UNIVERSITÉ PAUL CÉZANNE, AIX MARSEILLE III - IMEP

Résultats et discussion. Chapitre 3: Evaluation des facteurs de croissance
2.5.3. 13 C-nuclear magnetic resonance ( 13 C-NMR) analysis
Freeze-dried samples were used directly in NMR experiments without special
preparation. Owing to their size, the samples were gently ground (IKA Labortechnik,
Germany) in order to fill the rotor. Solid-state 13 C CPMAS NMR spectra were obtained on a
Bruker Avance-400 MHz spectrometer (Bruker, Bremen, Germany) operating at a 13 C
resonance frequency of 100.7 MHz. Samples were placed in a 7-mm zirconium rotor and spun
at the magic-angle at 6 kHz. All measurements were made at room temperature. The 13 C
chemical shifts were referred to tetramethylsilane and calibrated with the glycine carbonyl
signal, set at 172.5 ppm. Deconvolution of the NMR spectra was performed using the DmFit
software (Massiot et al., 2002). This software adjusts the spectra to obtain the line width and
the peak positions (in ppm) and to integrate each peak so as to obtain the percentage of each
contribution. The deconvolution and determination of different measurements were performed
as reported previously.
3. Results
3.1. Physico-chemical characterisation of substrates
The physical and chemical characteristics of the three substrates are presented in Table
5. The pH of all the three substrates was between 5.45 and 4.9 for OTL and OMW
respectively. While nitrogen content was the same for all substrates (0.82±0.1 %), the C/N
ratio was different for all substrate and OTL presented the lowest value (54.07±2.12) followed
by OC and OMW (60.11± 3.24 and 63.2±0.65 respectively). Statistical analysis (P=0.05)
showed no significant difference in carbohydrate and lignin content were observed for OMW
and OC but significant difference for OTL which presented the highest carbohydrate content
(68.64±2.68 %) and lowest lignin content (16.87±1.86 %).
97