studying some physical and chemical properties of chitosan produced from Rhizopus stolonifer by submerged fermentation and estimating its efficacy in inhibiting Escherichia coli and Staphylococcus aureus

Abstract

Cell wall of fungi is an alternative source of chitosan .chitosan was extracted from the cell wall of Rhizopus stolonifer after growing fungus in diluted  (3/7 v/v with distilled water) Sweet Sorghum Juice (SSJ) by submerged fermentation under 25º C degree for 6 days. Solubility of chitosan extracted from Rhizopus stolonifer was 70% compared to 100% solubility   for chitosan from shrimp shells (Sigma Aldrish) that used as standard. Degree of deactylation DD% of chitosan extracted from Rhizopus stolonifer was 85% and molecular weight MW was 3941.85 Dalton (D) compared to chitosan from shrimp shells (Sigma Aldrish) that has   DD%≥90% and MW 397 Kilo Dalton (KD).  

The antimicrobial effect of  fungal chitosan extracted from Rhizopus stolonifer  was studied against two typical human pathogenic microorganism, Escherichia coli and Staphylococcus aureus .The Minimum Inhibitory Concentration (MIC) of fungal chitosan was 600 and 800 ppm for E.coli and S.aureus respectively, and the Minimum Bactericidal Concentration (MBC) was 1200 and 800 ppm for E.coli and S.aureus respectively. The antimicrobial activity of fungal chitosan was lower than that of shrimp shells chitosan, which had MIC equal or less than 200 ppm for the above mentioned bacteria, and had MBC 800 and 600 ppm for E.coli and S.aureus respectively. Furthermore, fungal chitosan was similar to shrimp shells chitosan exhibited better inhibitory effects against gram- positive compared to gram-negative bacteria.