Kannan Krishnamurthi

Recent Advancements in Carbonic Anhydrase–Driven Processes for CO2 Sequestration: Minireview

The authors reviews the advancements in carbonic anhydrase– driven processes for CO2 sequestration research and engineering. Historical and recent discoveries of carbonic anhydrase and idea behind using it for CO2 sequestration are elaborated as well as the uses of this enzyme in free and immobilized forms are thoroughly discussed. New concepts such as extension of immobilized enzyme systems for bioreactor approach with the aim of CO2 abatement at the source are also introduced briefly toward the end of the review. The authors also suggest the possible future directions to employ carbonic anhydrase for CO2 sequestration.

Tracking of human cells in mice.

Tracking and tracing of transplanted cells in mice is required in many fields of research. Examples are transplantation of stem cells into organs of mice to study their differentiation capacity and injection of tumor cells to examine metastatic behavior. In the present study we tested the lipid dye CM-DiI and red fluorescent nanoparticles Qdot655 for their applicability in tagging and tracing of human cells in mice. Labeling of different cell types, including MCF-7 human breast cancer cells, human cord blood derived cells, human NeoHep cells and human hepatopancreatic precursor cells, is technically easy and did not compromise further cell culture. After transplantation of CM-DiI or Qdot655 marked cells, red fluorescent structures could be detected already in unprocessed paraffin slices of the studied organs, namely liver, lung, pancreas, kidney, spleen and bone marrow. Next, we examined whether the red fluorescent structures represent the transplanted human cells. For this purpose, we established an in situ hybridization (ISH) technique that allows clear-cut differentiation between human and murine nuclei, based on simultaneous hybridization with human alu and mouse major satellite (mms) probes. We observed a high degree of coincidence between CM-DiI-marked cells and alu positive nuclei. However, also some mms positive cells contained CM-DiI, suggesting phagocytosis of the transplanted CM-DiI-marked cells. The degree of such CM-DiI-positive mouse cells depended on the cell type and route of administration. From a technical point of view it was important that CM-DiI-positive structures in paraffin slices remained fluorescent also after ISH. In contrast, Qdot655 positive structures faded during further staining procedures. In conclusion, marking of cells with CM-DiI or Qdot655 prior to transplantation facilitates recovery of human cells, since a high fraction of positive structures in the host’s tissue originate from the transplanted cells. However, CM-DiI or Qdot655 positive staining of individual cells in transplanted tissues is not sufficient to prove their human origin. Additional procedures, such as ISH with alu-probes, are essential, when characterizing individual cells.

Heavy metal resistance in Arthrobacter ramosus strain G2 isolated from mercuric salt-contaminated soil.

Present study describes isolation of a multiple metal-resistant Arthrobacter ramosus strain from mercuric salt-contaminated soil. The isolate was found to resist and bioaccumulate several metals, such as cadmium, cobalt, zinc, chromium and mercury. Maximum tolerated concentrations for above metals were found to be 37, 525, 348, 1530 and 369 microM, respectively. The isolate could also reduce and detoxify redox-active metals like chromium and mercury, indicating that it has great potential in bioremediation of heavy metal-contaminated sites. Chromate reductase and mercuric reductase (MerA) activities in protein extract of the culture were found to be 2.3 and 0.17 units mg(-1) protein, respectively. MerA enzyme was isolated from the culture by (NH(4))(2)SO(4) precipitation followed by dye affinity chromatography and its identity was confirmed by nano-LC-MS/MS. Its monomeric molecular weight, and optimum pH and temperature were 57kDa, 7.4 and 55 degrees C, respectively. Thus, the enzyme was mildly thermophilic as compared to other MerA enzymes. K(m) and V(max) of the enzyme were 16.9 microM HgCl(2) and 6.2 micromol min(-1)mg(-1) enzyme, respectively. The enzyme was found to be NADPH-specific. To our knowledge this is the first report on characterization of MerA enzyme from an Arthrobacter sp.

Stress-induced lipids are unsuitable as a direct biodiesel feedstock: a case study with Chlorella pyrenoidosa.

