Nitrogen-Doped Carbon Nanosheets Decorated With Mn2O3 Nanoparticles for Excellent Oxygen Reduction Reaction.

The purpose of this study is to develop an active, low cost, non-precious, stable, and high-performance catalyst for oxygen reduction reaction (ORR). In this regard, Mn2O3-decorated nitrogen-doped carbon nanosheets (Mn2O3/NC) are fabricated by a two-step strategy involving a hydrothermal method and a solid-state method. In the resultant structures, very fine Mn2O3 nanoparticles with an average size of about 5 nm are strongly attached to nitrogen-doped carbon nanosheets. The role of the Mn2O3 nanoparticles is to provide active sites for ORR, while the presence of the nitrogen-doped carbon not only enhances the conductivity of the overall structure but is also helpful for overall stability. The Mn2O3/NC shows good onset potential (0.80 V@-1 mA/cm2), methanol crossover effect, and stability (90%).

Characterization of a Saccharomyces cerevisiae mutant with enhanced production of beta-D-fructofuranosidase.

The present study focused on the improvement of Saccharomyces cerevisiae through random mutagenesis for enhanced production of beta-D-fructofuranosidase (FFase) using sucrose salt media. Sixty strains of S. cerevisiae were isolated from different fruits and soil samples and screened for FFase production. Enzyme productivity of different yeast isolates ranged from 0.03 to 1.10 U/ml. The isolate with the highest activity was subjected to ultraviolet (UV) radiation and mutagenesis using N-methyl N-nitro N-nitroso guanidine (MNNG). One mutant produced FFase at a level of 17.8+/-0.9 U/ml. The MNNG-treated isolate was exposed to ethyl methane sulphonate (EMS), and a mutant with an enzyme activity of 25.56+/-1.4 U/ml was obtained. Further exposure to UV radiation and chemicals yielded a mutant exhibiting an activity of 34.12+/-1.8 U/ml. After optimization of incubation time (48 h), sucrose concentration (5.0 g/L), initial pH (6.0) and inoculum size (2.0% v/v), enzyme production reached 45.65+/-4.6 U/ml with a noticeable greater than 40-fold increase compared to the wild-type culture. On the basis of kinetic variables, notably Q(p) (0.723+/-0.2U/g/h), Y(p/s) (2.036+/-0.05 U/g) and q(p) (0.091+/-0.02 U/g yeast cells/h), the mutant S. cerevisiae UME-2 was found to be a hyperproducer of FFase (LSD 0.054, p0.05).

Kinetic characterization of extracellular alpha-amylase from a derepressed mutant of Bacillus licheniformis.

Three strains of Bacillus licheniformis were isolated and screened for alpha-amylase production by solid-state fermentation. Of these, IS-2 gave relatively higher enzyme production (32+/-2.3 U/[g.min]) and was selected for improvement after treatment with N-methylnN-nitro N-nitroso guanidine (NG) or nitrous acid (NA) to enhance its hydrolytic potential. Among the mutant variants, NA-14 gave higher enzyme production (98+/-1.6 U/[g.min]), and hence, was selected for kinetic and thermal characterization. M1 as a moistening agent (pH 7.0, optimized) supported 2.65-fold improved amylolytic activity by the derepressed mutant 72 h after inoculation. The values of product yield coefficient (Y p/x = 1833.3 U/g) and specific rate constant (qp = 25.46 U/[g.h]) with starch were severalfold improved over those from other carbon sources and the other cultures. The purified enzyme from NA-14 was most active at 40 degrees C; however, the activity remained almost constant up to 44 degrees C. The NA-induced random mutagenesis substantially improved the enthalpy (DeltaH D = 94.5+/-11 kJ/mol) and entropy of activation (DeltaS = -284+/-22J/[mol.K]) for alpha-amylase activity and substrate binding for starch hydrolysis. The results of this study (117.8+/-5.5 U/[g.min]) revealed a concomitant improvement in the endogenous metabolism of the mutant culture for alpha-amylase production.

