Characterization of polylactic acid (PLA)/kenaf composite degradation by immobilized mycelia of Pleurotus ostreatus Asep Hidayat a, b , Sanro Tachibana c, * a United Graduate School of Agricultural Sciences, Ehime University, 3-5-7 Tarumi Matsuyama, Ehime 790-8566, Japan b Forest Research and Development Agency (FORDA), Ministry of Forestry e Republic of Indonesia, Manggala Wanabakti Building, Jl. Jend. Gatot Subroto, Jakarta, Indonesia c Department of Applied Bioscience, Faculty of Agriculture, Ehime University 3-5-7 Tarumi, Matsuyama, Ehime 790-8566, Japan article info Article history: Received 27 December 2011 Received in revised form 20 January 2012 Accepted 15 February 2012 Available online 10 May 2012 Keywords: Polylactic acid Kenaf fiber Pleurotus ostreatus Degradation abstract Polylactic acid (PLA)/kenaf composite is the latest alternative to wood. Research was conducted to determine the degradation of this biocomposite based on its material weight and mechanical properties change as well as physical form observed via visual and scanning electron microscopy. Analysis was also conducted on enzymatic activity, and degradation characteristics were predicted. A natural isolate, Pleurotus ostreatus, was used as a degrader via entrapment of mycelia in immobilized Ca-alginate beads. This fungus degraded 12%, 21%, 30% and 48% of the (PLA)/kenaf composite in 1, 2, 3 and 6 months, respectively. Compared to the control, degradation caused the fibers to shorten and mechanical prop- erties to decrease by 84%. A color change also occurred in the composite, indicating a role for enzymes in the degradation. Activity of manganese peroxide was detected, with a maximum of 0.26 U mg 1 . P. ostreatus was able not only to degrade the kenaf fibers but also to break down the PLA to its oxidation products. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction The production of synthetic plastics was estimated to increase from over 130 million tons/yr in 2001 (Formin, 2001) to 245 million tons/yr in 2008 (Dacko et al., 2008) and accounts for about 10e11% of total waste in the world (Fukushima et al., 2010). Synthetic plastics are a problem because they are very difficult to break down or degrade. The discovery of biopolymers that are biologically biodegradable is the current leading edge of research. Biopolymers are divided into 2 groups: (1) agro-polymers (polysaccharides, protein, etc.) and (2) biopolyesters (polylactic acid [PLA], poly- hydroxyalkanoates [PHAs], aromatic and aliphatic copolyesters). Among them, PLA is the most widely developed and used. It is produced by condensation of lactic acid obtained by fermentation (Kolybaba et al., 2003). Biocomposites are defined as materials made with a combina- tion of natural fibers and biodegradable or non-biodegradable polymers, which, if derived from natural fibers and biodegradable plastics, are likely to be more eco-friendly (Shinoj et al., 2011). Demand for these products has continually increased. The devel- opment of biocomposites is based on polyester and fiber; therefore the micro-structure of each, especially the association between the polymer and fiber component, will affect its ability to be degraded (Pamula et al., 2001). There are several examples of the use of biocomposites. Daimler Chrysler use a flaxesisal fiber mat embedded in an epoxy matrix for the door panels of its Mercedes Benz E-class model (John and Thomas, 2008). Cambridge Industry is making flax-fiber-reinforced polypropylene for Freightliner century COE C-2 heavy trucks, and also for rear shelf trim panels of the 2000 model Chevrolet Impala (Shinoj et al., 2011). Besides the automobile industry, lignocellulosic fiber composites are also used for building and construction as panels, ceilings, and partition boards (Hariharan and Khalil, 2005). The PLA/kenaf composite is a biocomposite made from a combination of kenaf fiber (Hibiscus cannabinus) and PLA with a ratio of 70:30; it has properties similar to those of particleboard. Wood production is decreasing due to huge increases in the human population and forest degradation; therefore kenaf (or some other components such as bamboo, grass, palm oil, or straw (Pamula et al., 2001)) could be one of the substitute materials for wood. Kenaf is a plant that grows wild in the tropics and sub- tropics of Africa and Asia. It is a fast-growing species, reaching about 5e6 m in height and 2.5e3.5 cm in diameter within 5e6 months (Nishino et al., 2003). Kenaf also has cellulose, hemi- cellulose, and lignin 0.75e2.22 mm in length and 17.34e19.23 mm in width (Akil et al., 2011). * Corresponding author. Tel.: þ81 89 9469864. E-mail address: tatibana@agr.ehime-u.ac.jp (S. Tachibana). Contents lists available at SciVerse ScienceDirect International Biodeterioration & Biodegradation journal homepage: www.elsevier.com/locate/ibiod 0964-8305/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved. doi:10.1016/j.ibiod.2012.02.007 International Biodeterioration & Biodegradation 71 (2012) 50e54