Interactive metabolic regulations during biomethanation ofLeucaena leucocephala
01 Oct 1990-Applied Biochemistry and Biotechnology (Springer Science and Business Media LLC)-Vol. 26, Iss: 1, pp 73-84
TL;DR: 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.
Abstract: Biomethanation of leaves of the legumeL. 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.
Citations
More filters
TL;DR: Heat, moisture, chemical treatments, ensiling, rotation feeding, cutting management of the plant, new hybrids, introducing micro-organisms into the rumen of ruminants that are unable to detoxify mimosine, and preparing protein isolate from Leucaena seeds have all been used to overcome Mimosine toxicity.
Abstract: Leucaena leucocephala is one of the fastest-growing leguminous trees. Its foliage is used as animal feed, and its leaves and seeds are used as human food in Central America, Indonesia, and Thailand...
38 citations
Cites background from "Interactive metabolic regulations d..."
...It is an important crop encouraged under the social forestry schemes in drought-prone areas and semi-arid tracts in India, as it provides useful timber as well as leaves for fuel and energy and feed purposes [1, 3-6]....
[...]
TL;DR: The concept of interactive metabolic control earlier proposed has been validated based on the levels of various metabolites detected and the overall decrease in volatile solid level was 65%, whereas the collagen level declined by 85%.
Abstract: 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 4d, with 50% degradation and was followed by an acidogenic phase between 4-12 d with volatile 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.
26 citations
TL;DR: The results suggest that utilization of methanol by the mixed culture would involve metabolic interactions between the Pseudomonas sp.
Abstract: 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 ofPseudomonas 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 thePseudomonas 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.
8 citations
Cites background from "Interactive metabolic regulations d..."
...In addition, research from our laboratory provided evidence for an efficient interactive metabolic control prevailing during active biomethanation of polymeric carbohydrates (Krishnan and Lalitha 1990) or proteins (Swaminathan 1995)....
[...]
...Involvement of microbial consortia or communities composed of two or more taxa to effect efficient catabolism of different compounds were shown by many studies including those from our laboratory (Krishnan and Lalitha 1990; Lalitha et al 1994a; Wolfaardt et al 1994)....
[...]
TL;DR: Enrichment of methanogenic cultures on methanol from the microbial population in the anaerobic digesters operated on agricultural wastes revealed a high rate of biomethanation efficiency and signify metabolic partnerships in the methylotrophic biochemical mechanisms operative toward energy recovery.
Abstract: Enrichment of methanogenic cultures on methanol from the microbial population in the anaerobic digesters operated on agricultural wastes revealed a high rate of biomethanation efficiency. Routine maintenance of this enrichment in a minimal basal medium at room temperature resulted in maximal growth in 40–50 d, and indicated pigment production toward the end of the growth phase. The cultures grown in three different media, with different substrates under light and dark conditions, were analyzed for protein, pigment, and gaseous products, and morphological studies were carried out by light, phase-contrast, fluorescence, and electron microscopy. In different media with methanol as substrate, growth and pigment production were maximal for the light-grown cells, decreasing in the order: phototrophic (PS(m)) > mineral > basal medium. Methanation and phototrophic growth were inversely correlated under lightgrown conditions. In contrast, growth in the dark was predominently methanogenic in the decreasing order: mineral > basal > PS (m). Among other growth conditions tested, utilization of phototrophic substrates under light and dark conditions indicated the following:
1.
Basal and mineral media were supportive of methanogenic growth under both light and dark conditions, although methane yields under light-grown conditions were low;
2.
Among the different substrates tested, methanol-grown cells gave the highest methane yield in the dark and;
3.
Phototrophic growth in PS medium with succinate, malate, and pyruvate was better than that with methanol.
5 citations
References
More filters
TL;DR: Fermentation of cellobiose was more rapid than that of cellulose, and agents of fermentation stoppage were found to be low pH and high concentrations of ethanol in the monoculture and low pH in the coculture.
Abstract: The fermentation of cellulose and cellobiose by Clostridium thermocellum monocultures and C. thermocellum/Methanobacterium thermoautotrophicum cocultures was studied. All cultures were grown under anaerobic conditions in batch culture at 60 degrees C. When grown on cellulose, the coculture exhibited a shorter lag before initiation and growth and celluloysis than did the monoculture. Cellulase activity appeared earlier in the coculture than in the monoculture; however, after growth had ceased, cellulase activity was greater in the monoculture. Monocultures produced primarily ethanol, acetic acid, H2 and CO2. Cocultures produced more H2 and acetic acid and less ethanol than did the monoculture. In the coculture, conversion of H2 to methane was usually complete, and most of the methane produced was derived from CO2 reduction rather than from acetate conversion. Agents of fermentation stoppage were found to be low pH and high concentrations of ethanol in the monoculture and low pH in the coculture. Fermentation of cellobiose was more rapid than that of cellulose. In cellobiose medium, the methanogen caused only slight changes in the fermentation balance of the Clostridium, and free H2 was produced.