Influence of dissolved oxygen concentration on intracellular pH for regulation of Aspergillus niger growth rate during citric acid fermentation in a stirred tank bioreactor.

In this paper we report the regulation of Aspergillus niger growth rate during citric acid fermentation in a stirred tank bioreactor. For this, the influence of dissolved oxygen concentration in a medium on intracellular pH values and consequently on overall microbial metabolism was emphasized. Intracellular pH of mycelium grown under different concentrations of dissolved oxygen in the medium was determined. Sensitivity of proteins toward proton concentration is well recognized, therefore pH influences on the activities of key regulatory enzymes of Aspergillus niger were determined at pH values similar to those detected in the cells grown under lower dissolved oxygen concentrations. The results have shown significantly reduced specific activities of hexokinase, 6-phosphofructokinase and glucose-6-phosphate dehydrogenase in more acidic environment, while pyruvate kinase was found to be relatively insensitive towards higher proton concentration. As expected, due to the reduced specific activities of regulatory enzymes under more acidic conditions, overall metabolism should be hindered in the medium with lower dissolved oxygen concentration which was confirmed by detecting the reduced specific growth rates. From the studies, we conclude that dissolved oxygen concentration affects the intracellular pH and thus growth rate of Aspergillus niger during the fermentation process.

Pearl millet, a source of alpha amylase production by Bacillus licheniformis.

The present study is concerned with the selection of economically available agricultural starchy substrate for the production of alpha amylase by Bacillus licheniformis. Different agricultural starchy substrates such as soluble starch, hordium, pearl millet, rice, corn, gram and wheat starch were tested for the production of alpha amylase by parental and its mutant derivatives. The production of alpha amylase was 10-folds better by the mutant strain B. licheniformis GCUCM-30 than the parental strain when pearl millet starch at 1.5% level and nutrient broth concentrations at the level of 0.25% was supplemented to the fermentation medium.

Optimization of nitrogen for enhanced citric acid productivity by a 2-deoxy D-glucose resistant culture of Aspergillus niger NGd-280.

The present investigation is concerned with the optimization of nitrogen for enhanced citric acid productivity by a 2-deoxy D-glucose resistant culture of Aspergillus niger NGd-280 in a 15 l stirred tank bioreactor. Nutrients, especially nitrogen source have a marked influence on citrate productivity because it is an essential constituent of basal cell proteins. Citric acid has been known to be produced when the nitrogen source was the limiting factor. Ammonium nitrate was employed as a nitrogen source in the present study and batch culture experiments were carried out under various concentrations of ammonium nitrate. Specific growth rate was decreased and the biosynthesis of citric acid was delayed at higher concentrations of ammonium nitrate. Specific citric acid production rate was the highest when intracellular ammonium ion concentration was between 2.0 and 3.0 mmol g(-1) cells. Citrate production was however, stopped when intracellular ammonium ion concentration decreased below 1.0 mmol g(-1) cell.

Citric acid production by selected mutants of Aspergillus niger from cane molasses.

The present investigation deals with citric acid production by some selected mutant strains of Aspergillus niger from cane molasses in 250 ml Erlenmeyer flasks. For this purpose, a conidial suspension of A. niger GCB-75, which produced 31.1 g/l citric acid from 15% (w/v) molasses sugar, was subjected to UV-induced mutagenesis. Among the 3 variants, GCM-45 was found to be a better producer of citric acid (50.0 +/- 2a) and it was further improved by chemical mutagenesis using N-methyl, N-nitro-N-nitroso-guanidine (MNNG). Out of 3,2-deoxy-D-glucose resistant variants, GCMC-7 was selected as the best mutant, which produced 96.1 +/- 1.5 g/l citric acid 168 h after fermentation of potassium ferrocyanide and H2SO4 pre-treated blackstrap molasses in Vogel's medium. On the basis of kinetic parameters such as volumetric substrate uptake rate (Qs), and specific substrate uptake rate (qs), the volumetric productivity, theoretical yield and specific product formation rate, it was observed that the mutants were faster growing organisms and produced more citric acid. The mutant GCMC-7 has greater commercial potential than the parental strain with regard to citrate synthase activity. The addition of 2.0 x 10(-5) M MgSO4 x 5H2O into the fermentation medium reduced the Fe2+ ion concentration by counter-acting its deleterious effect on mycelial growth. The magnesium ions also induced a loose-pelleted form of growth (0.6 mm, diameter), reduced the biomass concentration (12.5 g/l) and increased the volumetric productivity of citric acid monohydrate (113.6 +/- 5 g/l).

