L-1.h-1). Thus, the improved oxygen levels provided by the NB system favored biomass growth rather than BNC production, suggesting that further optimization is needed to redirect carbon flux toward BNC production.
Sustainable Production of Poly(3-hydroxybutyrate) Using Eucalyptus Bark: Integration with Green Downstream Processing
Publication . Matias, João; Rodrigues, Thomas; Torres, Cristiana A. V.; Marques, Susana; Ribeiro, Belina; Gírio, Francisco; Reis, Maria A.; Freitas, Filomena
ABSTRACT: This study integrates the valorization of a lignocellulose material into poly(3-hydroxybutyrate), P(3HB), with biopolymer extraction from bacterial cells with the enzyme alcalase. The work focused on Burkholderia thailandensis DSM 13276 as the P(3HB) producer and on eucalyptus bark, a byproduct from the pulp industry, as the sole feedstock for bacterial cultivation. The eucalyptus bark was hydrolyzed by a cellulolytic enzymatic cocktail following steam explosion and further subjected to ultrafiltration for enzyme recovery. The resulting hydrolysate supported good cell growth, achieving a cell dry weight of 7.67 +/- 0.16 g/L within 72 h of cultivation, and high P(3HB) content (60.0 +/- 2.19 wt %) in the bacterial cells, clearly favoring biopolymer synthesis over cell growth, as demonstrated by the polymer and growth yields (0.190 gP(3HB)/gsugar and 0.026 gX/gsugar, respectively). High extraction efficiency (96%) and biopolymer purity (100 +/- 3.38%) were reached by enzymatic treatment, resulting in a sample with properties aligned with those of commercial P(3HB) in terms of molecular mass distribution, crystallinity, and thermal properties. These findings demonstrate the successful use of a sustainable feedstock together with the application of environmentally friendly technologies based on the use of enzymes for both lignocellulosic saccharification and biopolymer recovery to develop high-quality bioplastics, advancing the goals of a circular bioeconomy.
Palynological insights into the Eocene-Oligocene biostratigraphy , palaeoenvironment, and palaeoclimates of the Kwanza Basin, Angola
Publication . Pereira, Zélia; Silva Mendes, Márcia Cristina; Rodrigues, Cristina F.A.; Nsungani, P.C.
ABSTRACT: New biostratigraphic and palaeoenvironmental data from Cabo de Sao Bras in the Kwanza Basin reveal over 40 m of marine sediments (Cunga and Quifangondo formations) spanning the Eocene-Oligocene transition. Wellpreserved dinoflagellate cysts within these sediments provide precise age determinations and palaeoenvironmental insights. The Cunga Formation, ranging from the late Eocene to the Oligocene, is characterized by sporadic occurrences of Diphyes colligerum, Glaphyrocysta semitecta, Schematophora cf. speciosa, Deflandrea heterophlycta, Rhombodinium draco, and Rhombodinium porosum. The overlying interval reveals a Rupelian assemblage, including Achomosphaera alcicornu and Hystrichokolpoma cf. Pseudooceanicum. The uppermost part of the Cunga Formation is marked by the lowest occurrence of Tuberculodinium vancampoae and the highest occurrence of Achomosphaera alcicornu during the Chattian. In contrast to existing geological maps, the transition to the Quifangondo Formation reveals a continuous sequence from the uppermost Chattian, based on the cooccurrence of Distatodinium paradoxum and Phelodinium africanum, along with a significant acme of Hystrichokolpoma spp. Palaeoenvironmental analysis suggests a marine setting with periods of both low and high productivity. Significant environmental transitions are observed, ranging from outer neritic to oceanic conditions at the base of the Cunga Formation (late Eocene-Oligocene, late Rupelian-early Chattian). In the late Oligocene, despite considerable terrigenous input, palynological data suggest predominantly inner to outer neritic conditions at the top of the Cunga Formation and the base of the Quifangondo Formation. Fluctuations in dinoflagellate cyst influxes reflect changes in water temperatures, providing insights into past climate shifts, during the EoceneOligocene transition, and offering a valuable framework for future palaeoclimatic investigations.
Applicability Assessment of a Microbial Proteolytic Fermentation Broth to Leather Processing and Protein Stain Removal
Publication . Lageiro, Maria Manuela; Moura, Maria João; Simões, Fernanda; Alvarenga, Nuno; Reis, Alberto
ABSTRACT: Microbial proteases are fundamental towards the eco-sustainability of proteolysis at the industrial scale. A proteolytic broth was obtained from a bioreactor fermentation of a proteolytic Bacillus strain isolated from an industrial alkaline bath. Broth proteolytic activity was applied to leather tanning and to the removal of protein stains. The hide tanned with the microbial proteolytic fermentation broth showed better physical properties than the one tanned with commercial pancreatic proteases of the same activity (780 LVU). Proteinaceous stains on cotton fabric were removed more efficiently using the Bacillus proteolytic broth than water or a commercial detergent. Blood and egg yolk disappeared in less than 30 min. The removal of soya and English sauce stains was even faster. Broth proteolytic activity was characterised by caseinolytic (5200 LVU), collagenolytic (10.0 U mg-1), elastolytic (3.7 U mg-1), and keratinolytic (0.7 U mg-1) activities, which were compared with those of a commonly used commercial protease. Alkaline protease activity in the broth was demonstrated by a 20% increase in caseinolytic activity from pH 5 to 8. Besides the demonstrated applications in the leather and detergent industries, the produced alkaline microbial proteases can also be used in the treatment of proteinaceous wastes and effluents, offering potential environmental benefits reinforcing and impacting the bioeconomy.
Enhancing microalgal biohydrogen production: Unlocking higher yields with hydrothermal pretreatment with niobium phosphate
Publication . Silva, Thiago; Jesus Junior, Maurino Magno; Neves de Araujo, Matheus; Castro, Laressa Santos; Fuess, Lucas Tadeu; Rodrigues, Fábio de Ávila; Zaiat, Marcelo; Reis, Alberto; Calijuri, Maria Lucia
ABSTRACT: Microalgae cultivated in wastewater hold promise as a substrate for biohydrogen (bioH2) production. However, their rigid cell walls pose a challenge to fermentability. In this context, this study evaluated hydrothermal pretreatment with niobium phosphate (NbP) at 100-180 degrees C for 0-70 min, using up to 75 % NbP (relative to the dry weight of microalgal biomass). The hydrothermal pretreatment at 180 degrees C for 10 min with 75 % NbP released 7431 mg total carbohydrates (CHt) L-1, increasing the availability of fermentable substrates in subsequent dark fermentation (DF). When this pretreated biomass was subsequently fermented at pH 5.0 (sample PB5), bioH2 production reached 1.03 mmol H2 mol-1 CHt, with a maximum cumulative output of 0.17 mmol H2 and a CHt conversion efficiency of 83.6 %. In contrast, pH 5.5 and 6.0 reduced bioH2 yields and promoted methanogenic activity, while no pH control resulted in negligible bioH2 evolution. In conclusion, hydrothermal pretreatment with niobium phosphate and pH improvement synergize to enhance hydrogenogenesis, integrating wastewater treatment and renewable biohydrogen production.