Biomethanation of organic matter is now recognized as a viable alternative for production of energy. Among various biomass sources screened, Leucaena leucocephala, having a high biomethanation rate, has been identified as a potential substrate for large-scale methane generation. During semi-continuous fermentations at 30 °C with volatile solids (VS) ranging from 1.0-2.5 g l-1 at hydraulic retention time (HRT) ranging from 10-18 days, the yield of product gas per gram of volatile solids input was about 0.45-0.601 in the case of L leucocephala and 0.15-0.201 from cow-manure. Mass spectrometric analysis of the product gas from L leucocephala indicated a methane content of 78-80%. Batch fermentation for 80 days with input volatile solids of 40-44 g in a 21 digester resulted in a gas yield of 0.87 l g-1 volatile solids input for L leucocephala and 0.33 l g for cow-manure. The complex degradation of solid organic matter involves multiphase interactions between microbes and their environment; optimisation and separation of predominantly acidogenic and methanogenic species was achieved in a multi-stage digester with separate compartments. This design was used for degradation studies of L. leucocephala, which, from the results presented, appears to be a good candidate for an 'energy-farm' for large-scale biomethanation. © 1986.

Krishnamoorthy Sankar

P. M Chandra Sekaran

Kalyanaraman Lalitha

CHEMICAL EQUIPMENT - Reactors

CHEMICAL REACTIONS - FERMENTATION

Energy resources

Methane

BIOMETHANATION

LEUCAENA LEUCOCEPHALA

MULTISTAGE DIGESTER DESIGN

Biomass

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Biomethanation of Leucaena leucocephala: a potential biomass substrate

Fuel

Our observations on the growth stimulatory nature of mimosine, (β-(3-hydroxy-4-pyridon-1-yl)-L-alanine), the toxic non-protein plant amino acid, in some model experimental systems, warranted sensitive and selective routine estimations. For the determination of both mimosine and DHP, an indirect spectrophotometric method was developed based on their individual reaction with known excess of DZSAM and by estimating the remaining DZSAM with N-(1-naphthyl)ethylene-diamine (NEDA). The resultant decrease in the secondary coupled product was measured at 540 nm. On equimolar basis, DHP had 40% of the reactivity of mimosine while interference from other relevant compounds was 15-35%. The determination of mimosine and DHP in tissue samples under different physiological conditions was effected after paper chromatographic separation of mimosine and DHP with distinctly differing Rf, from other compounds. The indirect method is superior in terms of absolute selectivity, sensitivity and ease of applicability with linear decreases in absorbance, proportional to increasing concentrations of mimosine from 0.1 to 0.75 μM or DHP from 0.2 to 1.5 μM and with recoveries of 99.2 to 100.5%. © 2006 Springer-Verlag.

Amino Acids

Selective determination of mimosine and its dihydroxypyridinyl derivative in plant systems

A simple and sensitive indirect spectrophotometric method is described for the determination of mimosine based on its reaction with diazotized sulfanilamide (DZSAM). DZSAM couples with N-(1-naphthyl)ethylenediamine (NEDA) forming a pink colored azodye, absorbing maximally at 540 nm (εmax=27 mM-1 cm-1). In the present method, mimosine was first reacted with known excess of DZSAM and the unreacted DZSAM was determined by coupling with NEDA. The reaction of mimosine with DZSAM proceeded optimally at neutral pH. The decrease in absorbance of the DZSAM-NEDA-coupled product obeyed Beer's law in the concentration range of 0.005-0.15 μg ml-1 of mimosine. The present method was applied to estimate mimosine in plant extracts containing lesser than 0.05 μg ml -1 with recovery at 99±0.41%. The method described is superior to other reported methods in terms of ease of adaptability and sensitivity. © 2003 Elsevier B.V. All rights reserved.

