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- Bacterial cellulose biosynthesis in the presence of raw moist olive pomace: A green sustainable approach that enhances biopolymer production and propertiesPublication . Crugeira, Pedro; Khelifa, Halima; Barreira, Luísa; Halla, Noureddine; Barreiro, Filomena; Rodrigues, Paula; Peres, António M.; Schreiner, Tatiana B.; Schreiner, Tatiana B.In this study, the biosynthesis of bacterial cellulose (BC) by Komagataeibacter intermedius strain isolated from Kombucha tea in the presence of raw moist olive pomace (MOP) (concentration up to 40 % in the fermentation media) was studied. The BC membranes were characterized by their antioxidant activity, structural character- istics, crystallinity, thermal stability, and mechanical behavior. Using raw MOP activated the inherent activity of the phenolic compounds, leading to cellular adaptation under unfavorable conditions and increased BC pro- duction for all tested MOP concentrations (p < 0.0001). This led to a 166.61 % increase for the 20 % MOP group compared to the control (HS medium). For this sample, enhanced antioxidant activity (~40-fold higher than the control) was found, which might be associated with the molecular interactions established between hydroxyls of BC and phenolic compounds. Moreover, an increase of 603.03 % in strain capacity, and a 376.01 % improvement in stress at break compared to the control was observed. The study confirmed that BC can be synthesized using MOP in its natural state, supporting a sustainable circular economy while enhancing the biosynthesis of a value- added product. By reducing synthetic media and utilizing MOP, a greener bioprocess can be achieved, and BC’s applicability can be expanded.
- Saponins as natural emulsifiers for nanoemulsionsPublication . Schreiner, Tatiana B.; Dias, Madalena M.; Barreiro, M.F.; Pinho, SimãoThe awareness of sustainability approaches has focused attention on replacing synthetic emulsifiers with natural alternatives when formulating nanoemulsions. In this context, a comprehensive review of the different types of saponins being successfully used to form and stabilize nanoemulsions is presented, highlighting the most common natural sources and biosynthetic routes. Processes for their extraction and purification are also reviewed altogether with the recent advances for their characterization. Concerning the preparation of the nanoemulsions containing saponins, the focus has been initially given to screening methods, lipid phase used, and production procedures, but their characterization and delivery systems explored are also discussed. Most experimental outcomes showed that the saponins present high performance, but the challenges associated with the saponins’ broader application, mainly the standardization for industrial use, are identified. Future perspectives report, among others, the emerging biotechnological processes and the use of byproducts in a circular economy context.
- Evaluation of saponin-rich extracts as natural alternative emulsifiers: A comparative study with pure Quillaja Bark saponinPublication . Schreiner, Tatiana B.; Colucci, Giovana; Santamaria-Echart, Arantzazu; Fernandes, Isabel P.; Dias, Madalena M.; Pinho, Simão; Barreiro, M.F.Due to synthetic surfactants' environmental impact, their replacement by natural alternatives has gained relevance, with saponins emerging as sustainable approaches. In this work, three saponin-rich extracts from different sources (Tribulus terrestris (TT), Trigonella foenum-graecum (FG), and Ruscus aculeatus (RA)) were tested as emulsifiers, and their performance compared with Quillaja Bark saponin (PS). Characterisation comprised FTIR, solubility studies, CMC assays, and emulsifying properties (emulsifying capacity (EC) and foaming capacity (FC)). For all samples, solubility assays indicated high solubility in water and low in apolar solvents (e.g., n-hexane), compatible with their O/W emulsifier character. In general, the saponin content ruled extracts' performance (PS > TT > FG > RA). EC values (without pH adjustment) were found to be 82.5, 55.0, 47.5, 36.3%, respectively. When pH changed for 7 and 9, a shift in FG and RA order was observed. The pseudo-ternary diagrams, constructed to map emulsion's composition zones, indicate the formation of single-phase systems in the region of low oil and high extract content. Except for RA extract, gel samples were formed, which are interesting technological solutions for several applications. Among the studied samples, and in alternative to PS, TT extract showed the best performance.
