Abstract:
The use of Bio-wastes like whey as raw materials for production of ethanol is gaining
importance due to the environmental impact and exhaustion of fossil fuel sources
making renewable fuel alternatives highly attractive. The objective of the study
involved the isolation, characterization and identification of yeast strains from the
Kenyan Cheese Industries exhibiting robust whey-lactose fermentation to ethanol and
their potential application in bioethanol production from whey, Yeast strains were
isolated using PDA and YEPL Medias from samples collected from KCC, Sameer
and Browns cheese dairy industries. Genetically, the variable D1/D2 domain of the
large subunit (26S) ribosomal DNA of the isolates were amplified by the polymerase
chain reaction (PCR), sequenced and compared with known 26S rDNA sequences in
the GenBank database, the rDNA fragment containing the internal transcribed spacers
(ITS1 and ITS2) and 5.8S-ITS rDNA were PCR-amplified, sequenced and the PCR
product digested with the enzymes HinfI, and HaeIII. Twenty eight out of forty two
pure isolates were found to have fermentative ability. The sequence analysis of the
variable D1/D2 domain of the 26S rDNA, showed that the isolates belonged to
Kluyveromyces, Yarrowia, Pichia and Candida. In addition, the unique variability in
the size and profiles of the amplified product and in the restriction patterns enabled
differentiation between the isolates. The assessment of fermentative performance of 4
yeast strains showed that K. marxianus strain BM4, K. marxianus strain BM9 and K.
lactis strain P41 had higher ethanol productivity of 5.52, 4.92 and 5.05% w/v,
XVIII
respectively, from whey at pH 4.5 and 30oC while P. cactophila strain YB2 produced
1.40% w/v ethanol at 10% whey sugar and pH 4.5 at 30oC. It was concluded that
molecular methods based on the sequences of the 26S rDNA D1D2 domain and the
ITS region were rapid and precise compared with the physiological method for the
identification and typing of these species, The yeast strains isolated also showed
potential in whey to Bio-ethanol production.
