Estrazione, purificazione e valorizzazione di polisaccaridi di basidiomiceti
Author(s)
Di Mario, Francesca
Date Issued
April 22, 2008
Type
Doctoral Thesis
Abstract
With the aim to ascertain the possibility of obtaining high value compounds from basidiomycetes, different classes of polysaccharides (exopolysaccharides (EPS), β-glucans, chitin and chitosan) were extracted from the following strains collected at IBAF-CNR: Agaricus bisporus (SMR 13), Auricularia auricula-judae (SMR 54), Lentinula edodes (SMR 90), Trametes versicolor (SMR 117), Armillaria mellea (SMR 439), Pleurotus ostreatus (SMR 684) e Pleurotus eryngii (SMR 755).
EPS from growth liquid medium were extracted, the yield ranged between 4.6 and 11.0 %, depending on the fungal strain. For their ability as antioxidants, the effects of EPS on Aspergillus parasiticus growth and aflatoxin production were tested. Results showed that EPS from T. versicolor inhibited A. parasiticus growth. Aflatoxins production was completely inhibited by EPS from T. versicolor and A. auricula-judae and partially inhibited by EPS from L. edodes (85-90 %) and P. ostreatus (65-80 %).
β-glucans yield from mycelia and carpophores was about 6% (dry weight). FT-IR spectra obtained from P. ostreatus showed the characteristic bands of a standard glucan. Two fractions with the molecular weight of 59.8 e 37.5 KDa were obtained.
Chitin yield extracted from mycelium and fruit body ranged between 8.5 and 19.6 %, chitosan yield was about 1% d.w.
FT-IR spectra of chitin and chitosan were similar to the standard products.
To evaluate the purity of fungal chitin samples, the amount of glucosamine and crystallinity were determined. The glucosamine percentage obtained for fungal chitin samples ranged between 26.4 and 64.5% of chitin.
The degree of crystallinity of fungal chitin samples was lower than the value obtained in standard chitin (1.54).
The degree of acetylation (DA%) ranged between 80 and 95%, comparable with standard chitin (96%). Because of its high crystallinity, chitin must be deacetylated into chitosan for a wider range of applications.
Standard and fungal chitin samples underwent alkaline deacetylation twice. A great decrease of DA was evident, reaching values similar to the DA of the standard chitosan (DA= 7.5%). The yield of chitosan obtained after chitin deacetylation was on average about 70–75%.
The ability of mycelium, fruit body and the polysaccharide fractions to adsorb Cadmium (II) present in aqueous solutions was tested.
Given the great ability of chitosan of adsorbing Cd (II), further experiments were performed using solutions containing Cd (II), Cu (II), Zn (II), Ni (II), Pb (II) e Cr (III) in single system or in mixture.
Results showed an adsorbing capacity of about 170 mg of Cu(II) per g of chitosan. The adsorbing process well fitted with Langmuir e Freundlich equations.
Because of the regeneration of the sorbent may be important for keeping the process costs down and to open the possibility of recovering the pollutant extracted from the solution, 3 cycles of adsorption-elution-regeneration were performed on chitosan column with positive results.
Additional information
Dottorato di ricerca in Scienze ambientali
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