Studies on Bioethanol Production From Selected Agro-Residues
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Date
2011
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UAS Dharwad
Abstract
The present study was conducted on bioethanol production from selected agroresidues
with the objectives of achieving higher recovery of fermentable sugars
through delignification and saccharification followed by fermentation of the derived
sugars to bioethanol. Five agro-residues namely sugarcane bagasse, sugarcane tops,
sugarcane trash, corn husk and corn stover of particle sizes 0.5, 1.0 and 10.0 mm were
delignified by various pre-treatment methods such as alkali, autohydrolysis and
lignolytic fungi. The treatment combination of 3.0% NaOH with 1210C temperature
for one h on particle size 0.5 mm resulted in the highest recovery of cellulose and
hemicelluloses in sugarcane bagasse (0.813 g/g), sugarcane tops (0.786 g/g),
sugarcane trash (0.806 g/g), corn husk (0.806 g/g) and corn stover (0.806 g/g). The
delignified substrates were further saccharified using cellulolytic fungi and their crude
enzymes and commercial cellulase enzymes. Among these, the commercial cellulase
enzyme with 15 U/g along with b-glucosidase (10 U/g ) and Xylanase (5 U/g)
enzymes at 5% substrate produced significantly highest reducing sugars with per cent
saccharification in sugarcane bagasse (93.17%), sugarcane tops (90.33%), sugarcane
trash (84.61%), corn husk (80.61%) and in corn stover (80.80%) in 12 h of incubation
period. The pre-treated substrates were fermented to bioethanol by using six
microorganisms. The combined inoculation of Saccharomyces cerevisiae and
Candida shihatae on pre-treated substrates resulted in the highest ethanol yield in all
the substrates, sugarcane bagasse (278.40 mg/g) followed by sugarcane tops (262.75
mg/g), sugarcane trash (241.42 mg/g), corn stover (239.82 mg/g) and corn husk
(232.36 mg/g). The scaled up study on bioethanol production with sugarcane bagasse
under optimized conditions produced 223 g bioethanol from one kg pre-treated
substrate. Thus, it can be concluded that the substrates need to be alkali pretreated
followed by treatment with commercial enzymes and further conversion to ethanol.
The combined inoculation of the yeast cultures yields maximum ethanol.