Genetic improvement of Saccharomyces spp. for ethanol production from starch
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Date
2005
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CCSHAU
Abstract
A study was undertaken to improve ethanol production from starch by yeast
Saccharomyces spp. A total of 10 isolates of yeast were isolated. After
secondary screening in submerged culture conditions six isolates were
selected for further investigation. Based on Maximum (6.4U) amylase and
ethanol (8.8g/l) production, the Saccharomyces spp. B6 was selected and
mutagenized using UV rays and nitrous acid. The Saccharomyces spp.
mutant B6U3 produced maximum amylase (8.9U) & ethanol 16.4g/l (in
starch) and 26.8g/l (in dextrose) among various mutants and was selected
for further studies.
The optimization of culture conditions showed that Saccharomyces spp.
B6U3 produced increased level of amylase as compared to parent strain.
Ethanol production was found to increase with increase in the level of starch.
At high concentration of starch the ethanol production was decreased. Starch
at a concentration of 10% was found be the best for production of ethanol
by Saccharomyces spp. B6U3.
Peptone was found to be best nitrogen source for production of ethanol
by Saccharomyces Spp. B6U3 producing a maximum 33.4 g/l of ethanol in
48h. In media containing ammonium sulphate, ammonium nitrate casein &
urea less amount of ethanol was produced.
Peptone was found to the best nitrogen source at 2% level and
34.4g/l of ethanol was produced in 48h of fermentation. Increase in the
conc. of peptone led to decreased ethanol production.
On increasing the inoculum size upto 20% the ethanol production also
increased from 5.6g/l to 32.8g/l after 48h of fermentation.
A little variation was found on using 20% of starch grown and dextrose
grown inoculum. There was a slight increase in the ethanol production on
using dextrose grown inoculum (34.8g/l) than starch grown (33.2g/l) after
48h of fermentation. Ethanol production was found to be maximum after 48h
of fermentation.
Out of different starch sources used Soluble starch, Sorghum, spoiled
wheat, Potato and Cassava, soluble starch was found to be the best
substrate for production of ethanol by Sacchromyces spp. B6U3.