Pacifier nipples are in permanent contact with saliva and with the oral microflora therefore, act as a favoured site for the growth of biofilms. This research was conducted to identify the bacterial biofilms that has been found on the pacifiers that collected from local child nursery and to analyse the formation of biofilms by Cronobacter sp. during growth in infant formula milk. Pacifiers collected were analysed to obtain colony forming unit (CFU) and isolated bacteria were identified using several biochemical tests according to Bergey's Manual. Biofilm assay of three Cronobacter sp. were conducted using 24 wells microtiter plate and stained with 1% of crystal violet solution at different time interval: 6, 12, 18 and 24 h. The hydrophobicity of the bacterial cell suspension was evaluated using bacterial adhesion to hydrocarbons (BATH) method. Extracellular polymeric substances (EPS) analysis was done to identify percentage of carbohydrate and protein content by using phenol sulphuric acid method and Bradford method, respectively. The results obtained showed that the normal microflora bacteria were the most abundant microorganisms that were found on the pacifier with the main genus isolated was Staphylococcus sp., Enterobacteriaceae sp. and Clostridium sp. Based on biofilm and EPS analysis, Cronobacter sakazakii formed a strong biofilms after 18 h, with carbohydrate was identified as main component of EPS.
Poly(ethylene glycol)-polydimethylsiloxane (PEG-PDMS) crosslinked copolymers with mol ratios PEG:PDMS:Glycerol
of 5:3:2, 6:2:2 and 7:1:2 have been prepared and characterized. The synthesis of the copolymers was carried out
by the reaction between hydroxyl groups of PEG, PDMS and glycerol with isocyanate groups of 1,6-hexamethyelene
diisocyanate (HMDI). In the reaction, glycerol was acted as the cross linker. The copolymers were then characterized
by FTIR spectroscopy. The thermal behaviour was investigated by DSC and TGA. Based on FTIR results, the crosslinked
structure of the copolymers was confirmed by the presence of absorption peak at 3350 and 1710 cm-1 which indicated
the (-N-H) stretching and carbonyl (-C=O) correspond to urethane links. This showed that the hydroxyl groups of PEG,
PDMS and glycerol have reacted to isocyanate groups of HMDI. The copolymers showed melting temperature (Tm) of PEG
segments from 22°C to 27°C and glass transition temperature (Tg
) from -11°C to -6°C. Meanwhile, the PDMS segment
showed values from -53°C to -56°C for Tm, and Tg
from -118°C to -122°C. Data obtained from the thermal analysis
indicate that thermal stability increases with increasing PDMS mol ratio.
Microbial fuel cells (MFCs) have a high potential application for simultaneous wastewater treatment and electricity
generation. However, the choice of the electrode material and its design is critical and directly affect their performance.
As an electrode of MFCs, the anode material with surface modifications is an attractive strategy to improve the power
output. In this study, stainless steel (SS) and carbon steel (CS) was chosen as a metal anode, while graphite felt (GF)
was used as a common anode. Heat treatment was performed to convert SS, CS and GF into efficient anodes for MFCs.
The maximum current density and power density of the MFC-SS were achieved up till 762.14 mA/m2
and 827.25 mW/m2
,
respectively, which were higher than MFC-CS (641.95 mA/m2
and 260.14 mW/m2
) and MFC-GF (728.30 mA/m2
and 307.89
mW/m2
). Electrochemical impedance spectroscopy of MFC-SS showed better catalytic activity compared to MFC-CS and
MFC-GF anode, also supported by cyclic voltammetry test.