12.4.2 Effect of Fungal Pre-treatments on Kraft Pulping
Fungal pre-treated chips with endophytes and saprophytic fungi were subjected to
kraft pulping (Fig.12.5). Lower Kappa number and higher brightness values were
obtained for all the samples treated with fungi compared to control pulp (without
fungal treatment). However, no significant differences in polymerization degree
were found. Moreover, higher delignification was observed with endophytic strains
during kraft pulping compared toTrametessp. I-62, exceptP. smilacis. The highest
increment in delignification (27% compared to control) was found when
Hormonemasp. was applied compared with 9% obtained byTrametessp. I-62.
Moreover,Hormonemasp. andN. australeprovided higher brightness (46.0 and
44.3% ISO, respectively) thanTrametessp. I-62 (41.6% ISO). Other white-rot
fungi have improved delignification during kraft pulping in previous works, but the
results were worse than that observed for this endophytic fungus in most of the
cases: when chips from hardwood (eucalyptus and poplar) were pre-treated with
Ceriporiopsis subvermisporaan increase of 14% was obtained (Yadav et al. 2010 );
increases around 18% were produced from pine pre-treated withPycnoporus
sanguineus,Pycnoporussp. andStereumhirsutum(Wolfaardt et al. 2004 ). Higher
increases were measured when soda pulping was performed in rice straw pre-treated
withP. chrysosporiumandPleorotus ostreatus: 26 and 35%, respectively (El-Din
et al. 2013 ).
Among all the strains studied,Hormonemasp. showed the minor NaOH con-
sumption during pulping, 12% less than control and similar Na 2 S consumption.
N. australepre-treated samples consumed also around 8% less NaOH than control
andTrametessp. I-62 samples. However, Na 2 S consumption increased from 54 to
82%, and kappa number and brightness were worse than those found for pulps
pre-treated withHormonemasp. These reductions in the alkali dose necessary to
produce a target kappa number in chemical pulps have been associated with the
modifications in wood chips caused by fungi (Mardones et al. 2006 ).
Mechanical properties of handsheets of the obtained pulps were improved when
a fungal pre-treatment was performed before pulping. Endophytic fungi, except
Fig. 12.5 Scheme of the experimental procedure of biological pre-treatments to enhance Kraft
and mechanical pulping
274 Ú. Fillat et al.