Publication
Evaluation of sub-, supercritical fluids as solvents for extraction and impregnation of polyhydroxyalkanoates
| Summary: | Polyhydroxyalkanoates (PHA) are a class of biobased and biodegradable polymers with potential application on different areas, depending on their composition and specific properties that range from thermoplastics to elastomers. However, PHA development is still limited by several factors, including its extraction procedures that rely on organic solvents, such as chloroform. On the other hand, it is important to develop applications of the polymers that further increase their commercial value. This work included two parts: (1) the use of hot compressed water (HCW) as an eco-friendly solvent for the pre-treatment of mixed microbial culture (MMC) biomass for the extraction of poly-(3-hydroxybutyrate-co-3-hydroxyvalerate) (P(3HB-co-3HV)); (2) production of medium-chain-length PHA (mcl-PHA) and its impregnation with ibuprofen using supercritical carbon dioxide (sc-CO2). The results showed that using HCW at 150 °C, with a water flow rate of 10 mL/min during 30 min, it was possible to increase the polymer content of the samples from 66% to 77%. To further purify the obtained samples, a combination of HCW with digestion of the cellular residues with hypochlorite was experimented. With the combination of the two methods it was possible to decrease the hypochlorite concentration five times than when using only the hypochlorite step, while obtaining a higher purity of 82%. The main problem of applying the HCW step was the decrease of the molecular weight (Mw) from 3.0x105 to 0.3x105 g/mol and the increase of the polydispersity index. Bioreactor fermentation of Pseudomonas chlororaphis was performed to obtain mcl-PHA, using glycerol as carbon source. Besides PHA, two other products were obtained, namely, an exopolysaccharide (EPS) and phenazine. The mcl-PHA had a crystallinity of 13%, melting temperature (Tm) of 44.6 °C, glass transition temperature (Tg) of -50.4 °C and a Mw of 1.3x105 g/mol, which are in accordance to what is said in literature. sc-CO2 was used to impregnate ibuprofen in the mcl-PHA. The maximum impregnation yield obtained was 93.3 mg/g (at 200 bar for 3 h at 40 °C). The controlled release tests showed that the ibuprofen is released from the mcl-PHA with a controlled profile. |
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| Main Authors: | Meneses, Liane Pereira de |
| Subject: | Polyhydroxyalkanoates Hot Compressed Water Purification Pseudomonas chlororaphis Supercritical Carbon Dioxide Impregnation |
| Year: | 2017 |
| Country: | Portugal |
| Document type: | master thesis |
| Access type: | open access |
| Associated institution: | Universidade Nova de Lisboa |
| Language: | English |
| Origin: | Repositório Institucional da UNL |
| Summary: | Polyhydroxyalkanoates (PHA) are a class of biobased and biodegradable polymers with potential application on different areas, depending on their composition and specific properties that range from thermoplastics to elastomers. However, PHA development is still limited by several factors, including its extraction procedures that rely on organic solvents, such as chloroform. On the other hand, it is important to develop applications of the polymers that further increase their commercial value. This work included two parts: (1) the use of hot compressed water (HCW) as an eco-friendly solvent for the pre-treatment of mixed microbial culture (MMC) biomass for the extraction of poly-(3-hydroxybutyrate-co-3-hydroxyvalerate) (P(3HB-co-3HV)); (2) production of medium-chain-length PHA (mcl-PHA) and its impregnation with ibuprofen using supercritical carbon dioxide (sc-CO2). The results showed that using HCW at 150 °C, with a water flow rate of 10 mL/min during 30 min, it was possible to increase the polymer content of the samples from 66% to 77%. To further purify the obtained samples, a combination of HCW with digestion of the cellular residues with hypochlorite was experimented. With the combination of the two methods it was possible to decrease the hypochlorite concentration five times than when using only the hypochlorite step, while obtaining a higher purity of 82%. The main problem of applying the HCW step was the decrease of the molecular weight (Mw) from 3.0x105 to 0.3x105 g/mol and the increase of the polydispersity index. Bioreactor fermentation of Pseudomonas chlororaphis was performed to obtain mcl-PHA, using glycerol as carbon source. Besides PHA, two other products were obtained, namely, an exopolysaccharide (EPS) and phenazine. The mcl-PHA had a crystallinity of 13%, melting temperature (Tm) of 44.6 °C, glass transition temperature (Tg) of -50.4 °C and a Mw of 1.3x105 g/mol, which are in accordance to what is said in literature. sc-CO2 was used to impregnate ibuprofen in the mcl-PHA. The maximum impregnation yield obtained was 93.3 mg/g (at 200 bar for 3 h at 40 °C). The controlled release tests showed that the ibuprofen is released from the mcl-PHA with a controlled profile. |
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