Lata Agarwal

University of Delhi, Delhi, NCT, India

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Publications (17)35.32 Total impact

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    ABSTRACT: 1,2-Propanediol (propylene glycol) is an existing commodity chemical and can be produced from renewable resources using microbes. By virtue of being a natural product, relevant biochemical pathways can be harnessed into fermentation processes to produce 1,2-propanediol. In the present review, the chemical process and different biological strategies for the production of 1,2-propanediol are reviewed and compared with the potentials and limitations of all processes. For the successful commercial production of this diol, it is necessary to establish the metabolic pathways and production hosts (microorganisms), which are capable of delivering final product with high yields and volumetric productivity. Three pathways which have been recognized for 1,2-propanediol production are discussed here. In the first, de-oxy sugars like fucose and rhamnose are used as the carbon sources, while in the other route, the glycolytic intermediate-dihydroxyacetonephosphate (DHAP) is used to produce 1,2-propanediol via the formation of methylglyoxal. A new pathway of 1,2-propanediol production by lactic acid degradation under anoxic conditions and the enzymes involved is also discussed. The production of this diol has gained attention because of their newer applications in industries such as polymers, food, pharmaceuticals, textiles, etc. Furthermore, improvement in fermentation technology will permit its uses in other applications. Future prospect in the light of the current research and its potential as a major bulk chemical are discussed.
    Indian Journal of Microbiology 03/2010; 50(1):2-11. · 0.46 Impact Factor
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    ABSTRACT: Tannase from Penicillium variable IARI 2031 was purified by a two-step purification strategy comprising of ultra-filtration using 100 kDa molecular weight cutoff and gel-filtration using Sephadex G-200. A purification fold of 135 with 91% yield of tannase was obtained. The enzyme has temperature and pH optima of 50 degrees C and 5 degrees C, respectively. However, the functional temperature range is from 25 to 80 degrees C and functional pH range is from 3.0 to 8.0. This tannase could successfully be immobilized on Amberlite IR where it retains about 85% of the initial catalytic activity even after ninth cycle of its use. Based on the Michaelis-Menten constant (Km) of tannase, tannic acid is the best substrate with Km of 32 mM and Vmax of 1.11 micromol ml(-1)min(-1). Tannase is inhibited by phenyl methyl sulphonyl fluoride (PMSF) and N-ethylmaleimide retaining only 28.1% and 19% residual activity indicating that this enzyme belongs to the class of serine hydrolases. Tannase in both crude and crude lyophilized forms is stable for one year retaining more than 60% residual activity.
    Bioresource Technology 06/2008; 99(7):2544-51. · 4.75 Impact Factor
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    ABSTRACT: Cheese whey was the most suitable substrate for production of lactic acid under anaerobic conditions by Entercoccus flavescens which, on supplementating with corn steep liquor (5% v/v) and 10 mM CaCO(3) at pH 5.5, 37 degrees C, yielded 12.6 g lactic acid/l in 36 h. Production was scaled up to a 10 l bioreactor under controlled pH and continuous CO(2) supply and gave 28 g lactic acid/l in 30 h resulting in a net 8.7-fold increase in production as compared to unoptimized conditions.
    Biotechnology Letters 05/2008; 30(4):631-5. · 1.85 Impact Factor
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    ABSTRACT: Cheese whey was the most suitable sub-strate for production of lactic acid under anaerobic conditions by Entercoccus flavescens which, on sup-plementating with corn steep liquor (5% v/v) and 10 mM CaCO 3 at pH 5.5, 37°C, yielded 12.6 g lactic acid/l in 36 h. Production was scaled up to a 10 l bioreactor under controlled pH and continuous CO 2 supply and gave 28 g lactic acid/l in 30 h resulting in a net 8.7-fold increase in production as compared to unoptimized conditions.
    Biotechnology Letters 11/2007; 30(4):631. · 1.85 Impact Factor
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    ABSTRACT: Response surface methodology (RSM) was employed for optimization of medium components and cultural parameters in cost effective cane molasses based medium for attaining high yield of succinic acid. The important factors obtained by "one-variable-at-a-time-approach" (cane molasses, corn steep liquor, sodium carbonate, and inoculum density) were further optimized by RSM. The optimum values of the parameters obtained through RSM (cane molasses 12.5%, corn steep liquor 7.5%, and sodium carbonate 25 mM) led to almost double yield of succinic acid (15.2 g/l in 36 h) as against "one-variable-at-a-time-approach" (7.1 g/l in 36 h) in 500-ml anaerobic bottles containing 300-ml cane molasses based medium. Subsequently, in 10-l bioreactor succinic acid production from Escherichia coli was further improved to 26.2 g/l in 30 h under conditions optimized through RSM. This fermentation-derived succinic acid will definitely help in replacing existing environmentally hazardous and cost-intensive chemical methods for the production of succinic acid.
