International Journal of Applied Microbiology and Biotechnology Research
ISSN: 2053-1818
Vol. 9(6), pp. 122-128, December, 2021

Comparative ethanol tolerance of different yeast isolates obtained from spontaneously fermenting cocoa (Theobroma cacao L.) pod husk

Igbinadolor, R. O.1,2,3* and Onilude, A. A.2

1Department of End-use Research, Cocoa Research Institute of Nigeria, PMB 5244, Ibadan, Nigeria.
2Industrial Microbiology and Biotechnology Unit, Department of Microbiology, University of Ibadan, Nigeria.
3Department of Yeast Molecular Genetics, International Centre for Genetic Engineering and Biotechnology (ICGEB), Trieste, Italy.

*To whom correspondence should be addressed. E-mail:

Received 20 August, 2021; Received in revised form 24 September, 2021; Accepted 04 October, 2021.


Cocoa pod husk, Yeast, Ethanol.

Yeast strains are commonly associated with sugar rich environments. Spontaneously fermenting Cocoa pod husk samples were selected as source for isolating yeast cells, with the intent to genetically modify the selected yeasts for biofuel production from cocoa pod husk. The isolated yeast cultures were identified at Genus level by colony morphology, biochemical characteristics and cell morphological characters. The viability of yeast cells were monitored under different concentrations of ethanol. Ethanol tolerance of each strain was studied by allowing the yeast to grow in liquid yeast extract peptone dextrose (YEPD) medium having different concentrations of ethanol. A total of fifty yeast strains isolated from different samples and five were carefully selected based on frequency of occurrence for the study. Five strains of yeast obtained were screened for ethanol tolerance at different concentrations of 4 to 10%. The results obtained in this study show ranges of selected yeasts tolerance levels. Saccharomyces uvarum (MX3) was less tolerance at 6% concentration compared to MX4 and MX5. However, two strains of Saccharomyces cerevisiae (MX1 and MX2) had the highest level of tolerance (1.65 ± 0.00600b and 1.79 ± 0.05550a) respectively. Based on these qualities, genomic DNA of these two strains was carried out for further genetic modification studies and ethanol production.

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