Page 278 - Refining Biomass Residues for Sustainable Energy and Bioproducts

246 Refining Biomass Residues for Sustainable Energy and Bioproducts

the pretreated biomass. Several research activities are going on for the development
of a cost-effective strategy for bioethanol production.
Takano and Hoshino (2018) reported bioethanol production from alkali-
pretreated rice straw by simultaneous saccharification and fermentation (SSF) using
cellulase cocktail and a xylose fermenting fungus, Mucor circinelloides. The results
indicate that under optimized conditions, 30.5 g/L of bioethanol was produced with
a fermentation efficiency of 90%. Bioethanol production from sugarcane tops and
leaves was reported by Mamphweli and Okoh (2017). Different pretreatment strate-
gies, such as acid hydrolysis and alkaline peroxide pretreatment, were evaluated for
bioethanol production. The study revealed that alkaline peroxide pretreatment gave
better ethanol yield when compared to acid hydrolysis. The decrease in enzyme
yield for acid hydrolyzed samples is due to the inhibition of fermentative microbes
by the inhibitors generated during pretreatment. Momayez et al. (2017) used efflu-
ent from biogas plant for the pretreatment of rice straw for bioethanol production.
Biogas effluent contained different organic acids, such as acetic, butyric, lactic, and
propionic. The results indicate that among the different organic acids present in the

effluent, pretreatment with lactic acid was most effective. Pretreatment at 140 C
resulted in an increase of glucose and ethanol concentration by 42.4% and 47.5%,
respectively.
Enhanced bioethanol production from hemicelluloses of wheat straw by mutant
strain of pentose fermenting microorganisms—Pichia stipitis and Candida shehatae—
was evaluated by Koti et al. (2016). Mutagenesis was carried out by physical
and chemical mutagens. The study revealed that the mutated strains were capa-
ble of producing significantly higher ethanol yields (12.15 g/L) when com-
pared to wild strain (8.28 g/L). Wang et al. (2016) compared the effect of
different pretreatment strategies on ethanol production from cotton stalks.
Three different pretreatment strategies, such as dilute sulfuric acid pretreat-
ment, ultrasound-assisted alkali pretreatment, and high pressure assisted
alkali pretreatment, were evaluated for bioethanol production from cotton
stalk. The study revealed that high pressure assisted alkali pretreatment gave
the highest reducing sugar and ethanol yield with a better lignin removal from
the pretreated biomass (271.7 mg/g and 45.53%, respectively). Baig and
Dharmadhikari (2016) reported bioethanol production by immobilized cocul-
ture of Saccharomyces cerevisiae MTCC 36 and Pachysolon tannophilus
MTCC 1077 using cotton stalk hydrolyzate. Under optimized conditions the
coculture produced 3.94 g/L of bioethanol with a fermentation efficiency of
69.53%. The immobilized cocultures showed the same ethanol yield and fer-
mentation efficiency for three cycles.

11.2.1.2 Biobutanol
Butanol is a primary alcohol produced by acetone butanol ethanol (ABE) fermen-
tation. Butanol is compatible with current automobile engines. It has high energy as
well as low water solubility content that makes it a suitable candidate for the
replacement of gasoline (Kumar and Gayen, 2011).