Related Experiment Video
Updated: Jan 27, 2026
09:51
Purification of a High Molecular Mass Protein in Streptococcus mutans
Published on: September 14, 2019
6.3K
Acetoin and Diacetyl Formation by Streptococcus lactis subsp. diacetylactis DRC3
S M El-Gendy1, H Abdel-Galil1, Y Shahin1
1Department of Food Science, University of Assiut, Assiut, Egypt.
Journal of Food Protection
|March 30, 2019
Summary
Streptococcus lactis subsp. diacetylactis DRC3 requires energy and nitrogen sources for acetoin and diacetyl (AD) production from citrate. Optimal conditions enhance AD formation, with citrate yielding more than pyruvate.
Area of Science:
- Microbiology
- Biochemistry
Background:
- Streptococcus lactis subsp. diacetylactis DRC3 is known for producing flavor compounds.
- Acetoin and diacetyl (AD) are important flavor compounds in fermented dairy products.
Purpose of the Study:
- To investigate the optimal conditions for acetoin and diacetyl (AD) formation from citrate by Streptococcus lactis subsp. diacetylactis DRC3.
- To elucidate the metabolic pathways involved in AD production from citrate.
Main Methods:
- Cells were grown on lactose with citrate and suspended in succinate buffer at varying pH.
- Energy and nitrogen sources were added to the buffer to assess their effect on AD formation.
- AD concentrations were measured under different conditions and compared to pyruvate as a substrate.
Main Results:
- AD formation from citrate required energy and nitrogen sources.
- AD and diacetyl concentrations were significantly higher at pH 4.4 compared to pH 6.4.
- Citrate yielded more AD and diacetyl than pyruvate on a molar basis.
- Evidence suggests diacetyl is formed from both pyruvate and acetyl-CoA.
- Optimal AD formation rate was 0.047 μmoles mg (dry wt-1) cells ml-1 min-1.
- Acetate and acetaldehyde inhibited AD production.
Conclusions:
- Optimal conditions for AD production from citrate by S. lactis subsp. diacetylactis DRC3 involve the presence of energy and nitrogen sources.
- The metabolic pathway for AD formation from citrate is complex, involving citrate cleavage and potential involvement of acetyl-CoA.
- Environmental factors like pH and the presence of inhibitors significantly impact AD production.
Related Concept Videos
01:31Formation of Species
44.9K
Speciation describes the formation of one or more new species from one or sometimes multiple original species. The resulting species are discrete from the parent species, and barriers to reproduction will typically exist. There are two primary mechanisms, speciation with and without geographic isolation—allopatric and sympatric speciation, respectively.
44.9K
02:16Solution Formation
37.2K
There is no one solvent that can dissolve every type of solute. Some substances that readily dissolve in a certain solvent might be insoluble in a different solvent. A simple way to predict which substances dissolve in which solvent is the phrase "like dissolves like". This means that polar substances, such as salt and sugar, dissolve in a polar substance like water. In contrast, non-polar substances are more soluble in non-polar solvents such as carbon tetrachloride.
This selective...
This selective...
37.2K
02:37Standard Enthalpy of Formation
49.1K
Enthalpy changes are typically tabulated for reactions in which both the reactants and products are at the same conditions. A standard state is a commonly accepted set of conditions used as a reference point for the determination of properties under other different conditions. For chemists, the IUPAC standard state refers to materials under a pressure of 1 bar and solutions at 1 M and does not specify a temperature. Many thermochemical tables list values with a standard state of 1 atm. Because...
49.1K
03:45Formation of Complex Ions
25.9K
A type of Lewis acid-base chemistry involves the formation of a complex ion (or a coordination complex) comprising a central atom, typically a transition metal cation, surrounded by ions or molecules called ligands. These ligands can be neutral molecules like H2O or NH3, or ions such as CN− or OH−. Often, the ligands act as Lewis bases, donating a pair of electrons to the central atom. These types of Lewis acid-base reactions are examples of a broad subdiscipline called coordination...
25.9K
01:23Microtubule Formation
7.5K
Microtubules are dynamic structures that undergo continuous assembly and disassembly. They originate from specialized multi-protein complexes known as microtubule organizing centers or MTOCs. Within the MTOC, the point of origin of the microtubule is known as the minus end, while the end radiating outward is the plus end. Microtubules serve two primary functions — the organization of spindle complexes to separate sister chromatids during mitotic or meiotic cell division and the formation...
7.5K
02:12Relationship Formation
45.3K
What do you think is the single most influential factor in determining with whom you become friends and whom you form romantic relationships? You might be surprised to learn that the answer is simple: the people with whom you have the most contact. This most important factor is proximity. You are more likely to be friends with people you have regular contact with. For example, there are decades of research that shows that you are more likely to become friends with people who live in your dorm,...
45.3K