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Substrate Utilization (substrate + utilization)
Selected AbstractsNovel Hemoglobins to Enhance Microaerobic Growth and Substrate Utilization in Escherichiacoli,BIOTECHNOLOGY PROGRESS, Issue 5 2001Christian J. T. Bollinger Limited oxygen availability is a prevalent problem in microbial biotechnology. Recombinant Escherichia coli expressing the hemoglobin from Vitreoscilla (VHb) or the flavohemoglobin from Ralstonia eutropha (formerly Alcaligenes eutrophus) (FHP) demonstrate significantly increased cell growth and productivity under microaerobic conditions. We identify novel bacterial hemoglobin-like proteins and examine if these novel bacterial hemoglobins can elicit positive effects similar to VHb and FHP and if these hemoglobins alleviate oxygen limitation under microaerobic conditions when expressed in E. coli. Several finished and unfinished bacterial genomes were screened using R. eutropha FHP as a query sequence for genes (hmp) encoding hemoglobin-like proteins. Novel hmp genes were identified in Pseudomonas aeruginosa, Salmonella typhi, Klebsiellapneumoniae, Deinococcus radiodurans, and Campylobacter jejuni. Previously characterized hmp genes from E. coli and Bacillus subtilis and the novel hmpgenes from P. aeruginosa, S. typhi, C. jejuni, K.pneumoniae, and D. radiodurans were PCR amplified and introduced into a plasmid for expression in E. coli. Biochemically active hemoproteins were expressed in all constructs, as judged by the ability to abduct carbon monoxide. Growth behavior and byproduct formation of E. coli K-12 MG1655 cells expressing various hemoglobins were analyzed in microaerobic fed-batch cultivations and compared to plasmid-bearing control and to E. coli cells expressing VHb. The clones expressing hemoglobins from E. coli, D. radiodurans, P.aeruginosa, and S. typhi reached approximately 10%, 27%, 23%, and 36% higher final optical density values, respectively, relative to the plasmid bearing E. coli control (A600 5.5). E. coli cells expressing hemoproteins from P. aeruginosa, S. typhi, and D. radiodurans grew to similar final cell densities as did the strain expressing VHb (A600 7.5), although none of the novel constructs was able to outgrow the VHb-expressing E. coli strain. Additionally, increased yield of biomass on glucose was measured for all recombinant strains, and an approximately 2-fold yield enhancement was obtained with D.radiodurans hemoprotein-expressing E. colirelative to the E. coli control carrying the parental plasmid without any hemoglobin gene. [source] Arm and leg substrate utilization and muscle adaptation after prolonged low-intensity trainingACTA PHYSIOLOGICA, Issue 4 2010J. W. Helge Abstract This review will focus on current data where substrate metabolism in arm and leg muscle is investigated and discuss the presence of higher carbohydrate oxidation and lactate release observed during arm compared with leg exercise. Furthermore, a basis for a possible difference in substrate partitioning between endogenous and exogenous substrate during arm and leg exercise will be debated. Moreover the review will probe if differences between arm and leg muscle are merely a result of different training status rather than a qualitative difference in limb substrate regulation. Along this line the review will address the available studies on low-intensity training performed separately with arm or legs or as whole-body training to evaluate if this leads to different adaptations in arm and leg muscle resulting in different substrate utilization patterns during separate arm or leg exercise at comparable workloads. Finally, the influence and capacity of low-intensity training to influence metabolic fitness in the face of a limited effect on aerobic fitness will be challenged. [source] Batch kinetics and modelling of ethanolic fermentation of wheyINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 6 2005Salman Zafar Summary The fermentation of whey by Kluyveromyces marxianus strain MTCC 1288 was studied using varying lactose concentrations at constant temperature and pH. The increase in substrate concentration up to a certain limit was accompanied by an increase in ethanol formation, for example, at a substrate concentration of 10 g L,1, the production of ethanol was 0.618 g L,1 whereas at 50 g L,1 it was 3.98 g L,1. However, an increase in lactose concentration to 100 g L,1 led to a drastic decrease in product formation and substrate utilization. The maximum ethanol yield was obtained with an initial lactose concentration of 50 g L,1. A method of batch kinetics was utilized to formulate a mathematical model using substrate and product inhibition constants. The model successfully simulated the batch kinetics observed at