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Effect of Chitosan Acetate on Bacteria Occurring on Neungee Mushrooms, Sarcodon aspratus
Bom Soo Park1, Chang-Duck Koo, Kang Hyeon Ka
1Division of Life Science, Chungbuk National University, Cheongju 361-763, Korea.
Abstract:
Minimal growth inhibitory concentrations (MICs) of chitosan acetate (M.W. 60 kDa) on heterotrophic bacteria (strains MK1, S, and R) isolated from the soft-rotten tissues of Neungee mushroom (Sarcodon aspratus) were measured. The slimy substance produced by the MK1 strain was responsible for the diseased mushroom's appearance. The S and R strains were members of the Burkholderia cepacia complex. These strains showed different levels of susceptibility toward chitosan acetate. The MIC of chitosan acetate against the MK1 and S strains was 0.06%. The MIC against the R strain was greater than 0.10%. Survival fractions of the MK1 and S strains at the MIC were 3 × 10(-4) and 1.4 × 10(-3) after 24 h, and 2 × 10(-4) and 7 × 10(-4) after 48 h, respectively. Survival fractions of the R strain after 24 and 48 hr at 0.1% chitosan acetate were 1 × 10(-2) and 6.9 × 10(-3), respectively. Compared to the MK1 and S strains, the low susceptibility of the R stain towards chitosan acetate could be due to the ability of the R strain to utilize chitosan as a carbon source. Thirty-eight percent of Neungee pieces treated in a 0.06% chitosan acetate solution for 2~3 second did not show any bacterial growth at 4 days, whereas bacterial growth around untreated mushroom pieces occurred within 2 days. These data suggest that chitosan acetate is highly effective in controlling growth of indigenous microorganisms on Neungee. The scanning electron micrographs of the MK1 strain treated with chitosan revealed a higher degree of disintegrated and distorted cellular structures.
Insights
Chitosan acetate effectively controls bacterial growth on Neungee mushrooms. This study measured minimal growth inhibitory concentrations (MICs) against specific bacterial strains, finding it significantly reduces contamination.
Area of Science:
- Microbiology
- Mycology
- Biochemistry
Background:
- Neungee mushrooms (Sarcodon aspratus) are susceptible to bacterial soft rot caused by indigenous microorganisms.
- The MK1 strain produces a slimy substance contributing to disease appearance, while S and R strains belong to the Burkholderia cepacia complex.
Purpose of the Study:
- To determine the minimal growth inhibitory concentrations (MICs) of chitosan acetate against heterotrophic bacteria isolated from Neungee mushrooms.
- To evaluate the efficacy of chitosan acetate in controlling bacterial growth on Neungee mushroom tissues.
Main Methods:
- MICs of chitosan acetate (60 kDa) were determined for bacterial strains MK1, S, and R.
- Survival fractions of bacteria were assessed at various chitosan acetate concentrations and time points.
- Neungee mushroom pieces were treated with chitosan acetate and monitored for bacterial growth.
Main Results:
- Chitosan acetate exhibited varying efficacy, with MICs of 0.06% against MK1 and S strains, and >0.10% against the R strain.
- Survival fractions of MK1 and S strains were significantly reduced by chitosan acetate, while the R strain showed lower susceptibility, potentially due to chitosan utilization.
- Treatment of Neungee pieces with 0.06% chitosan acetate prevented bacterial growth for 4 days, compared to untreated controls.
Conclusions:
- Chitosan acetate demonstrates high effectiveness in controlling indigenous microorganisms on Neungee mushrooms.
- The differential susceptibility suggests the R strain may utilize chitosan as a carbon source.
- Scanning electron microscopy revealed chitosan acetate disrupts bacterial cellular structures.
