Sikander Ali - Academia.edu (original) (raw)
Papers by Sikander Ali
Study of structural and electrical properties of Al3+ doped Ni0.7Zn0.3Fe2-xAlxO4 (0.0&amp... more Study of structural and electrical properties of Al3+ doped Ni0.7Zn0.3Fe2-xAlxO4 (0.0&lex<=0.5) ferrite synthesized through citrate-gel method has been carried out. The samples were characterized by using XRD and dielectric technique in the frequency range 42 Hz-5 MHz at room temperature. X-ray diffraction studies confirmed that all the samples exhibit single phase cubic spinel structure. The variation in epsilo', and tandelta
Journal of Biological Sciences, 2001
Sixteen different cultures of Aspergillus niger were isolated from different soil samples. These ... more Sixteen different cultures of Aspergillus niger were isolated from different soil samples. These isolates of Aspergillus niger were evaluated for citric acid fermentation in shake flask. Sucrose salt media was used and the volume of fermentation medium was kept at 25 ml. The cultural conditions such as pH (3.5), temperature (30EC), incubation period (8 days) and sugar concentration (15%), were optimised.
Journal of Biological Sciences, 2001
Microbial examination of 50 samples of both packed and unpacked butter was carried out. The sampl... more Microbial examination of 50 samples of both packed and unpacked butter was carried out. The samples were examined for total viable count, mould and yeast count, spore formers and coliform. The microbial load in the unpacked sample of butter was highest i.e., 3.8 × 10 6 /gm-6.6 × 10 6 /gm. The coliform count was found maximum in unpacked sample and one of the packed sample of butter (Kausar brand) i.e., 39/ml. The unpacked sample of butter contained highest number of aerobic spore formers i.e., 280/gm. The anaerobic spore-formers were found absent in 20 samples of butter and the rest contained in the range of 0-170/gm. The yeast cultures were found only in the sample of Lyallpur and Kausar butter. The mould count of these samples ranged from 0-280/gm.
Journal of Basic Microbiology, 2005
Electronic Journal of Biotechnology, 2002
Substrate consumption parameters: µ (h-1) = specific growth rate Y x/s = g cells/g substrate util... more Substrate consumption parameters: µ (h-1) = specific growth rate Y x/s = g cells/g substrate utilized Q s = g substrate consumed/l/h qs = g substrate consumed/g cells/h Qx = g cells formed/l/h Production formation rates: Q p = g citric acid produced/litre/h Yp/s = g citric acid produced/g substrate consumed Yp/x = g citric acid produced/g cells formed qp = g citric acid produced/g cells/h. L-DOPA is a useful drug for Parkinson's disease. This 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 the parental and UV-irradiated mutant cultures. The mutant strain of Aspergillus oryzae UV-6 showed pelletlike mycelial morphology and improved tyrosinase activity. Mould mycelium was used for biochemical conversion of L-tyrosine to L-DOPA since tyrosinase is an intracellular enzyme. The mutant was found to give *Corresponding author 3.72 folds higher production of L-DOPA than the parental strain. The comparison of kinetic parameters was also done which showed greater ability of the mutant to yield L-DOPA (i.e. Y p/x 32.73 mg/mg with parent and 95.71 mg/mg with mutant). When cultures grown for various incubation periods, were monitored for Q p , Q s and q p , there was significant enhancement (p<0.0025-0.005) in these variables by the mutant strain of Aspergillus oryzae UV-7 over GCB-6 on all the rates.
Pak. J. Bot, 2010
The present study is concerned with the improvement of Bacillus amyloliquefaciens strain UNG-16 f... more The present study is concerned with the improvement of Bacillus amyloliquefaciens strain UNG-16 for alpha amylase production. The bacterial culture was exposed to UV irradiation at 1.6× 102 J/m2/S for 15-60 min. However, UV induced viables did not give ...
