Ploidy mosaicism and allele-specific gene expression differences in the allopolyploid Squalius alburnoides

<p>Abstract</p> <p>Background</p> <p><it>Squalius alburnoides </it>is an Iberian cyprinid fish resulting from an interspecific hybridisation between <it>Squalius pyrenaicus </it>females (P genome) and males of an unknown <it>Anaecypris hispanica-</it>like species (A genome). <it>S. alburnoides </it>is an allopolyploid hybridogenetic complex, which makes it a likely candidate for ploidy mosaicism occurrence, and is also an interesting model to address questions about gene expression regulation and genomic interactions. Indeed, it was previously suggested that in <it>S. alburnoides </it>triploids (PAA composition) silencing of one of the three alleles (mainly of the P allele) occurs. However, not a whole haplome is inactivated but a more or less random inactivation of alleles varying between individuals and even between organs of the same fish was seen.</p> <p>In this work we intended to correlate expression differences between individuals and/or between organs to the occurrence of mosaicism, evaluating if mosaics could explain previous observations and its impact on the assessment of gene expression patterns.</p> <p>Results</p> <p>To achieve our goal, we developed flow cytometry and cell sorting protocols for this system generating more homogenous cellular and transcriptional samples. With this set-up we detected 10% ploidy mosaicism within the <it>S. alburnoides </it>complex, and determined the allelic expression profiles of ubiquitously expressed genes (<it>rpl8</it>; <it>gapdh </it>and <it>β-actin</it>) in cells from liver and kidney of mosaic and non-mosaic individuals coming from different rivers over a wide geographic range.</p> <p>Conclusions</p> <p>Ploidy mosaicism occurs sporadically within the <it>S. alburnoides </it>complex, but in a frequency significantly higher than reported for other organisms. Moreover, we could exclude the influence of this phenomenon on the detection of variable allelic expression profiles of ubiquitously expressed genes (<it>rpl8</it>; <it>gapdh </it>and <it>β-actin</it>) in cells from liver and kidney of triploid individuals. Finally, we determined that the expression patterns previously detected only in a narrow geographic range is not a local restricted phenomenon but is pervasive in rivers where <it>S. pyrenaicus </it>is sympatric with <it>S. alburnoides</it>.</p> <p>We discuss mechanisms that could lead to the formation of mosaic <it>S. alburnoides </it>and hypothesise about a relaxation of the mechanisms that impose a tight control over mitosis and ploidy control in mixoploids.</p

Pretreatment of plastic waste: Removal of colorants from hdpe using biosolvents

UIDB/50011/2020 UIDP/50011/2020 CA18220, 2020.00647.CEECIND UIDB/50006/2020 UIDP/50006/2020Plastics recycling remains a challenge due to the relatively low quality of the recycled material, since most of the developed recycling processes cannot deal with the additives present in the plastic matrix, so the recycled products end up in lower-grade applications. The application of volatile organic solvents for additives removal is the preferred choice. In this study, pretreatment of plastic packaging waste to remove additives using biosolvents was investigated. The plastic waste used was high-density polyethylene (HDPE) with blue and orange colorants (pigment and/or dye). The first step was to identify the type of colorants present in the HDPE, and we found that both plastics presented only one colorant that was actually a pigment. Then, limonene, a renewable solvent, was used to solubilize HDPE. After HDPE dissolution, a wide range of alcohols (mono-, di-, and tri-alcohols) was evaluated as antisolvents in order to selectively precipitate the polymer and maximize its purity. The use of limonene as solvent for plastic dissolution, in combination with poly-alcohols with an intermediate alkyl chain length and a large number of hydroxyl (OH) groups, was found to work best as an antisolvent (1,2,3-propanetriol and 1,2,4-butanetriol), leading to a removal of up to 94% and 100% of the blue and orange pigments, respectively. Finally, three cycles of extraction were carried out, proving the capability of the solvent and antisolvent to be recovered and reused, ensuring the economic viability and sustainability of the process. This pretreatment provides a secondary source of raw materials and revenue for the recycling process, which may lead to an increase in the quality of recycled polymers, contributing to the development of an economical and sustainable recycling process.publishersversionpublishe

