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Page 60
alliedacademies
Archives of Industrial Biotechnology | Volume 2
May 14-15, 2018 | Montreal, Canada
World Yeast Congress
Second generation (2G) bioethanol is a clean and renewable
sourceofenergy,whichcouldbeproducedbylignocellulosic
biomass (LCB) such as agricultural, forestry, municipal, and
industrial wastes. LCB contains cellulosic and hemicellulosic
fractions, which is yielded into pentose and hexose sugars
using pretreatment and enzymatic saccharification. Most
of the ethanol producing microorganisms are either hexose
sugars utilizing or utilize pentose sugars inefficiently along
with hexose sugars. However, the utilization of both pentose
and hexose sugars is required for economical fuel ethanol
production. An isolated thermotolerant yeast Kluyveromyces
marxianus NIRE-K3 is able to utilize both pentose and
hexose sugars. However, the utilization of pentose sugar
(xylose) is very slow as compared to hexose sugar (glucose).
The present study was carried out to develop K. marxianus
NIRE-K3.2 for enhanced xylose utilization through two-
phase evolutionary adaptation, and analyzed the bioethanol
production potential of adapted K. marxianus NIRE-K3.2 from
sugarcane bagasse (SCB) in comparison to native yeast. The
two-phase evolutionary adaptation was carried out: first
in YEPX medium (20gl-1 xylose) for 60 generations followed
by second in minimal salt medium containing 20gl-1 xylose
for 55 generations. Liquid ammonia pretreated SCB was
enzymatically saccharified using Novozyme Cellic Ctec2. The
maximum concentrations of glucose and xylose in hydrolysate
were found to be 35.45gl-1 , and 14.92gl-1, respectively. The
fermentation of enzymatic hydrolysate was carried out using
nativeNIRE-K3 and adaptedNIRE-K3.2, separately at 45oC and
pH5.5. NIRE-K3 showed utilization of 43.23% xylose, whereas,
NIRE-K3.2 utilized 75.06% xylose present in hydrolysate.
The ethanol yields obtained by NIRE-K3.2 was equivalent to
92.15% of the theoretical yield, whereas, 60.78% in case of
NIRE-K3. The adapted strain NIRE-K3.2 showed 34% improved
ethanol yield by utilizing xylose efficiently along with glucose
as compared to that of native strain. The aforesaid results
show the importance of evolutionary adaptation to develop
enhanced xylose utilizing thermotolerant yeast K. marxianus
NIRE-K3.2 for bioethanol production by utilizing both pentose
and hexose sugars in SCB.
e:
Bioethanol production by thermotolerant yeast Kluyveromyces marxianus from sugarcane bagasse
Sachin Kumar, Meenu Hans and Nilesh K Sharma
Sardar Swaran Singh National Institute of Bio-Energy, India