The effect of carbon source supplementation on the production of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) by Cupriavidus necator.

The objective of the present study was to investigate the ability of Cupriavidus necator to produce poly-(3-hydroxybutyrate-co-3-hydroxyvalerate) on various carbon sources in batch cultivation. These results show that C. necator produces poly-3-hydroxybutyrate from single carbon sources. The highest poly-3-hydroxybutyrate (P3HB) content was achieved at growth on fructose in the exponential growth phase. The maximum yield of the P3HV content was obtained when fructose was mixed with acetate. The highest content P3HB-co-3HV was also achieved by C. necator when we supplied C-excess and N- and P-normal conditions. These results indicate that C. necator accumulates high polyhydroxyalkanoates (PHA) content by depleting these elements in the culture medium. Nitrogen and phosphorus limitation has no significant effect on the PHA production, whereas C-excess leads to an increase in PHA formation of up to 92% PHAs of cell dry weight after growth on 5 g/L acetate and 40 g/L fructose.

Biosorption equilibria of binary Cd(II) and Ni(II) systems onto Saccharomyces cerevisiae and Ralstonia eutropha cells: application of response surface methodology.

Present study investigated the biosorption of Cd(II) and Ni(II) from aqueous solution onto Saccharomyces cerevisiae and Ralstonia eutropha non-living biomass. Biomass inactivated by heat and pretreated by ethanol was used in determination of optimum conditions. The important process parameters, such as initial solution pH (2-8), initial Ni(II) concentration (11-42 mg/l), initial Cd(II) concentration (11-42 mg/l), and biomass dosage (0.2-4.7 g/l) were optimized using design of experiments (DOE). A central composite design (CCD) under response surface methodology (RSM) was applied to evaluate and optimize the efficiency of removing each adsorbent. Moreover, the two responses were simultaneously studied by using a numerical optimization methodology. The optimum removal efficiency of Cd(II) and Ni(II) onto S. cerevisiae was determined as 43.4 and 65.5% at 7.1 initial solution pH, 4.07 g/l biomass dosage, 16 mg/l initial Ni(II) concentration and 37 mg/l initial Cd(II) concentration. The optimum removal efficiency of Cd(II) and Ni(II) onto R. eutropha was ascertained as 52.7 and 50.1% at 5.0 initial solution pH, 2.32 g/l biomass dosage, 28 mg/l initial Ni(II) concentration and 37 mg/l initial Cd(II) concentration. The present analysis suggests that the predicted values are in good agreement with experimental data. The characteristics of the possible interactions between biosorbents and metal ions were also evaluated by scanning electron microscope (SEM) and Fourier transform infrared (FT-IR) spectroscopy analysis.

Application of response surface methodology for optimization of lead biosorption in an aqueous solution by Aspergillus niger.

Response surface methodology was applied to optimize the removal of lead ion by Aspergillus niger in an aqueous solution. Experiments were conducted based on a rotatable central composite design (CCD) and analyzed using response surface methodology (RSM). The biosorption process was investigated as a function of three independent factors viz. initial solution pH (2.8-7.2), initial lead concentration (8-30 mg/l) and biomass dosage (1.6-6 g/l). The optimum conditions for the lead biosorption were found to be 3.44, 19.28 mg/l and 3.74 g/l, respectively, for initial solution pH, initial lead ion concentration and biomass dosage. Lead biosorption capacity on dead A. niger fungal biomass was enhanced by pretreatment using NaOH. Under these conditions, maximum biosorption capacity of the biomass for removal of lead ions was obtained to 96.21%. The desirability function was used to evaluate all the factors and response in the biosorption experiments in order to find an optimum point where the desired conditions could be obtained. The A. niger particles with clean surface and high porosity may have application as biosorbent for heavy metal removal from wastewater effluents.