    Applied Biochemistry and Biotechnology 09/2007; 142(2):158-67. · 1.89 Impact Factor
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    S. Sharma, L. Agarwal, R. K. Saxena
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    ABSTRACT: Statistically based experimental design was employed for the optimization of fermentation conditions for maximum production of enzyme tannase from Aspergillus niger. Central composite rotatable design (CCRD) falling under response surface methodology (RSM) was used. Based on the results of ‘one-at-a-time’ approach in submerged fermentation, the most influencing factors for tannase production from A. niger were concentrations of tannic acid and sodium nitrate, agitation rate and incubation period. Hence, to achieve the maximum yield of tannase, interaction of these factors was studied at optimum production pH of 5.0 by RSM. The optimum values of parameters obtained through RSM were 5% tannic acid, 0.8% sodium nitrate, 5.0 pH, 5 × 107 spores/50mL inoculum density, 150 rpm agitation and incubation period of 48 h which resulted in production of 19.7 UmL−1 of the enzyme. This activity was almost double as compared to the amount obtained by ‘one-at-a-time’ approach (9.8 UmL−1).
    Indian Journal of Microbiology 06/2007; 47(2):132-138. · 0.46 Impact Factor
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    ABSTRACT: A statistical approach response surface methodology (RSM) was used to study the production of succinic acid from Bacteroides fragilis. The most influential parameters for succinic acid production obtained through one-at-a-time method were glucose, tryptone, sodium carbonate, inoculum size and incubation period. These resulted in the production of 5.4gL(-1) of succinic acid in 48h from B. fragilis under anaerobic conditions. Based on these results, a statistical method, face-centered central composite design (FCCCD) falling under RSM was employed for further enhancing the succinic acid production and to monitor the interactive effect of these parameters, which resulted in a more than 2-fold increase in yield (12.5gL(-1) in 24h). The analysis of variance (ANOVA) showed the adequacy of the model and the verification experiments confirmed its validity. On subsequent scale-up in a 10-L bioreactor using conditions optimized through RSM, 20.0gL(-1) of succinic acid was obtained in 24h. This clearly indicated that the model stood valid even on large scale. Thus, the statistical optimization strategy led to an approximately 4-fold increase in the yield of succinic acid. This is the first report on the use of FCCCD to improve succinic acid production from B. fragilis. The present study provides useful information about the regulation of succinic acid synthesis through manipulation of various physiochemical parameters.
    Anaerobe 05/2007; 13(2):50-6. · 2.02 Impact Factor
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    ABSTRACT: Effect of different environmental and nutritional factors on succinic acid production by batch fermentation of Enterococcus flavescens and enzymes involved in the acid production through reverse tricarboxylic acid cycle (TCA) cycle was investigated. An overall seven-fold increase in succinic acid production (from 0.92 g l−1 in 72 h initially to 6.7 g l−1 in 48 h) was achieved in 300-ml of optimized medium having 3% sucrose, 1:0.5 ratio of tryptone and ammonium hydrogen phosphate, 15 mM MgCO3 at pH 6.5 when inoculated with 4% (v/v) of seed inoculum and incubated at 39 °C for 48 h, as against initial un-optimized medium. Subsequent scale-up in a 10-l bioreactor using these optimized fermentation conditions under controlled pH and continuous CO2 supply resulted in 14.25 g l−1 of succinic acid in 30 h. Optimization of the environmental and nutritional parameters resulted in a maximum production of succinic acid by affecting the levels of the enzymes involved in its production via the reverse TCA cycle. A linear relationship was observed between succinic acid production and in the enzyme activities. The enzyme activity was found to be increase in order phosphoenol pyruvate carboxykinase < malate dehydrogenase < fumarase < fumarate reductase < phosphoenol pyruvate carboxylase.
    Enzyme and Microbial Technology 03/2007; 40(4):629. · 2.59 Impact Factor
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    ABSTRACT: A highly thermostable alkaline amylase producing Bacillus sp. PN5 was isolated from soil, which yielded 65.23 U mL(-1) of amylase in medium containing (%) 0.6 starch, 0.5 peptone and 0.3 yeast extract at 60 degrees C, pH 7.0 after 60 h of incubation. Maximum amylase activity was at pH 10.0 and 90 degrees C. The enzyme retained 80% activity after 1 h at pH 10.0. It exhibited 65% activity at 105 degrees C and had 100% stability in the temperature range between 80 and 100 degrees C for 1 h. In addition, there was 86.36% stability after 1-h incubation with sodium dodecylsulphate. These properties indicated possible use of this amylase in starch saccharification and detergent formulation.