BMC Genomics, 2007
Background: Reference genome sequences within the major taxa can be used to assist the developmen... more Background: Reference genome sequences within the major taxa can be used to assist the development of genomic tools for related organisms. A major constraint in the use of these sequenced and annotated genomes is divergent evolution. Divergence of organisms from a common ancestor may have occurred millions of years ago, leading to apparently unrelated and un-syntenic genomes when sequence alignment is attempted. Results: A series of programs were written to prepare 36 Mbp of Fusarium graminearum sequence in 19 scaffolds as a reference genome. Exactly 4,152 Bacterial artificial chromosome (BAC) end sequences from 2,178 large-insert Fusarium virguliforme clones were tested against this sequence. A total of 94 maps of F. graminearum sequence scaffolds, annotated exonic fragments and associated F. virguliforme sequences resulted. Conclusion: Developed here was a technique that allowed the comparison of genomes based on small, 15 bp regions of shared identity. The main power of this method lay in its ability to align diverged sequences. This work is unique in that discontinuous sequences were used for the analysis and information not readily apparent, such as match direction, are presented. The 94 maps and JAVA programs are freely available on the Web and by request.
BMC Biotechnology, 2007
Background: The 3,4-dihydroxy phenyl L-alanine (L-dopa) is a drug of choice for Parkinson's disea... more Background: The 3,4-dihydroxy phenyl L-alanine (L-dopa) is a drug of choice for Parkinson's disease, controlling changes in energy metabolism enzymes of the myocardium following neurogenic injury. Aspergillus oryzae is commonly used for L-dopa production; however, potential improvements in ease of handling, growth rate and environmental impact have led to an interest in exploiting alternative yeasts. The two important elements required for L-dopa production are intracellular tyrosinases (thus pre-grown yeast cells are required for the transformation of Ltyrosine to L-dopa) and L-ascorbate, which acts as a reducing agent. Results: Pre-grown cells of Yarrowia lipolytica NRRL-143 were used for the microbiological transformation of L-tyrosine to L-dopa. Different diatomite concentrations (0.5-3.0 mg/ml) were added to the acidic (pH 3.5) reaction mixture. Maximum L-dopa biosynthesis (2.96 mg/ml L-dopa from 2.68 mg/ml L-tyrosine) was obtained when 2.0 mg/ml diatomite was added 15 min after the start of the reaction. After optimizing reaction time (30 min), and yeast cell concentration (2.5 mg/ ml), an overall 12.5 fold higher L-dopa production rate was observed when compared to the control. Significant enhancements in Y p/s , Q s and q s over the control were observed. Conclusion: Diatomite (2.0 mg/ml) addition 15 min after reaction commencement improved microbiological transformation of L-tyrosine to L-dopa (3.48 mg/ml; p ≤ 0.05) by Y. lipolytica NRRL-143. A 35% higher substrate conversion rate was achieved when compared to the control.
BMC Biotechnology, 2010
Background: The amino acid derivative 3,4-dihydroxy L-phenylalanine (L-dopa) is gaining interest ... more Background: The amino acid derivative 3,4-dihydroxy L-phenylalanine (L-dopa) is gaining interest as a drug of choice for Parkinson's disease. Aspergillus oryzae is commonly used for L-dopa production; however, a slower growth rate and relatively lower tyrosinase activity of mycelia have led to an increasing interest in exploiting alternative fungal cultures. In the present investigation, we report on the microbiological transformation of L-tyrosine to L-dopa accomplished by a newly isolated filamentous fungus Aspergillus niger. Results: The culture A. niger (isolate GCBT-8) was propagated in 500 ml Erlenmeyer flasks and the pre-grown mycelia (48 h old) were used in the reaction mixture as a source of enzyme tyrosinase. Grinded mycelia gave 1.26 fold higher L-dopa production compared to the intact at 6% glucose (pH 5.5). The rate of L-tyrosine consumption was improved from 0.198 to 0.281 mg/ml. Among the various nitrogen sources, 1.5% peptone, 1% yeast extract and 0.2% ammonium chloride were optimized. The maximal L-dopa was produced (0.365 mg/ml) at 0.3% potassium dihydrogen phosphate with L-tyrosine consumption of 0.403 mg/ml. Conclusion: Over~73% yield was achieved (degree of freedom 3) when the process parameters were identified using 2k-Plackett-Burman experimental design. The results are highly significant (p ≤ 0.05) and mark the commercial utility (LSD 0.016) of the mould culture which is perhaps the first ever report on L-dopa production from A. niger.
