Browsing by Author "Salgado, Francisco"
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- Application of ionic liquids for bacterial carotenoid extractionPublication . Salgado, Francisco; Silva, Tiago; Alves, Luís; Roseiro, J. Carlos; Lukasik, Rafal M.; Paixão, Susana M.ABSTRACT: One of the ways to make microbial bioprocesses more economically viable is to enhance valorization of high added value products resulting from the biomass, like carotenoids, which have a high market value. To recover these pigments from microbial biomass a good extraction method is required. Solvent extraction is one of the methods commonly used to extract carotenoids, however, solvent extractions are both material and time-consuming, and moreover also present some health and safety concerns. Ionic liquids (ILs) are a promising step forward to tackle some of these problems, even with their high price, and has been tested for the extraction of microorganism’s components. These “molten salts” are a group of compounds that have been known for a long time, but only in the last decades they have been attracting more attention from both researchers and industry. ILs are solvents that have a high solvation power for a wide range of molecules. ILs are salts with a melting point below 100ºC, which possess unique properties that depend on both the cation and anion present, high thermal and chemical stability, a large electrochemical window, great solvent power, non-flammability, and a negligible vapor pressure. Their versatility is one of their most attractive features, making them adaptable to many technologies. Therefore, ILs can be used to facilitate chemical reactions, extraction and separation, biotransformation, and can be used in biorefineries and other processes. As shown in previous works, Gordonia alkanivorans strain 1B has the capacity to produce carotenoids, however, since it was originally isolated form hydrocarbon rich environments, it is highly resistant to different organic solvents commonly used in extraction protocols. This makes the process slow and laborious, lowering yields and increasing solvent spending. As such, new extraction protocols must be developed and tested to obtain higher pigments yield. So, herein, the potential of ILs for carotenoids extraction was evaluated, since these compounds have been described as a good option to extract pigments produced by microorganisms.
- Ionic liquids toward enhanced carotenoid extraction from bacterial biomassPublication . Silva, Tiago; Alves, Luís; Salgado, Francisco; Roseiro, J. Carlos; Lukasik, Rafal M.; Paixão, Susana M.ABSTRACT: Carotenoids are high added-value products primarily known for their intense coloration and high antioxidant activity. They can be extracted from a variety of natural sources, such as plants, animals, microalgae, yeasts, and bacteria. Gordonia alkanivorans strain 1B is a bacterium recognized as a hyper-pigment producer. However, due to its adaptations to its natural habitat, hydrocarbon-contaminated soils, strain 1B is resistant to different organic solvents, making carotenoid extraction through conventional methods more laborious and inefficient. Ionic liquids (ILs) have been abundantly shown to increase carotenoid extraction in plants, microalgae, and yeast; however, there is limited information regarding bacterial carotenoid extraction, especially for the Gordonia genus. Therefore, the main goal of this study was to evaluate the potential of ILs to mediate bacterial carotenoid extraction and develop a method to achieve higher yields with fewer pre-processing steps. In this context, an initial screening was performed with biomass of strain 1B and nineteen different ILs in various conditions, revealing that tributyl(ethyl)phosphonium diethyl phosphate (IL#18), combined with ethyl acetate (EAc) as a co-solvent, presented the highest level of carotenoid extraction. Afterward, to better understand the process and optimize the extraction results, two experimental designs were performed, varying the amounts of IL#18 and EAc used. These allowed the establishment of 50 µL of IL#18 with 1125 µL of EAc, for 400 µL of biomass (cell suspension with about 36 g/L), as the ideal conditions to achieve maximal carotenoid extraction. Compared to the conventional extraction method using DMSO, this novel procedure eliminates the need for biomass drying, reduces extraction temperatures from 50 °C to 22 ± 2 °C, and increases carotenoid extraction by 264%, allowing a near-complete recovery of carotenoids contained in the biomass. These results highlight the great potential of ILs for bacterial carotenoid extraction, increasing the process efficiency, while potentially reducing energy consumption, related costs, and emissions.
- Strawberry Tree Fruit Residue as Carbon Source Towards Sustainable Fuel Biodesulfurization by Gordonia alkanivorans Strain 1BPublication . Paixão, Susana M.; Silva, Tiago; Salgado, Francisco; Alves, LuísABSTRACT: Biodesulfurization (BDS) is a clean technology that uses microorganisms to efficiently remove sulfur from recalcitrant organosulfur compounds present in fuels (fossil fuels or new-generation fuels resulting from pyrolysis and hydrothermal liquefaction). One of the limitations of this technology is the low desulfurization rates. These result in the need for greater amounts of biocatalyst and lead to increased production costs. To mitigate this issue, several approaches have been pursued, such as the use of alternative carbon sources (C-sources) from agro-industrial waste streams or the co-production of high-added-value products by microorganisms. The main goal of this work is to assess the potential of strawberry tree fruit residue (STFr) as an alternative C-source for a BDS biorefinery using Gordonia alkanivorans strain 1B, a well-known desulfurizing bacterium with high biotechnological potential. Hence, the first step was to produce sugar-rich liquor from the STFr and employ it in shake-flask assays to evaluate the influence of different pretreatments (treatments with 1-4% activated charcoal for prior phenolics removal) on metabolic parameters and BDS rates. Afterwards, the liquor was used as the C-source in chemostat assays, compared to commercial sugars, to develop and optimize the use of STFr-liquor as a viable C-source towards cost-effective biocatalyst production. Moreover, the high-market-value bioproducts simultaneously produced during microbial growth were also evaluated. In this context, the best results, considering both the production of biocatalysts with BDS activity and simultaneous bioproduct production (carotenoids and gordofactin biosurfactant/bioemulsifier) were achieved when strain 1B was cultivated in a chemostat with untreated STFr-liquor (5.4 g/L fructose + glucose, 6:4 ratio) as the C-source and in a sulfur-free mineral-minimized culture medium at a dilution rate of 0.04 h-1. Cells from this steady-state culture (STFr L1) achieved the highest desulfurization with 250 mM of dibenzothiophene as a reference organosulfur compound, producing a maximum of approximate to 213 mM of 2-hydroxibyphenil (2-HBP) with a corresponding specific rate (q2-HBP) of 6.50 mu mol/g(DCW)/h (where DCW = dry cell weight). This demonstrates the potential of STFr as a sustainable alternative C-source for the production of cost-effective biocatalysts without compromising BDS ability. Additionally, cells grown in STFr L1 also presented the highest production of added-value products (338 +/- 15 mu g/g(DCW) of carotenoids and 8 U/mL of gordofactin). These results open prospects for a future G. alkanivorans strain 1B biorefinery that integrates BDS, waste valorization, and the production of added-value products, contributing to the global economic viability of a BDS process and making BDS scale-up a reality in the near future.