S0 = 10 and 50 g L,1 but failed in case of S0 = 100 g L,1 because of strong substrate inhibition. [source] Diversity of soil mycobacterium isolates from three sites that degrade polycyclic aromatic hydrocarbonsJOURNAL OF APPLIED MICROBIOLOGY, Issue 6 2007C.D. Miller Abstract Aims:, This paper investigates the diversity of polycyclic aromatic hydrocarbon (PAH)-degrading mycobacterium isolates from three different sites within United States: Montana, Texas and Indiana. Methods and Results:, All five mycobacterium isolates differed in chromosomal restriction enzyme-fragmentation patterns; three isolates possessed linear plasmids. The DNA sequence between the murA and rRNA genes were divergent but the sequence upstream of nidBA genes, encoding a dioxygenase involved in pyrene oxidation, was more highly conserved. Long-chain fatty acid analysis showed most similarity between three isolates from the same Montana site. All isolates were sensitive to rifampicin and isoniazid, used in tuberculosis treatment, and to syringopeptins, produced by plant-associated pseudomonads. Biofilm growth was least for isolate MCS that grew on plate medium as rough-edged colonies. The patterns of substrate utilization in Biolog plates showed clustering of the Montana isolates compared with Mycobacterium vanbaalenii and Mycobacterium gilvum. Conclusion:, The five PAH-degrading mycobacterium isolates studied differ in genetic and biochemical properties. Significance and Impact of the Study:, Different properties with respect to antibiotic susceptibility, substrate utilization and biofilm formation could influence the survival in soil of the microbe and their suitability for use in bioaugmentation. [source] A thermodynamic analysis of the activated sludge process: Application to soybean wastewater treatment in a sequencing batch reactorAICHE JOURNAL, Issue 10 2009Bing-jie Ni Abstract A bioenergetic methodology was integrated with a modified activated sludge model No.1 (ASM1) to analyze the activated sludge process, with the treatment of soybean-processing wastewater as an example. With the bioenergetic methodology established by McCarty and coworkers, the microbial yield was predicted and the overall stoichiometrics for biological reactions involving the key chemical and biological species in activated sludge were established. These obtained parameters were related to the ASM1 model, which was modified after coupling the biological reactions in activated sludge with electron balances. This approach was able to approximately describe the treatment of soybean wastewater by activated sludge in a sequencing batch reactor in terms of substrate utilization, biomass growth, and the elector acceptor consumption. Such an attempt provides useful information for accurate modeling of the complex activated sludge process. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Life history determines biogeographical patterns of soil bacterial communities over multiple spatial scalesMOLECULAR ECOLOGY, Issue 19 2010A. BISSETT Abstract The extent to which the distribution of soil bacteria is controlled by local environment vs. spatial factors (e.g. dispersal, colonization limitation, evolutionary events) is poorly understood and widely debated. Our understanding of biogeographic controls in microbial communities is likely hampered by the enormous environmental variability encountered across spatial scales and the broad diversity of microbial life histories. Here, we constrained environmental factors (soil chemistry, climate, above-ground plant community) to investigate the specific influence of space, by fitting all other variables first, on bacterial communities in soils over distances from m to 102 km. We found strong evidence for a spatial component to bacterial community structure that varies with scale and organism life history (dispersal and survival ability). Geographic distance had no influence over community structure for organisms known to have survival stages, but the converse was true for organisms thought to be less hardy. Community function (substrate utilization) was also shown to be highly correlated with community structure, but not to abiotic factors, suggesting nonstochastic determinants of community structure are important Our results support the view that bacterial soil communities are constrained by both edaphic factors and geographic distance and further show that the relative importance of such constraints depends critically on the taxonomic resolution used to evaluate spatio-temporal patterns of microbial diversity, as well as life history of the groups being investigated, much as is the case for macro-organisms. [source] Functional Complementation of the Yeast P-type H+ -ATPase, PMA1, by the Pneumocystis carinii P-type