Biotechnology(Faisalabad), 2003
Bioresource Technology, 2004
The present investigation deals with citric acid production by some selected mutant strains of As... more 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-nitrosoguanidine (MNNG). Out of 3,2-deoxy-D 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 H 2 SO 4 pre-treated blackstrap molasses in Vogel's medium. On the basis of kinetic parameters such as volumetric substrate uptake rate (Q s), and specific substrate uptake rate (q s), 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 • 10 À5 M MgSO 4 AE 5H 2 O into the fermentation medium reduced the Fe 2þ ion concentration by counteracting 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).
Bioresource Technology, 2003
The present study describes citric acid fermentation by Aspergillus niger GCB-47 in a 15-l stainl... more The present study describes citric acid fermentation by Aspergillus niger GCB-47 in a 15-l 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 AE 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 AE 3:8 g/l and 80:39 AE 4:5%, respectively. The desirable mycelial morphology was in the form of small round pellets having dry cell mass 14:5 AE 0:8 g/l. Addition of ethanol, however, did not found to enhance citric acid production, significantly. The maximum value of Y p=x (i.e., 5:825 AE 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.
Bioresource Technology, 2005
The present investigation is concerned with the optimization of nitrogen for enhanced citric acid... more The present investigation is concerned with the optimization of nitrogen for enhanced citric acid productivity by a 2-deoxy D Dglucose resistant culture of Aspergillus niger NG d-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 À1 cells. Citrate production was however, stopped when intracellular ammonium ion concentration decreased below 1.0 mmol g À1 cell.
Applied Biochemistry and Biotechnology, 2007
Three strains of Bacillus licheniformis were isolated and screened for α-amy-lase production by s... more Three strains of Bacillus licheniformis were isolated and screened for α-amy-lase production by solid-state fermentation. Of these, IS-2 gave relatively higher enzyme production (32 ± 2.3 U/[g˙min]) and was selected for improve-ment after treatment with N-methyl N-nitro ...
Study of structural and electrical properties of Al3+ doped Ni0.7Zn0.3Fe2-xAlxO4 (0.0&amp... more Study of structural and electrical properties of Al3+ doped Ni0.7Zn0.3Fe2-xAlxO4 (0.0&amp;lex&lt;=0.5) ferrite synthesized through citrate-gel method has been carried out. The samples were characterized by using XRD and dielectric technique in the frequency range 42 Hz-5 MHz at room temperature. X-ray diffraction studies confirmed that all the samples exhibit single phase cubic spinel structure. The variation in epsilo', and tandelta
Journal of Biological Sciences, 2001
Sixteen different cultures of Aspergillus niger were isolated from different soil samples. These ... more Sixteen different cultures of Aspergillus niger were isolated from different soil samples. These isolates of Aspergillus niger were evaluated for citric acid fermentation in shake flask. Sucrose salt media was used and the volume of fermentation medium was kept at 25 ml. The cultural conditions such as pH (3.5), temperature (30EC), incubation period (8 days) and sugar concentration (15%), were optimised.
Journal of Biological Sciences, 2001
Microbial examination of 50 samples of both packed and unpacked butter was carried out. The sampl... more Microbial examination of 50 samples of both packed and unpacked butter was carried out. The samples were examined for total viable count, mould and yeast count, spore formers and coliform. The microbial load in the unpacked sample of butter was highest i.e., 3.8 × 10 6 /gm-6.6 × 10 6 /gm. The coliform count was found maximum in unpacked sample and one of the packed sample of butter (Kausar brand) i.e., 39/ml. The unpacked sample of butter contained highest number of aerobic spore formers i.e., 280/gm. The anaerobic spore-formers were found absent in 20 samples of butter and the rest contained in the range of 0-170/gm. The yeast cultures were found only in the sample of Lyallpur and Kausar butter. The mould count of these samples ranged from 0-280/gm.
