Onkar Nath Tiwari

Characterization and Optimization of Bioflocculant Exopolysaccharide Production by Cyanobacteria Nostoc sp. BTA97 and Anabaena sp. BTA990 in Culture Conditions

Bioflocculant exopolysaccharide (EPS) production by 40 cyanobacterial strains during their photoautotrophic growth was investigated. Highest levels of EPS were produced by Nostoc sp. BTA97 and Anabaena sp. BTA990. EPS production was maximum during stationary growth phase, when nitrogenase activity was very low. Maximum EPS production occurred at pH 8.0 in the absence of any combined nitrogen source. The cyanobacterial EPS consisted of soluble protein and polysaccharide that included substantial amounts of neutral sugars and uronic acid. The EPS isolated from Anabaena sp. BTA990 and Nostoc sp. BTA97 demonstrated high flocculation capacity. There was a positive correlation between uronic acid content and flocculation activity. The flocculant bound a cationic dye, Alcian Blue, indicating it to be polyanionic. The 16S rRNA gene sequences for Nostoc sp. BTA97 and Anabaena sp. BTA990 were deposited at NCBI GenBank, and accession numbers were obtained as KJ830951 and KJ830948, respectively. The results of these experiments indicate that strains Anabaena sp. BTA990 and Nostoc sp. BTA97 are good candidates for the commercial production of EPS and might be utilized in industrial applications as an alternative to synthetic and abiotic flocculants.

Production of biodiesel from microalgae through biological carbon capture: a review

Gradual increase in concentration of carbon dioxide (CO2) in the atmosphere due to the various anthropogenic interventions leading to significant alteration in the global carbon cycle has been a subject of worldwide attention and matter of potential research over the last few decades. In these alarming scenario microalgae seems to be an attractive medium for capturing the excess CO2 present in the atmosphere generated from different sources such as power plants, automobiles, volcanic eruption, decomposition of organic matters and forest fires. This captured CO2 through microalgae could be used as potential carbon source to produce lipids for the generation of biofuel for replacing petroleum-derived transport fuel without affecting the supply of food and crops. This comprehensive review strives to provide a systematic account of recent developments in the field of biological carbon capture through microalgae for its utilization towards the generation of biodiesel highlighting the significance of certain key parameters such as selection of efficient strain, microalgal metabolism, cultivation systems (open and closed) and biomass production along with the national and international biodiesel specifications and properties. The potential use of photobioreactors for biodiesel production under the influence of various factors viz., light intensity, pH, time, temperature, CO2 concentration and flow rate has been discussed. The review also provides an economic overview and future outlook on biodiesel production from microalgae.

Isolation, screening and characterization of a novel extracellular xylanase from Aspergillus niger (KP874102.1) and its application in orange peel hydrolysis

In the present work, a potent xylanase producing fungal strain Aspergillus niger (KP874102.1) was isolated through cultural and morphological observations from soil sample of Baramura forest, Tripura west, India. 28S rDNA technique was applied for genomic identification of this fungal strain. The isolated strain was found to be phylogenetically closely related to Aspergillus niger. Kinetic constants such as Km and Vmax for extracellular xylanase were determined using various substrate such as beech wood xylan, oat spelt xylan and CM cellulose through Lineweaver-Burk plot. Km, Vmax and Kcat for beech wood xylan are found to be 2.89mg/ml, 2442U and 426178Umlmg-1 respectively. Crude enzyme did not show also CM cellulose activity. The relative efficiency of oat spelt xylan was found to be 0.819 with respect to beech wood xylan. After acid hydrolysis, enzyme was able to produce reducing sugar with 17.7, 35.5, 50.8 and 65% (w/w) from orange peel after 15, 30, 45 and 60min incubation with cellulase free xylanase and maximum reducing sugar formation rate was found to be 55.96μg/ml/min. Therefore, the Aspergillus niger (KP874102.1) is considered as a potential candidate for enzymatic hydrolysis of orange peel.

Characterization, genetic regulation and production of cyanobacterial exopolysaccharides and its applicability for heavy metal removal

Cyanobacteria are uniquely suited for the development of sustainable bioproduction platforms but are currently underutilized due to lack of genetic tools. Exopolysaccharide (EPS) is of significant biotechnological importance due to their technological application in various industries. It has been found that most of the research works are focused on isolation and characterization of new exopolysaccharides from microbial sources. The exopolysaccharides from cyanobacteria have been poorly explored despite their original structural features associated with specific biological and physicochemical properties. However, it could increase in a near future through the use of inexpensive cyanobacterial platform as well as available information on the structural data and specific properties of these biopolymers. This review covers genetic regulation for production of exopolysaccharide, analytical strategies for their characterization, evaluation of structure property relationship and design of extraction protocol from cyanobacterial biomass. In addition applications of exopolysaccharide for removal of heavy metal from wastewater are critically reviewed.

Advances in exopolysaccharides based bioremediation of heavy metals in soil and water: A critical review

Extracellular polysaccharides or Exopolysaccharides (EPS) are extensively studied bacterial byproducts with high molecular weight attributed to several applications. In spite of their application in the field of food, pharmaceutical, nutraceutical, herbicidal and cosmeceutical industries they were well known for their efficiency in the bioremediation of water and soil tainted with heavy metals. These heavy metals are comparatively high in density than water and are involved in several biological processes. But slight increase in levels can create toxicological bias. The techniques like electrodialysis, chemical precipitation, ion exchange and membrane separation have a lot of disadvantages akin to high energy consumption, high cost, partial exclusion, and creation of poisonous mire. In this context, EPS has a top role to play in the bioremediation of heavy metals. This review gives the critical assessment of the extensive work done to deal this issue by different groups in the last five years. It also explains how different natural circumstances have attributed to the advancement of EPS production, thereby increasing the capacity of bioremediation to deal the issue of heavy metal contamination in both soil and water. A detailed discussion of the EPS formation by bacteria and fungi with their applicability was reported.