Available online 25 January 2023

Author links open overlay panelAbstract

Polyhydroxyalkanoates (PHA) are biodegradable polymers and have the potential to substitute with fossil-fuel based polymers since they have similar properties. Many studies on the production of PHA have been conducted, but the extraction/purification processes have received less attention. Mostly, solvent extraction has been studied, and the effect of different solvent types on the separation processes have been investigated. A better extraction method for PHA makes it a feasible alternative to fossil-fuel based polymers. In this study, a new protocol for the extraction of PHA from activated sludge by supercritical carbon dioxide disruption (sCO2) and biopolymer recovery from disrupted cells were proposed. Extraction experiments were carried out with sCO2 at different pressures, temperatures, times, biomass amounts, and modifier volumes. The operation yield was expressed based on the polyhydroxybutyrate (PHB) release efficiency. The biomass for the extraction experiments was obtained from a PHA production reactor where activated sludge was fed with anaerobically pretreated yeast industry wastewater. 80% PHB releasing efficiency was achieved by disturbing 2 g of biomass at a density of 57 g/L (biomass/volume) with sCO2 at 200 bar pressure for 15 minutes at 40°C. The PHB purity and molecular weight (Mv) of biopolymers were 80% and 0.27•106 respectively. The use of methanol as a modifier during the sCO2 disruption increased the Mv to 0.37•106. Characterization studies by Fourier transform infrared spectroscopy (FTIR) and thermal degradation analysis (TGA) demonstrated that the biopolymer recovered with this extraction protocol was comparable to commercial PHB. As a clear advantage over the other extraction protocols; operationally fast and simple extraction procedure was achieved.

Section snippetsIntroductıon

There is a considerable interest in waste valorization for a more sustainable future and circular economy goals. One of the waste valorization products are biopolymers such as polyhydroxyalkanoates (PHAs), which are gaining attention with their biobased, biocompatible, biodegradable, and non-toxic nature (Yadav et al., 2021). PHAs, are synthesized by a wide variety of microorganisms under proper operation conditions by the meaning of excess carbon and nutrient limitations (Surendran et al., 2020

Biomass materials

PHA accumulation experiments were carried out in a 3 L sequencing batch reactor (SBR), which was operated under the feast-famine regime. Anaerobically pretreated yeast industry wastewater was used as a substrate for activated sludge. Dissolved oxygen (DO) was monitored during the SBR operation, and slurry was withdrawn when the DO increased, indicating the end of the feast. Slurry was centrifuged at 9000 rpm for 5 minutes and freeze-dried. PHB content was quantified with gas chromatography

REsults and dıscussıon

PHA recovery from microorganisms was studied by SCO2 process and these were investigated as sCO2 disruption, biopolymer recovery and biopolymer characterization.

Conclusion

This study demonstrates the extraction of PHA from activated sludge with a new protocol that is based on the disruption of cells by sCO2 and biopolymer recovery from disrupted cells with chloroform. The effects of CDW, time, pressure, temperature, and volume of MeOH as a modifier on Yrel were investigated. By disrupting 2 g of biomass at 200 bar pressure for 15 minutes at 40°C, 0.13 g biopolymer/g biomass was extracted with 80% releasing efficiency, and 80% PHB content was obtained in the

CRediT authorship contribution statement

Tülin Yılmaz Nayır: Investigation, Writing- Original draft preparation Methodology, Writing- Reviewing and Editing. Selver Konuk: Investigation. Serdar Kara: Writing- Reviewing and Editing, Supervision, Funding acquisition.

Uncited references

(Choi and S.Y., 1997, Salehizadeh and van Loosdrecht, 2004)

Declaration of Competing Interest

The authors declare the following financial interests/personal relationships which may be considered as potential competing interests Serdar KARA reports financial support was provided by Scientific and Technological Research Council of Turkey.

Acknowledgement

This study was funded by Scientific and Technological Research Council of Turkey (TUBITAK, project number: 119Y027).

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