The effects of various stresses on the suitability of lipid synthesized by Chlorella pyrenoidosa for biodiesel production were investigated. Lipids were characterized for detailed fatty acid methyl ester profiling and biodiesel properties like cetane number (CN), iodine value, cold filter plugging point (CFPP). Maximum biomass productivity (106.63 mgL(-1)d(-1)) and lipid content (29.68%) were obtained at indoor cultivation (nitrate sufficient, pH 8-10, 24h illumination). However, compared to this condition, other nitrate sufficient cultures [pH 6-8 and 10-12 (24h illumination), and at ambient CO2 and 16:8h light:dark photoperiod (pH unadjusted)] showed ∼12-14% lower lipid productivity. Upon 50% nitrate depletion (at indoor and outdoor; pH unadjusted) lipid content has increased by 7.62% and 17%, respectively. Though stress conditions helped enhancing lipid accumulation, there was two-fold increase in PUFA content compared to that observed at pH 8-10. This resulted in fuel properties which did not comply with the biodiesel standards.

Biological decolourization of C.I. Direct Black 38 by E. gallinarum.

In the present study, an Enterococcus gallinarum strain was isolated from effluent treatment plant of a textile industry based on its ability to decolourize C.I. Direct Black 38 (DB38), a benzidine-based azo dye. Effects of dye concentration and medium composition on dye decolourization were studied. The strain was found to decolourize DB38 even under aerobic conditions. Kinetics of DB38 decolourization was also examined, and V(max) and K(s) of decolourization were found to be higher in Luria broth (12.8 mg l(-1)h(-1) and 490.6 mg l(-1)) than in minimal medium (4.09 mg l(-1)h(-1) and 161.84 mg l(-1)). However, decolourization rate/biomass was found to be higher in minimal medium than in Luria broth, indicating greater decolourization efficiency of biomass in the former. The study also revealed biodegradation of DB38 to benzidine and its further deamination to 4-aminobiphenyl (4-ABP) by the culture. Ammonia released during this process was used as nitrogen source for growth of the culture.

Heavy Metal Status and Oxidative Stress in Diesel Engine Tuning Workers of Central Indian Population

Objective: To assess the oxidative stress induced due to heavy metal exposure. Exposed populations are selected from an engine tuning station and control from the same area with no occupational exposure. Method: Standard methods were followed for enzymatic assay, and heavy metals in blood and urine were analyzed by using inductively coupled plasma-optical emission spectrophotometer after microwave digestion. Result: Changes in mean blood Pb, Cd, and Ni concentrations in blood and urine of exposed population of all age groups (20 to 35, 35 to 45, and 46 to 58 years) and exposure durations (≤10, 11 to 20, and >20 years) were statistically not significant. However, exposed workers exhibited statistically significant higher antioxidant status in terms of serum glutathione-S-transferase activity, malondialdehyde level, and catalase activity. Conclusion: The findings in this article suggest that occupational exposure to diesel exhaust of engine tuning workers causes induction of oxidative stress, which cannot be correlated with the heavy metals status in blood and urine of an exposed population.

DNA repair gene polymorphisms at XRCC1, XRCC3, XPD, and OGG1 loci in Maharashtrian population of central India

Reduction in DNA repair capacity is associated with increased rates of birth defects, cancer, and accelerated ageing. Genetic polymorphisms in DNA repair genes might influence the repair activities of the enzymes predisposing individuals to cancer risk. Owing to the presence of these genetic variants, inter-individual and ethnic differences in DNA repair capacity have been observed in various populations. India harbors enormous genetic, cultural and linguistic diversity. The present study was undertaken to determine the allele and genotype frequencies of four non-synonymous SNPs, XRCC1 Arg399Gln (C>T, rs25487), XRCC3 Thr241Met (G>A, rs861539), XPD Lys751Gln (T>G, rs13181), and OGG1 Ser326Cys (C>G, rs1052133) in the Maharashtrian population, residing in the Vidarbha region of central India and to compare them with HapMap and other Indian populations. The variant alleles of these polymorphisms have been found to be positively associated with different forms of cancer in several genetic epidemiological studies. The basic prevalence of these polymorphisms in the general population must be known to evaluate their significance in risk assessment in cancer and other phenotypes. About 215 healthy and unrelated individuals from the Maharashtrian population were genotyped for each of these four polymorphisms using PCR-RFLP. The allele and genotype frequency distribution at the four DNA repair gene loci among Maharashtrians revealed a characteristic pattern. To the best of our knowledge, this is the first report of these DNA repair gene polymorphisms in a central Indian population.

