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Full Length Research Paper
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Effect of chemical
pretreatment of some lignocellulosic wastes on the recovery
of cellulase from Aspergillus niger AH3 mutant
Damisa, D.1*, Ameh, J. B.2 and Umoh,
V. J.2
1Section
of Microbiology, Department of Applied Science, Kaduna
Polytechnic, PMB 2021, Kaduna, Nigeria.
2Department
of Microbiology, Ahmadu Bello University, Zaria, Nigeria.
*Corresponding author. E-mail:
damisaduro@yahoo.com,
Tel.: +2348023348264.
Accepted
9 June, 2008 |
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Abstract |
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Lignocellulosic biomass holds remarkable potential for
conversion into commodity products presenting dual advantage
of sustainable resource supply and environmental quality.
Though their utilization does not compete with food and feed
demand, its bioconversion and utilizability is facilitated
by pretreatment. The effect of the substrate pre-treatment
using acid and alkali at two different concentrations (0.5
and 2 M) for two different residence timings (1 and 3 h) on
cellulase production from corncob, corn straw and bagasse
was studied using Aspergillus niger AH3. The strain
was inoculated into 10 g/L of the processed pre-treated
lignocellulosic substrates previously added to batches of
the Mandels basal medium. The pH of the medium was adjusted
to optimum (4.8) and the flasks with the contents
autoclaved, thereafter fermentation begun. Samples of each
flask were taken aseptically at regular interval (24 h)
throughout the growth phase until the enzyme activity peaked
off (between 110 and 170 h), centrifuged and the clear
supernatant was used for the enzyme assay. Enzyme expression
in all the pretreated biomass increased steadily from day
one and peaked off at day four or five for the alkali
pretreated residues whereas it was at day six for acid
pretreated residues. Generally for the alkali treated
residues irrespective of residence time, maximum cellulase
yield was at day 5 while for the acid treated residues,
maximum cellulase yield was at day 6. Enzyme yield from
residues treated for longer period (3 h) using alkali when
compared to those using acid under the same condition of
fermentation was highly significant. The alkali treated
residues showed higher cellulase yield than the acid treated
residues. Highest cellulase activity (0.06777 IU/ml/min) was
displayed by the organism grown on bagasse substrate
pretreated with 2M NaOH for one hour. The proximate analysis
of the cellulosic residues differed from one substrate to
another, with the bagasse being the best. Pulverized
substrates syndicated with alkali pretreatment using 2 M
NaOH for one hour was optimal for cellulase production from
the cellulosic residues.
Key
words:
Lignocellulosic biomass, utilization, pretreatment,
cellulase, substrates, Aspergillus niger AH3,
fermentation, supernatant, substrate |
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