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Biofilm formation and partial biodegradation of polystyrene - PDF

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					Biodegradation (2008) 19:851–858
DOI 10.1007/s10532-008-9188-0

 ORIGINAL PAPER



Biofilm formation and partial biodegradation of polystyrene
by the actinomycete Rhodococcus ruber
Biodegradation of polystyrene

Roi Mor Æ Alex Sivan




Received: 18 December 2007 / Accepted: 28 March 2008 / Published online: 10 April 2008
Ó Springer Science+Business Media B.V. 2008


Abstract Polystyrene, which is one of the most                  biomass. Extended incubation of the biofilm for up
utilized thermoplastics, is highly durable and is               to 8 weeks resulted in a small reduction in the
considered to be non-biodegradable. Hence, polysty-             polystyrene weight (0.8% of gravimetric weight loss).
rene waste accumulates in the environment posing an             This study demonstrates the high affinity of C208 to
increasing ecological threat. In a previous study we            polystyrene which lead to biofilm formation and,
have isolated a biofilm-producing strain (C208) of the           presumably, induced partial biodegradation.
actinomycete Rhodococcus ruber that degraded poly-
ethylene films. Formation of biofilm, by C208,                    Keywords       Biofilm Á Polystyrene Á Rhodococcus
improved the biodegradation of polyethylene. Conse-             ruber
quently, the present study aimed at monitoring the
kinetics of biofilm formation by C208 on polystyrene,
determining the physiological activity of the biofilm            Introduction
and analyzing its capacity to degrade polystyrene.
Quantification of the biofilm biomass was performed               Non-biodegradable plastic waste from a wide variety of
using a modified crystal violet (CV) staining or by              applications continues to accumulate in the environ-
monitoring the protein content in the biofilm. When              ment, causing a severe pollution problem (Pinto et al.
cultured on polystyrene flakes, most of the bacterial            1998). In this regard, a particularly troublesome
cells adhered to the polystyrene surface within few             synthetic polymer is polystyrene, which is considered
hours, forming a biofilm. The growth of the on                   to be the most durable thermoplastic polymer. Due to its
polystyrene showed a pattern similar to that of a               versatile properties, including resistance to biodegrada-
planktonic culture. Furthermore, the respiration rate,          tion, stiffness or flexibility (as required), light weight,
of the biofilm, exhibited a pattern similar to that of the       good insulation properties, and facile synthesis, poly-
biofilm growth. In contrast, the respiration activity of         styrene is used in a wide range of products (Robertson
the planktonic population showed a constant decline             1993). Sales of polystyrene in the US alone reach
with time. Addition of mineral oil (0.005% w/v), but            25–30 million tons/year. The major habitats polluted
not non-ionic surfactants, increased the biofilm                 by plastic wastes, including polystyrene waste, are
                                                                pelagic zones and sedimentary habitats, where most of
                                                                the plastic debris accumulates in microscopic—but not
R. Mor Á A. Sivan (&)                                           degraded—fragments. Sampling in different marine
Department of Biotechnology Engineering, Ben-Gurion
University of the Negev, Beer-Sheva 84105, Israel               habitats has revealed that this plastic debris is ingested
e-mail: sivan@bgu.ac.il; sivan@bgumail.bgu.ac.il                by planktonic populations (Thompson et al. 2004), and


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