Journal of Basic Microbiology, 2005
Electronic Journal of Biotechnology, 2002
Substrate consumption parameters: µ (h-1) = specific growth rate Y x/s = g cells/g substrate util... more Substrate consumption parameters: µ (h-1) = specific growth rate Y x/s = g cells/g substrate utilized Q s = g substrate consumed/l/h qs = g substrate consumed/g cells/h Qx = g cells formed/l/h Production formation rates: Q p = g citric acid produced/litre/h Yp/s = g citric acid produced/g substrate consumed Yp/x = g citric acid produced/g cells formed qp = g citric acid produced/g cells/h. L-DOPA is a useful drug for Parkinson's disease. This 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 the parental and UV-irradiated mutant cultures. The mutant strain of Aspergillus oryzae UV-6 showed pelletlike mycelial morphology and improved tyrosinase activity. Mould mycelium was used for biochemical conversion of L-tyrosine to L-DOPA since tyrosinase is an intracellular enzyme. The mutant was found to give *Corresponding author 3.72 folds higher production of L-DOPA than the parental strain. The comparison of kinetic parameters was also done which showed greater ability of the mutant to yield L-DOPA (i.e. Y p/x 32.73 mg/mg with parent and 95.71 mg/mg with mutant). When cultures grown for various incubation periods, were monitored for Q p , Q s and q p , there was significant enhancement (p<0.0025-0.005) in these variables by the mutant strain of Aspergillus oryzae UV-7 over GCB-6 on all the rates.
Pak. J. Bot, 2010
The present study is concerned with the improvement of Bacillus amyloliquefaciens strain UNG-16 f... more The present study is concerned with the improvement of Bacillus amyloliquefaciens strain UNG-16 for alpha amylase production. The bacterial culture was exposed to UV irradiation at 1.6× 102 J/m2/S for 15-60 min. However, UV induced viables did not give ...
BMC Genomics, 2007
Background: Reference genome sequences within the major taxa can be used to assist the developmen... more Background: Reference genome sequences within the major taxa can be used to assist the development of genomic tools for related organisms. A major constraint in the use of these sequenced and annotated genomes is divergent evolution. Divergence of organisms from a common ancestor may have occurred millions of years ago, leading to apparently unrelated and un-syntenic genomes when sequence alignment is attempted. Results: A series of programs were written to prepare 36 Mbp of Fusarium graminearum sequence in 19 scaffolds as a reference genome. Exactly 4,152 Bacterial artificial chromosome (BAC) end sequences from 2,178 large-insert Fusarium virguliforme clones were tested against this sequence. A total of 94 maps of F. graminearum sequence scaffolds, annotated exonic fragments and associated F. virguliforme sequences resulted. Conclusion: Developed here was a technique that allowed the comparison of genomes based on small, 15 bp regions of shared identity. The main power of this method lay in its ability to align diverged sequences. This work is unique in that discontinuous sequences were used for the analysis and information not readily apparent, such as match direction, are presented. The 94 maps and JAVA programs are freely available on the Web and by request.
BMC Biotechnology, 2007
Background: The 3,4-dihydroxy phenyl L-alanine (L-dopa) is a drug of choice for Parkinson's disea... more Background: The 3,4-dihydroxy phenyl L-alanine (L-dopa) is a drug of choice for Parkinson's disease, controlling changes in energy metabolism enzymes of the myocardium following neurogenic injury. Aspergillus oryzae is commonly used for L-dopa production; however, potential improvements in ease of handling, growth rate and environmental impact have led to an interest in exploiting alternative yeasts. The two important elements required for L-dopa production are intracellular tyrosinases (thus pre-grown yeast cells are required for the transformation of Ltyrosine to L-dopa) and L-ascorbate, which acts as a reducing agent. Results: Pre-grown cells of Yarrowia lipolytica NRRL-143 were used for the microbiological transformation of L-tyrosine to L-dopa. Different diatomite concentrations (0.5-3.0 mg/ml) were added to the acidic (pH 3.5) reaction mixture. Maximum L-dopa biosynthesis (2.96 mg/ml L-dopa from 2.68 mg/ml L-tyrosine) was obtained when 2.0 mg/ml diatomite was added 15 min after the start of the reaction. After optimizing reaction time (30 min), and yeast cell concentration (2.5 mg/ ml), an overall 12.5 fold higher L-dopa production rate was observed when compared to the control. Significant enhancements in Y p/s , Q s and q s over the control were observed. Conclusion: Diatomite (2.0 mg/ml) addition 15 min after reaction commencement improved microbiological transformation of L-tyrosine to L-dopa (3.48 mg/ml; p ≤ 0.05) by Y. lipolytica NRRL-143. A 35% higher substrate conversion rate was achieved when compared to the control.
