Abstract:
In this study of twenty-five samples which were collected from dairy producing
centers in the city of Isfahan, 30 yeast strains were isolated using Malt Extract
Broth (MEB) containing 0.1 gl¯1 chloramphenicol
and Yeast Extract Glucose Chloramphenicol Agar (YGCA). Of the isolated strains,
11 with the ability to lactose fermentation were isolated (M1-M11). These strains
were identified by morphological and physiological properties. From these 11
strains, six were identified as Kluyveromyces lactis, four as Kluyveromyces
marxianus and one as Candida versatilis. In the next step, the amount
of produced single cell protein, SCP, from whey; whey including nitrogen supplementation
and whey with mixed yeast cultures in these strains was measured. Among these
strains, M2 that was identified as K. lactis had the most SCP production
from whey with 11.79 gl¯1. It was found
that the ammonium sulfate as a nitrogen source has a significant effect on biomass
yield so that amount of produced biomass of the M11 strain (K. marxianus)
increase from 11.54 gl¯1 (from whey
without nitrogen supplementation) to 15.75 gl¯1
(in the presence of nitrogen source). The co-cultures of yeast strains with
Saccharomyces cerevisiae were evaluated. In the mixed yeast cultures
of these yeast strains and S. cerevisiae, the M2 strain which was identified
as K. lactis had the most biomass production, 22.38 gl¯1.
ONPG assay of beta-galactosidase in yeast strains found that a strain of K.
lactis (M2) has the highest enzyme activity (8103 Eu ml¯1).
These strains can be used for removal of whey pollutant, SCP & ethanol production
and treatment of lactose in dairy food.
I. Nahvi and H. Moeini , 2004. Isolation and Identification of Yeast Strains with High Beta-galactosidase Activity from Dairy Products. Biotechnology, 3: 35-40.
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