Biomethanation of leaves of the legume L. leucocephala operated in batch reactors at different input volatile solids (12-18 g/L) proceeded in distinct metabolic phases. An initial cellulolytic phase of 4 d was followed by an early and active methanogenic phases (5-21 d) and a terminal phase of low-rate methanogenesis. Hydrolysis of cellulose was concentration-dependent and resulted in increased volatile acid levels. The trend of changes showed some variations at different input volatile solids. The changes in the levels of volatile acids followed an oscillatory pattern. The controlled rate of cellulose hydrolysis, levels of volatile acids, and steady-state levels of soluble carbohydrates and reducing sugars observed during active methanogenesis are indicative of interactive metabolic regulations. © 1990 Humana Press Inc.

Kalyanaraman Lalitha

carbohydrate

cellulose

ANAEROBIC METABOLISM

article

higher plant

nonhuman

EMBRYOPHYTA

LEUCAENA LEUCOCEPHALA

LEUCOCEPHALA

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

Interactive metabolic regulations during biomethanation ofLeucaena leucocephala

Applied Biochemistry and Biotechnology

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

Anaerobic digestion of calf skin collagenous waste was optimized for a batch process based on accelerated maximal methane yield per gram of input volatile solid. A kinetic analysis with respect to changes in the levels of volatile solid, collagen, amino sugars, amino acids, hydroxyproline, ammonium ions, and volatile fatty acid were followed for a period of 80 d. Distinct metabolic phases included an initial high rate collagenolysis for 4 d, with 50% degradation and was followed by an acidogenic phase between 4-12 d with voltatile fatty acids levels increasing to 215 mmol/L. Subsequently methanogenesis ensued and was maximal between 12-24 d when volatile fatty acids attained steady state levels. During the period of 80 d, the overall decrease in volatile solid level was 65%, whereas the collagen level declined by 85% with 0.45 L of methane yield/g of volatile solid degraded. Based on the levels of various metabolites detected, the concept of interactive metabolic control earlier proposed has been validated. © 1994 Humana Press Inc.

Journal	Applied Biochemistry and Biotechnology
Publisher	Humana Press
ISSN	02732289
Open Access	No