Many publications mentioned that a Chitosan MW has a correlation with its antimicrobial activity (high MW = higher microbial activity). Is the reasoning solely that higher MW means a higher positive side chain that inhibits bacterial growth?
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7114974/
According to Popova et al. (2017) chitosan samples from 5 to 50 kDa have antibacterial activity against gram-negative (P. syringae, E. carotovora) and gram positive (B. polymyxa) bacteria. Reducing the MM polymer to 3kDa and increasing it to 150 kDa reduces the inhibitory effect of chitosan on bacterial growth. The gram-negative bacterium E. carotovora has the greatest sensitivity to chitosan polymers. All chitosan samples are characterized by fungistatic activity. They inhibit the growth of mycelium of the fungus F. oxysporum by 44.4-80.0%, and mycelium of the fungus S. sclerotiorum by 60.6-86.3% during 10 days of cultivation compared to the control. At the same time, a low molecular weight sample (3 kDa) effectively restrained the growth of the mycelium of the fungus S. sclerotiorum up to 80% on the 10th day, but less effectively suppressed micellar growth. ascomycete F. oxysporum, inhibiting mycelium growth by 44% compared to the control. On the contrary, high-molecular chitosan (150 kDa) suppressed the radial growth of F. oxysporum mycelium more strongly than S.sclerotior
Dear Forbes Avila . The presence of several types of functional groups in the structure of the chitosan and the fact that it has cationic properties are determinant for the increased reactive properties of chitosan. See the very useful RG link: Article Factors Influencing the Antibacterial Activity of Chitosan a...
Kindly see also the following very good RG link: Article Effect of chitosan molecular weight as micro and nanoparticl...
Also check kindly the following useful RG link: Article Effect of molecular weight of chitosan on antimicrobial prop...
Thank you for the answers and references Mr. Andrey Nagdalian and Mr. Aref Wazwaz
Dear Forbes Avila thanks for posting this interesting technical question on RG. Yes, it is true that some scholars believe that the antibacterial properties of chitosan increase with an increase of its molar mass (molecular weight). However, despite the fact that there are many reports discussing the antimicrobial activity of chitosan under different conditions, there are also conflicting results. The discussion about this is going on, and to the best of my knowledge the issue has not yet been finally clarified. For a good overview please have a look at the Introduction section of the following relevant article:
Study on antimicrobial activity of chitosan with different molecular weights
Article Study on antimicrobial activity of chitosan with different m...
Unfortunately this paper is not freely available as public full text on RG. Please check if you can access it through your institution.
Also please see the following potentially useful article:
The Effect of MolecularWeight on the Antimicrobial Activity of Chitosan from Loligo opalescens for Food Packaging Applications
This paper has been published Open Access so that it is freely available on the internet (please see attached pdf file).
I hope this helps. Good luck with your work and best wishes, Frank Edelmann
Here are some worthy references about your topic of interest.
Chung YC et al / Acta Pharmacol Sin 2004 Jul; 25 (7): 932-936;
Int J Food Microbiol. 2002 Mar 25: 74(1-2):65-72;
Polímeros: Ciência e Tecnologia, vol. 19, nº 3, p. 241-247, 2009.
Sincerely,
Guy Jobin, Ph. D. (Biology)
Thank you for the answers and references, Mr. Frank T. Edelmann . Does higher MW which equals higher density (less porous) make the chitosan less penetrable either to impurities (nutrition for bacterial growth) and/or bacteria?