This document reports on a study that isolated and identified yeast species from grape surfaces in Dehradun, India. 52 yeast isolates were obtained from grapes collected from different locations and subjected to morphological and biochemical characterization. Morphological analysis involved gram staining and capsule staining under the microscope. Biochemical tests included carbon assimilation testing with 9 sugars, fermentation testing with 8 sugars, and a urease test. The isolates showed variation in colony characteristics, cell shapes, and abilities to utilize different carbon sources and ferment sugars. 29 isolates tested positive for urease production. The study identified yeast at the species level based on their phenotypic properties.

1. FOR MEMBERS ONLY
Yeast as a versatile model organism approaches us with
a vast majority of industrial and medical applications
beneficial to human life (Zott et al., 2010). The ability of yeast
to convert sugar into ethanol has been harnessed by
biotechnology industry to produce ethanol fuel (Barata et al.,
2012). The useful physiological properties of yeast have lead
to their use in the field of alcoholic beverages, baking,
bioremediation, non-alcoholic beverages, nutritional
supplements and probiotics (Botstein and Fink, 2011).
The major objectives of the present day study was
isolation of different yeasts species from fruits surfaces of
grapes, cultural characterization of isolated yeasts,
morphological characterization of yeasts and biochemical
characterization of yeasts.
Grapes were collected in polythene bags from different
locations of Dehradun for the isolation of yeast. The grapes
samples were taken to laboratory of Microbiology Department
of SBSPGI, Balawala, Dehradun. The samples collected from
different locations were subjected to streaking on YEPD
(yeast extract peptone dextrose agar) medium using
chloramphenicol antibiotic. After maintaining pure culture of
yeast, identification was done by employing various
morphological and biochemical methods. Morphological
methods include gram staining and capsule staining.
Biochemical methods are further classified as:
Sugar fermentation test: Yeast fermentation broth is
used as an aid in the identification yeast based on
fermentation pattern. Most yeast will produce acid and gas
as by product of fermentation of certain carbohydrates.
Carbon assimilation test: Basically this test is used
for identification of yeast. Yeast uses carbon as a sole
substrate for growth. In practical terms, yeast shows growth
on carbon assimilation media.
Urease test: Urea is a diamide of carbonic acid. Urease,
the enzyme produced by bacteria and fungi, hydrolyses and
releases ammonia and carbon dioxide. Ammonia reacts in
solution to form ammonium carbonate, which is alkaline
leading to an increase in the pH of medium. Phenol red that
is incorporated in the medium changes its color from yellow
to red in alkaline pH, thus indicating the presence of urease
activity.
All the 52 isolates were evaluated and identified
morphologically on the basis of colony characteristics. The
surface, margin and color of the colonies were observed.
The most of the yeast isolates have smooth and mucoid
surface while three isolates were having raised and dry
surface. Similarly the margins of the yeast colonies were
also observed. Most of the isolates have circular margin while
irregular margins were also found in some yeast. Colony
color is also observed by interpreting the plates. Majority of
yeast are giving creamy white color colony where as one
yeast is orange in color (Fig.1). Microscopic evaluation is
also done by simple staining for yeast identification on the
basis of cell shape. All yeast isolates were giving mixed
response some are round shaped some isolates are oval in
shape and bean pod shape is also observed (Fig.2).
Carbon assimilation test: In the carbon assimilation
study, nime sugars were used (glucose, sucrose, lactose,
maltose, mannitol, xylose, glycerol, sorbose and fructose).
52 isolates were identified on the basis of assimilation of
these sugars (Fig.3). All the 52 isolates were able to utilize
glucose as a growth substrate. Sucrose were utilized by most
of the isolates i.e., 33 isolates, after glucose. Other carbon
sources like sorbose, xylose, and glycerol were utilized by
19, 25 and 30 isolates, respectively. Among all the carbon
sources maltose was only to be utilized by maximum 36
isolates. On the other hand, sorbose is utilized by 19 isolates.
seven isolates were found, utilizing all of these sugars.
Sugar fermentation test: In the sugar fermentation
study, the eight sugars were used (glucose, maltose, sucrose,
mannitol, lactose, trehalose, inulin, fructose). 52 isolates were
identified on the basis of fermentation by utilization of sugars
and the color of medium changes from red to yellow. All the
52 isolates were able to ferment glucose and produce acid.
The maltose were utilized by most of the isolates i.e. 44
isolates after glucose. The other sugars sucrose, trehalose,
mannitol and lactose were utilized by 28, 25, 21and 24
isolates, respectively. Among all the sugars, inulin was the
Isolation and Identification of Yeast from Grapes
Ravnoor Kaur, Amandeep Kaur*and V.K. Gupta1
Department of Microbiology, Sardar Bhagwan Singh Post Graduate Institute of Biomedical Sciences
and Research, Balawala, Dehradun,Uttrakhand, India
1
Department of Biotechnology, Guru Nanak College for Girls, Sri Muktsar Sahib-152 026, India
*E-mail: amanbrarmscbt2.cgc@gmail.com
Indian J. Ecol. (2014) 41(1) : 182-183
Indian Journal
of Ecology

2. 183
FOR MEMBERS ONLYonly one to be least utilized by isolates i.e., 11 isolates.
Urease test: Urease test is performed to detect the
capsule around the yeast cell on the basis of color change
from yellow to pink purple (in case of positive). Among 52
isolates, 29 were found positive for urease test i.e., these
produces urease enzyme and hydrolyse urea and released
ammonia and carbon dioxide.
REFERENCES
Barata,A., Malfeito-Ferreira, M. and Loureiro, V. (2012) The microbial
Fig.2. Microscopic features of isolated yeast under 100x
Fig.1. Cultural characteristics of isolated yeast on YEPD agar
medium
ecology of winegrape berries. Inter. Food Microbiol. 153:243-
259.
Botstein, D. and Fink, G.R. (2011) Yeast: An experimental organism
for 21st century biology. Genetics 189:695-704.
Zott, K., Claisse, O., Lucas, P., Coulon, J., Lonvaud-Funel, A. and
Masneuf-Pomarede, I. (2010) Characterization of the yeast
ecosystem in grape must and wine using real-time PCR. Food
Microbio. 27( 5):559–567.
Fig. 3. Growth of yeast isolates on medium containing different
sugars as source of carbon
Received 27 December, 2013; Accepted 24 March, 2014
Isolation and Identification of Yeast from Grapes