H+ -ATPase, PCA1THE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 3 2006DANIELA GRIGORE ABSTRACT. The opportunistic fungus Pneumocystis is the etiologic agent of an interstitial plasma cell pneumonia that primarily afflicts immunocompromised individuals. Like other fungi Pneumocystis maintains a H+ plasma membrane gradient to drive nutrient uptake and regulates intracellular pH by ATP-dependent proton efflux. Previously, we identified a Pneumocystis gene, PCA1, whose predicted protein product was homologous to fungal proton pumps. In this study, we show by functional complementation in a Saccharomyces strain whose endogenous PMA1 proton pump activity is repressed that the Pneumocystis PCA1 encodes a H+ -ATPase. The properties of PCA1 characterized in this system closely resemble those of yeast PMA1. Yeast expressing PCA1 grow at low pH and are able to acidify the external media. Maximal enzyme activity (Vmax) and efficiency of substrate utilization (Km) in plasma membranes were nearly identical for PCA1 and PMA1. PCA1 contains an inhibitory COOH-terminal domain; removal of the final 40 amino acids significantly increased Vmax and growth at pH 6.5. PCA1 activity was inhibited by proton pump inhibitors omeprazole and lansoprazole, but was unaffected by H+/K+ -ATPase inhibitor SCH28080. Thus, H+ homeostasis in Pneumocystis is likely regulated as in other fungi. This work also establishes a system for screening PCA1 inhibitors to identify new anti- Pneumocystis agents. [source] AMP kinase activation with AICAR further increases fatty acid oxidation and blunts triacylglycerol hydrolysis in contracting rat soleus muscleTHE JOURNAL OF PHYSIOLOGY, Issue 2 2005Angela C. Smith Muscle contraction increases glucose uptake and fatty acid (FA) metabolism in isolated rat skeletal muscle, due at least in part to an increase in AMP-activated kinase activity (AMPK). However, the extent to which AMPK plays a role in the regulation of substrate utilization during contraction is not fully understood. We examined the acute effects of 5-aminoimidazole-4-carboxamide riboside (AICAR; 2 mm), a pharmacological activator of AMPK, on FA metabolism and glucose oxidation during high intensity tetanic contraction in isolated rat soleus muscle strips. Muscle strips were exposed to two different FA concentrations (low fatty acid, LFA, 0.2 mm; high fatty acid, HFA, 1 mm) to examine the role that FA availability may play in both exogenous and endogenous FA metabolism with contraction and AICAR. Synergistic increases in AMPK ,2 activity (+45%; P < 0.05) were observed after 30 min of contraction with AICAR, which further increased exogenous FA oxidation (LFA: +71%, P < 0.05; HFA: +46%, P < 0.05) regardless of FA availability. While there were no changes in triacylglycerol (TAG) esterification, AICAR did increase the ratio of FA partitioned to oxidation relative to TAG esterification (LFA: +65%, P < 0.05). AICAR significantly blunted endogenous TAG hydrolysis (LFA: ,294%, P < 0.001; HFA: ,117%, P < 0.05), but had no effect on endogenous oxidation rates, suggesting a better matching between TAG hydrolysis and subsequent oxidative needs of the muscle. There was no effect of AICAR on the already elevated rates of glucose oxidation during contraction. These results suggest that FA metabolism is very sensitive to AMPK ,2 stimulation during contraction. [source] Optimization of catechol production by membrane-immobilized polyphenol oxidase: A modeling approachBIOTECHNOLOGY & BIOENGINEERING, Issue 1 2003A. Boshoff Abstract Although previous research has focused on phenol removal efficiencies using polyphenol oxidase in nonimmobilized and immobilized forms, there has been little consideration of the use of polyphenol oxidase in a biotransformation system for the production of catechols. In this study, polyphenol oxidase was successfully immobilized on various synthetic membranes and used to convert phenolic substrates to catechol products. A neural network model was developed and used to model the rates of substrate utilization and catechol production for both nonimmobilized and immobilized polyphenol oxidase. The results indicate that the biotransformation of the phenols to their corresponding catechols was strongly influenced by the immobilization support, resulting in differing yields of catechols. Hydrophilic membranes were found to be the most suitable immobilization supports for catechol production. The successful biocatalytic production of 3-methylcatechol, 4-methylcatechol, catechol, and 4-chlorocatechol is demonstrated. