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From the seaweeds' carrageenan composition to the hybrid carrageenans’ hydrogel elasticity
Publication . Hilliou, Loic; Moraes, Izabel Cristina Freitas; Almeida, Pedro Lúcio; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); DCM - Departamento de Ciência dos Materiais; ELSEVIER SCI LTD
The carrageenan composition of 12 commercial seaweeds used in the production of hybrid carrageenans (HC) is estimated from the analysis of solid-state NMR spectra and is systematically compared with the chemical structure of HC extracted in hot water. 1H NMR showed that the isolated HC contain from 5 to 80 mol% kappa-carrageenan, from 90 to 10 mol% iota-carrageenan, while from 8 to 23 mol% biological precursors are present in the copolymer's chain. A good correlation is found between the iota-carrageenan content in the seaweeds and in the extracted HC. The shear elastic modulus of 1 wt% HC gels in the presence of 0.1 M KCl is significantly weaker and gels form at lower temperatures when the iota-content in the seaweed is larger than the kappa-content. However, these weaker gels show strain hardening. A cut-off of 30 mol.% of iota-carrageenan in the polysaccharide is identified that separates strain softening stiffer gels from strain hardening softer gels. Overall, the set of data suggests that the carrageenan gel elasticity is ruled by the self-assembly of iota-carrageenan moieties in the HC, and HC gel elasticity can be directly linked to the iota-carrageenan composition of seaweeds.
Can Biomass Mastication Assist the Downstreaming of Polyhydroxyalkanoates Produced from Mixed Microbial Cultures?
Publication . Souza, Hiléia K. S.; Matos, Mariana; Reis, Maria A. M.; Covas, José A.; Hilliou, Loïc; DQ - Departamento de Química; UCIBIO - Applied Molecular Biosciences Unit; MDPI - Multidisciplinary Digital Publishing Institute
Polyhydroxyalkanoates (PHAs) are natural polyesters which biodegrade in soils and oceans but have more than double the cost of comparable oil-based polymers. PHA downstreaming from its biomass represents 50% of its overall cost. Here, in an attempt to assist downstreaming, mastication of wet biomasses is tested as a new mechanical continuous biomass pretreatment with potential for industrial upscaling. Downstreaming conditions where both product recovery and purity are low due to the large amount of treated wet biomass (50% water) were targeted with the following process: extraction of 20 g in 100 mL solvent at 30 °C for 2 h, followed by 4.8 h digestion of 20 g in 0.3 M NaOH. Under the studied conditions, NaOH digestion was more effective than solvent extraction in recovering larger PHA amounts, but with less purity. A nearly 50% loss of PHA was seen during digestion after mastication. PHAs downstreamed by digestion with large amounts of impurities started to degrade at lower temperatures, but their melt elasticity was thermally stable at 170 °C. As such, these materials are attractive as fully PHA-compatible processing aids, reinforcing fillers or viscosity modifiers. On the other hand, wet biomass mastication before solvent extraction improves PHA purity and thermal stability as well as the melt rheology, which recovers the viscoelasticity measured with a PHA extracted from a dried biomass.
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Fundação para a Ciência e a Tecnologia
Programa de financiamento
3599-PPCDT
Número da atribuição
PTDC/BII-BIO/5626/2020