A statistical approach response surface methodology (RSM) was used to study the production of suc... more 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 5.4 g L À1 of succinic acid in 48 h 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 (12.5 g L À1 in 24 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, 20.0 g L À1 of succinic acid was obtained in 24 h. 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.
We report the effect of different physiological and nutritional parameters on succinic acid produ... more We report the effect of different physiological and nutritional parameters on succinic acid production from Bacteroides fragilis. This strain initially produced 0.70 g L À1 of succinic acid in 60 h. However, when process optimization was employed, 5.4 g L À1 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 1C, 100 rpm for 48 h. A marked enhancement in succinic acid production was observed when the optimized conditions were employed in a 10 L bioreactor. A total of 12.5 g L À1 of succinic acid was produced in 30 h. 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.
Your article is protected by copyright and all rights are held exclusively by Springer Science +B... more Your article is protected by copyright and all rights are held exclusively by Springer Science +Business Media New York. This e-offprint is for personal use only and shall not be selfarchived in electronic repositories. If you wish to self-archive your article, please use the accepted manuscript version for posting on your own website. You may further deposit the accepted manuscript version in any repository, provided it is only made publicly available 12 months after official publication or later and provided acknowledgement is given to the original source of publication and a link is inserted to the published article on Springer's website. The link must be accompanied by the following text: "The final publication is available at link.springer.com".
Journal of Biochemical and Biophysical Methods, 2005
Succinic acid, an intermediate of tricarboxylic acid cycle, is produced and accumulated by anaero... more 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, 2007
In routine assay for the screening of microbes producing proteases, 10% trichloroaceticacid (TCA)... more In routine assay for the screening of microbes producing proteases, 10% trichloroaceticacid (TCA) is flooded on the milk agar plates after inoculation and required incubation to precipitate the protein. However, the clarity of the hydrolyzed zone is not very sharp and distinct. We herein present an improved assay for detecting the presence of extracellular protease from microorganisms on agar plates. In this method 10% tannic acid is flooded on the milk agar plate (in place of, TCA) to observe the zone of hydrolysis. Tannic acid sharply increases the colour intensity of the plate, as it favours the precipitation of the unhydrolyzed protein in the plate, thereby improving the contrast between the intact zones and the enzymatic lyses zones of the substrate. Our results indicate that this method is useful to detect extracellular proteases produced by both fungi as well as bacteria. The method used in the present study is sensitive, and can be easily performed for screening of large number of microbial cultures. This is the first report on the use of tannic acid for the detection of microbial proteases.
Aim: Development and optimization of an efficient and inexpensive medium for succinic acid produc... more Aim: Development and optimization of an efficient and inexpensive medium for succinic acid production by Escherichia coli under anaerobic conditions. Methods and Results: Initially, 0AE8 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 7AE1 gl)1 of succinic acid in 36 h. Scale up in a 10-l fermentor under conditions of controlled pH and continuous CO 2 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 2AE5-fold increase in succinic acid production as against optimized medium used in 500ml 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.
Propanediol (propylene glycol) is an existing commodity chemical and can be produced from renewab... more 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 productivity. Three pathways which have been recognized for 1,2-propanediol production are discussed here. In the 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.
Effect of different environmental and nutritional factors on succinic acid production by batch fe... more 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 MgCO 3 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 CO 2 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.
The effect of process optimization on succinic acid production by Escherichia coli W3110 and on e... more 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 a...
Propanediol, a valuable bifunctional molecule, can be produced from renewable resources using mic... more Propanediol, a valuable bifunctional molecule, can be produced from renewable resources using microorganisms. It has several promising properties for many synthetic reactions, particularly for polymer and cosmetic industries. By virtue of being a natural product, relevant biochemical pathways can be harnessed into fermentation processes to produce 1,3-propanediol. Various strategies for the microbial production of 1,3-propanediol are reviewed and compared in this article with their promises and constraints. Furthermore, genetic and metabolic engineering could significantly improve product yields and overcome the limitations of fermentation technology. Present review gives an overview on 1,3-propanediol production by wild and recombinant strains. It also attempts to encompass the various issues concerned in utilization of crude glycerol for 1,3-propanediol production, with particular emphasis laid on biodiesel industries. This review also summarizes the present state of strategies studied for the downstream processing and purification of biologically produced 1,3-propanediol. The future prospect of 1,3-propanediol and its potential as a major bulk chemical are discussed under the light of the current research.
