Corrosion caused by sulphate-reducing bacteria (SRB) isolated from seawater nearby to Pasir Gudang has been studied. The test coupon was a AISI 304 stainless steel. Potential and corrosion rate measurements were carried out in various types of culturing solutions, with SRB1, SRB2, combination of SRB1 & SRB2 and without SRBs inoculated (sterilized). From Tafel plots a higher corrosion rate has been found in medium inoculated with SRBs than that of the sterilized medium (control). When SRBs were present in the medium, the Tafel plot shifted towards more negative values (Ecorr was shifted to much less anodic values) and increase in current density compared to that of the sterilized medium (control). Localized corrosion was observed on the metal surface, and it was associated to the SRB activity. X-ray analysis (EDAX) showed that the corrosion product has higher content of sulphur for medium containing SRBs than that of the sterilized medium. X-Ray Diffraction analysis carried out on corrosion products which showed the presence of iron sulphide. This indicates the influence of the presence of SRB in corrosion process.
The aim of this study was to determine the surface chemistry during biocorrosion process on growth and on the production of exopolymeric substances (EPS) in batch cultures of mix-strains of marine sulphate-reducing bacteria (SRB) isolated from Malaysian Shipyard and Engineering Harbours, Pasir Gudang. The EPS and precipitates were analyzed by x-ray photoelectron spectroscopy (XPS). The XPS results indicate that Fe(2p3/2) spectrum for iron sulphide can be fitted with Fe(II) and Fe(III) components, both corresponding to Fe-S bond types. The absence of oxide oxygen in the O(1s) spectrum and Fe(III)-O bond types in the Fe(2p3/2) spectrum supports the conclusion that iron sulphides are composed of both ferric and ferrous iron coordinated with monosulphide and disulphide.
The corrosion potential of AISI 304 stainless steel coupons influenced by sulphate-reducing bacteria (SRB) has been studied. Pure colony of SRB was isolated from the Malaysia Marine and Heavy Engineering, Pasir Gudang, Johor. Open circuit potential measurements were carried out in variable types of culturing solutions with SRB1, SRB2, combination of SRB1 & SRB2 and without SRBs inoculated. Results showed that the corrosion potential, Eoc increased in the presence of SRBs (in pure and mixed culture) compared to that of control. EDS analysis showed the strong peak of sulphur in coupon containing SRB cultures compared to the control. ESEM data showed that the high density cell of SRBs were associated with corroding sections of surface steel comparing with non-corroding sections for coupons immersed in VMNI medium containing SRBs.
In the attempt to isolate indigenous marine sulphate-reducing bacteria (SRB) from coastal samples, we obtained some swarm forming bacteria. The isolates were screening using Starkey’s medium and detection of main groups of SRB were carried out using commercially kits (SRB BART kits, Droycon Bioconcepts Inc., Canada). From the growth characteristic, only two isolates were strongly suggested as marine SRB. Based on the 16S rRNA gene sequence analysis these SRB were closely related and could be designated as Desulfovibrio sp. and Citrobacter freundii, with the highest sequence similarity of 98% and 93%, respectively.
Sulphate-reducing bacteria (SRB), implicated in microbiologically influenced corrosion were isolated from the deep subsurface at the vicinity of Pasir Gudang, Johor, Malaysia. Electrochemical impedance spectroscopic (EIS) study was carried out to determine the polarization resistance in various types of culturing solutions, with SRB1, SRB2, combination of SRB1 and SRB2 and without SRBs inoculated (control). EIS results showed that in the presence of SRB1, SRB2 and mixed culture SRB1 and SRB2, polarisation resistance values were 7170, 6370 and 7190 ohms respectively compared to that of control, 92400 ohm. X-ray analysis (EDS) of the specimens indicated high sulphur content in the medium containing SRBs. Localized corrosion was observed on the metal surface which was associated with the SRB activity.
In this study, we investigate the ability of the bacterial isolates from an Iraqi oil
reservoir, namely POS and PCO Oil to decolorize commercially used model azo dye Acid
Red-27(AR-27). The effects of inoculation volume and glycerol concentrations were
optimized to develop an economically feasible decolourization process. The isolates
were able to decolourize azo dye (AR27) at the highest decolorization efficiency of 98%
in 10 mL bacterial solution consisted of POS and PCO Oil and in the presence of 6.34
g/L glycerol. An optimized MFC using this bacterial consortium (POS + PCO Oil) and
graphite rod electrodes produced a maximum open circuit voltage (OCV) of 175 mV, in
the presence of potassium ferricyanide as the electron acceptor at the cathode. The
maximum current density of 1.7 μA/cm² and power density of 59.3 μW/cm² were
achieved when an external load of 5 kΩ was applied. Morphological analysis was
performed using Scanning Electron Microscope (SEM) to prove the bacterial
attachment onto the anode surface (graphite rod) in the MFC operation. This work
proposed that the bacterial strains POS and PCO Oil possess the ability to decolorize
Azo dye AR27 and generate electricity in the absence of nitrogen source.