    Bioresource Technology 02/2007; 98(2):260-5. · 4.75 Impact Factor
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    ABSTRACT: Effect of different environmental and nutritional factors on succinic acid production by batch fermentation of Enterococcus flavescens and enzymes involved in the acid production through reverse tricarboxylic acid cycle (TCA) cycle was investigated. An overall seven-fold increase in succinic acid production (from 0.92gl−1 in 72h initially to 6.7gl−1 in 48h) was achieved in 300-ml of optimized medium having 3% sucrose, 1:0.5 ratio of tryptone and ammonium hydrogen phosphate, 15mM MgCO3 at pH 6.5 when inoculated with 4% (v/v) of seed inoculum and incubated at 39°C for 48h, as against initial un-optimized medium. Subsequent scale-up in a 10-l bioreactor using these optimized fermentation conditions under controlled pH and continuous CO2 supply resulted in 14.25gl−1 of succinic acid in 30h. Optimization of the environmental and nutritional parameters resulted in a maximum production of succinic acid by affecting the levels of the enzymes involved in its production via the reverse TCA cycle. A linear relationship was observed between succinic acid production and in the enzyme activities. The enzyme activity was found to be increase in order phosphoenol pyruvate carboxykinase
    Enzyme and Microbial Technology - ENZYME MICROB TECHNOL. 01/2007; 40(4):629-636.
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    ABSTRACT: The most influential parameters for succinic acid production obtained through one at a time method were sucrose, tryptone, magnesium carbonate, inoculum size and incubation period. These resulted in the production of 7.0 g L(-1) of succinic acid in 60 h from Escherichia coli W3110 under anaerobic conditions. Based on these results, a statistical method, face centered central composite design (FCCCD) falling under response surface method (RSM) was employed for further enhancing the succinic acid production and to monitor the interactive effect of these parameters, which resulted in a twofold increase in yield (14.3 g L(-1) in 48 h). The analysis of variance (ANOVA) showed the adequacy of the model and the verification experiments confirmed its validity. On subsequent scale-up in a 10-L bioreactor using conditions optimized through RSM, 24.2 g L(-1) of succinic acid was obtained in 30 h. This clearly indicated that the model stood valid even on large-scale. Thus, the statistical optimization strategy led to a 3.5-fold increase in the yield of succinic acid. This is the first report on the use of FCCCD to improve succinic acid production from E. coli.
    Bioresource Technology 10/2006; 97(13):1443-8. · 4.75 Impact Factor
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    ABSTRACT: The effect of process optimization on succinic acid production by Escherichia coli W3110 and on enzymes involved in the reverse tricarboxylic acid cycle was studied. Approximately, 7.02 g L-1 of succinic acid was produced in 60 h at pH 7.0 in 500 mL anaerobic bottles containing 300 mL of the medium, wherein the sucrose concentration was 2.5%, the ratio of tryptone to ammonium hydrogen phosphate was 1:1, and the concentration of magnesium carbon ate was 1.5%. When these optimized fermentation conditions were employed in a 10 L bioreactor, 11.2 g L-1 of succinic acid was produced in 48 h. This is a 10-fold increase in succinic acid production from the initial titer of 0.94 g L-1. This clearly indicates the importance of process optimization, where by manipulating the media composition and production conditions, a remarkable increase in the production of the desired biomolecule can be obtained. The production of succinic acid is a multi-step reaction through the reverse tricarboxylic acid cycle. A linear relationship was observed between succinic acid production and the enzyme activities. The enzyme activities were found to increase in the order phospho-enol-pyruvate carboxylase<malate dehydrogenase<fumarase<fumarate reductase. The activity of phospho-enol-pyruvate carboxykinase was also estimated. Results indicate that this enzyme was not a very active participant in the production of succinic acid, since it catalyzes the phosphorylation of oxaloacetic acid to yield phospho-enol-pyruvate.
    Canadian Journal of Microbiology 09/2006; 52(9):893-902. · 1.20 Impact Factor
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    ABSTRACT: Development and optimization of an efficient and inexpensive medium for succinic acid production by Escherichia coli under anaerobic conditions. Initially, 0.8 gl(-1) of succinic acid was produced in 60 h in 300-ml medium. On optimization, glucose and peptone were replaced by cane molasses and corn steep liquor. Three hundred ml of this medium was inoculated with 4% (v/v) of seed inoculum, incubated at 39 degrees C for 72 h, resulted in 7.1 gl(-1) of succinic acid in 36 h. Scale up in a 10-l fermentor under conditions of controlled pH and continuous CO2 supply in this medium resulted in 17 gl(-1) of succinic acid in 30 h. A ninefold increase in succinic acid production was obtained in 500-ml anaerobic bottles with optimized medium having cane molasses and corn steep liquor as against initial medium containing glucose and peptone. However, a subsequent scale up in a 10-l fermentor resulted in a 2.5-fold increase in succinic acid production as against optimized medium used in 500-ml anaerobic bottles. Succinic acid production was enhanced in medium consisting of inexpensive carbon and nitrogen sources in a shorter span of time.
