Effect Of Nitrogen Source Concentration Research Articles

Effect of nitrogen source concentration on decolouration rates of laboratory dyes by immobilized cells of two bacterial species.

The aim of this study was to assess the effect of sodium nitrate concentration on the decolouration of laboratory dyes (bromothymol blue, crystal violet, eosin blue, eosin yellow and methylene blue), by alginate immobilized cells of Pseudomonas aeruginosa and Bacillus subtilis. The sodium nitrate concentrations used in the study were 5, 10, 15 and 20g/L. A control setup that contained no sodium nitrate was also studied. During incubation, aliquot samples were withdrawn from each flask every 24 for 144h duration for the estimation of decolouration rate of the dyes, using standard procedures. The results revealed remarkable decolouration of the bromothymol blue and crystal violet in presence of the P. aeruginosa occurring at sodium nitrate concentrations of 10 and 15g/L, respectively. In the case of media that was inoculated with the B. subtilis cells, although no remarkable decolouration of the bromothymol blue and crystal violet was observed throughout the period of incubation, highest decolouration were observed at sodium nitrate concentration of 5 and 10g/L, respectively. For the eosin blue and methylene dyes, no remarkable decolouration were observed in presence of the test bacterial species at the respective sodium nitrate concentrations. Highest decolouration of the eosin yellow was however observed in media with sodium nitrate concentration of 5g/L. The results of this study could be applied in scale up studies and continuous process, for implementation in biological decolouration of dye effluents.

Effect of nitrogen source concentration on curdlan production by Agrobacterium sp. ATCC 31749 grown on prairie cordgrass hydrolysates

ABSTRACTThe effect of nitrogen source concentration on the production of the polysaccharide curdlan by the bacterium Agrobacterium sp. ATCC 31749 from hydrolysates of prairie cordgrass was examined. The highest curdlan concentrations were produced by ATCC 31749 when grown on a medium containing a solids-only hydrolysate and the nitrogen source ammonium phosphate (2.2 mM) or on a medium containing a complete hydrolysate and 3.3 mM ammonium phosphate. The latter medium sustained a higher level of bacterial curdlan production than the former medium after 144 hr. Biomass production by ATCC 31749 was highest after 144 hr when grown on a medium containing a solids-only hydrolysate and 2.2 or 8.7 mM ammonium phosphate. On the medium containing the complete hydrolysate, biomass production by ATCC 31749 was highest after 144 hr when 3.3 mM ammonium phosphate was present. Bacterial biomass production after 144 hr was greater on the complete hydrolysate medium compared to the solids-only hydrolysate medium. Curdlan yield produced by ATCC 31749 after 144 hr from the complete hydrolysate medium containing 3.3 mM ammonium phosphate was higher than from the solids-only hydrolysate medium containing 2.2 mM ammonium phosphate.

Production of branched-chain alcohols by recombinant Ralstonia eutropha in fed-batch cultivation

Branched-chain alcohols are considered promising green energy sources due to their compatibility with existing infrastructure and their high energy density. We utilized a strain of Ralstonia eutropha capable of producing branched-chain alcohols and examined its production in flask cultures. In order to increase isobutanol and 3-methyl-1-butanol (isoamyl alcohol) productivity in the engineered strain, batch, fed-batch, and two-stage fed-batch cultures were carried out in this work. The effects of nitrogen source concentration on branched-chain alcohol production were investigated under four different initial concentrations in fermenters. A maximum 380 g m−3 of branched-chain alcohol production was observed with 2 kg m−3 initial NH4Cl concentration in batch cultures. A pH-stat control strategy was utilized to investigate the optimum carbon source amount fed during fed-batch cultures for higher cell density. In cultures of R. eutropha strains that did not produce polyhydroxyalkanoate or branched-chain alcohols, a maximum cell dry weight of 36 kg m−3 was observed using a fed-batch strategy, when 10 kg m−3 carbon source was fed into culture medium. Finally, a total branched-chain alcohol titer of 790 g m−3, the highest branched-chain alcohol yield of 0.03 g g−1, and the maximum branched-chain alcohol productivity of 8.23 g m−3 h−1 were obtained from the engineered strain Re2410/pJL26 in a two-stage fed-batch culture system with pH-stat control. Isobutanol made up over 95% (mass fraction) of the total branched-chain alcohols titer produced in this study.

Empirical modeling of olive oil mill wastewater treatment using loofa-immobilized Phanerochaete chrysosporium

Central composite design (CCD) technique was used to develop an empirical model for the treatment of olive oil mill wastewater (OMW) by loofa-immobilized Phanerochaete chrysosporium. The concentration of OMW ( A) (i.e., 20%, 30% and 40%), concentration of ammonium sulfate as a source of nitrogen ( B) (i.e., 0.25, 0.5 and 0.75 g/l) and glucose as a carbon source ( C) (i.e., 3, 5 and 7 g/l), both of which used for the fungus growth, were considered as independent variables. The influence of these three regressors on the four dependent variables, i.e., chemical oxygen demand (COD), total phenols (TP), color and aromaticity removals was evaluated using second-order polynomial multiple regression model. Analysis of variance (ANOVA) showed a high coefficient of determination ( R 2) value of 0.912–0.982, thus ensuring a satisfactory adjustment of the regression model with the experimental data. The positive sign for the coefficient of OMW concentration in the model, indicated that the COD, color and aromaticity removals increased with increased levels of this factor. While TP removal decreased with the increased concentration of OMW. The negative effect of nitrogen source concentration on the COD and color removals indicated that the response levels decreased as B increased. The positive sign for the coefficient of the interaction between two factors A and B on the removal of TP and color, indicated that a simultaneous increase in the OMW and the nitrogen source concentrations led to an increase in those responses. Although simultaneous increase in the concentrations of nitrogen source and glucose, decreased COD removal. Quadratic models were predicted for the response variables, i.e., pollutant removals, and the maximum values predicted were 64%, 88%, 48% and 39% for COD, TP, color and aromaticity, respectively. Optimum conditions for this wastewater treatment were obtained based on the performance of the loofa-immobilized P. chrysosporium in the experiment where OMW concentration was at the high level and variables B and C were each at their midrange value.

Effects of Nitrogen Source and Gellan-gum Concentration in Medium on Plant Regeneration from Somatic Embryos in Cyclamen (Cyclamen persicum Mill.).

シクラメン体細胞胚からの植物体再生に及ぼす培地中の窒素形態の影響を調査した結果，微量のビタミン類以外に硝酸態窒素を含まない培地では体細胞胚が発芽せず，体細胞胚の発芽には硝酸態窒素が必須であると考えられた．体細胞胚の発芽は，1/2MS培地の窒素源を20 mM 硝酸カリウム，または2 mM塩化アンモニウムと18 mM 硝酸カリウムに置き換えた修正1/2MS培地で最も促進された．また，体細胞胚からの植物体再生に及ぼす培地中のジェランガム濃度の影響を調査した結果，根および葉を有する個体数は1.0% ジェランガム添加培地で最も大きな値を示した．1.0および2.0%ジェランガム添加培地ではハイパーハイドリック個体の形成は認められなかった．一方，0.25%ジェランガム添加培地でハイパーハイドリック個体の割合が最も高くなった．