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Selection and characterisation of high ethanol tolerant
Saccharomyces yeasts from orchard soil
A. N. Moneke*, B. N. Okolo, A. I. Nweke, L. I. Ezeogu and F.
S. Ire
Department of Microbiology, University of Nigeria, Nsukka,
Nigeria.
*Corresponding author. E-mail:
annymoneke@yahoo.com.
Tel: 234-08033357734.
Accepted
14 November, 2008 |
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Six
yeast strains with different levels of ethanol tolerance
were isolated from orchard soil. Out of the six isolates,
isolate Orc 6 showed the highest ethanol tolerance (20%)
while isolates Orc 2 and Orc 11 had 15% ethanol tolerance.
High level ethanol tolerant Saccharomyces yeast, Orc 6, was
investigated for its potential application in ethanologenic
fermentations. Data presented in this study revealed that
Orc 6 yeast isolate tolerated osmotic stress above 12% (w/v)
sorbitol and 15% (w/v) sucrose equivalent of osmotic
pressure thus exhibiting superior osmotolerance than the
reference production wine yeast strain. Invertase activity
was also higher for Orc 6 yeast when grown in both sorbitol
and sucrose media. Sorbitol increased yeast sedimentation
rate in contrast to sucrose. Generally, the new yeast
strain, Orc 6, showed superior fermentative performance
compared to the reference production yeast strain.
Key
words:
Saccharomyces yeasts, osmotic pressure, invertase activity,
sedimentation rate, sucrose. |
