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Articles by G. Sibi
Total Records ( 13 ) for G. Sibi
  Shoaib Hamid and G. Sibi
  Background and Objective: Reactive oxygen species (ROS) are produced due to imbalance between cellular ROS production and elimination leading to oxidative stress. Antioxidants are known to involve in protecting cells from oxidative stress induced by various stresses in micro-algae. This study was carried out with the objective of determining the antioxidant system responses in micro-algae grown under nutrient stress conditions. Materials and Methods: Chlorococcopsis minuta was cultivated in nitrogen and phosphorous reprieve and deprived conditions and enzymatic (superoxide dismutase, catalase, ascorbate peroxidase) and non-enzymatic (Hydrogen peroxide, proline, polyphenol content and lipid per-oxidation level) antioxidants were analyzed. Results: Activities of antioxidant enzymes in C. minuta during nutrient stress showed that the activities of SOD, CAT and APX were increased in nutrient stress cultures when compared to nutrient fulfilled conditions. There was a 33% increase in lipid per-oxidation N-P- media than N-P+ media. Proline content increased with nutrient stress and reached 8 folds higher in nitrogen and phosphorous deprived media than the control. Total phenolic content was greater in N-P- indicating the nutrient stress triggered antioxidant system in the micro-algae. Conclusion: Nitrogen deprivation with phosphorous depletion condition demonstrated the oxidative stress and enhanced activation of enzymatic and non-enzymatic antioxidant systems at various levels.
  Sagar Grover , Shaily Rubina Tirkey , Veeramallegowda , Saroj Yadav and G. Sibi
  Background and Objective: The mutualistic interaction between microalgae and bacteria when co-culturing aid each other by promoting growth. This work was planned to determine the benefits of co-culturing Chlorella vulgaris with Nitrobacter sp. in terms of enhanced microalgal biomass and lipid production. Materials and Methods: Different growth media viz., Bristol media, synthetic waste water and dilutions of waste water were used for co-culturing for a period of 16 days. Enhancement of microalgal growth in terms of growth rate, biomass, protein, carbohydrates, chlorophyll and total lipid content in microalgae were determined at regular intervals and at the end of cultivation period. Results: Specific growth rate was promoted in co-culture after 4th day of cultivation whereas monoculture has resulted in highest growth rate after 13th day of cultivation. Protein and carbohydrate contents of mono- and co-cultured C. vulgaris were 20.03 and 9.413 μg mg1, respectively in 50% sewage water. There was a down trend in dissolved oxygen levels when the microalgae were co-cultured with bacteria. Biomass productivity was 0.0371 g L1/day in monoculture after 16th day of cultivation and was 0.0285 g L1/day after 4 days of cultivation as co-culture. Highest lipid content of 20.69% was observed in monoculture and the co-culture has resulted in 17.93%. Conclusion: The results indicated that co-culturing of C. vulgaris with Nitrobacter resulted in enhanced growth promotion as evidenced by increased cellular composition and biomass content. This interaction could be utilized in enhancing microalgal biomass, especially by replacing nitrogen fertilizers in the growth medium.
  G. Sibi , Saurabh Awasthi , K. Dhananjaya , H. Mallesha and K.R. Ravikumar
  Development of effective means with low risk to human health and environment is needed to control postharvest pathogens as fruits are vulnerable to attacks of various microorganisms upon harvest due to high moisture and nutrient content. Leaves and flowers of Plumeria alba, P. acutifolia and P. rubra were extracted with different solvents to compare the profile of phytochemicals. C. sinensis (sweet orange) was selected to determine the postharvest fungal pathogens of its fruits. Various methods were followed to isolate the fungal pathogens from oranges and investigated their control by using Plumeria species extracts. Phytochemical analysis has revealed the presence of alkaloids as the major phytoconstituent irrespective of plant species and parts used followed by flavonoids and glycosides. Terpenoids, tannins, phenols were the other major phytochemicals found in the extracts. Six fungi were isolated from sweet oranges with Penicillium digitatum as the predominant one followed by Aspergillus sp. and Rhizopus arrhizus. Antifungal assay revealed the potential fungistatic activity of petroleum ether leaf and flower extracts whereas chloroform, methanol and aqueous extracts were completely failed to control the growth of fungal isolates. Flower extracts of P. rubra had the best antifungal activity against all the isolates but with no activity of leaf extracts. However, a significant fungistatic activity was observed with both leaf and flower extracts of P. acutifolia and P. alba. The extracts exhibited significant activity against the blue green mold, P. digitatum. This study suggests the potential value of using crude flower and leaf extracts of Plumeria species to combat postharvest fungal pathogens of sweet oranges thereby extending their shelf life.
