Novel alternative recovery of polyhydroxyalkanoates from mixed microbial cultures using microwave-assisted extraction

BACKGROUND: Polyhydroxyalkanoates (PHAs) are a class of biodegradable biopolymers produced and accumulated by microorganisms. PHAs are recovered from microbial biomass through the stages of pretreatment, extraction and purification. An alternative recovery method is microwave-assisted extraction (MAE), which involves the supply of energy through an electromagnetic field, generating high temperatures in reduced times. A study to evaluate the recovery of PHAs from mixed microbial cultures was conducted using MAE. This method was evaluated through a four-factorial experimental design, with the efficiency as the evaluated response. PHAs were also recovered using conventional heat extraction as control. RESULTS: It was found that the highest efficiency achieved using MAE was 68 +/- 1.2% (w/w), which was close to the 66 +/- 5.3% (w/w) obtained using conventional heat extraction. The following combination of factors corresponded to the optimum conditions of experimental design: extraction time of 1 min, temperature of 130 degrees C, chloroform-to-methanol ratio of 1:1 and solvent-to-biomass ratio of 20 volumes. The efficiency increased substantially when the solvent-to-biomass ratio and chloroform-to-methanol ratio increased, although the temperature was the least significant factor. Functional groups, decomposition temperatures (263-309 degrees C) and melting point (158 degrees C) of MAE-recovered PHAs were similar to those measured for commercial poly[(3-hydroxybutyrate)-co-(3-hydroxyvalerate)]. CONCLUSIONS: MAE is a never-before-reported useful method for recovering PHAs from mixed microbial cultures, which provides for a high extraction efficiency and quality of the recovered biopolymers. (c) 2021 Society of Chemical Industry (SCI).