Extraction of plant biopolymers and their use in gas sensitive hybrid materials

• Autor(a) principal: Gonçalves, Marta Sofia Banza
• Data de Publicação: 2017
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10362/25869
• topic: biopolymer; ionic liquid; liquid crystal; gas sensing; volatile organic compound; Domínio/Área Científica::Engenharia e Tecnologia::Engenharia Química

Biopolymers have spurred interest because of their outstanding properties, such as waterproofing, antimicrobial activity and resistance, as well as the ability to help form hybrid materials with stimuli-responsive properties. With this purpose, extractions of suberin from cork (Quercus suber) and white potato skin (Solanum tuberosum L. cv. Monalisa), and cutin from tomato skin (Solanum lycopersicum) have been achieved through a novel process based on cholinium hexanoate’s selective cleavage of acylglycerol ester bonds, allowing the partially intact recovery of the biopolymers mentioned. The extraction of suberin from cork resulted in yields ranging from ≈2-20%, using extraction periods of 30 minutes, 1 hour and 2 hours, while 2-hour extraction from white potato peels yielded ≈4% suberin and 2-hour extraction from both natural and enzymatically digested tomato skin yielded ≈6% and ≈1% cutin, respectively. The application of the extracted biopolymers as sensing materials for an electronic nose (E-Nose) under development was tested by combining the biopolymers suberin and cutin with water and the liquid crystal 2-cyano-4-pentylbiphenyl (5CB). The hybrid materials obtained were processed as thin films and further exposed to five volatile organic compounds (VOCs) with different polarities – hexane, toluene, dichloromethane, ethanol and acetone. An optical response was recorded upon VOC exposure and the results revealed a tendency from suberin-based films to higher optical responses to toluene, dichloromethane and acetone and maintenance of their yield and morphology after exposure, while cutin-based films disintegrated after exposure to toluene and revealed much lower optical responses to all VOCs. No film gave an optical signal in the presence of ethanol or hexane in the E-Nose. These findings strengthen the interest in exploiting plant biopolymers, specifically the polyester suberin, as valuable components for the production of hybrid materials with stimuli responsive properties.