Biomedical Engineering Reference
In-Depth Information
chelating agent. EDTA may remove some metal ion components of the cell wall, such as Ca
2
þ
,
Mg
2
þ
,andZn
2
þ
andmay cause cell wall disintegration. Citric acid can be metabolized by some
bacteria. Chelating agents are included in media in low concentrations (e.g. 1 mmol/L).
Growth factors stimulate the growth and synthesis of some metabolites. Vitamins, hormones,
and amino acids are major growth factors. Vitamins usually function as coenzymes. Some
commonly required vitamins are thiamine (B
1
), riboflavin (B
2
), pyridoxine (B
6
), biotin, cyano-
cobalamin (B
12
), folic acid, lipoic acid, p-amino benzoic acid, and vitamin K. Vitamins are
required at a concentration range of 10
6
e
10
12
mol/L. Depending on the organism, some
or all of the amino acids may need to be supplied externally in concentrations from
10
6
e
10
13
mol/L. Some fatty acids, such as oleic acid and sterols, are also needed in small
quantities by some organisms. Higher forms of life, such as animal and plant cells, require
hormones to regulate their metabolism. Insulin is a common hormone for animal cells, and
auxin and cytokinins are plant-growth hormones.
2.4.3. Growth Media
The two types of growth media are defined media and complex media. Defined media
contain specific amounts of pure chemical compounds with known chemical compositions.
TABLE 2.10
Compositions of Typical Defined Media
Constituent
Purpose
Concentration, g/L
GROUP A
Glucose
C, energy
30
KH
2
PO
4
K, P
1.5
MgSO
4
$
7H
2
O
Mg, S
0.6
CaCl
2
Ca
0.05
10
4
Fe
2
(SO
4
)
3
Fe
1.5
10
4
ZnSO
4
$
7H
2
O
Zn
6
10
4
CuSO
4
$
5H
2
O
Cu
6
10
4
MnSO
4
$
H
2
O
Mn
6
GROUP B
(NH
4
)
2
HPO
4
N, P
6
NH
4
H
2
PO
4
N, P
5
GROUP C
C
6
H
5
Na
3
O
7
$
2H
2
O
Chelator
4
GROUP D
Na
2
HPO
4
Buffer
20
KH
2
PO
4
Buffer
10
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