Natural Degradation and Biodegradation of Poly(3-Hydroxybutyrate-co-3-Hydroxyvalerate) in Liquid and Solid Marine Environments

Abstract

In this study, natural degradation and biodegradation of poly(3-hydroxybuyrate-co-3-hydroxyvalerate) (PHBV) films were followed in different marine environments. First of all, ageing of PHBV films was investigated in natural seawater for 180 days and degradation was followed by means of weight loss measurements, scanning electron microscopy (SEM), differential scanning calorimetry and steric exclusion chromatography. In a second part, biodegradation tests were performed on PHBV powder, by following carbon dioxide (CO2) release(,) to highlight the PHBV bioassimilation of marine microorganisms. Three different marine environments were considered for biodegradation tests: a solid inoculum with foreshore sand, a solid-liquid inoculum with sand and seawater and a liquid inoculum with seawater. In the latter, a biofilm was added to study the influence of microorganisms on biodegradation kinetics. The films aged under natural conditions show a large loss of weight after 180 days in immersion, around 36 %, confirmed by SEM pictures which show an increase of the surface erosion and a decrease of the sample thickness. Microorganisms' attack occurred as suggested by CO2 release during biodegradation tests, whatever the environment studied.

Colonization of Non-biodegradable and Biodegradable Plastics by Marine Microorganisms

“…Polymer degradation is considered to proceed through several stages (i.e., biodeterioration, biofragmentation, assimilation, and mineralization), which result from complex synergetic interactions between bacterial communities that also change over the biodegradation process ( Lucas et al, 2008 ; Dussud and Ghiglione, 2014 ). Even if biodegradation processes occurring in both AA-OXO and PHBV are becoming better understood for bacteria cultured in the laboratory ( Deroiné et al, 2015 ; Eyheraguibel et al, 2017 ), further studies are needed to describe the complex interactions between bacterial communities in the biofilm and their role in plastic biodegradation in natural conditions.…”

“…In particular, the type of inoculum and the presence of organic matter are potential sources of uncertainties on the biodegradability tests, generally based on respirometric measurements ( Sharabi and Bartha, 1993 ). For example, a study on PHBV aged film demonstrated a large loss of weight after 180 days in natural seawater and a biodegradation by respirometry ( Deroiné et al, 2015 ). To complete this study a characterization of the microorganisms diversity would have been important to better understand the mechanisms of PHBV biodegradation in seawater.…”

Review of recent advances in the biodegradability of polyhydroxyalkanoate (PHA) bioplastics and their composites

“…These characteristics are seen within 30 days of soil biodegradation 175 and 60 days within marine biodegradation. 176 However, given enough time the crystallinity is expected to be reduced by up to 60%, which occurs in soil biodegradation after 200 days or 30 days in a controlled composting environment due to the intensified conditions. 175 The amorphous region is known to allow permeation of moisture and enzymes, and therefore its degradation would increase the surface area of available crystalline regions.…”

Degradability comparison of poly(butylene adipate terephthalate) and its composites filled with starch and calcium carbonate in different aquatic environments

“…for polyester biodegradation. However, an increasing number of studies have shown that most polyester‐based materials with good biodegradability in soil do not degrade or degrade very slowly in oceans; these materials include poly(lactic acid), polyhydroxybutyrate, poly(butylene succinate), and polycaprolactone . Oceans are characterized by high‐salt, high‐pressure, low‐temperature environments containing mobile and diluted nutrients.…”