Valorization of food waste derived anaerobic digestate into polyhydroxyalkanoate (PHA) using Thauera mechernichensis TL1

Rasita Raunhan; Krittayapong Jantharadej; Wuttichai Mhuantong; Suchada Chanprateep Napathorn; Benjaporn Boonchayaanant Suwannasilp

doi:10.1016/j.wasman.2023.08.039

Valorization of food waste derived anaerobic digestate into polyhydroxyalkanoate (PHA) using Thauera mechernichensis TL1

Waste Manag. 2023 Sep 5:171:248-258. doi: 10.1016/j.wasman.2023.08.039. Online ahead of print.

Authors

Rasita Raunhan¹, Krittayapong Jantharadej¹, Wuttichai Mhuantong², Suchada Chanprateep Napathorn³, Benjaporn Boonchayaanant Suwannasilp⁴

Affiliations

¹ Department of Environmental Engineering, Faculty of Engineering, Chulalongkorn University, Bangkok, Thailand.
² National Center for Genetic Engineering and Biotechnology, Enzyme Technology Research Team, Pathum Thani, Thailand.
³ Department of Microbiology, Faculty of Science, Chulalongkorn University, Bangkok, Thailand.
⁴ Department of Environmental Engineering, Faculty of Engineering, Chulalongkorn University, Bangkok, Thailand; Biotechnology for Wastewater Engineering Research Unit, Chulalongkorn University, Bangkok, Thailand; Research Network of NANOTEC-CU (RNN), Bangkok, Thailand. Electronic address: benjaporn.bo@chula.ac.th.

PMID: 37678073
DOI: 10.1016/j.wasman.2023.08.039

Abstract

Polyhydroxyalkanoate (PHA) is a biopolymer that can be used as a bioplastic, offering a green alternative to petroleum-based plastics. In this study, we investigated PHA production using Thauera mechernichensis TL1. The optimal molar C/N ratio was determined to be 20 from among the ratios of 4, 20, 40, 80, and 200 and in the absence of nitrogen. Food waste anaerobic digestate, mainly comprised of acetate and propionate, was used as the carbon source for PHA production by T. mechernichensis TL1, resulting in a maximum PHA content of 23.98 ± 0.52 wt% (0.52 ± 0.02 g/L PHA) with a PHA productivity of 0.043 g/L-h PHA. In addition, when using acetate and propionate, T. mechernichensis TL1 produced PHA with a maximum PHA content of 57.43 ± 2.84 wt% (2.04 ± 0.11 g/L PHA) and 50.94 ± 1.61 wt% (2.62 ± 0.16 g/L PHA), with a PHA productivity of 0.092 g/L-h PHA and 0.070 g/L-h PHA, respectively. Proton nuclear magnetic resonance spectroscopy (¹H NMR) confirmed polyhydroxybutyrate (PHB) production using acetate as a carbon source, and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) production using propionate or food waste anaerobic digestate as the carbon source. The whole-genome analysis of T. mechernichensis TL1 confirmed the existence of a PHA biosynthesis pathway, with the presence of phaA, phaB, phaC (Class I and Class II), and phaJ genes. This study was the first to demonstrate Thauera sp.'s ability to produce PHA from food waste anaerobic digestate, rendering it as a promising candidate for PHA-producing bacteria for the valorization of food waste.

Keywords: C/N ratio; Carbon source; Food waste; Polyhydroxyalkanoate; Thauera.