Production of alpha amylase by Bacillus licheniformis using an economical medium.

The present study is concerned with the selection of new medium for the production of alpha amylase by Bacillus licheniformis. Different agricultural by-products such as wheat bran, sunflower meal, cotton seed meal, soybean meal, rice husk or rice bran were tested for the production of alpha amylase. Among different agricultural by-products evaluated, wheat bran was found to be the best basal and standardized medium for optimal production of alpha amylase. The production was increased 2-folds when soluble starch was replaced with pearl millet starch at 1% level and nutrient broth concentrations was reduced from 1% level to 0.5%. The newly selected fermentation medium containing (% w/v) wheat bran 1.25, nutrient broth 0.5, pearl millet starch 1.0, lactose 0.5, NaCl 0.5, CaCl2 0.2 in 100 ml of phosphate buffer. The kinetic values of Y(p/x), Y(p/s), and Q(p) indicated that the production of enzyme was greater in newly selected medium than the conventional more expensive medium.

Stimulatory effect of alcohols (methanol and ethanol) on citric acid productivity by a 2-deoxy D-glucose resistant culture of aspergillus niger GCB-47.

The present study describes citric acid fermentation by Aspergillus niger GCB-47 in a 15-1 stainless steel stirred fermentor. Among the alcohols tested as stimulating agents, 1.0% (v/v) methanol was found to give maximum amount of anhydrous citric acid (90.02 +/- 2.2 g/l), 24 h after inoculation. This yield of citric acid was 1.96 fold higher than the control. Methanol has a direct effect on mycelial morphology and it promotes pellet formation. It also increases the cell membrane permeability to provoke more citric acid excretion from the mycelial cells. The sugar consumed and % citric acid was 108 +/- 3.8 g/l and 80.39 +/- 4.5%, respectively. The desirable mycelial morphology was in the form of small round pellets having dry cell mass 14.5 +/- 0.8 g/l. Addition of ethanol, however, did not found to enhance citric acid production, significantly. The maximum value of Yp/x (i.e., 5.825 +/- 0.25 g/g) was observed when methanol was used as a stimulating agent. The best results of anhydrous citric acid were observed, 6 days after inoculation when the initial pH of fermentation medium was kept at 6.0.

Inducive effect of cresoquinone on microbiological transformation of L-tyrosine to 3,4 dihydroxy phenyl L-alanine by Aspergillus oryzae NG-11(P1).

The present work describes the inducive effect of cresoquinone on microbiological transformation of L-tyrosine to 3,4 dihydroxy phenyl L-alanine ( L-DOPA) by Aspergillus oryzae NG-11(P1). Mould mycelium was used for biochemical conversion of L-tyrosine to L-DOPA because tyrosinases, beta-carboxylases and tyrosine hydroxylases are intracellular enzymes. The maximum conversion of L-tyrosine to L-DOPA (0.428 mg/ml) was achieved after 60 min of biochemical reaction. To enhance the production of L-DOPA, cresoquinone was added to the reaction mixture. Best L-DOPA biosynthesis results were observed when the concentration of cresoquinone was 3.5 x 10(-6) M (1.686 mg/ml L-DOPA produced with 1.525 mg/ml consumption of L-tyrosine). Cresoquinone not only increased enzyme activity but also enhanced cell membrane permeability to facilitate secretion of enzymes into the reaction broth. Comparison of kinetic parameters revealed the ability of the mutant to yield L-DOPA [Y(p/x) [i.e., mg L-DOPA formed (mg cells formed)(-1)] =7.360+/-0.04]. When the culture grown on various cresoquinone levels was monitored for Q(p), Q(s) and q(p) [ Q(p): mg L-DOPA produced ml(-1) x h(-1); Q(s): mg substrate consumed ml(-1) x h(-1); q(p): mg L-DOPA formed (mg cells)(-1) h(-1)], there was significant enhancement ( P<0.025) of these variables.