  Totiya Ishchi and G. Sibi
  Background and Objective: Azo dyes are most widely used in various industries due to their ease of synthesis and chemical stability. But many azo dyes and their breakdown derivatives have been suggested to be toxic to life. Biological treatments of dyes with microorganisms are relatively cost effective and eco-friendly due to lower sludge production. In this study, the microalgae Chlorella vulgaris was examined for its degrading ability of azo dyes viz., Reactive Black 5, Direct Blue 71 and Disperse Red 1. Materials and Methods: The experiments included dye decolorization experiments and factors affecting decolorization such as initial dye concentration, pH and temperature. Further, azoreductase enzyme specific activity and its kinetics were determined. Results: The results revealed that azo degradation based on the initial dye concentration varied among the dyes tested and the same was reflected for pH. In specific, 200 mg L1 was found optimum for Reactive Black 71 and Direct Blue 71 whereas 300 mg L1 was for Disperse Red 1. The optimum pH for decolorization of RB5, DB71 and DR1 was 5, 8 and 8, respectively. The optimum temperature for degradation of all the dyes was found as 40°C. Maximum azoreductase activity of 0.127 U mg1 protein was observed for DR1 and the enzyme activity was not pH dependent but substrate specific. Conclusion: The results revealed the azo dye degrading potential of Chlorella vulgaris and the decolorizing conditions were optimized for the microalgae.
  Vishaka Shetty , Keyuri Mokashi and G. Sibi
  Up-scaling the production of value added products from microalgae requires reliable techniques. This study has been carried out in order to determine whether microalgae have an inherent tendency to contain similar proportions of antioxidant properties in its lipid and phenolic extracts under varying growth medium. Chlorella vulgaris and Acutodesmus obliquus (Scenedesmus obliquus) were cultivated in normal water, Bold’s medium and sewage water followed by extraction of lipids and phenolics. The extracts were subjected to in vitro antioxidant assays performed in triplicates in which higher scavenging activity of DPPH and super oxide radical was observed in phenolic extracts. However, there was a significantly higher antioxidant potential found in lipid extracts suggests that next to the well studied phenolic compounds, microalgal lipids should also be considered when using microalgae as a source of natural antioxidants. Further, antioxidant profile of lipid and phenolic extracts from same species varied with growth medium.
  Vishaka Shetty and G. Sibi
  A study was carried out to explore the relationship between growth conditions and antioxidant properties of microalgae. Further, correlation between phenolics and antioxidant activities were studied to determine whether antioxidant activity depends on microalgal phenolics content under varying culture conditions. Total phenolics and antioxidant properties of Chlorella vulgaris and Scenedesmus obliquus grown under autotrophic, heterotrophic and mixotrophic conditions were evaluated. Domestic water, Bold’s medium and sewage water were used to cultivate the microalgae and the extracts were prepared in methanol and analyzed for biochemical (total phenolics) and antioxidant properties (DPPH assay, super oxide scavenging assay and antioxidant potential). The experiments were done in triplicates and significant correlation coefficients between antioxidant properties against phenolic content and growth conditions were interrelated. The amount of total phenolics content varied in growth conditions and ranged from 0.11-0.55 mg GAE g-1. Significant correlation co-efficient between phenolics and antioxidant properties of microalgae determined by DPPH, superoxide anion scavenging and total antioxidant activities were found in the study. The strongest positive correlation was found to be between total phenolics and DPPH activity in C. vulgaris (r = 0.997). In S. obliquus, the strongest positive correlation was between total phenolics and antioxidant potential (r = 0.091) at p<0.01 followed by superoxide scavenging (p<0.05). The findings indicated that phenolic compounds were the major contributors to the antioxidant properties of microalgae. The results demonstrated that strongest positive correlation was observed in mixotrophic conditions followed by autotrophic conditions in Chlorella whereas the correlation was significant under heterotrophic conditions in Scenedesmus followed by mixotrophic conditions.
