anotated bibliography

tomatoedgeBiotechnology

Feb 20, 2013 (4 years and 4 months ago)

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References



1.
Chen Y, Yang X, Zhang S, Wang X, Guo C, Guo X, Xiao D. Development of
saccharomyces cerevisiae producing higher levels of sulfur dioxide and
glutathione to improve beer flavor stability. Applied Biochemistry and
Biotechnology 2012;166
(2):402
-
13.


Sulfur compounds like sulfite and glutathione are important for flavor
stability while hydrogen sulfide contributes a rotten egg smell to
beer. The experiment carried out by Chen et al. aimed to decrease
hydrogen sulfide concentration in ferme
ntation by inducing mutagenesis
in S. cerevisiae strains S5, M8, And MV16, each a mutant from the
previously listed strain. Yeast cell suspensions were placed under a UV
lamp and irradiated and

inoculated in YPDL plates for colony growth,
after which they
were assayed for sulfur compound synthesis rates.




2. Dasari S, Kölling R. Cytosolic localization of acetohydroxyacid synthase
Ilv2 and its impact on diacetyl formation during beer fermentation. Applied
and Environmental Microbiology February 1, 2011 Fe
bruary 1, 2011;77(3):727
-
31.

A

common

off

flavor

produced

in

beer

is

a

slick

and

unpleasant

taste

of

butter

and

butterscotch,

which

is

caused

by

concentrations

of

Diacetyl (2,3
-
butanedione). With this in mind, reducing and
maintaining low levels of diacetyl is of great importance when it comes to producing a quality
beer.
This experiment presented evidence on the correlation of diacetyl concentrations and small
mutations of
Sac
charomyces

cerevisiae.

Several

strains

of

yeast

had

insertions

and

deletions

in

the

genome

that

would

alter

diacetyl

formation,

which

were

verified

by

PCR.

Fermentation

was

carried

out

and

then

the

cells

were

homogenate
d

and

run

through

a

chromatography.



3. Procopio S, Qian F, Becker T. Function and regulation of yeast genes
involved in higher alcohol and ester metabolism during beverage fermentation.
European Food Research and Technology 2011;233(5):721
-
9.


4.
Anna Kutyła
-
Olesiuk, Michał Zaborowski, Piotr

Prokaryn, Patrycja Ciosek,
Monitoring of beer fermentation based on hybrid electronic tongue,
Bioelectrochemistry, Available online 26 January 2012, ISSN 1567
-
5394,
10.1016/j.bioelechem.2012.01.003.


Researchers at Warsaw University of Technology created
a novel method to
monitor the fermentation process of beer through the use of a hybrid
electronic tongue. It utilizes a sensor array of 10 miniaturized electrodes
to take chemical images of samples collected throughout the fermentation and
maturation cycle

of beer; the data was processed using (PLS) and (PLS
-
DA).
The experimental data indicated that the h
-
ET could correctly identify the
characteristics of dozens of beer samples from sweetness, acidity, to
bitterness.






4. Lei H, Zhao H, Yu Z, Zhao M. E
ffects of wort gravity and nitrogen level on fermentation
performance of Brewer’s yeast and the formation of flavor volatiles. Applied Biochemistry
and Biotechnology 2012;166(6):1562
-
74.


The gravity of wort along with its chemical composition
has

great effect on
yeast

productivity and
the final beer flavor
. With this in mind, Lei et al.
experiment focused on the whether the gravity of t
he wort and its nitrogen
levels affected yeast performance and flavor volatiles. A lager yeast strain
FBY0095

was

pitched in four different wort mixtures of varying gravity and
Free amino nitrogen (FAN) levels. Results indicated a decrease in yeast cell
growth rates when the gravity is increased or if FAN levels are decreased.


5. Olaniran AO, Maharaj YR, Pillay B. E
ffects of fermentation temperature on the
composition of beer volatile compounds, organoleptic quality and spent yeast density. EJB
2011;14(2):5
-
.


Fermentation temperature plays a large role in the quality and characteristics of beer, as well as
determine
s the overall efficiency of the fermentation process. The experiment conducted by
Olaniran et al investigated the effects
that

fermentation temperature

and yeast types have on
production of volatile compounds and spent yeast. Three fermentation temperatur
es of 18

° C
,
22.5

° C,

and 30

° C

were used along with two strains of yeast. Gas evolution was monitored to
determine fermentation rates. Gas chromatography and mass spectrometry was used to
analyze the volatile compounds in the beer and color and clarity of the beer was assessed as
well.

Results indicated the highest spent yeast density at room temperature, no real significance
in color difference or clarity, and
volatile compound concentrations did have some correlation
with temperature.