Pushpito Kumar Ghosh

Kappaphycus alvarezii as a source of bioethanol.

The present study describes production of bio-ethanol from fresh red alga, Kappaphycus alvarezii. It was crushed to expel sap--a biofertilizer--while residual biomass was saccharified at 100 °C in 0.9 N H2SO4. The hydrolysate was repeatedly treated with additional granules to achieve desired reducing sugar concentration. The best yields for saccharification, inclusive of sugar loss in residue, were 26.2% and 30.6% (w/w) at laboratory (250 g) and bench (16 kg) scales, respectively. The hydrolysate was neutralized with lime and the filtrate was desalted by electrodialysis. Saccharomyces cerevisiae (NCIM 3523) was used for ethanol production from this non-traditional bio-resource. Fermentation at laboratory and bench scales converted ca. 80% of reducing sugar into ethanol in near quantitative selectivity. A petrol vehicle was successfully run with E10 gasoline made from the seaweed-based ethanol. Co-production of ethanol and bio-fertilizer from this seaweed may emerge as a promising alternative to land-based bio-ethanol.

An alternative method for the regio- and stereoselective bromination of alkenes, alkynes, toluene derivatives and ketones using a bromide/bromate couple

Mixtures of NaBr and NaBrO3 in two different ratios have been used for highly stereoselective bromination of alkenes and alkynes, and regioselective bromine substitution at the α-carbon of ketones and at the benzylic position of toluene derivatives. The reactions were conducted in an aqueous acidic medium under ambient conditions. The solid reagents were prepared from the intermediate obtained in the “cold process” of bromine manufacture and are stable, non-hazardous and inexpensive to prepare. This procedure provides an efficient and practical alternative to conventional procedures using liquid bromine directly or indirectly.

Eco-friendly and versatile brominating reagent prepared from a liquid bromine precursor

Facile bromination of various organic substrates has been demonstrated with a 2 : 1 bromide:bromate reagent prepared from the alkaline intermediate of the conventional bromine recovery process. The reagent is acidified in situ to generate HOBr as the reactive species, which effects bromination. Aromatic substrates that have been successfully brominated under ambient conditions without use of any catalyst include phenols, anilines, aromatic ethers and even benzene. Non-aromatic compounds bearing active methylene group were monobrominated selectively with the present reagent and olefinic compounds were converted into the corresponding bromohydrins in moderate yields. By obtaining the present reagent from the liquid bromine precursor, the twin advantages of avoiding liquid bromine and producing the reagent in a cost-effective manner are realised. When coupled with the additional advantage of high bromine atom efficiency, the present protocol becomes attractive all the way from “cradle to grave”.

A new, environment friendly protocol for iodination of electron-rich aromatic compounds

A new environment friendly procedure for effective aromatic iodination is presented. A mixture of potassium iodide and potassium iodate is used in the presence of an acid for in situ iodination of aromatic compounds.

Detection and quantification of some plant growth regulators in a seaweed-based foliar spray employing a mass spectrometric technique sans chromatographic separation.

The sap expelled from the fresh harvest of Kappaphycus alvarezii , a red seaweed growing in tropical waters, has been reported to be a potent foliar spray. Tandem mass spectrometry of various organic extracts of the sap confirmed the presence of the plant growth regulators (PGRs) indole 3-acetic acid, gibberellin GA(3), kinetin, and zeatin. These PGRs were quantified in fresh state and after 1 year of storage by ESI-MS without recourse to chromatographic separation. Quantification was validated against HPLC data. The results may be useful in correlating with the efficacy of the sap. The methodology was extended to two other seaweeds. The method developed is convenient and precise and may find application in other agricultural formulations containing these growth hormones.

Electroactive Coatings of Tris(bipyridyl)‐ and Tris(o‐phenanthroline)‐Ruthenium(II) Attached to Electrodes via Hydrosilylation or Electropolymerization of Vinyl Derivatives

Synthetic methods are given for the introduction of a vinyl group into αα-bipyridine (bipy) and o-phenanthroline (phen). These groups have beenemployed to attach Ru(bipy) 3 2+ and Ru(phen) 3 2+ to Pt electrodes by (i)hydrosilylation followed by polycondensation with the electrode, or (ii) cycling the electrode to negative potentials to induce anionic polymerization at the surface. The thickness of silanized films increased linearly withcontact time, after an induction period, and also increased with increasingtemperature. Ru(bipy) 3 2+ coatings prepared in this way showed reversiblecyclic voltammograms up to about 20 layers. For thicker films the electrodekinetics became increasingly slow, and the amount of electroactive materialactually decreased. Silanized Ru(phen) 3 2+ coatings showed sluggish behavioreven at lower coverages. The films were stable upon anaerobic storage (exposure to air reduced stability), but showed electrochemical instabilities.Scanning to potentials sufficiently negative to reduce Ru 2+ produced immediate loss of electroactivity. Holding the electrode at a potential sufficiently positive to produce Ru 3+ led to a slow loss of electroactivity, whilecontinuous scanning of the Ru -3+ /2+ wave led to much faster losses (time scaleof minutes), the rate increasing with scan rate. A still more rapid loss wasobserved after scanning the redox wave of ferrocene dissolved in the electrolyte, although the amplitude of the ferrocene wave was nearly undiminished with respect to that observed at an uncoated electrode. Thus thesilanized film is permeable to counterions and solution redox species, but isalso fragile, and susceptible to disruption by the ion fluxes. Electropolymerization gave a Ru(phen) 3 2+ coating which was much more stable, showing verylittle loss upon continuous cycling. However the cathodic peak, but not theanodic peak, gradually became less reversible. A slow conformation changeresulting in inhibited counterion efflux from the film upon reduction is suggested. When electropolymerized at a TiO 2 electrode, the Ru(phen) 3 2+ film,in contact with an aqueous solution containing hydroquinone as mediator,supports a steady photocurrent which is stable for at least 15 hr.

