Chitosan has many applications – in cosmetics, pharma, food industries…
To produce chitosan, chitin, the exoskeleton of shrimps, crabs and lobsters, is broken down chemically. However, chitosan produced thus has high molecular weight and many impurities. But such chitosan is useful for applications in agriculture.
For medical applications, however, we need high purity, low molecular weight chitosan. And more importantly, most acetyl groups should be removed for better biological activity. And, for all these, chitosan from fungi is better.
Fungal biomass is available in plenty as industrial waste, from mushroom cultivation, wine production etc. But which is the best fungal source of chitosan with optimum biological activities for medical applications?
Mukund Deshpande and team have been studying Benjaminiella poitrasii to understand the mechanism of transitions between the yeast, the single celled form, and hyphae, the thread like form of fungi. While doing experiments, they realised that the fungus has adequate chitosan and that too, in the highly de-acetylated form required for medical applications.
So they did a comparative study recently, to understand the differences between chitosan from different sources. They physically and chemically characterised the chitosan derived from shells of marine animals, from two cultivated mushrooms, from three fungi commonly used in industries and from Benjaminiella poitrasii.
The molecular weight of chitosan from marine sources was more than 500 kilodaltons; chitosan from industrial and edible fungi hovered around 6 kilodaltons; Benjaminiella poitrasii yeast had chitosan of 25 and the hyphal form 46 kilodalton molecules, somewhere in between.
“Moreover, de-acetylation was more prominent in chitosan from Benjaminiella poitrasii– more than 90 percent – while those from other sources varied from 70 to 90 percent”, says Ejaj Pathan, IIT Bombay.
The researchers then made nanoparticles of chitosan from different sources to test their activity against pathogenic fungi. To inhibit the growth of pathogenic fungi, they had to use a much larger quantity of chitosan from marine sources.
“The minimum inhibitory concentration of nanoparticles of chitosan from Benjaminiella poitrasii was the lowest”, says Vandana Ghormade, ARI Pune.
The team then tested the nanoparticles against red blood cells. The haemo-compatibility of B. poitriasii chitosan was better.
“Thus for medical applications, chitosan from Benjaminiella poitrasii seems to be the best among those tested”, says Santosh Tupe.
“Since biomass from industrially used fungi is waste, people believe that it should be put to good use. But we must consider that chitosan from Benjaminiella poitrasii is biologically more active, more useful. And the total yield of chitosan from a one litre culture of the fungus is about 600 milligrams, almost double the yield from industrial fungi. So it is worthwhile exploring it as an independent source, especially for biomedical applications”, argues Mukund Deshpande, the leader of the team.
What started out two decades ago, as basic research to understand the shifts between yeast and hyphal forms in fungi, has now led the team to applications of their research in pharmaceutical industries. The team seems to have more up its sleeves: since it is the hyphal form that causes fungal diseases, they are now looking for ways to stop the yeast from becoming hyphae – a simple way to prevent and treat fungal infections.
More on that story, later.
Udham P K
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