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Related Concept Videos

Enzymes and Activation Energy01:13

Enzymes and Activation Energy

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The activation energy (or free energy of activation), abbreviated as Ea, is the small amount of energy input necessary for all chemical reactions to occur. During chemical reactions, certain chemical bonds break, and new ones form. For example, when a glucose molecule breaks down, bonds between the molecule's carbon atoms break. Since these are energy-storing bonds, they release energy when broken. However, the molecule must be somewhat contorted to get into a state that allows the bonds to...
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tRNA Activation

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Aminoacyl-tRNA synthetases are present in both eukaryotes and bacteria. Though eukaryotes have 20 different aminoacyl-tRNA synthetases to couple to 20 amino acids, many bacteria do not have genes for all of these aminoacyl-tRNA synthetases. Despite this, they still use all 20 amino acids to synthesize their proteins. For instance, some bacteria do not have the gene encoding the enzyme that couples glutamine with its partner tRNA. In these organisms, one enzyme adds glutamic acid to all of the...
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Co-activators and Co-repressors02:04

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Gene transcription is regulated by the synergistic action of several proteins that form a complex at a gene regulatory site. This is observed in eukaryotes, where the regulation of gene expression is a complex process. Regulatory proteins in eukaryotes can broadly be classified into two types – regulators that bind directly to specific DNA sequences and co-regulators that associate with regulatory proteins but cannot directly bind to the DNA. These co-regulators are further divided into...
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Activation Energy01:26

Activation Energy

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Activation energy is the minimum amount of energy necessary for a chemical reaction to move forward. The higher the activation energy, the slower the rate of the reaction. However, adding heat to the reaction will increase the rate, since it causes molecules to move faster and increase the likelihood that molecules will collide. The collision and breaking of bonds represents the uphill phase of a reaction and generates the transition state. The transition state is an unstable high-energy state...
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Secondary Active Transport01:55

Secondary Active Transport

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One example of how cells use the energy contained in electrochemical gradients is demonstrated by glucose transport into cells. The ion vital to this process is sodium (Na+), which is typically present in higher concentrations extracellularly than in the cytosol. Such a concentration difference is due, in part, to the action of an enzyme “pump” embedded in the cellular membrane that actively expels Na+ from a cell. Importantly, as this pump contributes to the high concentration of...
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Primary Active Transport01:47

Primary Active Transport

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In contrast to passive transport, active transport involves a substance being moved through membranes in a direction against its concentration or electrochemical gradient. There are two types of active transport: primary active transport and secondary active transport. Primary active transport utilizes chemical energy from ATP to drive protein pumps that are embedded in the cell membrane. With energy from ATP, the pumps transport ions against their electrochemical gradients—a direction...
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Related Experiment Video

Updated: Feb 7, 2026

Determination of Microbial Extracellular Enzyme Activity in Waters, Soils, and Sediments using High Throughput Microplate Assays
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Determination of Microbial Extracellular Enzyme Activity in Waters, Soils, and Sediments using High Throughput Microplate Assays

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Microbial extracellular enzyme activity affects performance in a full-scale modified activated sludge process.

Francis Hassard1, Jeremy Biddle2, Richard Harnett2

  • 1Cranfield University, Cranfield MK43 0AL, UK.

The Science of the Total Environment
|July 13, 2018
PubMed
Summary
This summary is machine-generated.

Rotating biofilm reactors (RBRs) significantly enhance extracellular enzyme activity (EEA) in wastewater treatment. This improved enzyme breakdown of polymers is crucial for optimizing activated sludge processes, especially under high organic loading rates (OLR).

Keywords:
BiofilmHybrid activated sludgeHydrolytic activityMicrobial extracellular enzyme activityPerformance

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Area of Science:

  • Environmental Microbiology
  • Biochemical Engineering
  • Wastewater Treatment Technologies

Background:

  • Polymer breakdown by extracellular enzyme activity (EEA) is a rate-limiting step in wastewater treatment.
  • Conventional activated sludge (AS) processes have limitations in achieving high efficiency.
  • Rotating biofilm reactors (RBRs) offer a potential modification to enhance biological wastewater treatment.

Purpose of the Study:

  • To compare the extracellular enzyme activity (EEA) of biomass from conventional activated sludge (AS) and modified AS using rotating biofilm reactors (RBRs).
  • To investigate the impact of organic loading rate (OLR) on EEA in RBRs.
  • To assess the role of RBR-mediated EEA in improving the performance of modified activated sludge processes.

Main Methods:

  • Comparative analysis of EEA (amino-peptidase, α-glucosidase, phosphatase) in bench-scale and full-scale RBRs versus conventional AS biomass.
  • Controlled overloading experiments on bench-scale RBRs to determine the effect of OLR on EEA.
  • Evaluation of the performance of modified activated sludge processes with RBR pretreatment.

Main Results:

  • Bench-scale RBRs exhibited significantly higher amino-peptidase EEA compared to α-glucosidase and phosphatase.
  • Full-scale RBRs demonstrated substantially greater EEA for all measured enzymes compared to conventional AS.
  • EEA in RBRs increased with OLR up to 190 g tCOD m⁻²d⁻¹, after which it decreased.

Conclusions:

  • RBRs significantly enhance extracellular enzyme activity, particularly amino-peptidase.
  • High EEA maintained in RBR biofilms is critical for designing efficient, high OLR wastewater treatment systems.
  • Pretreatment using RBRs improves the performance of modified activated sludge processes.