Characterization of chitosan produced from fermented shrimp shell waste by Bacillus subtilis NA 12 using gamma radiation

الملخص EN

This study focused on characterization of chitosan obtained in a previous study from fermented shrimp shell waste (SSW) by Bacillus subtilis NA12.

Extracted chitin was exposed to different gamma radiation doses (5-35 kGy).

The molecular weight of the resultant chitosan decreased constantly with increasing radiation dose from 1.9 × 106 (g/mol) (non-irradiated) to 3.7 × 104 (g/mol) (at 35 kGy).

The degree of deacetylation (DDA%) was determined by using potentiometric titration.

The structural properties of chitin and chitosan were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction analysis (XRD), and thermogravimetric analysis (TGA).

The prepared chitosan has higher solubility and DDA% compared to the standard chitosan.

FT-IR analysis clearly confirmed the successful extraction of pure chitin and chitosan.

TGA showed that chitin exhibited a stable structure toward thermal decomposition than chitosan.

XRD analysis revealed that extracted chitin was more crystalline than prepared chitosan.

Chitosan with different molecular weights was evaluated as an antibacterial agent against representative pathogenic bacterial strains.

Chitosan obtained at 35 kGy, with molecular weight 3.7 × 104 (g/mol) and DDA of 87.9 %, showed the highest antimicrobial activity against Escherichia coli, Klebsiella sp., Staphylococcus aureus and Pseudomonas aeruginosa.

It revealed inhibition zone diameter of 5.4 ± 0.2, 5.4 ± 0.12, 3.5 ± 0.21 and 1.4 ± 0.06 cm, respectively.