3. FOOD ChEMISTRy & bIOTEChNOLOGy 3.1. Lectures

Chem. Listy, 102, s265–s1311 (2008) Food Chemistry & Biotechnology
ing machine for 20 minutes at 60 °C, 460 nm. After curing,
the discs were removed from the mold and sterilized in autoclave.
M i c r o b i a l W o r k
An oral ral cavity isolant Streptococcus mutans P2093 has
been chosen as a tested microorganism. S. mutans is oral
bacteria, that is assumed to be the main infander of the dental
caries. The bacterial strain S. mutans used in this study
was clinical isolates from child mouth (obtained from prof.
MUDr. Martina Kukletová, CSc., Brno Masaryk University).
The microorganism was stored in commercially available
Petri dish with Blood agar IMA VLAC and IMA VLGP
(Laboratory of Medical Microbiology, Třinec).
Fig. 1. s.mutans growing on composite polymer disc
The microorganisms were cultivated in liquid culture
medium BHIB. In order to improve the bacteria growth a
certain amount of further source of sugar was added into the
medium. 0.1; 1; 5 and 10 wt% of sacharose and glucose were
tested.
The samples were prepared by placing the sterilized disc
in 5 ml BHIB medium in test tube and inoculating with bacteria
suspension. The appropriate volume of bacteria suspension
and incubation time had to be tested. First one was tested
by inoculation of 0.2; 0.4; 0.6; 0.8 a 1.0 ml of bacteria suspension
into 5 ml BHIB and evaluation of bacterial growth.
The incubation time was varied up to 28 hours and appropriated
incubation time was evaluated from the growing curve.
Results
First of all the appropriate composition of the culture
medium was investigated. 0,1; 1; 5 and 10 wt% of sacharose
and glucose were added to BHIB and the influence of additives
on bacteria growth were evaluated see Fig. 2. Best
growing results were obtained for the medium with 1 wt%
of glucose.
When testing the influence of inoculated volume on bacteria
growth, the volume was varied up to 1.0 ml. The results
are presented in Table I. The highest absorbance was mea-
s769
A 540nm
0,500
0,450
0,400
0,350
0,300
0,250
0,200
0,150
0,100
0,050
0,000
S. mutans in BHIB+
Glucose
S. mutans in BHIB+
Sucrose
0,1 1 5 10
Amount of glucose/sucrose (percentage by
weight)
Fig. 2. s. mutans growing in bhIb with glucose or sacharose
Table I
Influence of suspension volume on S. mutans growth
Inoculated volume [ml] Absorbance [540 nm]
0.2 0.290
0.4 0.288
0.6 0.285
0.8 0.286
1.0 0.270
sured when using 0.2 ml of bacteira suspension. This volume
was used for further testing.
Growing curve (Fig. 3.) presents influence of incubation
time on the bacterial growth respectively on absorbance. It
could be seen that the amount of bacteria increases with increasing
of the incubation time until it reached maximal value.
In our experiment the maximal absorbance resp. amount of
bacteria was obtained for the samples incubated for 18 hours.
When incubating the bacteria in medium for longer time the
nutriens in medium are exhausted. This results in dying out
of bacteria and thus decreasing of absorbance.
A 540nm
0,50
0,45
0,40
0,35
0,30
0,25
0,20
0,15
0,10
0 5 10 15 20 25 30
Time [hour]
Fig. 3. s.mutans growing curve