Chitosan extracted from Aspergillus flavus shows synergistic effect, eases quorum sensing mediated virulence factors and biofilm against nosocomial pathogen Pseudomonas aeruginosa

Int J Biol Macromol. 2018 Feb;107(Pt A):52-58. doi: 10.1016/j.ijbiomac.2017.08.146. Epub 2017 Aug 30.


The biological methods for extraction of chitosan were used as alternative procedures for chemical methods In biological methods, the chitosan was extracted from A. flavus by using of Lactobacillus paracasei for demineralization and Bacillus subtilis for deproteinization. The yield of extracted chitosan reached to 53.8%, pH was 7.8 and complete solubility in 1% acitic acid. Purified chitosan had the ability to reduce the biofilm forming capacity of P. aeruginosa clearly visible in light microscopic staining and scanning electron microscopy. The QS dependent phenotype and QS regulated gene expression was significantly reduced in the influence of chitosan. A significant decrease in biofilm formation was seen in the presence of chitosan. The chitosan treatment showed a decrease in the expression of lasR and rhlR genes. Same time production of pyocyanin and proteases was also inhibited in dose dependent manner. Chitosan led to increasing antimicrobial activity of antibiotics and had synergism effect, thus chitosan may be a useful adjuvant agent for the treatment of many bacterial infections in combination with antibiotics.

Keywords: Antibacterial activity; Aspergillus flavus; Chitosan.

MeSH terms

  • Aspergillus flavus / chemistry*
  • Bacterial Proteins / genetics
  • Biofilms / drug effects
  • Chitosan / chemistry
  • Chitosan / isolation & purification
  • Chitosan / pharmacology*
  • Cross Infection / drug therapy*
  • Cross Infection / genetics
  • Cross Infection / microbiology
  • Gene Expression Regulation, Bacterial / drug effects
  • Humans
  • Microbial Sensitivity Tests
  • Pseudomonas aeruginosa / drug effects
  • Pseudomonas aeruginosa / genetics
  • Pseudomonas aeruginosa / pathogenicity
  • Quorum Sensing / drug effects
  • Trans-Activators / genetics


  • Bacterial Proteins
  • LasR protein, Pseudomonas aeruginosa
  • RhlR protein, Pseudomonas aeruginosa
  • Trans-Activators
  • Chitosan