  G. Sibi , Rashmi Wadhavan , Sneha Singh , Abhilasha Shukla , K. Dhananjaya , K.R. Ravikumar and H. Mallesha
  Bioactive compounds from plant latex are potential source of antifungic against post harvest pathogens. Latex from a total of seven plant species was investigated for its phytochemical and antifungal properties. Six fungi namely Aspergillus fumigatus, A. niger, A. terreus, F. solani, P. digitatum and R. arrhizus were isolated from infected fruits and vegetables and tested against various solvent extracts of latex. Analysis of latex extracts with phytochemical tests showed the presence of alkaloids, flavonoids, glycosides, phenols, saponins, steroids, tannins and terpenoids. Antifungal assay revealed the potential inhibitory activity of petroleum ether extracts against the postharvest fungal isolates. Various degree of sensitivity was observed irrespective of plant species studied with A. terreus and P. digitatum as the most susceptible ones. F. solani and A. fumigatus were moderately sensitive to the latex extracts tested. Among the plants, latex of Thevetia peruviana (75.2%) and Artocarpus heterophyllus (64.8%) were having potential antifungal activity against the isolates followed by Manilkara zapota (51.1%). In conclusion, use of plant latex makes interest to control postharvest fungal diseases and is fitting well with the concept of safety for human health and environment.
  G. Sibi
  Autotrophic cultivation of microalgae induces low biomass and lipid production and is difficult to be used in pilot scale production. Heterotrophic and mixotrophic algae allows higher growth rate, which in turn can accumulate higher biomass and lipid. Enhanced biomass and lipid production is crucial to use oleaginous microalgae for industrial application of biodiesel production. A fresh water microalga was isolated from waste water treatment plant and identified as Scenedesmus obliquus. The isolate was grown under varying cultural and nutrient conditions to increase biomass and lipid production. For this purpose, CO2 (10-160 mL min–1), temperature (20-45°C), fructose, maltose, glucose, sucrose and starch (10-50 g L–1), urea, sodium nitrate, potassium nitrate, ammonium nitrate and ammonium chloride (0.2-1.0 g L–1) were used. Optimum conditions were found by calculating specific growth rate and used to determine their influence on biomass and lipid production. At 40 mL min–1 (0.51%) CO2 concentration, 18.17 g L–1 biomass and 64.2% lipid production was obtained from the isolate. Glucose at 20 g L‾1 have produced 18.62 g L–1 and 62.6% whereas sodium nitrate at 0.8 g L–1 resulted in 14.64 g L–1 and 65.1% of biomass and lipid production at the end of 20 days culturing period. Temperature of 25°C was found optimum where 12.38 g L–1 and 60.9% of biomass and lipid were obtained. Based on the results, by choosing optimum cultural conditions and nutrient composition of the growth medium it is possible to increase both biomass and lipid production in microalgae.
  G. Sibi , Parul Chatly , Sayak Adhikari and K.R. Ravikumar
  Morinda citrifolia L., also known as noni or Indian mulberry is a small evergreen tree having antimicrobial, antitumor, antidepressant and immune enhancing effects. Various parts of M. citrifolia have been investigated for its phytochemical and antimicrobial properties. In the present study, methanolic extracts of leaf, stem and roots of M. citrifolia has been prepared and analyzed for their phytoconstituents. Qualitative analysis of the extracts revealed the presence of phenols, tannins, saponins, alkaloids, glycosides, flavonoids and steroids at various levels. Further, the extracts were tested against pathogenic bacterial and fungal strains at different concentrations to determine the influence of phytochemicals. The results revealed that root and leaf extracts has significant antimicrobial activities mainly due to phenolics and tannins. Staphylococcus epidermidis and Pseudomonas aeruginosa, major pathogens of nosocomial infections were effectively controlled by the extracts at various concentrations and root extract exhibited significant activity against Penicillium sp. and Fusarium sp. It has been revealed that, the bioactive substances have influenced the antimicrobial properties of M. citrifolia which could be exploited to formulate novel drugs from plant origin against bacterial and fungal infections.
