ANABEL ITOHOWO EKERE¹, BRIAN JOHNSTON¹, MAGDALENA ZIĘBA², PAWEŁ CHABER², GRAZYNA ADAMUS², FIDELINE TCHUENBOU-MAGAIA¹, DAVID BARSI³, LUCÍA PÉREZ AMARO³, EMO CHIELLINI³*, IZA RADECKA¹, MAREK KOWALCZUK^1,2
*Corresponding author
1. Wolverhampton School of Sciences, Faculty of Science and Engineering, University of Wolverhampton, Wolverhampton, United Kindom
2. Centre of Polymer and Carbon Materials, Polish Academy of Sciences, Zabrze, Poland
3. Laboratorio Materiali Polimerici Ecocompatibili (LMPE), Capannori (LU), Italy

Abstract

The innovative recycling method, we are proposing, relies upon the controlled oxidative fragmentation of waste LDPE plastic to the inexpensive substrates for future sustainable production of PHAs with the aid of  Cupriavidus necator. LDPE oxidized fragments (PE-F) were obtained from the re-engineering LDPE film by means of pro-oxidant/pro-degradant additives, followed by treatment under natural UV light. Cupriavidus necator was grown in either tryptone soya broth (TSB) or basal salt medium (BSM) supplemented with PE-F for 48 h.  PHA production was higher in TSB supplemented with PE-F (29%) than in TSB alone (only 0.6%). No PHA was detected in either BSM alone or BSM supplemented with PE-F. The recovered PHA was characterized using GPC, NMR, and electrospray ionization tandem mass spectrometry (ESI-MS/MS). These analytical tools applied confirmed that the resulting PHA was a terpolymer having an average molar mass of 624 kg/mol and consisting of 3-hydroxybutyrate (HB), 3-hydroxyvalerates (HV) and 3-hydroxyhexanoate (HH) co-monomer units randomly distributed along the chain backbone.

INTRODUCTION

Petrochemical plastics have gradually become an integral part of our daily life and it is almost impossible to do without them due to their increased applications in a wide range of daily activities (1). However, their inappropriate usage along with the abuse of these materials in an increased range of applications comes with severe environmental consequences due to their recalcitrance to biodegradation that leads to their accumulation in different environmental compartments (terrestrial and aquatic) in high quantities and difficulties in managing them (1, 2). One severe environmental consequence owing to their littering in marine and freshwater compartments is represented by  their detrimental effect on life cycles of aquatic plants and living organisms (1, 2). Alternatively, there is a group of bio-based polymers named Polyhydroxyalkanoates (PHAs) that are synthesized by selected bacterial strains under unbalanced nutrient conditions. They are biodegradable and have unique properties similar to traditional plastics (1,3). For these reasons, PHAs are perceived to be a better