Plastic waste recycling: removal of pigments using alternative solvents

O objetivo desta dissertação recai sob o desenvolvimento de um pré-tratamento sustentável para remover aditivos de resíduos plásticos utilizando solventes alternativos. O interesse da aplicação deste pré-tratamento deve-se ao facto de a reciclagem de plásticos continuar a ser um grande desafio a nível da obtenção de material reciclado de elevada qualidade, já que a maioria dos processos de reciclagem não conseguem lidar com os aditivos presentes nos mesmos. A indústria das embalagens é responsável por 40% do valor total do consumo de plástico, e o polietileno de alta densidade (HDPE) é um dos plásticos mais utilizados neste setor, sendo por isso o resíduo plástico escolhido para este estudo. Em particular, avaliou-se a capacidade de remoção de colorantes (pigmento ou corante) de duas embalagens de plástico HDPE, uma de cor azul e outra de cor laranja, através do processo de dissolução/precipitação. Começou-se por identificar o tipo de colorantes presentes nos resíduos plásticos, verificando-se que os colorantes presentes em ambos os plásticos eram pigmentos, e ambos continham apenas um tipo de pigmento. Contudo, até ao momento não foi possível identificar a composição química dos pigmentos. Em seguida, avaliou-se a remoção dos pigmentos dos resíduos plásticos. Primeiro selecionou-se o melhor solvente alternativo para a dissolução da matriz, constatando-se que o limoneno foi o mais eficaz. Depois, uma ampla gama de álcoois (mono-, di-, tri-álcoois, com cadeias alquílicas até 6 carbonos) foram usados como anti-solvente em diferentes proporções de solvente:anti-solvente (1:residual, 1:1 e 1:3) para maximizar o rendimento do polímero precipitado, sendo a razão 1:3 a mais efficiente. É importante mencionar que o tolueno (solvente orgânico tradicional) também foi usado como solvente de dissolução para fins comparativos. A remoção dos pigmentos foi mais eficiente quando se utilizou o limoneno como solvente, e os álcoois com uma cadeia alquílica intermédia e com maior número de grupos OH como anti-solvente. Conseguiu-se remover até 94% do pigmento azul e 100% do pigmento laranja com os tri-álcoois (1,2,3-propanotriol e 1,2,4-butanotriol). Depois, verificou-se que a composição estrutural, temperatura de fusão e de degradação térmica dos plásticos, após o pré-tratamento desenvolvido, não sofreram alterações significativas em relação ao plástico virgem. Por fim, foram realizados 3 ciclos de extração, com reaproveitamento do solvente (limoneno) e anti-solvente (1,2,3-propanotriol), para garantir a viabilidade económica e sustentável do processo, comprovando-se a capacidade de reciclagem e reaproveitamento dos solventes. Em suma, esta dissertação demonstra que o pré-tratamento sustentável desenvolvido tem potencial para remover os aditivos presentes no polímero. Este método será um primeiro passo para potencializar uma fonte secundária de matéria-prima e quiçá beneficiar o processo de reciclagem, através de um processo de despolimerização mais eficiente, contribuindo para o desenvolvimento de um processo de reciclagem económico e sustentável.The objective of this dissertation is the development of a sustainable pre-treatment to remove additives from plastic waste using alternative solvents. The interest in applying this pre-treatment to plastic recycling is that obtaining high-quality recycled material remains a challenge, since most recycling processes cannot handle the additives present in them. The packaging industry accounts for 40% of the total consumption of plastics, with the high-density polyethylene (HDPE) being one of the most used plastics in this sector, thus being the one chosen for this study. More specifically, the ability to remove colourants (pigment or dye) from two HDPE plastic packaging (one blue and one orange) was evaluated, through the dissolution/precipitation processes. The first step was to identify the type of colourants present in the plastic waste, and the results showed the colourants presents in both plastics are pigments, and both plastics contain only one type of pigment. However, the tests carried out so far have not been conclusive regarding the identification of the chemical composition of these pigments. After that, the removal of pigments from plastic residues was evaluated. Firstly, limonene was chosen as the best solvent for matrix dissolution, after testing a panoply of different (bio)solvents. Then, a wide range of alcohols (mono-alcohols, diols, triols, with alkyl chains of up to 6 carbons) was used as anti-solvent in different solvent:anti-solvent ratios (1:residual, 1:1 and 1:3) to maximize the yield of the precipitated polymer, being the 1:3 ratio the most effective. It is worth to mention that toluene (a traditional organic solvent) was also used as a dissolution solvent for comparative purposes. It was found that the removal of pigments was more efficient when using limonene as solvent for the plastic dissolution and alcohols with an intermediate alkyl chain and a high number of OH groups as anti-solvent. It was possible to remove up to 94% of the blue pigment and up to 100% of the orange pigment with the triols (1,2,3-propanetriol and 1,2,4-butanetriol). Then, it was found that the structural composition, fusion and thermal degradation temperature of the plastics, did not suffer significant changes compared to virgin plastic, after being submitted to the designed pre-treatment. Finally, 3 cycles of extraction were carried out, by reusing the solvent (limonene) and anti-solvent (alcohol), to ensure the economic and sustainable viability of the process, proving their capability to be recycled and reused. In summary, this dissertation demonstrates that the sustainable pre-treatment developed has the potential to remove additives from plastics. This should allow for an easier plastic depolymerization, providing a secondary source of raw materials and revenue for the recycling process, contributing to the development of an economical and sustainable recycling process.Mestrado em Engenharia Químic