Polyhydroxyalkanoates from mixed microbial culture: Production and extraction through green methods

Risultato della ricerca: Otherpeer review


Large scale polyhydroxyalkanoates (PHA) production is limited by high production costs compared to that of petroleum-based plastics. Two key factors can be pin down to reduce costs: i) the use of mixed microbial cultures (MMC) instead of pure cultures and ii) the application of cheap and environmental friendly recovery technologies.In this work, the MMC biomass with PHA-accumulating capacity was selected in a sequencing batch reactor fed with a synthetic effluent emulating a fermented oil mill wastewater. The biomass was harvested and transferred to an accumulation reactor, where PHA contents up to 54% of the dry cell weight were obtained, using a mixture of acetic and propionic acids. A copolymer of 3-hydroxybutyrate and 3-hydroxyvalerate with 47% (wt) 3-hydroxyvalerate was obtained.The polymer extraction was done in aqueous phase using chemicals that destroy the non-PHA cellular material releasing the polymer’s granules. The effectiveness of the switchable anionic surfactant NH4-Laurate was investigated and compared with that of sodium dodecyl sulphate and NH4OH by testing them on lyophilized biomass, with and without a NaClO pre-treatment. Further, a purification post-treatment was performed on some of the samples as well.When operating the extraction at 90°C for 3h with a ratio surfactant to biomass of 200:100 w/w, gas chromatography analysis showed that all the tested extraction agents allow obtaining PHA with an excellent purity (≈100%) after a pre-treatment with NaClO at 100°C for 1 h. The highest recovery yield (73 %) was obtained when using NH4-Laurate for which operating conditions of the extraction process such as temperature, concentration and contact time have been optimized.When the extracted polymer was washed with a 0.1 N NH4OH solution and ethanol, purity was improved, but lower recovery yields were obtained.To determine the effect of extraction process on the PHA purity, Nuclear Magnetic Resonance Spectroscopy was used.
Lingua originaleEnglish
Numero di pagine1
Stato di pubblicazionePublished - 2018


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