"Biofilm formation and partial biodegradation of polystyrene"
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: firstname.lastname@example.org; email@example.com by planktonic populations (Thompson et al. 2004), and 123