2. Experimental
2.1. Bacterial strain The organism used was a native strain of G. xylinus obtained from the Persian Type Culture Collection (PTCC 1734), Iran. The strain was cultured on glucose yeast extract (GYE) agar containing100 g D-glucose, 10 g yeast extract, 5 g peptone, 20 g CaCO3, 25 gagar per liter at 28◦C for 3 days. Working cultures were routinely prepared on GYE and stored at 4◦C until use.