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 83: 1,7, 2003. [source] Effects of glucose and nitrogen source concentration on batch fermentation kinetics of Lactococcus lactis under hemin-stimulated respirative conditionBIOTECHNOLOGY PROGRESS, Issue 4 2008Azher Razvi Abstract Analytical solutions to the ordinary differential equations governing the kinetics of cell growth, substrate utilization, and product formation of batch fermentation processes were derived and used to study the kinetics of the hemin-stimulated respiratory cultivation of Lactococcus lactis at varied initial glucose concentrations and nitrogen source concentrations. Studies revealed that initial glucose concentration varying in the range of 60 to 90 g/L had no significant substrate inhibitive effect. Furthermore, elevating the concentration of complex nitrogen sources while maintaining glucose concentration at 60% led to a high final biomass concentration of 6.6 g/L, substantially higher than that obtained with the basic medium, which was 4.1 g/L. [source] Cybernetic Modeling and Regulation of Metabolic Pathways in Multiple Steady States of Hybridoma CellsBIOTECHNOLOGY PROGRESS, Issue 5 2000Maria Jesus Guardia Hybridoma cells utilize a pair of complementary and partially substitutable substrates, glucose and glutamine, for growth. It has been shown that cellular metabolism shifts under different culture conditions. When those cultures at different metabolic states are switched to a continuous mode, they reach different steady states under the same operating conditions. A cybernetic model was constructed to describe the complementary and partial substitutable nature of substrate utilization. The model successfully predicted the metabolic shift and multiple steady-state behavior. The results are consistent with the experimental observation that the history of the culture affects the resulting steady state. [source] Aerobic granules for low-strength wastewater treatment: formation, structure, and microbial communityJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 7 2009Shu-Guang Wang Abstract BACKGROUND: To validate the possibility of aerobic granulation at a lower organic loading rate (OLR) than 2 kg COD m,3 day,1 (GS 1) in a sequencing batch reactor (SBR), the formation, structure, and microbial community of granular sludge (GS) were investigated. RESULTS: The overall experimental process involved the following stages: acclimation, granulation, maturation, and stabilization. The optical microscopic showed the structural changes from fluffy activated sludge (AS) to GS and scanning electron microscope (SEM) examination revealed that GS 1 was irregular filamentous aggregates composed mainly of various filamentous species, while the aerobic granules cultivated at OLR 1.68,4.20 kg COD m,3 day,1 (GS 2) was mycelial pellets consisting of fungi and filamentous microorganisms. A Biolog Ecoplate analysis indicated that significant differences existed between the microbial community structure and the substrate's utilization of AS and different GS samples. CONCLUSION: GS 1 was achieved and different from GS 2 in the formation, structure, and microbial community. Aerobic granulation with low strength wastewater is of importance for the full-scale application of this technology. Copyright © 2009 Society of Chemical Industry [source] Degradation of phthalate esters (PAEs) in soil and the effects of PAEs on soil microcosm activityJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 8 2010Hui-Jun Xie Abstract BACKGROUND: Phthalate esters (PAEs), a class of refractory and toxic organic compounds, are becoming one of the most widespread contaminants in the environment. Degradation of PAEs in soil has been investigated, but limited to one or a few kinds of PAEs. Microorganisms could be regarded as a sensitive bio-indicator for soil contaminants. Therefore, four commonly used PAEs were chosen to investigate their degradation patterns and potential impacts on soil microbial activity with a series of bioassays. RESULT: PAEs in sterile soils changed slightly, while degradation of PAEs in non-sterile soil followed a single first-order kinetic. Higher concentrations of PAEs led to lower ,-glucosidase activity and higher protease activity, with smooth changes of phosphatase and urease activities. PAEs decreased average well color development (AWCD), while Shannon index (H) showed a tendency to increase after a decrease. Carbon utilization profile was affected significantly by PAEs, especially at 10 mg kg,1 soil. CONCLUSION: Degradation of PAEs was driven mainly by microbial mediated processes. PAEs affected carbon, nitrogen and phosphorus cycles variously, and had temporal effects on metabolic diversity, owing to the adaptation of microbes. Carbon substrates utilization changed from easily degradable sugars and carboxylic acids to recalcitrant compounds during the simulation. Copyright © 2010 Society of Chemical Industry [source] | |||||||||||||