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. 2022 May 16;12:8084. doi: 10.1038/s41598-022-12150-3

Table 1.

Diameters (mm) of inhibition zones formed by bleached and unbleached chitosan samples produced from H. illucens larvae (L), pupal exuviae (PE) and dead adults (A), commercial chitosan and acetic acid at five different concentrations (1.25, 0.6, 0.3 and 0.15 mg/ml) on E. coli and M. flavus. Distilled water was tested as negative control. Results are expressed as mean ± standard deviation of diameters measured with agar diffusion test of three independent biological replicates. Different letters indicate significant differences (p < 0.05) among treatments for the same concentration (capital letters) and among different concentrations in the same treatment (lowercase letters). The intensity of the antibacterial activity of each sample was evaluated according to the scale proposed by El-masry et al.63 and expressed with different symbols depending on the diameter of the respective inhibition zone: +  +  + (inhibition zone > 12 mm, high activity), +  + (inhibition zone 9–12 mm, moderate activity), + (inhibition zone 6–9 mm, slight activity).

Bacterial species Sample 1.25 mg/ml 0.6 mg/ml 0.3 mg/ml 0.15 mg/ml 1.25 mg/ml 0.6 mg/ml 0.3 mg/ml 0.15 mg/ml
E. coli L bleached chitosan 9 ± 0.5a A 9 ± 0.8a A 8 ± 0.5ab A 7 ± 0.5b AB  ++   ++   +   + 
PE bleached chitosan 9 ± 0.4a A 9 ± 0.4a A 9 ± 0.5a AB 8 ± 0.5a A  ++   + +   + +   + 
A bleached chitosan 10 ± 0.5a A 10 ± 0.8a A 10 ± 0.8a BD 8 ± 0.5b A  ++   + +   +  +   + 
L unbleached chitosan 9 ± 0.5a A 9 ± 0.2a A 8 ± 0.3ab AC 7 ± 0.5b AB  + +   + +   +   + 
PE unbleached chitosan 9 ± 0.3a A 9 ± 0.5a A 9 ± 0.3a ACD 8 ± 0.2b A  + +   + +   + +   + 
A unbleached chitosan 10 ± 0.3a A 10 ± 0.5a A 10 ± 0.7a BD 8 ± 0.2b A  + +   + +   + +   + 
Commercial chitosan 6 ± 0.5a B 6 ± 0.8a B 6 ± 0.8a E 6 ± 1a AB  +   +   +   + 
Acetic acid – – – – – – – –
Distilled water – – – – – – – –
M. flavus L bleached chitosan 7 ± 0.3a A 7 ± 0.5a A 7 ± 0.5a A 6 ± 0.5a A  +   +   +   + 
PE bleached chitosan 10 ± 0.4a B 10 ± 0.4a B 10 ± 0.5a B 7 ± 0.4b AC  ++   + +   +  +   + 
A bleached chitosan 10 ± 0.5a B 10 ± 0.7a B 10 ± 0.7a B 8 ± 0.5b BC  ++   + +   +  +   + 
L unbleached chitosan 7 ± 0.3a A 7 ± 0.7a A 7 ± 0.5a A 6 ± 0.2a A  +   +   +   + 
PE unbleached chitosan 9 ± 0.8a B 8 ± 0.5ab A 7 ± 0.5b A 7 ± 0.8b AC  +  +   +   +   + 
A unbleached chitosan 10 ± 0.2a B 10 ± 0.7a B 10 ± 0.5a B 8 ± 0.2b BC  +  +   +  +   +  +   + 
Commercial chitosan 7 ± 0.5a A 7 ± 0.5a A 7 ± 0.5a A 6 ± 0.5a A  +   +   +   + 
Acetic acid – – – – – – – –
Distilled water – – – – – – – –