    Journal of Applied Microbiology 07/2006; 100(6):1348-54. · 2.20 Impact Factor
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    ABSTRACT: We report the effect of different physiological and nutritional parameters on succinic acid production from Bacteroides fragilis. This strain initially produced 0.70gL(-1) of succinic acid in 60h. However, when process optimization was employed, 5.4gL(-1) of succinic acid was produced in medium consisting of glucose (1.5%); tryptone (2.5%); Na(2)CO(3) (1.5%), at pH 7.0, when inoculated with 4% inoculum and incubated at 37 degrees C, 100rpm for 48h. A marked enhancement in succinic acid production was observed when the optimized conditions were employed in a 10L bioreactor. A total of 12.5gL(-1) of succinic acid was produced in 30h. This is approximately 12-fold increase in succinic acid production when compared to the initial un-optimized medium production. This enhancement in succinic acid production may be due to the control of CO(2) supply and the impeller speed. This is also resulted in the reduction of the production time. The present study provides useful information to the industrialists seeking environmentally benign technology for the production of bulk biomolecules through manipulation of various chemical parameters.
    Anaerobe 01/2006; 12(5-6):231-7. · 2.02 Impact Factor
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    ABSTRACT: Lipase producing ability of 120 bacterial isolates was examined qualitatively, resulting in 32 lipase producers, which were further screened for 1,3-regiospecificity. Three Bacillus (GK-8, GK-31 and GK-42) and one Pseudomonas (GK-80) were found to produce 1,3-regiospecific lipases. These lipases were alkaline in nature as they showed pH optima of 9.0 and high stability in the alkaline pH range of 8.0–11.0. The lipases from three Bacillus isolates, viz. GK-8, GK-31 and GK-42 showed temperature optima of 37 °C, whereas the Pseudomonas (GK-80) lipase showed optimum activity at 50 °C. The lipase of GK-8 was highly stable and showed enhanced activity in different organic solvents like petroleum ether (172%), diethyl ether (143%) and acetone (135%).
    Journal of Molecular Catalysis B: Enzymatic. 01/2006;
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    ABSTRACT: Aim: Development and optimization of an efficient and inexpensive medium for succinic acid production by Escherichia coli under anaerobic conditions. Methods and Results: Initially, 0Æ8 gl)1 of succinic acid was produced in 60 h in 300-ml medium. On optimization, glucose and peptone were replaced by cane molasses and corn steep liquor. Three hundred ml of this medium was inoculated with 4% (v/v) of seed inoculum, incubated at 39�C for 72 h, resulted in 7Æ1 gl)1 of succinic acid in 36 h. Scale up in a 10-l fermentor under conditions of controlled pH and continuous CO2 supply in this medium resulted in 17 gl)1 of succinic acid in 30 h. Conclusions: A ninefold increase in succinic acid production was obtained in 500-ml anaerobic bottles with optimized medium having cane molasses and corn steep liquor as against initial medium containing glucose and peptone. However, a subsequent scale up in a 10-l fermentor resulted in a 2Æ5-fold increase in succinic acid production as against optimized medium used in 500- ml anaerobic bottles. Significance and Impact of the Study: Succinic acid production was enhanced in medium consisting of inexpensive carbon and nitrogen sources in a shorter span of time.
    Journal of Applied Microbiology 11/2005; 100:1348. · 2.20 Impact Factor
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    ABSTRACT: Succinic acid, an intermediate of tricarboxylic acid cycle, is produced and accumulated by anaerobic microorganisms. The long-standing interest in the production of this organic acid is because it is a key compound in producing more than 30 commercially important products. The detection of succinic acid is generally carried out by gas chromatography (GC), enzymatic assays, ion-exclusion chromatography (IEC) or by high performance liquid chromatography (HPLC). However, these methods are time consuming, require sophisticated instrumentation and are expensive. In the present investigation we are reporting two rapid, cost effective screening methods for the detection of this important organic acid. These methods can be utilized to screen a large number of microbes producing succinic acid in a very short span of time.
    Journal of Biochemical and Biophysical Methods 05/2005; 63(1):24-32. · 2.33 Impact Factor