S.C. Lahiri

Cellulose degrading capabilities of cellulolytic bacteria isolated from the intestinal fluids of the silver cricket

Cellulose degrading bacteria were isolated from the intestinal fluid of the silver cricket Lepisma Sp. and a culture was developed anoxigenically in the cellulose degrading medium following standard laboratory techniques. The cellulolytic activity of the microbe was examined in a broth culture using Whatman 42 filter paper as the source of insoluble cellulose. Activity was measured spectrophotometrically (620nm) following Anthrone reaction of the culture filtrate and the sugar produced was quantified as a factor of time. The pH optimum was found to be between 7 and 8. Temperature profile optimum was between 30–37°C.The microbes appeared as white colonies on a solid medium. Morphologically the bacterium is a gram-positive nonspore forming rod which was tentatively identified as a new strain of Cellulomonas sp.

Methane emission from rice paddy soils, aerotolerance of methanogens and global thermal warming.

In vitro methane emissions from different rice paddy soils and algal mats were studied under anoxic and atmospheric conditions. Methane production from rice paddy soils cultivating different strains of rice was found to be appreciable under anoxic conditions, but considerably reduced under atmospheric conditions, and dependent on rice cultivars (strains). A contradictory result was obtained with a Gobindabhog cultivated rice field (a strain of rice with aroma), where methane yield under anoxic was greater than that under atmospheric conditions. The results indicated aerotolerance of methanogens or the possible existence of microaerophilic methanogens. The results from algal mats corroborated these findings.Methane has been considered to be an important greenhouse gas contributing significantly to global thermal warming (GTW). Flooded rice paddy fields have been considered to be a most prominent source of abiogenic methane emission, though considerable uncertainty exists regarding the true estimates of methane emission. Factors affecting methane emission and its abatement have been examined. In spite of increasing methane emission, rice cultivation leads to enormous utilization of the ‘green house gas’ carbon dioxide and release of oxygen to the atmosphere. Thus, the contribution of methane to GTW (from rice paddy cultivation) is more than compensated by carbon dioxide absorption.Appropriate steps have been suggested for the reduction of methane emissions, the most important of which is the restoration of methane sinks.

Thermodynamics of 1,10-phenanthrolium ion in ethanol—water

Abstract Dissociation constants of the 1,10-phenanthrolium ion in different aqueous ethanolic solutions have been determined spectrophotometrically and pH-metrically. Some aspects of the role of the solvent have been discussed.

Effect of physical irradiation and chemical mutagen treatment on methane production by methanogenic bacteria

Biomethanation is one of the desirable options for obtaining clean fuel from abundant renewable biomass resources. Improvement of biomethane production may be achieved by using improved strains of microbes, particularly the terminal microbes – the methanogens. Attempts have been made to improve the efficiency of the methanogens isolated from local sources by subjecting the methanogens to mutagenic changes by physical (by γ irradiation, neutron bombardment) or chemical (by addition of chemicals like acridine orange, colchicine) means. The effects of the treated methanogens on biomethanation were studied. γ Irradiation or neutron bombardment mutagenesis was dose-dependent and time-dependent. High doses proved to be lethal but methanogens were found to be to some extent radiation resistant when subjected to irradiation at small doses for short duration (∼5–10 s). No or marginal improvement of methane production occurred for the two strains TDM and TRM. Improvement of methane production occurred from successive transfers of radiation treated strain SSM. Chemical mutagens invariably inhibited biomethanation and the inhibition was dose dependent.

Biomethanation of a cellulose-based substrate in the presence and absence of a cellulolytic bacterium

The effect of co-culturing a methanogen isolated from a paper mill waste (PMW) with cellulolytic bacteria isolated from the intestinal fluids of the silver cricket (Lepisma saccharina) on the biomethanation of filter paper strips was examined. The autoclaved filter paper strips were subjected to biomethanation in AC 21 medium inoculated with methanogen PMW in the presence and in absence of a co-culture of cellulolytic bacteria. In spite of poor initial response, methane production in the presence of the cellulolytic co-culture were found to increase gradually upto 25 days, after which a reduction in methane production was observed. Analysis of the results in terms of increased cellulose degradation in the presence of cellulolytic bacteria has been made.

