Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/30/2005
Publication Date: 5/25/2005
Citation: Wu, T., Zivanovic, S., Draughon, A., Conway, W.S., Sams, C.E. 2005. Physiochemical properties and bioactivity of fungal chitin and chitosan. Journal of Agricultural and Food Chemistry. 53:3888-3894. Interpretive Summary: We continue to look for ways to reduce losses of fresh produce to postharvest decays. Consumers are increasingly demanding lower or no chemical residues on produce due to health and environmental concerns; but many fungi are becoming more tolerant to the common fungicides. Chitin is a component of fungi such as mushrooms. We extracted chitin from various fungi, wounded and treated apples with the chitin and then inoculated them with the postharvest decay causing fungi Botrytis cinerea and Penicillium expansum. Chitin from the fungi made the harvested apples more resistant to fungi. The apple industry may find chitin useful as an alternative to postharvest decay control using fungicides. The mushroom industry may find the production of chitin from the waste resulting from mushroom production to be a profitable solution for the use of this waste.
Technical Abstract: Chitinous material was extracted from mycelia of Aspergillus niger and Mucor rouxii grown in yeast peptone dextrose broth for 15 and 21 days, respectively. The extracted material was characterized for purity, degree of acetylation and crystallinity, and tested for antibacterial and eliciting properties. The maximum glucosamine level determined in mycelium of A. niger was 11.10 % dw and in mycelium of M. rouxii was 20.13 % dw. Based on the stepwise extraction of freeze-dried mycelia, it appeared that M. rouxii mycelia contained both chitin and chitosan while A. niger contained only chitin. The yield of crude chitin from A. niger and M. rouxii was 24.01 % and 13.25 %, respectively, and the yield of chitosan from M. rouxii was 12.49 %. Significant amounts (7.42 to 39.81 %) of glucan were associated with chitinous compounds from both species and could not be eliminated by the extraction method used. The degree of acetylation was determined to be 76.53 % and 50.07 % for chitin from A. niger and M. rouxii, respectively, and 19.5 % for M. rouxii chitosan. The crystallinity of fungal chitin and chitosan was estimated to be less intensive than in corresponding materials from shrimp shells. The extracted chitin and chitosan reduced Salmonella Typhimurium DT104 2576 counts by 0.5 to 1.5 logs during a 4-day incubation in tryptic soy broth at 25 degree C. Furthermore, all tested chitinous materials from fungal sources significantly enhanced disease resistance in harvested apples against Botrytis cinerea and Penicillium expansum.