Talanta

Determination of mimosine by a sensitive indirect spectrophotometric method

An anaerobic methylotrophic methanogenic enrichment culture, with sustained metabolic characteristics, including that of methanation for over a decade, was the choice of the present study on interspecies interactions. Growth and methanation by the enrichment were suppressed in the presence of antibiotics, and no methanogen grown on methanol could be isolated using stringent techniques. The present study confirmed syntrophic metabolic interactions in this enrichment with the isolation of a strain of Pseudomonas sp. The organism had characteristic metabolic versatility in metabolizing a variety of substrates including alcohols, aliphatic acids, amino acids, and sugars. Anaerobic growth was favoured with nitrate in the growth medium. Cells grown anaerobically with methanol, revealed maximal nitrate reductase activity. Constitutive oxidative activity of the membrane system emerged from the high-specific oxygen uptake and nitrate reductase activities of the aerobically and anerobically grown cells respectively. Cells grown anaerobically on various alcohols effectively oxidized methanol in the presence of flavins, cofactor FAD and the methanogenic cofactor F420, suggesting a constitutive alcohol oxidizing capacity. In cells grown anaerobically on methanol, the rate of methanol oxidation with F420 was three times that of FAD. Efficient utilization of alcohols in the presence of F420 is a novel feature of the present study. The results suggest that utilization of methanol by the mixed culture would involve metabolic interactions between the Pseudomonas sp. and the methanogen(s). Methylotrophic, methanogenic partnership involving an aerobe is a novel feature hitherto unreported among anaerobic syntrophic associations and is of ecological significance.

Journal of Biosciences

Metabolic characteristics of an aerobe isolated from a methylotrophic methanogenic enrichment culture

Glycohydrolases assume significance in the metabolism of biological systems and have important industrial applications in the areas of pharmaceuticals, food, and medicine. Glycosidases were screened in germinating seeds, and attempts were made to enhance their levels. Screening of glycosidases in the seedlings during a 72 h germination period revealed higher levels of β-glucosidase and β-galactosidase in Trigonella foenum- graecum compared to Cicer arietinum and Vigna radiata. Activity of β- galactosidase was in general higher than that of β-glucosidase in all the seedlings tested. During growth, exposure of the seedlings to an allelochemical, mimosine, at 0.1 mM resulted in the enhancement of enzyme levels by 50% in the seedlings of T. foenum-graecum, whereas the addition of mimosine to the assay medium in vitro did not affect the enzyme activities. Hydrolytic activity was enhanced by addition of glycerol in the medium up to 0.1 M in the case of β-glucosidase and with 0.05 M in the case of β- galactosidase. In general, the hydrolytic rate was higher by about 30% in the seedlings exposed to mimosine compared to that of the control. Concomitant enhancement in the rates of transgalactosidation by 51% and transglucosidation by 23% was also noted, underscoring the relevance of plant glycohydrolases for appropriate applications.

Journal of Agricultural and Food Chemistry

Enhancement of β-glucosidase and β-galactosidase of Trigonella foenum- graecum by exposure to the allelochemical mimosine

Uptake of Na275SeO3 by mitochondria of the larvae of the insect C. cephalonica reared at different dietary selenium (Se) levels revealed: 1. A proportional increase in the uptake with externally added Na275SeO3 in concentrations upto 25.32 μM; and 2. At each added selenite concentration, an increase up to 60 min, with linearity up to 15-30 min. A differential affinity for Na275SeO3 was elicited in the mitochondrial protein fractions of different dietary Se groups and correlated well with the pattern and the ratio of distribution of incorporated75Se in protein to nonprotein fractions. Kinetic studies on75Se uptake by whole mitochondria negated passive diffusion of selenite and revealed a trend of negative cooperativity confirmed by Hill and Scatchard plots. Half saturation value was estimated to be approx 13 nmole Se/mg mitochondrial protein. Scatchard plot for75Se uptake was biphasic and the high affinity binding sites were estimated to be around 5 nmole/mg mitochondrial protein. Calculated dissociation constants revealed maximal affinity for75Se in the 1.5 ppm group (KSe 0.0034 n M) and minimal in the basal group (KSe 0.007 n M). In the mitochondria of all the three dietary Se groups, the estimated low affinity sites amounted to be 15-19 nmole/mg mitochondrial protein. Inherent Se in the mitochondria of the high Se group positively enhanced the incorporation of75Se in the mitochondrial protein fraction. About 20-30% of the total uptake was indicated to be energy linked as revealed by studies with respiratory inhibitors. Addition of sulfite and sulfate (5-25 μM) in the medium, inhibited75Se uptake by 35-55%, suggestive of the involvement of the dicarboxylate port. Thiol interactive75Se uptake was confirmed by the inhibition mediated by mersalyl and NEM up to 50-70%. The study revealed thiol-selenite interactions of metabolic significance during selenite uptake. © 1995 Humana Press Inc.

Journal	Fuel
ISSN	00162361
Open Access	No