- Study of binary mixtures of Tribulus terrestris extract and Quillaja bark saponin as oil‐in‐water nanoemulsion emulsifiersPublication . Schreiner, Tatiana B.; Santamaria-Echart, Arantzazu; Peres, António M.; Dias, Madalena M.; Pinho, Simão; Barreiro, M.F.Several industrial fields use emulsifiers in their products, with the ones of natural origin gaining increasing relevance. Identifying and using diversified sources for their extraction is a pertinent topic regarding sustainability principles, biodiversity preservation, or cost rationalization. This is the case of Quillaja bark saponin (QS), for which saponin-rich extracts, for example, Tribulus terrestris (TT), are being highlighted as viable alternatives, even though constraints like performance are still on the table. In this context, an experimental design using binary emulsifier mixtures of TT with pure QS was carried out by changing their composition (50–90%wt. TT), content (1.5–4.5%wt.), and high-pressure homogenization conditions (5–15 cycles). The emulsions were characterized by zeta potential, morphology, droplet size, and stability (expressed as the number of days without creaming formation). Moreover, the cream index for 30 days was determined to indicate the destabilization extent. The zeta potential showed stable emulsions (values below 41 mV); even still, creaming formed for samples using a low emulsifier and high TT contents. The emulsions’ mean droplet diameter (D [3, 2]) was between 78 and 921 nm, with smaller sizes agreeing with higher stability. The statistical analysis indicated an optimum composition range comprising an emulsifier content between 3.9 and 4.5%wt. and TT content between 50 and 56%wt. to reach stable products. Overall, TT can provide an effective solution when combined with QS, decreasing the dependence on Quillaja bark.
- Solubility and solid phase studies of isomeric phenolic acids in pure solventsPublication . Vilas-Boas, Sérgio M.; Brandão, Paula; Martins, Mónia A.R.; Silva, Liliana P.; Schreiner, Tatiana B.; Fernandes, Luciano; Ferreira, Olga; Pinho, SimãoThe solubilities of gallic, protocatechuic, gentisic or α-resorcylic acids were measured in nine pure solvents (water, methanol, ethanol, 1-propanol, 2-propanol, 2-butanone, ethyl acetate, acetonitrile and dimethylformamide) at 298.15 K and 313.15 K, using the analytical isothermal shake-flask method. Additionally, solid phase studies of the selected phenolic acids were carried out using differential scanning calorimetry (DSC) and X-ray diffraction (XRD), giving access to important data on melting properties as well as on the structure of the solid phase before and after the dissolution. The NRTL-SAC model coupled to the reference solvent approach (RSA) were applied to correlate the solubility data in a set of seven solvents and, after used to predict the solubility in 1-propanol and dimethylformamide. Average relative deviations (ARD) between 28 and 40% for the correlation and between 16 and 59% for the predictions were obtained. These values are within the order of magnitude usually found for such type of semi-predictive models, using a limited set of data.
- Saponin-based natural nanoemulsions as alpha-tocopherol delivery systems for dermal applicationsPublication . Schreiner, Tatiana B.; Santamaria-Echart, Arantzazu; Colucci, Giovana; Plasencia, Paula; Costa, Patrícia Santos; Dias, Madalena M.; Pinho, Simão; Barreiro, M.F.Nanoemulsions can be produced using simple methods and compounds from natural sources. They can increase water dispersibility and bioavailability and optimise active ingredient dispersion in particular skin layers. Lipophilic compounds of the vitamin E family (tocopherols and tocotrienols) are well-known for their high antioxidant activity and capacity to protect the skin from oxidative stress. In this context, oil-in-water (o/w) nanoemulsions with and without α-tocopherol (Vitamin E, VE) were formulated with two emulsifier alternatives, Quillaja saponin (QS), and a combination of QS with Tribulus terrestris (QSTT) (50/50, w/w). The emulsions were evaluated concerning stability, microstructure, droplet size, colour attributes, encapsulation efficiency, UV photostability, antioxidant activity, and in vitro permeation studies to assess the delivery potential. Results showed highly stable systems, with round-shape droplets of 80–121 nm size. QS and QSTT samples’ colours were close to white and light brownish, respectively. The topical nano cream had the capacity to entrap VE, producing a protective effect from UV degradation, and very significant antioxidant activity, with IC50 values around 0.01 %wt. The skin permeation profiles showed the efficiency of the formulations in the delivery of VE, with permeabilities between 64 and 74 μg/cm2, while the control sample showed no VE permeation.
