Isolation and Characterization of Potential Bioethanol Producing Indigenous Wild Yeasts from Local Alcoholic Raw Materials (Areke Difdif and Tenses)

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Addis Ababa University


Shortage of fossil fuel supplies has increased a great deal of interest in worldwide production of renewable energy. Bioethanol produced from renewable biomass like molasses has received considerable attention as an alternative biofuel in recent years. Thus, the main purpose of this research work was to isolate, screen and characterize ethanol tolerant wild indigenous yeasts with high bioethanol yield from areke difdif and tinses samples collected from different areke producing sites. The wild yeast isolates were retrieved from the alcoholic beverages following standard methods. From a total of 270 isolates, ten (3.7%) of the yeast isolates tolerated 22% and four (1.5%) isolates from the same 10 isolates tolerated 23% ethanol concentration, and were selected for further characterization. Based on morphological appearance of vegetative cells under microscope, colony characters and molecular analysis, the isolates were identified as Saccharomyces cervicae and Kluyvermyces marixianus. Ten (Mda, Mdb, Mdd, D5f, D5b, D5d, D5e, Dt1e, Dt1c and Dtlj) isolates were found thermotolerant (45oC and Mda able to tolerate 47 oC) and also all ten isolates grow at low pH (>=2.5). Ethanol production from sugar cane molasses by the yeast isolates was determined by using Hall method and was crosschecked with Ebulliometer. From 10 isolates, two isolates (Mda and Dt1e) showed the highest bioethanol production capacity of 14.3% v/v and 13.2% v/v, respectively at pH 4.39 and temperature 35oC in 30 degree brix molasses concentration at 150 rpm shaking condition. During this study potentially useful and excellent ethanol producing indigenous yeasts with high ethanol tolerant features from areki difdif and tenses were isolated, identified and characterized. This study exhibited the potential of local fermentation processes and products (areke difdif and tenses) as possible sources of industrially useful microbial isolates.



Yeasts, Areki Difdif/Tenses, Tolerance, Bioethanol, Molasses