BIOCONVERSION OF CELLULOSIC WASTE INTO BIOETHANOL AS BIOFUEL
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Date
2013
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Abstract
ABSTRACT
The present investigation was carried out to isolate, screen and identify the most efficient cellulolytic
and xylanolytic microorganisms from soil. Mutation of hypercellulase and xylanase producers, enzyme
production, optimization, partial purification, bioconversion of cellulosic waste into bioethanol and scale up
studies were performed with selected strains to recommend their use for industries. In total 89 microorganisms
including 84 bacteria and 5 fungi were isolated. Among them, ten hypercellulase and xylanase producing
bacteria were subjected to mutation for enhanced enzyme production. N12 (M) and Kd1 (M) were screened for
cellulase and xylanase enzyme production studies. The wild and mutant bacterial isolates were identified as B.
stratosphericus N12 (W), B. stratosphericus N12 (M), B. altitudinis Kd1 (W) and B. altitudinis Kd1 (M)
respectively by 16S rRNA PCR technique and registered with NCBI under accession no. |KC995116|,
|KC995118|, |KC995115| and |KC995117|. Cellulase and xylanase enzymes were optimized through classical
approach one factor at a time (OFAT) under submerged fermentation varying medium, pH, temperature,
inoculum size, incubation time, carbon source and substrate concentration. The percent increase in enzyme
activity obtained after optimization of different process parameters was 85.23% for cellulase of B.
stratosphericus N12 (M) and 85.60% for xylanase of B. altitudinis Kd1 (M). To reduce the production cost of
enzymes, cheap untreated and pretreated lignocellulosic forest biomass i.e. hardwood and softwood were used
as a substrate under SmF by B. stratosphericus N12 (M) and B. altitudinis Kd1 (M), SSF by M. thermophila SH1
and among them alkaline hydrogen peroxide pretreated P. deltoides wood was found the best for hypercellulase
and xylanase production under SmF as well as SSF. The partial purification of hydrolytic enzymes was done by
ammonium sulphate precipitation. Scale up of cellulase from B. stratosphericus N12 (M) as well as xylanase
from B. altitudinis Kd1 (M) was performed in 7.5 L bioreactor at 200 rpm, 1 vvm and 300C, achieving 2.443 IU
cellulase and 11.10 IU xylanase respectively, after only 8 h of fermentation. Bioconversion of alkaline hydrogen
peroxide pretreated P. deltoides wood to ethanol was studied under three different fermentation processes i.e
separate hydrolysis and fermentation (SHF), simultaneous saccharification and fermentation (SSF) and
simultaneous saccharification and co-fermentation (SSCF). Different strategies had been designed to delimit the
constraints of fermentation process. SHF was evaluated by modifying four different sub-processes of
detoxification and non-detoxification as well as pooling and nonpooling of pretreated liquor. Maximum ethanol
was achieved in method –IV of SHF i.e. 18.47g/l by co-culture of S. cerevisiae II and P. stipitis with the
fermentation efficiency of 72.46%. Among all the three processes of fermentation evaluated in the present
study, SHF was found to be the best and in case of strains used for fermentation, co-culture of S. cerevisiae II
and P. stipitis was observed the best combination for highest bioethanol production.
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Keywords
cotton, inorganic acid salts, foliar application, crops, soybeans, boron, magnesium, zinc, yields, intercropping, Bioethnol ,Biofuel, cotton, inorganic acid salts, foliar application, crops, soybeans, boron, magnesium, zinc, yields, intercropping