352 citations
TL;DR: A background concentration of lauric acid below its MIC strongly enhanced the toxicity of capric acid and (to an even greater extent) myristic acid.
Abstract: The effect of four saturated long-chain fatty acids (caprylic, capric, lauric, and myristic) and one unsaturated long-chain fatty acid (oleic) on the microbial formation of methane from acetate was investigated in batch anaerobic toxicity assays. The tests were carried out with granular sludge from an upflow anaerobic sludge bed reactor. In this sludge, Methanothrix spp. are the predominant acetoclastic methanogens. Lauric acid appeared to be the most versatile inhibitor: inhibition started at 1.6 mM, and at 4.3 mM the maximum specific acetoclastic methanogenic activity had been reduced to 50%. Caprylic acid appeared to be only slightly inhibitory. Oleic acid was almost as inhibitory as lauric acid. Although adsorption of the inhibitor on the cell wall might play an important role in the mechanism of inhibition, the inhibition was found to be correlated with concentration rather than with the amount per unit of biomass. In practical situations, as in anaerobic waste treatment processes, synergism can be expected to enhance the inhibition of methanogenesis. In the present research a background concentration of lauric acid below its MIC strongly enhanced the toxicity of capric acid and (to an even greater extent) myristic acid.
318 citations
TL;DR: An acetate-fermenting strain of Methanosarcina was isolated from an acetate enrichment culture inoculated with anaerobic sludge from a waste treatment digestor and labeling studies indicated that acetate was converted to methane and CO2 as predicted by previous studies on mixed cultures.
Abstract: An acetate-fermenting strain of Methanosarcina was isolated from an acetate enrichment culture inoculated with anaerobic sludge from a waste treatment digestor. In pure culture, this organism fermented acetate in the absence of added hydrogen at rates comparable in magnitude to those found in digestor systems. This rate was significantly higher than previously obtained for pure cultures of this genus. Mineral components of yeast extract were highly stimulatory for cultures growing on methanol. Comparable stimulation was not observed for cultures growing on acetate. Labeling studies indicated that acetate was converted to methane and CO2 as predicted by previous studies on mixed cultures. Total oxidation or reduction of acetate was not the mechanism of conversion of acetate to methane by the pure culture. The ability of this strain to form colonies or to produce methane from acetate was apparently influenced by the choice of substrate and conditions used for growing the inoculum.
217 citations
Book•
31 Dec 1981
TL;DR: In this article, the authors present several promising processes for the conversion of biomass into energy and fuels, and the technical and economic considerations in biomass conversion, including the Andco-Torrax system, thermochemical conversion, and biochemical conversion.
Abstract: The book treats biomass sources, promising processes for the conversion of biomass into energy and fuels, and the technical and economic considerations in biomass conversion. Sources of biomass examined include crop residues and municipal, animal and industrial wastes, agricultural and forestry residues, aquatic biomass, marine biomass and silvicultural energy farms. Processes for biomass energy and fuel conversion by direct combustion (the Andco-Torrax system), thermochemical conversion (flash pyrolysis, carboxylolysis, pyrolysis, Purox process, gasification and syngas recycling) and biochemical conversion (anaerobic digestion, methanogenesis and ethanol fermentation) are discussed, and mass and energy balances are presented for each system.
128 citations
TL;DR: This age-dependent inhibition of methanogenesis by H2 and formate indicated that microbial interactions of the mixed enrichment population may play a regulatory role in methane formation and a model is presented to illustrate the possible interrelationships between methanogenic and nonmethanogenic bacteria in their growth and formation of methane and carbon dioxide from acetate.
Abstract: An acetate enrichment culture was initiated by inoculating anaerobic sludge from a mesophilic methane digestor into a mineral salts medium with calcium acetate as the sole carbon and energy source. This enrichment was maintained indefinitely by weekly transfer into medium of the same composition. A study of this enrichment disclosed an unexpected age-dependent inhibition of methanogenesis by H2 and formate which apparently differed from the inhibition by chloroform and benzyl viologen. This age-dependent inhibition indicated that microbial interactions of the mixed enrichment population may play a regulatory role in methane formation. Futhermore, stimulation of methanogenesis in the acetate enrichment by addition of yeast extract showed a nutrient limitation which indicated that syntrophic interactions leading to formation of growth factors may also occur. A model is presented to illustrate the possible interrelationships between methanogenic and nonmethanogenic bacteria in their growth and formation of methane and carbon dioxide from acetate.
88 citations