Nutritional Requirements in Fermentation Processes

Vocabulary practice flashcards covering microbial nutrient classifications, energy pathways, cellular respiration, industrial fermentation media, and nutrient membrane transport mechanisms.

Metabolism

The complete network of chemical reactions that occur within living organisms to maintain life, support cellular structures, and facilitate growth and division.

Anabolism

The metabolic pathway involving the synthesis of complex biomolecules from simpler precursors, requiring an input of energy (e.g., polymerizing amino acids into proteins or nucleotides into nucleic acids).

Catabolism

The metabolic pathway that breaks down larger, complex molecules into simpler constituents, during which energy is released, trapped, and made available for cellular work.

Organotrophs

Organisms that utilize organic compounds (such as glucose or succinate) as their primary energy and electron source.

Lithotrophs

Organisms that derive metabolic energy from the oxidation of inorganic chemical compounds, such as $S$, $Fe^{2+}$, $CO_2$, or $H_2$.

Phototrophs

Organisms that absorb and transform radiant light energy to support metabolic and biosynthetic processes.

Chemotrophs

Organisms that harvest energy through the oxidation of chemical compounds present in their environment rather than from light.

Autotrophs

Organisms that utilize inorganic carbon dioxide ($CO_2$) as their principal source of carbon for biomass synthesis.

Heterotrophs

Organisms that require preformed organic compounds (such as sugars or organic acids) as their principal source of carbon.

Chemoheterotrophic

A nutritional category of organisms that utilize chemical compounds for energy and organic compounds as their principal carbon source (e.g., animals, fungi, and many bacteria).

Photoheterotrophic

A nutritional category of organisms that depend on light as an energy source and preformed organic compounds as a principal carbon source (e.g., purple and green photosynthetic bacteria).

Chemoautotrophic

A nutritional category of organisms that extract energy from chemical reactions while fixing inorganic carbon dioxide ($CO_2$) as their primary carbon source (e.g., methanogenic bacteria).

Photoautotrophic

A nutritional category of organisms that convert light energy into chemical energy and fix carbon dioxide ($CO_2$) into organic matter (e.g., plants and algae).

Adenosine Triphosphate (ATP)

The universal cellular energy carrier composed of adenine, ribose, and three phosphate groups; the hydrolysis of its high-energy phosphoanhydride bonds releases approximately $-32\,kJ\,mol^{-1}$ of free energy.

Typical Sugar Content of Molasses

The standard industrial sugar content profile of molasses: beet molasses contains $50\,\%\,w/v$ sucrose and $1\,\%\,w/v$ invert sugar, whereas cane molasses contains $35\,\%\,w/v$ sucrose and $20\,\%\,w/v$ invert sugar.

Glycolysis

The central catabolic pathway in which one molecule of glucose ($6C$) is converted into two molecules of pyruvic acid ($3C$), consuming $2\,ATP$ and generating $4\,ATP$ (net gain of $2\,ATP$) and $2\,NADH$.

Aerobic Cellular Respiration

The complete oxidation of glucose in the presence of oxygen ($6O_2 + C_6H_{12}O_6 \rightarrow 6CO_2 + 6H_2O$) within eukaryotic mitochondria or prokaryotic membranes, yielding up to $38$ molecules of $ATP$ per glucose molecule.

Alcohol Fermentation

An anaerobic pathway carried out by yeast and specific bacteria that degrades glucose without oxygen according to the overall reaction $C_6H_{12}O_6 \rightarrow 2CO_2 + 2C_2H_5OH$, generating a net yield of $2\,ATP$ per glucose molecule.

Lactic Acid Fermentation

An anaerobic catabolic pathway utilized by lactic acid bacteria, fungi, and exercising muscle cells that converts glucose into lactic acid according to $C_6H_{12}O_6 \rightarrow 2C_3H_6O_3$, yielding $2\,ATP$ per glucose molecule.

Microbial Fermentation End-Products

Diverse commercial organic products produced from pyruvic acid by specific microorganisms: propionic acid and $CO_2$ by Propionibacterium (Swiss cheese), lactic acid by Lactobacillus/Streptococcus (yogurt, cheddar cheese), ethanol and $CO_2$ by Saccharomyces (wine, beer), acetone/isopropanol by Clostridium, and acetic acid by Acetobacter (vinegar).

Carbon-to-Nitrogen-to-Phosphorus (C/N/P) Ratio

The stoichiometric elemental ratio essential for formulating balanced microbial culture media, typically maintained around $100:10:1$ to avoid nutrient limitation during biomass generation.

Coenzyme

A non-protein organic cofactor (such as $NAD^+$ or Coenzyme A) that transiently binds to an enzyme's active site to mediate group transfer or oxidation-reduction reactions.

Growth Factors

Specific organic compounds (including vitamins, purines, and pyrimidines) required by microorganisms in minute amounts ($\mu g\,L^{-1}$) because the cell cannot synthesize them de novo.

Synthetic Medium

A chemically defined culture medium prepared exclusively from known chemical ingredients at precisely measured concentrations, minimizing batch variation and simplifying downstream processing.

Semi-synthetic Medium

A culture medium prepared by combining precisely quantified, chemically defined components with unrefined natural ingredients, leaving the total composition partially unknown.

Complex Medium

An undefined industrial growth medium prepared predominantly from crude plant or animal hydrolysates (e.g., yeast extract, corn steep liquor, molasses) that exhibits natural batch-to-batch variation.

Minimal Medium

A simple defined growth medium formulated with only the fundamental salts, water, and simple carbon/energy source strictly necessary to support wild-type microbial growth.

Selective Medium

A growth medium containing specific inhibitory agents, dyes, or antibiotics that suppress the proliferation of non-target organisms while permitting the isolation of a desired strain.

Differential Medium

A diagnostic medium containing chemical indicators (such as phenol red, neutral red, or methylene blue) that visibly distinguishes between different microbial species based on characteristic metabolic changes.

Enriched Medium

A highly nutritious culture medium supplemented with complex biological fluids (such as $5\text{--}10\,\%$ animal or human blood in blood agar) to support the growth of fastidious microorganisms.

Krebs Cycle (TCA Cycle)

A cyclic biochemical pathway in eukaryotic mitochondria or prokaryotic cytosol that oxidizes acetyl-CoA, producing $3\,NADH$, $1\,FADH_2$, $1\,GTP$, and $2\,CO_2$ per cycle turn ($6\,NADH$, $2\,FADH_2$, $2\,GTP$, and $4\,CO_2$ per original glucose molecule).

Cell Membrane (Fluid Mosaic Structure)

A selectively permeable bilayer of amphipathic phospholipids embedded with cholesterol, integral transport proteins, peripheral proteins, glycoproteins, and glycolipids that controls cellular entry and exit.

Simple Diffusion

The unassisted passive movement of small, nonpolar solutes (such as $O_2$ and $CO_2$) directly across the hydrophobic interior of the phospholipid bilayer down their concentration gradient.

Facilitated Diffusion

A form of passive membrane transport in which polar molecules (such as water or glucose) or ions traverse the lipid bilayer along their concentration gradient through dedicated channel or carrier proteins without consuming energy.

Active Transport

The transport of solutes or ions across a biological membrane against their concentration gradient (from low to high concentration), requiring cellular energy expenditure through direct or coupled ATP hydrolysis.