UNIVERSITÉ PAUL CÉZANNE, AIX MARSEILLE III - IMEP

1. Introduction
Résultats et discussion. Chapitre 2: Optimisation de la production du spawn
Ergosterol is principal sterol present in fungi biomass (Czub and Baginski, 2006) with
its two forms, as free ergosterol and esterified ergosterol. The relative abundances of free to
esterified ergosterol are different among the various species of fungi (Czub and Baginski
2006; Yuan et al., 2007). Therefore, the determination of ergosterol consists in measuring of
living fungal biomass, because of the assumption of its instability after death of biomass
(Mille-Lindblom et al., 2004). This ergosterol was also subject for certain investigations in
order to study its conversion to Vitamin D2 (Jasinghe and Perera, 2005; 2006) which has been
suggested for therapeutic applications in the treatment of several diseases including
hyperproliferative diseases, secondary hyperparathyroidism, post-transplant survival, and
various malignancies (Morgan, 2001).
Culture of L. edodes attracks attention of several authors for its proved medicinal
properties and antimicrobial effect (Kitzberger et al., 2007; Israilides et al., 2008; Rao et al.,
2009) and biodegradation as well as biotransformation abilities of phenolic compound as
lignin by producing large spectrum of enzymes involved in transformation of these
recalcitrant compounds (Philippoussis al., 2007). While the kinetics of growth of the
mycelium is related to nutritional and environmental factors, several authors (Mamiro and
Royse 2008; Kuforiji and Fasidi 2009; Royse and Chalupa 2009) demonstrated that the high
quality crop of mushroom depends primarily on the quality of the spawn, which in turn
depends on the purity and size of biomass and physiological state of the culture. However,
direct quantification of biomass during spawn running is very difficult or even impossible,
owing to the problem of separating the fungal mycelium from the substrate, where the fungal
hyphae penetrate into and bind tightly to the substrate (Bellon-Maurel et al., 2003; Singhania
et al., 2009).
However, several techniques of indirect fungal biomass in Solid state fermentation
(SSF) were reported depending to measuring the biological activity (e.g respiration O2 intake
and/or CO2 production) or measuring the content of certain cell components. Recently digital
image processing has been developed as a tool for measuring of biomass of Aspergillus niger
strains in SSF (Couri et al., 2006). The growth of this strain was quantified as the total area
occupied by the hyphae, while this technique was poorly correlated with glucosamine test.
The drawback of this technique consists in setting up of the focus and illumination parameters
which become more difficult when complex substrates are used (Couri et al., 2006).
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