Isolation and Characterization of Cellulolytic Yeasts for Bioethanol Production
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Date
2013
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Publisher
UAS, Dharwad
Abstract
The present study was conducted in the Department of Agricultural Microbiology on
bioethanol production from selected agro-residues with the objectives whether two step
process i.e. hydrolysis and fermentation could be transformed into single step with the help of
efficient cellulolytic yeast strains, thus reducing the cost of bioethanol production.
A total of 104 yeast isolates from various natural habitat mainly rotten fruit rinds,
forest leaf litter, compost, fruit samples, food stuff and over matured paragrass were isolated
on the basis of zone of hydrolysis of cellulose and release of reducing sugars. Among these
31 cellulolytic yeasts were screened. Five efficient strains CY-52, CY-58, CY-59, CY-62 and
CY-81 were chosen on the basis of release of maximum reducing sugars. The isolates were
subjected for utilization of various carbon sources namely glucose, maltose, ribose, lactose,
sucrose, arabinose, galactose, xylose and starch to know the sugar utilization efficiency.
The efficient yeast strains were subjected on two delignified substrates i.e. paddy
straw and sugarcane bagasse. Delignification was carried out using alkali at 3 per cent for 8 h.
Recovery of cellulose was highest in case of sugarcane bagasse i.e. 695 mg g-1 as compared
to paddy straw 564 mg g-1.To know the enzymatic assay, filter paper activity and CMCase
activity was conducted with the efficient strains out of which strain CY-59 isolate showed
the highest activity i.e. 16.82 U ml-1 and 12.99 U ml-1 respectively.
The yeast isolate CY-59 showed the maximum bioethanol production of 48.18 mg g-1
and 60.51 mg g-1 from paddy straw and sugarcane bagasse respectively which was on par to
reference strain NCIM-3200and commercial cellulase. Thus, it can be concluded that yeasts
are able to induce cellulase for hydrolysis of the substrates and produce ethanol.
Extrapolating more sources from nature can yield better strains.