In Vitro Study of Microbial Community Changes and Fungal Suppression Property of Mushroom Substrate and Chicken Dung Vermicompost

Lim, Wei Cheng (2020) In Vitro Study of Microbial Community Changes and Fungal Suppression Property of Mushroom Substrate and Chicken Dung Vermicompost. Final Year Project (Bachelor), Tunku Abdul Rahman University College.

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Abstract

Vermicomposting is a method of waste treatment in which organic wastes are processed by the activities of earthworms and microorganisms. The process is known to alter the microbial community of the vermicompost, decreasing abundances of harmful pathogens while supporting beneficial species. Besides, studies also found that products of vermicompost are able to suppress plant pathogenic fungi through antagonistic activity, making them useful for plantation. Therefore, the objectives of this study was to determine the bacterial population changes in such vermicomposts which included Azotobacter sp., Rhizobium sp., Bacillus sp., Pseudomonas sp., Salmonella sp., Escherichia coli, and Enterococcus faecalis. Tests had also been done to determine the inhibitory property of the vermicomposts against ginger (Zingiber officinale) infecting Fusarium sp. Five ratios of spent mushroom to chicken dung were prepared which were 10 : 0, 9 : 1, 8 : 2, 7 : 3, and 6 : 4. Vermicompost samples were collected on day 0, 30, and 60. Microbial populations were quantified as CFU/g of the vermicompost. The differences in abundance between different ratios and age of samples were analysed with one-way ANOVA by Past v4.02. The selected bacteria species were isolated and tested with Gram-staining, KOH test, methyl-red test, catalase test, and citrate utilization test. Inhibitory property of vermicomposts against Fusarium sp. was evaluated by dual culture method. Results showed that 9 : 1 samples gave the most favourable microbial changes with significant increases (p ≤ 0.05) of Azotobacter sp. and Rhizobium sp., and significant reduction of E. coli and absence of Salmonella sp. However, the population of E. faecalis was stable (p ≥ 0.05), and Pseudomonas sp. increased significantly. Dual culture tests revealed that the vermicomposts were able to suppress the mycelium growth of Fusarium sp. on PDA ranging from 54% up to 74%. Hence, the potential of the vermicompost to be valuable fertilizer and pathogenic fungus control could be further explored. However, the pathogens inactivation of the vermicompost was not ideal.