- Formulation and optimization of nanoemulsions using the natural surfactant saponin from Quillaja barkPublication . Schreiner, Tatiana B.; Santamaria-Echart, Arantzazu; Ribeiro, Andreia; Peres, António M.; Dias, Madalena M.; Pinho, Simão; Barreiro, M.F.Replacing synthetic surfactants by natural alternatives when formulating nanoemulsions has gained attention as a sustainable approach. In this context, nanoemulsions based on sweet almond oil and stabilized by saponin from Quillaja bark with glycerol as cosurfactant were prepared by the high-pressure homogenization method. The e ects of oil/water (O/W) ratio, total surfactant amount, and saponin/glycerol ratio on their stability were analyzed. The formation and stabilization of the oil-in-water nanoemulsions were analyzed through the evaluation of stability over time, pH, zeta potential, and particle size distribution analysis. Moreover, a design of experiments was performed to assess the most suitable composition based on particle size and stability parameters. The prepared nanoemulsions are, in general, highly stable over time, showing zeta potential values lower than 40 mV, a slight acid behavior due to the character of the components, and particle size (in volume) in the range of 1.1 to 4.3 m. Response surface methodology revealed that formulations using an O/W ratio of 10/90 and 1.5 wt% surfactant resulted in lower particle sizes and zeta potential, presenting higher stability. The use of glycerol did not positively a ect the formulations, which reinforces the suitability of preparing highly stable nanoemulsions based on natural surfactants such as saponins.
- Polimorfismo e solubilidade de sais na presença de solventes mistosPublication . Schreiner, Tatiana B.; Pinho, Simão; Duarte, Elis Regina; Thomsen, KajA representação experimental e teórica de propriedades termofísicas, e do equilíbrio de fases de sistemas contendo eletrólitos é ainda muito limitada, apesar da sua elevada importância. Isso ocorre devido às dificuldades na representação das interações eletrostáticas, além daquelas que derivam da utilização de diferentes estados padrão, escalas de concentração e coeficientes de atividade. Assim, no presente trabalho foi realizado o estudo do equilíbrio sólido-líquido em sistemas de solventes mistos contendo eletrólitos, medindo solubilidades e desenvolvendo a modelação termodinâmica. Os sais estudados foram o brometo de sódio e o cloreto de lítio, nos sistemas água/metanol, água/etanol e metanol/etanol às temperaturas de 298.15 e 323.15 K, e em toda a gama de composições. Para a determinação da solubilidade, o método dos frascos agitados foi usado em combinação com dois métodos analíticos distintos, a gravimetria e medição de índice de refração. Ambos mostraram serem fiáveis, estando em geral concordantes com os encontrados na literatura. No entanto, há indicadores que as solubilidades obtidas por gravimetria são mais consistentes. Os novos dados obtidos de solubilidade, junto a informações publicadas na literatura, sobre equilíbrio sólido-líquido, coeficientes de atividade médios iónicos e coeficientes osmóticos constituíram uma base de dados relevante para o desenvolvimento do modelo termodinâmico. O modelo Extended UNIQUAC foi o selecionado, permitindo a representação da solubilidade de fases sólidas hidratadas com elevada qualidade, obtendo erros relativos entre 1.1 e 6.7%. Foram identificadas maiores dificuldades no cálculo da solubilidade quando as fases sólidas são anidras e também na descrição dos coeficientes de atividade médios iónicos ou osmóticos. Portanto, sugere-se reestimar os parâmetros do modelo quer usando propriedades como entalpia e capacidade calorífica, bem como incluindo na base de dados outros sais contendo os iões Li+ e Br-.
- Emulsions preparation based on ternary phase diagrams: comparative study using two oils (Miglyol and sweet almond) with two distinct surfactants (Tween 80 and Saponin)Publication . Schreiner, Tatiana B.; Dias, Madalena M.; Pinho, Simão; Barreiro, M.F.An emulsion is a colloidal dispersion composed by a mixture of two immiscible liquids, being one the dispersed phase, as droplets, and the other one the continuous phase. In this work, a comparative study comprising the surfactants Tween 80 (synthetic surfactant) and Saponin (natural surfactant) and the oils Miglyol 812 and Sweet Almond was performed. The development of emulsions based on ternary phase diagrams showed that different phases can be formed giving rise to different formulations: microemulsions, gels, and mixtures with 1, 2 and 3 phases. The application of the HPH technique produced stable nanoemulsions with narrow distributions. Considering Tween 80, and comparing the two oils, Miglyol 812 gave rise to emulsions with lower particle size (0.023μm), comparatively to Sweet Almond Oil (1.009μm). This difference can be related with the oil viscosity, which is lower for Miglyol 812. Comparing the two surfactants, natural Saponin was very effective in the o/w composition range.
- Formation and stabilisation of oil-in-water nanoemulsions using binary emulsifier mixtures of Tribulus terrestris extract and Quillaja bark saponinPublication . Schreiner, Tatiana B.; Santamaria-Echart, Arantzazu; Peres, António M.; Dias, Madalena M.; Pinho, Simão; Barreiro, FilomenaEmulsifiers are used in many industrial fields, with the natural origin ones gaining increasing relevance. Identifying diversified sources as natural emulsifiers is a pertinent topic for sustainability principles