3. FOOD ChEMISTRy & bIOTEChNOLOGy 3.1. Lectures

Chem. Listy, 102, s265–s1311 (2008) Food Chemistry & Biotechnology
P59 ThE EFFECT OF CELL ADhESION ON
POLLuTANT bIODEGRADATION
TEREZA KRULIKOVSKá, OLGA SCHREIBEROVá,
JITKA HRDInOVá, JAn MASáK, ALEnA ČEJKOVá
and VLADIMíR JIRKů
Institute of Chemical Technology Prague, Department of
Fermentation Chemistry and Bioengineering
Technicka 5, 166 28 Prague, Czech Republic,
tereza.krulikovska@vscht.cz
Introduction
The unicellular microorganisms naturally form multicellular
communities called biofilm. Bacterial biofilms are generally
described as surface associated community consisting of
microcolonies surrounded by a matrix of exopolymers (EPS)
with varied composition. The characteristics of biofilm which
are in focus of present research are the ability to withstand
and degrade high concentration of various toxic substances.
Phenol and catechol are toxic and persistent pollutants
of the environment. They enter the environment from a number
of industrial sources, namely from the production of pesticides,
herbicides and many others. The method of removal
by bacterial population is one of the possible solutions 1 .
For our experiments gram-positive Rhodococcus erythropolis
was chosen as a bacterium with a broad degradation
potential, owning to its highly versatile metabolism.
Experimental
Rhodococcus erythropolis CCM 2595 was cultivated in
BSM 2 medium at 28 °C. Carbon source was added (phenol or
catechol 0.7 g dm –3 ) after sterilisation.
Phenol and catechol concentration in media were determined
by HPLC: Watrex column 250 × 4 mm, nucleosil
100 C18, acetonitrile/deionized water (40/60), 1.0 ml min –1 ,
UV detection 254 nm.
Changes in biomass concentration were measured by
spectrophotometric method at 595 nm as a total protein concentration
3 .
The cell surface hydrophobicity was assayed using a
procedure according to Rosenberg 4 – BATH test. Polymer
material surface hydrophobicity was measured by a contact
angle measurement method 5 .
For EPS composition analysis the biomass was removed
from carrier by ultrasound and 2% EDTA addition. Saccharides
were assayed according to Dubois 6 , proteins according
to Bradford 3 .
Rate of adhesion during initial period of cultivation was
determined by fluorescent microscopy (Microscope nikon
Eclipse E400). After staining of biofilm by SYTO 13 the part
of colonized area was measured by the method of image analysis
(LUCIA, Laboratory Imaging Ltd., CZ).
s703
Results
S u s p e n d e d C e l l s
Experiments were carried out in shaken flasks (120 rpm)
in medium with phenol or catechol as a sole carbon source.
The concentration of 0.7 dm l –3 of the pollutant was chosen
as a stressed concentration according to previous experiments
(data not shown). The changes of biomass concentration
during cultivation were expressed as a total protein
concentration. The results are presented in the Fig. 1. The
biomass concentrations at the end of both cultivations were
13 mg dm –3 . The phenol (0.7 g dm –3 ) was totally degraded after
49.5 h, catechol (0.7 g dm –3 ) after 119.4 h.
Experiments have shown that catechol biodegradation
is affected by day light. During cultivation catechol was
decomposed to compounds which interacted with glass. The
repeated use of glass vessels was impossible.
Fig. 1. rhodococcus erythopolis suspended cells growth and
pollutant biodegradation. The cells were cultivated in shaken
flasks in BSM medium at 28 °C. The phenol or catechol was used
as sole carbon source (concentration 0.7 g dm –3 ). The phenol/catechol
and biomass (expressed as a total protein) concentration
were monitored.
B i o f i l m
The cell adhesion on solid materials is significantly
affected by cell envelope composition and by hydrophobic/
hydrophilic interactions between cells and carrier materials.
The hydrophobicity and variance in EPS composition were
studied.
Table I
Carrier materials hydrophobocity
Material hydrophobicity Contact angle
[°]
Glass (microscopic slide) 26.4 ± 6.6
Silicone 97.0 ± 3.6