Bioconversion of waste-derived carbon and nitrogen streams into a poly(3-hydroxybutyrate)-rich bioplastic film by extremely halophilic archaeon Haloarcula sp. PLQ.
TL;DR
The present study demonstrates the potential of the haloarchaeal strain for converting carbon- and nitrogen-rich waste streams into biodegradable PHB, aligning with circular bioeconomy principles.
Abstract
Microbial polyhydroxyalkanoates (PHAs) have drawn increasing attention as sustainable alternatives to conventional plastics. However, PHA market growth remains limited because of their elevated production costs. To address this challenge, this study investigated the valorization of food waste as a low-cost feedstock and the combination of yeast extract and nitrogen-rich waste as a co-nitrogen source for sustainable poly(3-hydroxybutyrate) (PHB) production by extremely halophilic archaeon Haloarcula sp. PLQ. Implementation of this strategy resulted in the production of 1.099 ± 0.205 g L-1 of biomass with a PHB concentration of 0.634 ± 0.0063 g L-1, corresponding to a gravimetric PHB content of approximately 60 ± 11.755% of its cell dry weight (CDW). However, the strain achieved a lower PHB content as determined by gas chromatography analysis (GC) of approximately 27.87 ± 0.067% of its CDW, which may be related to the co-extraction of non-PHB cellular components during gravimetric determination. Regarding the characterization of PHB film, the SEM-EDS analysis revealed a porous and heterogeneous surface morphology that was composed of approximately 56.38 wt% carbon and 35.27 wt% oxygen with minor amounts of sodium, chlorine, and magnesium. Regarding FTIR and Raman spectroscopy analyses, the functional groups were found to be similar to those of commercial PHB. The XRD pattern was also similar to that of pure PHB. TGA and DSC results confirmed that the film is a semi-crystalline polymer-based material, with a degree of crystallinity of 61.3%, as determined from the first DSC heating scan. The melting point and the maximum degradation temperature of PHB were found to be 157.3 and 293.35 °C, respectively. This present study demonstrates the potential of the haloarchaeal strain for converting carbon- and nitrogen-rich waste streams into biodegradable PHB, aligning with circular bioeconomy principles.