Morphological and Physiological Changes on Rhizopus stolonifer by Effect of Chitosan, Oligochitosan or Essential Oils

Effects of chitosan, oligochitosan and the essential oils of clove and cinnamon were evaluated on hyphal morphology, cell wall thickness, minimum medium pH changes and respiration of Rhizopus stolonifer. Changes in hyphal morphology were observed due to chitosan or oligochitosan treatment in this fungus. Mycelial branching, abnormal shapes and swelling were showed on hyphae of R. stolonifer treated with chitosan, whereas the development of hyphae was markedly inhibited by the effect of oligochitosan. Clove and cinnamon oils caused few morphological changes in the hyphae of R. stolonifer. Cell wall thickness was increased approximately 2- to 3-fold by effect of chitosan, oligochitosan and the essential oil of clove. R. stolonifer grown in minimum medium generated a decrease in the medium's pH. However, the addition of chitosan or oligochitosan caused increases in pH of medium culture. The highest pH value (5.4) was observed in the presence of chitosan. The respiration of R. stolonifer was stimulated at low concentrations of chitosan, oligochitosan or essential oils. Significant changes in morphology and physiology of this fungus were demonstrated by the effect of all evaluated compounds. The most important changes were induced on cells of R. stolonifer treated with chitosan and oligochitosan.