Effect of pesticide (Tara-909) on biomethanation of sewage sludge and isolated methanogens

Pesticides (like Tara-909, etc.) have been used extensively to control pests and insects in the rice paddy cultivation which is also an important abiogenic source of methane, a green house gas. In order to study the inhibiting effect of Tara-909 on methanogens, in vitro studies of the effect of the pesticide Tara-909, on the biomethanation of: (i) sewage; (ii) prereduced enriched methanogenic medium inoculated with methanogens; (iii) sewage and prereduced enriched methanogenic medium inoculated with isolated methanogens; and (iv) autoclaved sewage sludge inoculated with methanogens were completed. Tara-909 has been found to inhibit biomethanation in all cases, i.e., methane generation from rice paddy fields is likely to be reduced considerably.

Thermodynamics of 1,10-phenanthrolinium ion and ferrous-1,10 phenanthroline complex in dioxane—water and ethanol—water at 25°c

Abstract Enthalpies of formation of 1,10-phenanthrolinium ion and ferrous-1,10-phenanthroline (tris) complex in dioxane—water and ethanol—water media at 25°C have been determined by calorimetry. Results are discussed in the light of ion—solvent and solvent—solvent interactions.

Thermodynamics of 2,2′-dipyridinium ion and its iron(II) complex in methanol—water mixture at 25°C

Abstract The enthalpies of formation of the 2,2′-dipyridinium ion and the 2,2′-dipyridyl-iron(II) complex in methanol—water media at 25°C have been determined by caloriumetry. The entropy-changes have been calculated combining the enthalpy values with the corresponding free-energy changes previously reported. The role of solvents on the thermodynamic parameters has been discussed.

Solvent effects on the dissociation of 2,2'-bipyridine and 1,10-phenanthroline in aqueous binary mixtures of 2-methoxyethanol and 1,2-dimethoxyethane

Abstract The thermodynamic dissociation constants for isoelectric reactions of the type LH + ⇌ L + H + (where L = 2,2-bipyridine or 1,10-phenanthrolme) have been determined pH-metrically and spectrophotometrically at 298 K in aqueous binary mixtures of 2-methoxyethanol and 1,2-dimethoxyethane (0–90 wt% of organic solvent). The p K values were found to decrease gradually and pass through minima at around 70–80 wt% of the organic solvents. The effect of the solvent on the dissociation of the protonated forms of the ligands is discussed in terms of the standard Gibbs energy of transfer of H + Δ G t XXX (H + ) from water to the mixed solvents, and also in terms of the individual species involved in the dissociation process. The overall dissociation behaviour was found to be governed by specific solute-solvent interactions in the solvent media besides the relative solvent basicities.

Biomethanation of plant materials and agricultural residues using dung samples as wild population of microbes and also with isolated methanogens

Recycling of plant materials and agricultural residues for biomethanation was attempted in vials. The methanogenic activities of certain sewage samples have also been tested. Both sterilized and non-sterilized biomasses were used. Biomethanation was carried out with dung samples (cow, goat, buffalo, piggery wastes and poultry wash) as wild populations of microbes and in combination with other microbial isolates (isolated in the laboratory).Biomethanation had been observed to be good in most cases and particularly with the sterilized biomass. Mixed inoculum (dung samples and poultry wash) was found to be best for biomethanation. Of the microbe isolates, isolates from buffalo, pig and paper mill wastes appear to be most effective. Pretreated sawdust and rice straw were found to be good subtrates for biomethanation. Of the different plant biomass used Spirogyra (algae), Ipomea and water hyacinth were most effective whereas Jatropa gossypifolia and Parthenium sp. were the least effective. Biomethanation of Spirogyra was carried out both in anoxic and oxic conditions. Though methane production decreased enormously under oxic conditions, definite methane production continued indicating that the biomethanation process is not exclusively anoxic. Similarly, biomethanation of sewage samples from different sewage treatment plants were carried out with and without isolated methanogens and methane production was found to be moderate.