Chitosan has been shown to be fungicidal against several fungi, including B. cinerea ( Ben-Shalom et al., 2003). The minimum inhibitory concentration (MIC) reported for B. cinerea was 10 ppm ( Rabea et al., 2003). The MICs reported for specific target organisms range from 0.0018% to 1.0% and are influenced by a multitude of factors such as the pH of the growth medium, the degree of polymerization of chitosan, and the presence or absence of interfering substances such as lipids and proteins ( Roller and Covill, 1999 and Rhoades and Roller, 2000).
Inhibition of mold growth by the embedded coating components in PDA plates is shown in Fig. 2. All antifungal substances added to the medium could effectively inhibit the radial growth of B. cinerea. The results were in good agreement with those of Fig. 1. At the end of 3 days incubation, the control plates were completely covered with B. cinerea mycelia, whereas only partial coverage was observed on the plates added with antifungal substances in Fig. 2. The most significant inhibition was observed on the plates with 0.5% GSE, with only 34.9% of the length of the mycelial growth compared with the control, but relatively sparse hyphae. The combination of 0.1% GSE and 1% chitosan also achieved a good result, reducing the mycelium growth to 3.84 cm in length, as compared to 8.4 cm for the control. However, chitosan alone was not as effective as those formulae containing GSE, which resulted in a radial growth reduction of 36.1%, indicating an apparent combined antifungal effect of chitosan and GSE.