3. FOOD ChEMISTRy & bIOTEChNOLOGy 3.1. Lectures

Chem. Listy, 102, s265–s1311 (2008) Food Chemistry & Biotechnology
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rose (invertase) was probably not formed (Fig. 1.).
In both systems, maximal cells growth was achieved on
lactose (Fig. 1., 2.). Total biomass concentration after
50 hours: 1.7 ± 0,2 g dm –3 in vials and 2.7 ± 0,4 g dm –3
in the fermentor.
Total biomass concentration on others substrates was as
follows (Fig. 1., 2.): glucose 0.6 ± 0.2 g dm –3 (vials) and
1.9 ± 0.5 g dm –3 (fermentor), maltose 0.3 ± 0.1 g dm –3
(vials) and 1.4 ± 0.3 g dm –3 (fermentor), sacharose
0,1 g dm –3 (vials) and 1.3 ± 0.2 g dm –3 (fermentor).
The difference between total biomass concentration in
the vials and in the fermentor is statistically significant
on statistic level 0.05. It follows from these results that
tested culture has mainly aerobic character.
The biggest biomass productivity was reached in cultivation
in fermentor, on lactose: 0.054 ± 0.009 g dm –3 h –1 .
Lag-phase period (Fig. 1., Fig 2.) was the shortest in cultivations
in the aerobic fermentor sytems (~ 3h on all
substrates). In anaerobic vials was this phase very long:
on maltose ~ 8h, on lactose (~ 25h). (Sacharose is not
comparised).
Specific growth rates: glucose 0.19 ± 0.05 h –1 (vials)
and 0.10 ± 0.05 h –1 , maltose: 0,05 ± 0.01 h –1 (vials) and
0.06 ± 0.02 h –1 (fermentor), sacharose 0.06 ± 0.02 h –1
(fermentor only). The difference between specific
growth rates in the vials and in the fermentor is not statistically
significant on statistic level 0.05.
It is possible to differ two exponential growth phases
(I: 3–15 h., specific growth rate 0.25 ± 0.03 h –1 and
II: 22–38 h. specific growth rate 0.12 ± 0.02 h –1 ) in the
bioreactor cultivation on lactose. Lactose served as the
main carbon source in the first phase of cultivation, in
the second phase lactose was consumed immedately and
the growth proceeds on organics acids by metabolic way
generated (Fig. 2.).
In vials on lactose was observed different situation, there
was one exponential growth phase with specific growth
rate: 0.31 ± 0.01 h –1 .(Fig. 1.).
It follows from our experiments that the biggest growth
rate was achieved in bacteria cultivation on lactose (in
both systems – in the fermentor and in the vials).
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Conclusions
The dramatically differences between growth rate and
total biomass concentration in cultivations on lactose and
others substrates were detected. Lactose was the most suitable
substrate in growth aspect in both aerobic and anaerobic
conditions. With regard to better growth results in the fermentor
cultivations, the main population of the mixture of
bacteria tested is aerobic.
Maltose and glucose were utilised by thermophilic microorganisms
too, but growth was slower. Sacharose was not
utilised in anarobic vials, thermophilic bacteria was not able
to decompose this substrate.
In conclusion, this work described growth and growth
characteristics of tested microorganisms and contributed to
better knowledge of thermophilic mixed bacteria cultures.
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