A total of 57 (36 and 21) Azotobacter chroococcum were isolated from wheat (Triticum aestivum) rh... more A total of 57 (36 and 21) Azotobacter chroococcum were isolated from wheat (Triticum aestivum) rhizospheric soil irrigated with industrial wastewater (about a decade) and ground water (uncontaminated) and characterized on the basis of morphological, cultural and biochemical characteristics. Rhizospheric soils were analyzed for metal concentrations by atomic absorption spectrophotometery and the test soil samples were contaminated with Fe, Zn, Cu, Cr, Ni and Pb. All the isolates of A. chroococcum were tested for their resistance against Hg 2þ , Cd 2þ , Cu 2þ , Cr 3þ , Cr 6þ , Zn 2þ , Ni 2þ and Pb 2þ. Among 36 isolates of Azotobacter from soil irrigated with industrial wastewater, 94.4% were resistant to Pb 2þ and Hg 2þ and 86.1%, 77.5% and 63.8% were resistant to Zn 2þ , Cr 6þ and Cr 3þ respectively. The highest minimum inhibitory concentration of 200 lg/ml for Hg 2þ and 1600 lg/ml for other metals were observed against these bacteria from soil. The incidences of metal resistance and MICs of metals for A. chroococcum from wastewater irrigated soil were significantly different to those of uncontaminated soil. All A. chroococcum isolates were tested for their resistance against 11 commonly used antibiotics/drugs. 91.6% were found to be resistant against nitrofurantoin while 86.4% and 80.5% were found to be resistant against polymyxin-B and co-trimoxazole respectively. Agarose gel electrophoresis using the miniprep method for plasmid isolation revealed that these isolates harboured plasmids of molecular weights 58.8 and 64.5 kb using EcoRI and HindIII digests of k DNA and undigested k DNA as standard markers.
The most influential parameters for succinic acid production obtained through one at a time metho... more 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 À1 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 À1 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 À1 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.
Studies were carried out on interaction of Trichoderma viride with copper and reports bioaccumula... more Studies were carried out on interaction of Trichoderma viride with copper and reports bioaccumulation as a mechanism of copper tolerance during growth. There was a marked increase in the lag phase of the growth, which was concentration dependent. At a concentration of 100 mg/L of CuCl 2 AE 2H 2 O, 81% of Cu(II) were removed by 3.4 g/L of the biomass in 72 h. The process was temperature and pH dependent. The maximum copper bioaccumulation occurred at 30°C, pH 5.0. Metabolic inhibitors such as sodium azide (NaN 3) and 2,4-dinitrophenol (2,4-DNP) drastically reduced the extent of Cu(II) bioaccumulation. Electron microscopy and cell fractionation studies revealed that 70-80% of copper was present as a layer on the cell wall surface.
A statistical approach response surface methodology (RSM) was used to study the production of suc... more 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 5.4 g L À1 of succinic acid in 48 h 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 (12.5 g L À1 in 24 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, 20.0 g L À1 of succinic acid was obtained in 24 h. 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.
We report the effect of different physiological and nutritional parameters on succinic acid produ... more We report the effect of different physiological and nutritional parameters on succinic acid production from Bacteroides fragilis. This strain initially produced 0.70 g L À1 of succinic acid in 60 h. However, when process optimization was employed, 5.4 g L À1 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 1C, 100 rpm for 48 h. A marked enhancement in succinic acid production was observed when the optimized conditions were employed in a 10 L bioreactor. A total of 12.5 g L À1 of succinic acid was produced in 30 h. 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.
Your article is protected by copyright and all rights are held exclusively by Springer Science +B... more Your article is protected by copyright and all rights are held exclusively by Springer Science +Business Media New York. This e-offprint is for personal use only and shall not be selfarchived in electronic repositories. If you wish to self-archive your article, please use the accepted manuscript version for posting on your own website. You may further deposit the accepted manuscript version in any repository, provided it is only made publicly available 12 months after official publication or later and provided acknowledgement is given to the original source of publication and a link is inserted to the published article on Springer's website. The link must be accompanied by the following text: "The final publication is available at link.springer.com".
Journal of Biochemical and Biophysical Methods, 2005
Succinic acid, an intermediate of tricarboxylic acid cycle, is produced and accumulated by anaero... more 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, 2007
In routine assay for the screening of microbes producing proteases, 10% trichloroaceticacid (TCA)... more In routine assay for the screening of microbes producing proteases, 10% trichloroaceticacid (TCA) is flooded on the milk agar plates after inoculation and required incubation to precipitate the protein. However, the clarity of the hydrolyzed zone is not very sharp and distinct. We herein present an improved assay for detecting the presence of extracellular protease from microorganisms on agar plates. In this method 10% tannic acid is flooded on the milk agar plate (in place of, TCA) to observe the zone of hydrolysis. Tannic acid sharply increases the colour intensity of the plate, as it favours the precipitation of the unhydrolyzed protein in the plate, thereby improving the contrast between the intact zones and the enzymatic lyses zones of the substrate. Our results indicate that this method is useful to detect extracellular proteases produced by both fungi as well as bacteria. The method used in the present study is sensitive, and can be easily performed for screening of large number of microbial cultures. This is the first report on the use of tannic acid for the detection of microbial proteases.
