Molecular identification and technological properties of yeasts isolated from spontaneously fermented cassava waste pulp

Abstract

The aim of this work was to report on molecular identification and technological properties of the yeast flora isolated from spontaneously fermented cassava waste pulp. This was done with a view of obtaining yeast strains that could be used as a starter culture for the fermentation of cassava waste pulp. Molecular identification was based on the nucleotide sequence of the ITS region of the genomic DNA of the yeast isolates while the technological properties evaluated include linamarase (U/mL), gelatinase, and haemolytic activity; growth at pH 2.5 and tolerance to 2 % bile salt. All the representative five isolated yeasts were identified as Geotrichum silvicola KLP04 – KLP08. The isolates exhibited linamarase activity ranging between 3.3 and 4.2 with strain KLP04 having the highest value and strain KLP05 the least. None of the isolates demonstrated gelatinase and haemolytic activity except strain KLP08 which was partially haemolytic. All the examined yeasts exhibited good growth at pH 2.5, with strain KLP08 having the highest viable counts of 4.1 log₁₀cfu/ml and strain KLP04 the least value of 3.5 log₁₀cfu/ml after 72 h of growth. All the identified yeasts showed strain-specific tolerance to 2% bile salt with strain KLP04 having the highest viable count of 4.3 log₁₀cfu/ml and strain KLP08 the least value of 2.2 log₁₀cfu/ml at the end of 72 h of incubation. Based on all the examined technological properties, Candida silvicola KLP04 strain had the highest potential to be considered for starter culture for the fermentation of cassava waste pulp.