Athens, Greece
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Papaspyridi L.-M.,BIOtechMASS Unit | Katapodis P.,BIOtechMASS Unit | Katapodis P.,University of Ioannina | Gonou-Zagou Z.,National and Kapodistrian University of Athens | And 2 more authors.
Biochemical Engineering Journal | Year: 2010

This work was aimed at optimizing biomass production by the edible basidiomycete Pleurotus ostreatus ATHUM 4438 in a submerged process with enhanced glucan and dietary fibres content. β-Glucan from Pleurotus sp. (pleuran) has been used as food supplements due to its immunosuppressive activity. Like other dietary fibre components, oyster mushroom polysaccharides can stimulate the growth of colon microorganisms (probiotics), i.e. act as prebiotics. We used the FF MicroPlate for substrate utilization and growth monitoring. The pattern of substrate catabolism forms a substrate assimilation fingerprint which is useful in selecting media components for media optimization of maximum biomass production. Different carbon sources (95) were used and then 8 of them were tested in shake flask cultures. The effect of various organic and complex nitrogen sources on biomass production was also examined and response surface methodology based on central composite design was applied to explore the optimal medium composition. When the optimized culture medium was tested in a 20-L stirred tank bioreactor, using 57 g L-1 xylose and 37 g L-1 corn steep liquor, high yields (39.2 g L-1) of dry biomass was obtained. The yield coefficients for total glucan and dietary fibres on mycelial biomass formed were 140 ± 4 and 625 ± 9 mg g-1 mycelium dry weight, respectively. © 2010 Elsevier B.V. All rights reserved.

Vafiadi C.,BIOtechMASS Unit | Christakopoulos P.,BIOtechMASS Unit | Topakas E.,BIOtechMASS Unit
Process Biochemistry | Year: 2010

Two xylanases were purified to electrophoretic homogeneity from the thermophilic fungus Sporotrichum thermophile grown in a submerged liquid culture using wheat straw as carbon source. The enzymes, StXyn1 and StXyn2, have molecular masses of 24 kDa and 48 kDa, respectively, and are optimally active at pH 5 and at 60 °C. Both enzymes displayed remarkable stability up to 50 °C for 1 h, exhibiting a half-life of 60 min (StXyn1) and 115 min (StXyn2) at 60 °C. Biochemical characterization of the two xylanases against poly- and oligosaccharides indicated that StXyn1 and StXyn2 hydrolytic profiles match those of xylanase family 11 and family 10, respectively. LC-MS/MS analysis provided peptide mass and sequence information that assisted the identification of the corresponding xylanase genes from the S. thermophile genome and the classification of the two purified StXyn1 and StXyn2 as a family GH11 and GH10 endo-1,4-β-xylanases, respectively. © 2009 Elsevier Ltd. All rights reserved.

Topakas E.,BIOtechMASS Unit | Kyriakopoulos S.,BIOtechMASS Unit | Biely P.,Slovak Academy of Sciences | Hirsch J.,Slovak Academy of Sciences | And 2 more authors.
FEBS Letters | Year: 2010

Three acetyl esterases (AcEs) from the saprophytic bacteria Cellvibrio japonicus and Clostridium thermocellum, members of the carbohydrate esterase (CE) family 2, were tested for their activity against a series of model substrates including partially acetylated gluco-, manno- and xylopyranosides. All three enzymes showed a strong preference for deacetylation of the 6-position in aldohexoses. This regioselectivity is different from that of typical acetylxylan esterases (AcXEs). In aqueous medium saturated with vinyl acetate, the CE-2 enzymes catalyzed transacetylation to the same position, i.e., to the primary hydroxyl group of mono- and disaccharides. Xylose and xylooligosaccharides did not serve as acetyl group acceptors, therefore the CE-2 enzymes appear to be 6-O-deacetylases. © 2009 Federation of European Biochemical Societies.

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