The present study aims to investigate the performance of batch culture of Geobacter sulfurreducens (G. sulfurreducens) for electrical current generation via cyclic voltammetry (CV) method. The CV study was performed with an applied voltage in the range of -0.1 to 0.1 V against the standard calomel electrode (SCE) during the cell growth and attachment of G. sulfurreducens on graphite felt and initial acetate concentration of 20 mM. The kinetics of electrode reaction was investigated by conducting CV experiments at different scanning rates of 5, 10, 20, 50 and 100 mVs -1. The diffusion coefficients (D) and heterogeneous electron transfer rate constant (k o) of both anodic and cathodic process were 1.04×10 -5 cm 2·s -1, 1.73×10 -6 cm 2.s -1, 0.0004 cm.s -1 and 0.0011 cm.s -1, respectively. The obtained results showed that the anode exhibits high bioeletrocatalytic activity due to the attachment of G. sulfurreducens on the anode surface.

In this study, the optimization and kinetic analysis on the effect of process parameters for the production of hyaluronic acid production by S. zooepidemicus were performed in batch system. The fermentation condition such as inoculum size (2 to 20 %), pH (4 to 10), temperature (30 to 45) and agitation (50 to 500) were optimized using “one-factor-at-a-time” method. It was found that the inoculum size of 10 % had the greatest effect on the fermentation process which gave the highest value of specific growth rate, cell biomass and HA production of 0.72 h−1, 1.96 gl−1 and 0.82 gl−1, respectively. Furthermore, the other process parameters such as pH, temperature and agitation speed were also found to improve the cell biomass, HA production and kinetic analysis. The highest cell biomass (0.17 gcell gglucose−1) and HA yield (0.096 gHA g glucose−1) were obtained at pH 7.0, 37 °C and agitation speed 300 rpm for 12 h. The overall kinetics analysis of maximum specific growth rate, volumetric cell biomass productivity and volumetric HA productivity obtained at optimum parameters were, 0.81 h−1, 0.183 gcell l−1 h−1 and 0.111 gHA l−1 h−1, respectively.

Iron has played a crucial role in the human ecosystem currently in transportation, manufacturing, and infrastructure. Iron oxide is known as rust, usually the reddish-brown oxide formed by iron and oxygen reactions in moisture from water or air. Microbiologically influenced corrosion (MIC) is a significant problem to the economic damage, especially in industrial sectors and its direct presence with nitrate/iron-reducing bacteria. This paper aims to explore the MIC of iron by nitrate-reducing Bacillus sp. including the redox reaction occurs, microbiologically influenced corrosion, iron/nitrate-reducing and mechanisms of microbial iron/nitrate reduction.

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