Fuel intermediates, agricultural nutrients and pure water from Kappaphycus alvarezii seaweed

The present work reports a standalone integrated scheme for the production of 5-hydroxymethyl furfural (HMF) and potassium sulphate (K2SO4) from granular biomass rich in the sulphated polysaccharide, κ-carrageenan. Fresh Kappaphycus alvarezii seaweed was crushed to expel the juice rich in KCl (0.7 m3 t−1 of fresh seaweed) and granular biomass (0.04 t dry weight per t of fresh seaweed). The latter yielded κ-carrageenan through seawater extraction. HMF was derived from this phycocolloid through reaction with Mg(HSO4)2 acid catalyst and isolated in pure form. Galactose was a co-product which remained in the aqueous phase. The aqueous phase was recycled up to 10 times by maintaining a constant acid strength, and utilized thereafter for the recovery of K2SO4. Selective crystallization of K2SO4 was guided by the phase diagram and use was made of a part of the seaweed juice in this process. The spent aqueous phase rich in galactose was subjected to further reaction with HCl obtainable through bipolar electro-dialysis (ED) of seaweed juice. The reaction yielded levulinic acid (LA) and formic acid (FA) in nearly equal proportions. The processing of 1 t of granular biomass was computed to require 30.15 GJ of energy and would yield 0.18 t HMF, 0.056 t LA, 0.020 t FA, 0.27 t K2SO4, and 5.77 m3 pure water. The process energy requirement for the scheme can be met from additional supplies of granule (3.35 t). Combustion/gasification of this biomass would yield additionally 0.74 t glaserite fertilizer and the required amount of H2SO4 for Mg(HSO4)2 preparation.

Microbial synthesis of polyhydroxyalkanoate using seaweed-derived crude levulinic acid as co-nutrient.

Production of polyhydroxyalkanoates (PHAs) from Jatropha biodiesel residues, namely crude glycerol and oil cake hydrolysate, has been reported previously. Halomonas hydrothermalis (MTCC accession no. 5445; NCBI Genbank accession no. GU938192), a wild marine strain, was used in the bio-synthesis. The present study was initiated to vary the properties of the polymer. Seaweed-derived crude levulinic acid (SDCLA), containing formic acid, residual sugars and dissolved minerals additionally, was proposed as co-feed along with the biodiesel residues. Experiments were conducted at 100mL scale in batch process. Whereas the PHA yield was only 0.40 ± 0.01 g when only biodiesel residues were employed, it rose to 1.07 ± 0.02 g in presence of 0.35% (w/v) of SDCLA. The corresponding carbon utilisation efficiencies were 29.3% and 57.5%, respectively. 3-Hydroxy valerate incorporation in the PHA was pronounced in presence of SDCLA, with associated changes in polymer properties. The microbial synthesis fared poorly when SDCLA was substituted with pure levulinic acid. Thus, Halomonas hydrothermalis had a poor response to levulinic acid, as such, and other constituents present in SDCLA appear to have played a vital role in bacterial cell division and accumulation of PHA. Biodegradability tests in moist soil were also conducted as part of the study. Marine microalgal cultivation for biodiesel and seaweed cultivation for fuels may help generate biodiesel residues and crude levulinic acid in proximity, which would open up the possibility of large scale PHA manufacture in efficient and practical manner in the future through the methodology of the present study.

Surfactant-induced coagulation of agarose from aqueous extract of Gracilaria dura seaweed as an energy-efficient alternative to the conventional freeze–thaw process

Surfactant-induced coagulation of agarose from alkali-treated Gracilaria dura seaweed extract (SE) is reported. The new approach, which was suitable for linear galactans with low sulphate content is an alternative to the traditional energy intensive process of “freeze–thaw” cycles employed for product isolation from the extract. Only nonionic surfactants were effective, and detailed studies were undertaken with octyl phenol ethoxylate (Triton X-100). The coagulated product was successively washed with water and water–isopropyl alcohol (IPA) to yield a fine powder of agarose in 13–15% yield (with respect to dry biomass). The product exhibited excellent properties [sulphate content: 0.2% w/w; degree of electro-endosmosis: 0.13; gel strength: 2200 g cm−2 (1% gel, w/v); and gelling temperature: 35 ± 1 °C] essential for demanding molecular biology applications, and the desired gel electrophoretic separation of DNA and RNA was demonstrated. It was further confirmed that there was no degradation of nucleic acids in the gel. The agarose-depleted extract, along with water used for washings, was subjected to reverse osmosis for recovering the surfactant in concentrated form for its subsequent reuse. Energy savings from the improved process were assessed.

Electrolytic synthesis of succinic acid in a flow reactor with solid polymer electrolyte membrane

This paper describes the galvanostatic synthesis of succinic acid from maleic acid in an ion exchange membrane flow cell. The electrolysis was carried out at stainless steel, lead and copper cathodes under variable conditions of current density and substrate concentration. Depending upon the experimental conditions, the yield of succinic acid varied from 95 and 99% with a coulombic efficiency of 80–99%. The product was characterized by various physicochemical techniques, viz. 1H-NMR, IR and UV–Visible spectroscopy and elemental analysis. The operational conditions giving maximum yield of product were identified. The mechanism of electrochemical reduction of maleic acid and advantages of using a catholyte without supporting electrolyte are discussed.