The Genotoxicity of Priority Polycyclic Aromatic Hydrocarbons (PAHs) Containing Sludge Samples

ABSTRACT In this research work we developed in vitro tests utilizing mammalian cell cultures, which can rapidly assess effect of exposure of oily sludge-derived chemicals on human and ecological health. Many of these are hazardous to health and environment due to their toxicity and/or accumulation potential in sediments as well as in organisms. Petroleum refinery and petrochemical industry-derived oily sludges contain toxic polycyclic aromatic hydrocarbons (PAHs), some of which are lipophilic in nature. Risk assessment of environmental samples suffers from inadequate availability of toxicity data, lack of knowledge about behavior of genotoxic substances in complex matrices, paucity of information on synergistic and antagonistic interactions of mixture of components, etc.; the literature describing the behavior of genotoxic substances in complex mixtures is sparse and sometimes contradictory. The present study aims at assessing the genotoxic potential of oily sludges collected from an integrated petroleum refinery and petrochemical industry located in the southwestern part of India and a petrochemical industry located in the western part of India using a battery of genotoxicity assays such as DNA damage/strand break, chromosomal aberration, p53 protein induction, and apoptosis in CHO-K1 cell culture system. Exposure with different dose levels of sludge extracts (25, 50, 100 μL) in CHO-K1 cells could cause statistically significant level of (P < 0.001) DNA damage, chromosomal aberration, p53 protein induction, and apoptosis in comparison to negative control treatment groups, and the genotoxicity was attributed to PAHs present in the sludge as identified by GC-MS. This implies that the sludges are genotoxic in nature in mammalian cells tested, and the exposure to these may pose a potential genotoxic risk to human beings.

Statistical optimization of thermal pretreatment conditions for enhanced biomethane production from defatted algal biomass.

The present study analyzes the effect of thermal pretreatment for enhancing the biomethane potential of defatted algal biomass of Scenedesmus dimorphus through statistically guided experimental design. To this end, defatted microalgal biomass at various concentrations (1, 3 and 5 g L(-1)) was pretreated at elevated temperatures (100, 120 and 150°C) for 20, 40 and 60 min. The solubilised TOC was favourably enhanced up to 71 mg L(-1) after pretreatment at a temperature of 150°C for reaction time of 60 min. The methane yield was substantially enhanced (up to 60%) and could be correlated with an increase in organic matter solubilisation and enhanced biodegradability via thermal pretreatment. The optimisation of the integrated thermal pretreatment-biomethanation process resulted in up to 1.6-fold increase in methane yield.

An integrated genomic and proteomic approach to identify signatures of endosulfan exposure in hepatocellular carcinoma cells

Present study reports the identification of genomic and proteomic signatures of endosulfan exposure in hepatocellular carcinoma cells (HepG2). HepG2 cells were exposed to sublethal concentration (15μM) of endosulfan for 24h. DNA microarray and MALDI-TOF-MS analyses revealed that endosulfan induced significant alterations in the expression level of genes and proteins involved in multiple cellular pathways (apoptosis, transcription, immune/inflammatory response, carbohydrate metabolism, etc.). Furthermore, downregulation of PHLDA gene, upregulation of ACIN1 protein and caspase-3 activation in exposed cells indicated that endosulfan can trigger apoptotic cascade in hepatocellular carcinoma cells. In total 135 transcripts and 19 proteins were differentially expressed. This study presents an integrated approach to identify the alteration of biological/cellular pathways in HepG2 cells upon endosulfan exposure.