Could you elaborate your question a bit, so that a precise answer can be provided.

so, 

i know aspergillus niger is producing chitosan. how can we know this? i have many microorganisms species but i dont know they are producing or not. can i use special media or special experiment to understand producing chitosan? 

Godzi,

A. niger produces chitin. Chistosan is an artificial polymer obtained by de-acetylation of chitin in NaOH. Including chitin from the fungi you have mentioned... 

1: Kumaresapillai N, Ameer Basha R, Sathish R. Production and Evaluation of

Chitosan from Aspergillus Niger MTCC Strains. Iran J Pharm Res. 2011

Summer;10(3):553-8.

2: Tayel AA, Moussa SH, El-Tras WF, Elguindy NM, Opwis K. Antimicrobial textile

treated with chitosan from Aspergillus niger mycelial waste. Int J Biol Macromol.

2011 Aug 1;49(2):241-5.

3: Wu T, Zivanovic S, Draughon FA, Conway WS, Sams CE. Physicochemical properties and bioactivity of fungal chitin and chitosan. J Agric Food Chem. 2005 May 18;53can be done by chemical and (10):3888-94. .

Chitin  quantification  in fungi can be done by different methods, see:

1: Lamps CA, Oeltmann TN, Collins MJ Jr, Robinson RD, Logan RA, Head WS, O'Day DM. Development of a chitin assay for the quantification of fungus. Curr Eye Res.1995 Aug;14(8):637-41.

http://www.sciencedirect.com/science/article/pii/S0008621511001662

http://wsmbmp.org/proceedings/7th%20international%20conference/1/ICMBMP7-Oral-3-13-%20Molleken.pdf

Regards

Alex

The references quoted will answer your question.

Not sure why the statement that chitosan  is an "artificial" polymer.    As noted above, it's found in some Aspergilli and some zygomycetes "produce" chitosan - http://www.sciencedirect.com/science/article/pii/S0308814697000393

It has been described as a product of deacetylated chitin http://pubs.acs.org/doi/abs/10.1021/bi00301a005

and in that context may exist at some level in any biological chitin.

Phil,

The first reference describe isolation of chitin with deproteinization of the mycelia by 2% NaOH treatment at 90 °C for 2 h. It turns part of chitin into chitosan.

Alex

Yes - one may synthesize chitosan from chitin by chemical or enzymatic deacetylation but chitosan occurs naturally.

Check for the presence of chitin deacetylase in its genome. e.g. Sac. cerevisiae produces it as a component of the spore cell wall. (see link)

However, as said above, commercially is mostly is produced from crustacean shells treated with alkali.

PS: check the other link for the gene

http://pathway.yeastgenome.org/YEAST/NEW-IMAGE?type=PATHWAY&object=PWY3O-70

http://genome.jgi.doe.gov/cgi-bin/dispGeneModel?db=Aspni7&id=1096039

I agree with Phil Geis answers ..good luck.