  Geetika Pant , Chirag Simaria , Riyaz A.H. Varsi , Pooja Bhan and G. Sibi
  Methanolic extract from flaxseeds was investigated for its effect on anti-cholesterol and antioxidant activity. In vitro anti-cholesterol activity was measured by cholesterol enzymatic endpoint method using simvastatin as positive control. The total amount of phenolic compounds was determined spectrophotometrically and the results were expressed as Gallic Acid Equivalent (GAE g–1). Antioxidant activity of flaxseeds in vitro was measured in terms of DPPH free radical scavenging and total antioxidant potential assay. Increasing anti-cholesterol activity by flaxseeds was observed up to 20 min and a maximum inhibition was found as 93.04%, which was comparable to the anti-hyperlipidemic drug simvastatin (95.1%). Phenolic compound content of flaxseeds was found as 0.059 mg GAE g–1 and antioxidant potential was 1.037 mg mL–1. Lower DPPH free radical scavenging activity was observed after 30 min of incubation. The results indicated that flaxseed might reduce or control the cholesterol levels and oxidative damage and it is apparent that flaxseeds could contribute to new formulations with potential anti-cholesterol and antioxidant effects.
  G. Sibi , Aheibam Premita Devi , K. Fouzia and Bhimanagouda R. Patil
  Urinary Tract Infection (UTI) defines a condition in which the urinary tract is infected with a pathogen causing inflammation which is a common, distressing and occasionally life threatening condition. UTI in patients with diabetes mellitus are reported with asymptomatic bacteriuria. To ensure appropriate therapy, current knowledge of the organisms that cause UTI and their antibiotic susceptibility is mandatory. This study focused on the frequency of uropathogens and their antibiotic susceptibility in different gender of diabetic patients. Biochemical characterization of uropathogens revealed the prevalence of gram negative organisms and E. coli as the predominant isolate. Among the antibiotics tested, trimethoprim was found to be effective for empirical treatment of UTI and has covered the majority of urinary pathogens followed by nalidixic acid, chloramphenicol and kanamycin. Most of the isolates were resistant to oxytetracycline which is more frequently prescribed and indicates that increased consumption of a particular antibiotic can be a pathway to its resistance by the uropathogens. Conclusively, resistance rates among common uropathogens continue to evolve and appear to be increasing too many commonly used antimicrobial agents and a continued surveillance of resistance rates among uropathogens is needed to ensure appropriate recommendations for the treatment of the urinary tract infections.
  Shoaib Hamid and G. Sibi
  Background and Objectives: Physiological response in micro-algae triggered by nutrient stress to induce triacylglycerol accumulation is a promising solution to produce micro-algae based biofuel. The main objective of the study was to determine the response of micro-algae to nutrient stress by means of lipid accumulation. Materials and Methods: This study investigated the effect of nitrogen sufficient and nitrogen deficient conditions (N+ and N-) in micro-algal biomass and lipid productivity to determine the response to nutrient stress by micro-algae. A micro-alga was isolated from fresh water lake and amplification of 18S rDNA genes with the primers NS1 and NS4 resulted in 1300 bp fragments. The 18s rDNA sequences obtained were compared against sequences in the GenBank nucleotide collection through the Basic Local Alignment Search Tool (BLAST). Results: The micro-algae were identified as Chlorococcopsis minuta based on sequence similarities. In the case of micro-algae grown in nutrient limited conditions (N- media), the biomass content was lower with the yield of 8.4 g L1, however, there was a 62.5% increase in the total lipid content (11.7%) compared to nutrient sufficient conditions. Confocal imaging of lipid droplets stained by Nile red showed that lipid droplets was increased in N deficient (N-) conditions when compared to N sufficient (N+) conditions. Conclusion: Increase in lipid content of C. minuta was confirmed by accumulation of more lipid droplets under nutrient stress conditions.
  Sagar Grover , Shaily Rubina , Veera Malle Gowda and G. Sibi
  Background and Objective: Inorganic fertilizers are used to cultivate microalgae causing adverse environmental effects and increase the cost of microalgal cultivation. The objective of this study was to find a cheap, nutrient rich alternate to cultivate freshwater microalgae. Materials and Methods: Vermiwash at a concentrations of 25, 50, 75 and 100% were used to cultivate microalgae isolated from fresh water habitats. Specific growth rate and biomass concentrations were determined to evaluate the effect of vermiwash medium in comparison with Bold’s basal medium. Results: A total of 13 microalgae that belonged to the family Cyanophyceae and Chlorophyceae were isolated. Growth rate and biomass of microalgae were increased with higher concentrations when the vermiwash was used at a concentration of 25, 50 and 75%. At the same time, both the parameters were declined in undiluted vermiwash indicating the algal growth inhibition under high levels of nutrients. Conclusion: Utilization of vermiwash is feasible to cultivate fresh water microalgae thereby fulfilling the nutrient requirements and reducing the use of inorganic fertilizers.
 
 
 
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