Grafting of medium chain length polyhydroxyalkanoates (mcl-PHA) produced by Comamonas testosteroni onto carboxymethylchitosan (CMCH) using ceric ammonium nitrate (CAN) as an initiator was carried out under nitrogen atmosphere in aqueous medium. The grafting composition was 2 g CMCH, 0.2M CAN, and 0.5 g mcl-PHA. The reaction was carried out at 40 C +/- 1 C for 4.5 h, and reaction product was extracted by acetone precipitation. The CMCH-g-mcl-PHA copolymers were characterized by Fourier transform infrared spectroscopy, Thermogravimetric analysis, differential scanning calorimetry, and scanning electron microscopy. The data obtained showed successful grafting of mcl-PHA onto CMCH polymer. TGA results indicated that the graft was stable up to 380 C, and the solubility studies revealed a high % grafting efficiency. Biodegradation studies of the graft in terms of microbial growth, extracellular protein concentration, and % weight loss in the graft were carried out for 30 days using a bacterial isolate Burkholderia cepacia 202 and a fungal isolate Aspergillys fumigatus 202. 93% weight loss of the graft was obtained in case of A. fumigatus 202, whereas B. cepacis 202 showed 76% loss in weight of the graft. (c) 2008 Wiley Periodicals, Inc.