Biosynthesis of L-DOPA by Aspergillus oryzae.

The present investigation deals with the biosynthesis of L-DOPA by parental (GCB-6) and mutant (UV-7) strains of Aspergillus oryzae. There was a marked difference between the mycelial morphology and pellet type of parental and UV-irradiated mutant culture. The mutant strain of A. oryzae UV-6 exhibited pellet-like mycelial morphology and improved tyrosinase activity. Mould mycelium was used for biochemical conversion of L-tyrosine to L-DOPA because tyrosinase is an intracellular enzyme. The mutant was found to yield 3.72 fold higher production of L-DOPA than the parental strain. The mutant strain is stable and D-glc-resistant. The comparison of kinetic parameters was also done which showed the greater ability of the mutant to yield L-DOPA (i.e., Yp/x 40.00+/-0.01 d mg/mg with parent and 182.86+/-0.02a mg/mg in case of mutant). When cultures grown for various incubation periods, were monitored for Qp, Qs and q(p), there was significant enhancement (p < 0.0025-0.005) in these variables by the mutant strain of A. oryzae UV-7 over GCB-6 on all the rates. L-DOPA (3,4-dihydroxy phenyl L-alanine) is a drug of choice in the treatment of Parkinson's disease and myocardium following neurogenic injury.

An assessment of Pakistan's urban policies 1947-1997.

PIP: This paper aims at analyzing and assessing the evolution and outcomes of Pakistan's urban policies during 1947-97. One-third of Pakistan's population live in urban areas, and the level of urbanization increased from 18% in 1951 to 32% in 1991. The rapid rate of urbanization has produced two megacities, Karachi with a population of 8-10 million and Lahore with a population of about 5 million, and 6 other cities with populations of 1 million or more. Pakistan is one of the pioneering countries in implementing physical planning and planned housing; this is reflected in its urban policies as constituted by the Five-Year Plan and national development budgets. The programs through which the policies were implemented are divided into three phases. Phase 1 (1947-70) involved the resettlement of refugees and laying of the institutional framework; core housing schemes (consisting of 1- to 2-room quarters) were the key element of the urban strategy in this period. Phase 2 (1971-78) policies were guided by the promise of mass housing, particularly for the working and lower classes. At this time, too, a set of squatter settlements known as Katchi Abadis emerged, and international organizations started funding Pakistan's urban development programs. Phase 3 (1980-95) saw the steady "privatization" of the housing and land markets and improved housing conditions, while urban policy continued to concentrate on public works, plots and construction. Despite the improvements, urban crises persist, and policies are shifting towards more complex issues of quality and the provision of new collective goods. In general, the achievements of Pakistan's urban policies have outweighed its failures, as both the rich and the poor have benefitted from them.^ieng

Effect of guar gum on blood lipids.

The effect of guar gum in capsule form on serum total cholesterol, triglycerides, and lipoprotein cholesterol (very low-density lipoproteins, low-density lipoproteins, and high-density lipoproteins) was studied in healthy volunteers in this double-blind study. Twenty-four subjects equally divided into treatment and placebo groups, received 9.0 g/day of guar and glucose in 600 mg identical capsules, respectively, for 4 wk under conditions of constant body weight and dietary stability. Guar significantly lowered serum total cholesterol (16.6% p less than 0.05) and low-density lipoprotein cholesterol (25.6% p less than 0.05) but had no significant effect (p less than 0.05) on serum triglycerides, high-density lipoproteins and very low-density-lipoprotein cholesterol. No significant changes (p greater than 0.05) were seen in blood lipids in the placebo group.