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2019-03-21 - Colloque/Présentation - poster - Anglais - page(s)

Delacuvellerie Alice , Wattiez Ruddy , "ALCANIVORAX BORKUMENSIS, A KEY PLAYER FOR THE LOW-DENSITY POLYETHYLENE DEGRADATION" in Which sustainable future for plastic?, Mons, Belgique, 2019

  • Codes CREF : Microbiologie et protistologie [bacteriol.,virolog.,mycolog.] (DI3130)
  • Unités de recherche UMONS : Protéomie et Microbiologie (S828)
  • Instituts UMONS : Institut des Biosciences (Biosciences)
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Abstract(s) :

(Anglais) Introduction Plastic production has increased every year over the last century. Most of these synthetic polymers, (i.e., 72% of the world's annually produced plastic), are released into the environment, either in landfills or in the sea [1]. The Mediterranean Sea has, on average, the highest density of plastics in the world [2,3]. Once released in the environment, synthetic polymers are rapidly colonized by microorganisms such as fungi, diatoms or bacteria, which form a biofilm on the plastic surface. Consequently, the term "plastisphere" is used to describe the environmental niche formed by these plastics [4]. The bacterial communities of the plastisphere seemingly include bacteria capable of degrading synthetic polymers. However, the rate of degradation is very slow, and the development of plastic-associated communities is still poorly understood [5]. Previous study conducted by our lab showed that Alcanivorax borkumensis, a hydrocarbon-degrading bacterium [6], was strongly selected on Low-Density PolyEthylene (LDPE) after 2 months of enrichment culture and can be considered as a potential LDPE degrader. The aim of this study is to quantify the capacity of this bacterium to form biofilm on plastics and its capacity to degrade synthetic polymer. Methods: After the selection and isolation of Alcanivorax borkumensis, its capacity to form biofilm on four plastics (PolyEthylene Terepthtalate (PET), PolyVinyl Chloride (PVC), PolyStyrene (PS), LDPE) and degrade them was monitored by crystal violet and the weight loss methods respectively. Results: Our results demonstrate clearly that A. borkumensis forms large biofilms on the plastic surface and mainly on LDPE (Fig.1A; 1C) in hexadecane medium. This bacterium clearly displays a higher affinity for the LDPE than the others supporting our previous experiments that showed its specific enrichment after two months on LDPE and not on other plastics. In presence of alkanes, Alcanivorax spp. is known to modify its cell membrane hydrophobicity and produce biosurfactants to better interact with these lasts [75-78]. Interestingly, simultaneously to the biofilm formation, a significant plastic weight loss of 3.5% ± 0.34 was observed after 80 days showing the ability of this bacterium to degrade LDPE (Fig.1B). The efficiency of the process seems to be very limited but this degradation rate is similar to those observed with other microorganisms such as fungi or other bacteria [79]. It is noticed that no degradation was observed during the first 40 days. This latency can be due to the presence of 0.05% hexadecane in the culture medium which is preferentially consumed. An optimization of degradation conditions (temperature, supplemental carbon source, agitation, UV treatment…) must be investigated and will allow to open new perspectives to use this bacterium alone or in consortium to recycle LDPE, one of the most abundant petroleum-based plastic. Conclusion For the first time, our results show that this bacterium is able to degrade LDPE. We showed its capacity to degrade a solid structure based on alkane such as petroleum-based plastic LDPE. The mechanism of a partial depolymerization of LDPE – a crucial step for its degradation by Alcanivorax borkumensis is unknown and will be further investigated.