Aim: Development and optimization of an efficient and inexpensive medium for succinic acid produc... more Aim: Development and optimization of an efficient and inexpensive medium for succinic acid production by Escherichia coli under anaerobic conditions. Methods and Results: Initially, 0AE8 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 7AE1 gl)1 of succinic acid in 36 h. Scale up in a 10-l fermentor under conditions of controlled pH and continuous CO 2 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 2AE5-fold increase in succinic acid production as against optimized medium used in 500ml 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.
Propanediol (propylene glycol) is an existing commodity chemical and can be produced from renewab... more 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 productivity. Three pathways which have been recognized for 1,2-propanediol production are discussed here. In the 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.
Effect of different environmental and nutritional factors on succinic acid production by batch fe... more 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 MgCO 3 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 CO 2 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.
The effect of process optimization on succinic acid production by Escherichia coli W3110 and on e... more 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 a...
Propanediol, a valuable bifunctional molecule, can be produced from renewable resources using mic... more Propanediol, a valuable bifunctional molecule, can be produced from renewable resources using microorganisms. It has several promising properties for many synthetic reactions, particularly for polymer and cosmetic industries. By virtue of being a natural product, relevant biochemical pathways can be harnessed into fermentation processes to produce 1,3-propanediol. Various strategies for the microbial production of 1,3-propanediol are reviewed and compared in this article with their promises and constraints. Furthermore, genetic and metabolic engineering could significantly improve product yields and overcome the limitations of fermentation technology. Present review gives an overview on 1,3-propanediol production by wild and recombinant strains. It also attempts to encompass the various issues concerned in utilization of crude glycerol for 1,3-propanediol production, with particular emphasis laid on biodiesel industries. This review also summarizes the present state of strategies studied for the downstream processing and purification of biologically produced 1,3-propanediol. The future prospect of 1,3-propanediol and its potential as a major bulk chemical are discussed under the light of the current research.
A total of 57 (36 and 21) Azotobacter chroococcum were isolated from wheat (Triticum aestivum) rh... more A total of 57 (36 and 21) Azotobacter chroococcum were isolated from wheat (Triticum aestivum) rhizospheric soil irrigated with industrial wastewater (about a decade) and ground water (uncontaminated) and characterized on the basis of morphological, cultural and biochemical characteristics. Rhizospheric soils were analyzed for metal concentrations by atomic absorption spectrophotometery and the test soil samples were contaminated with Fe, Zn, Cu, Cr, Ni and Pb. All the isolates of A. chroococcum were tested for their resistance against Hg 2þ , Cd 2þ , Cu 2þ , Cr 3þ , Cr 6þ , Zn 2þ , Ni 2þ and Pb 2þ. Among 36 isolates of Azotobacter from soil irrigated with industrial wastewater, 94.4% were resistant to Pb 2þ and Hg 2þ and 86.1%, 77.5% and 63.8% were resistant to Zn 2þ , Cr 6þ and Cr 3þ respectively. The highest minimum inhibitory concentration of 200 lg/ml for Hg 2þ and 1600 lg/ml for other metals were observed against these bacteria from soil. The incidences of metal resistance and MICs of metals for A. chroococcum from wastewater irrigated soil were significantly different to those of uncontaminated soil. All A. chroococcum isolates were tested for their resistance against 11 commonly used antibiotics/drugs. 91.6% were found to be resistant against nitrofurantoin while 86.4% and 80.5% were found to be resistant against polymyxin-B and co-trimoxazole respectively. Agarose gel electrophoresis using the miniprep method for plasmid isolation revealed that these isolates harboured plasmids of molecular weights 58.8 and 64.5 kb using EcoRI and HindIII digests of k DNA and undigested k DNA as standard markers.
The most influential parameters for succinic acid production obtained through one at a time metho... more 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 À1 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 À1 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 À1 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.
Studies were carried out on interaction of Trichoderma viride with copper and reports bioaccumula... more Studies were carried out on interaction of Trichoderma viride with copper and reports bioaccumulation as a mechanism of copper tolerance during growth. There was a marked increase in the lag phase of the growth, which was concentration dependent. At a concentration of 100 mg/L of CuCl 2 AE 2H 2 O, 81% of Cu(II) were removed by 3.4 g/L of the biomass in 72 h. The process was temperature and pH dependent. The maximum copper bioaccumulation occurred at 30°C, pH 5.0. Metabolic inhibitors such as sodium azide (NaN 3) and 2,4-dinitrophenol (2,4-DNP) drastically reduced the extent of Cu(II) bioaccumulation. Electron microscopy and cell fractionation studies revealed that 70-80% of copper was present as a layer on the cell wall surface.
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