BMC Biotechnology, 2010
Background: The amino acid derivative 3,4-dihydroxy L-phenylalanine (L-dopa) is gaining interest ... more Background: The amino acid derivative 3,4-dihydroxy L-phenylalanine (L-dopa) is gaining interest as a drug of choice for Parkinson's disease. Aspergillus oryzae is commonly used for L-dopa production; however, a slower growth rate and relatively lower tyrosinase activity of mycelia have led to an increasing interest in exploiting alternative fungal cultures. In the present investigation, we report on the microbiological transformation of L-tyrosine to L-dopa accomplished by a newly isolated filamentous fungus Aspergillus niger. Results: The culture A. niger (isolate GCBT-8) was propagated in 500 ml Erlenmeyer flasks and the pre-grown mycelia (48 h old) were used in the reaction mixture as a source of enzyme tyrosinase. Grinded mycelia gave 1.26 fold higher L-dopa production compared to the intact at 6% glucose (pH 5.5). The rate of L-tyrosine consumption was improved from 0.198 to 0.281 mg/ml. Among the various nitrogen sources, 1.5% peptone, 1% yeast extract and 0.2% ammonium chloride were optimized. The maximal L-dopa was produced (0.365 mg/ml) at 0.3% potassium dihydrogen phosphate with L-tyrosine consumption of 0.403 mg/ml. Conclusion: Over~73% yield was achieved (degree of freedom 3) when the process parameters were identified using 2k-Plackett-Burman experimental design. The results are highly significant (p ≤ 0.05) and mark the commercial utility (LSD 0.016) of the mould culture which is perhaps the first ever report on L-dopa production from A. niger.
Biotechnology(Faisalabad), 2003
Bioresource Technology, 2004
The present investigation deals with citric acid production by some selected mutant strains of As... more 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-nitrosoguanidine (MNNG). Out of 3,2-deoxy-D 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 H 2 SO 4 pre-treated blackstrap molasses in Vogel's medium. On the basis of kinetic parameters such as volumetric substrate uptake rate (Q s), and specific substrate uptake rate (q s), 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 • 10 À5 M MgSO 4 AE 5H 2 O into the fermentation medium reduced the Fe 2þ ion concentration by counteracting 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).
Bioresource Technology, 2003
The present study describes citric acid fermentation by Aspergillus niger GCB-47 in a 15-l stainl... more The present study describes citric acid fermentation by Aspergillus niger GCB-47 in a 15-l 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 AE 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 AE 3:8 g/l and 80:39 AE 4:5%, respectively. The desirable mycelial morphology was in the form of small round pellets having dry cell mass 14:5 AE 0:8 g/l. Addition of ethanol, however, did not found to enhance citric acid production, significantly. The maximum value of Y p=x (i.e., 5:825 AE 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.
Bioresource Technology, 2005
The present investigation is concerned with the optimization of nitrogen for enhanced citric acid... more The present investigation is concerned with the optimization of nitrogen for enhanced citric acid productivity by a 2-deoxy D Dglucose resistant culture of Aspergillus niger NG d-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 À1 cells. Citrate production was however, stopped when intracellular ammonium ion concentration decreased below 1.0 mmol g À1 cell.
Applied Biochemistry and Biotechnology, 2007
Three strains of Bacillus licheniformis were isolated and screened for α-amy-lase production by s... more Three strains of Bacillus licheniformis were isolated and screened for α-amy-lase production by solid-state fermentation. Of these, IS-2 gave relatively higher enzyme production (32 ± 2.3 U/[g˙min]) and was selected for improve-ment after treatment with N-methyl N-nitro ...