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).

Automated summary

MAE is an effective method for recovering PHAs from mixed microbial cultures with high extraction efficiency and quality, similar to conventional heat extraction. Optimal conditions for MAE include a 1-minute extraction at 130 degrees Celsius with a chloroform-to-methanol ratio of 1:1 and a solvent-to-biomass ratio of 20 volumes.