The use of microorganisms for the biodegradation of pollutants is increasingly being studied. But at high concentrations, these pollutants become rather inhibitors for the metabolism of microorganisms. In this study, the biodegradation of ammonium formate at various concentrations (1.59–7.94 mM) by Yarrowia Lipolytica and Pichia guilliermondii isolated from the rubber effluent is studied by following the variation of ammonium ions and formate. A fitting of eight models of substrate inhibition was performed and the parameters were determined by nonlinear regression using MATLAB 8.5 ©. The R2 and the RSME allow to choose the best model. The results show that ammonium ions (3.17 mM ammonium formate) are used as substrate; no inhibition is observed. But beyond this concentration, the inhibition effect begins to be observed with the specific rates of ammonium biodegradation which decrease. Formate monitoring reveals that is used as the main source of energy and does not inhibit the growth of yeasts. The models of Luong and Webb seem to be more appropriate for predicting the observed phenomena of inhibition. For Yarrowia lipolytica, R2 = 0.958 and 0.998 with RSME = 0.005342 and 0.003433, for Pichia guillermondii, R2 = 0.999 and 0.992 with RSME = 0.0005121 and 0.001212.

Abstracts: Despite the many services that natural rubber provides to humanity, its production generates significant quantities of polluted effluents which have a negative impact on health and the environment. In order to reduce this pollution and allow water to be reused after treatment, a synthetic effluent treatment trial was carried out in a submerged membrane bioreactor in the presence of two strains of yeast (Yarrowia lipolytica, Pichia guilliermondii) and biodegradation parameters (COD, NH4+, NO2-, NO3-) were followed. The Mohlman Index (MI), the particle size distribution, the Lowry method for proteins and the Dubois method for sugars have made it possible to characterize the sludge generated during biodegradation. It appears from these experiments that the reduction rate of COD was 98% and that of nitrification and denitrification 90%. There is a decreasing linear relationship between the MI and SS (Suspended Solids) with an R2 of 95%. The distribution of the particle size of the sludge is tri-modal with a maximum of sludge having an average size of 1000 µm. The sludge formed resists filtration with a polysaccharide/protein ratio of 0.45.

Abstracts: Despite the many services that natural rubber provides to humanity, its production generates significant quantities of polluted effluents which have a negative impact on health and the environment. In order to reduce this pollution and allow water to be reused after treatment, a synthetic effluent treatment trial was carried out in a submerged membrane bioreactor in the presence of two strains of yeast (Yarrowia lipolytica, Pichia guilliermondii) and biodegradation parameters (COD, NH4+, NO2-, NO3-) were followed. The Mohlman Index (MI), the particle size distribution, the Lowry method for proteins and the Dubois method for sugars have made it possible to characterize the sludge generated during biodegradation. It appears from these experiments that the reduction rate of COD was 98% and that of nitrification and denitrification 90%. There is a decreasing linear relationship between the MI and SS (Suspended Solids) with an R2 of 95%. The distribution of the particle size of the sludge is tri-modal with a maximum of sludge having an average size of 1000 µm. The sludge formed resists filtration with a polysaccharide/protein ratio of 0.45.

In this study, Grewia spp. biopolymer was utilized as a biosorbent for elimination of hexavalent chromium from water. Fourier-transform infrared spectrometry (FTIR) and X-ray diffraction (XRD) were performed for characterization of the biosorbent. Experiments were conducted in a batch mode at room temperature (25 ± 2°C) and agitation speed of 100 rpm to determine the influence of biosorbent dose, contact time, Cr(VI) concentration, and initial solution pH. It was found that equilibrium was attained in 50 min. A pseudo-first-order model suited well than a pseudo-second-order model. Biosorption capacity of Grewia spp. biopolymer increased with increase in concentration and depended on the solution pH. Langmuir and Freundlich models described experimental data very well. These findings showed that Grewia spp. biopolymer can serve as a biosorbent for elimination of Cr(VI) from water.