Biotechnology
The chemical equation for this reaction is:
\text{Glucose} \rightarrow \text{Ethanol} + \text{Carbon Dioxide}
This single process serves two distinct industrial purposes depending on which product is desired or retained:
| Mechanism / Outcome |
|---|
| The ethanol is collected and purified. It serves as a renewable fuel source (bioethanol) that can be mixed with petrol. |
| The ethanol evaporates during baking. The CO_2 gas forms bubbles in the dough, causing it to rise (leavening). This creates the spongy texture of bread. |
In fruit juice production, pectinase is added to crushed fruit. It digests the pectin holding the fruit cells together, releasing the cell contents and breaking down the cloudy pectin particles suspended in the juice.
When pectinase is used in fruit juice production, two main benefits occur:
- Increased Yield: The breakdown of cell walls releases more liquid from the fruit pulp, increasing the total volume of juice obtained.
- Clarification: Pectin normally keeps fruit particles suspended, making juice cloudy. By breaking down pectin, the particles settle out, resulting in a clear, transparent juice.
Correct Understanding: Pectinase specifically targets pectin.
- To break down starch, you need amylase.
- To break down proteins, you need protease.
- To break down fats, you need lipase.
Always match the enzyme name to its specific substrate. 'Pectinase' breaks down 'pectin'.
Why examiners accept this: Examiners look for specific keywords related to physical changes in the juice, not just 'it works better.'
Correct Phrasing: "Pectinase breaks down pectin in the cell walls/middle lamella, releasing more juice and clarifying the juice by allowing particles to settle."
Example: If a graph shows juice volume increasing with pectinase concentration then leveling off, you must state: "The volume increases because more pectin is broken down, but levels off when all available pectin has been digested (substrate limitation)."
Learning Objective 4: Biological washing powders contain enzymes (typically protease and lipase) that break down protein-based stains (e.g., blood, egg) and fat-based stains (e.g., grease, oil).
Investigation of Conditions: Enzymes are sensitive to temperature and pH. To determine the optimum conditions for a biological washing powder, you would investigate:
- Temperature: Wash clothes at different temperatures (e.g., 20°C, 30°C, 40°C, 50°C, 60°C). Measure the time taken for a stain to disappear or the area of the remaining stain.
- Result: Activity increases with temperature up to an optimum (usually around 30-40°C), then drops sharply as the enzyme denatures above 45-50°C.
- pH: Wash clothes in solutions with different pH levels. Measure stain removal.
- Result: Each enzyme has an optimum pH (often alkaline, pH 9-10 for washing powders). Activity is low at acidic pH.
Learning Objective 5: Lactase is an enzyme that breaks down the sugar lactose (found in milk) into two simpler sugars: glucose and galactose.
Process:
- Milk is passed over or mixed with immobilized lactase enzymes.
- Lactose is hydrolyzed into glucose and galactose.
- The resulting milk is 'lactose-free' (suitable for people with lactose intolerance).
Benefits:
- Taste: Glucose and galactose are sweeter than lactose, so the milk tastes sweeter without added sugar.
- Shelf-life: Simpler sugars crystallize less easily and are less prone to bacterial fermentation that causes souring, extending shelf-life.
Correct Understanding:
- Lactose is the substrate (the sugar).
- Lactase is the enzyme (the catalyst).
- Lactose breaks down into glucose and galactose.
Remember: Enzymes usually end in '-ase'. Substrates are often named after the substance they act on.
Why examiners accept this: You must link the chemical change (hydrolysis) to a physical property (taste/stability).
Correct Phrasing: "Lactase breaks down lactose into glucose and galactose. These monosaccharides are sweeter than lactose, improving taste. Also, they do not crystallize as easily, preventing grittiness in ice cream or souring in milk."
Avoid: Saying 'it removes the sugar.' It does not remove sugar; it changes its type.
Learning Objective 6: Fermenters are large vessels used to grow microorganisms (bacteria or fungi) under controlled conditions to produce useful products.
Key Products and Organisms:
- Insulin: Produced by genetically modified bacteria. The bacteria are engineered with the human gene for insulin. They are grown in fermenters, and insulin is extracted from the culture.
- Penicillin: Produced by the fungus Penicillium. Grown in fermenters to produce the antibiotic.
- Mycoprotein: Produced by the fungus Fusarium venenatum. The fungus is grown in large tanks on a sugar-rich medium (glucose syrup). It forms a mass of fungal threads called mycelium. This mycelium is harvested, processed, and flavored to resemble meat.
| How it is controlled |
|---|
| A water jacket circulates water to remove excess heat generated by respiration and maintain a constant temperature. |
| Buffers are added, or acid/alkali is automatically added to keep pH constant. |
| Sterile air is pumped into the fermenter via an aerator (impeller/stirrer ensures even distribution). |
| A nutrient solution is continuously added (in continuous fermentation) or added at the start (batch fermentation). |
| In continuous fermentation, waste products are removed along with the harvested product. In batch processes, conditions are managed to delay toxicity. |
Correct Understanding: Waste products are not just 'trash'; they are biologically active. For example, in ethanol production, high concentrations of ethanol kill the yeast (product inhibition). In other fermentations, metabolic acids lower the pH, which can denature enzymes. Therefore, waste removal or dilution is critical to prevent toxicity and maintain yield.
Why examiners accept this: You must link respiration, heat generation, and enzyme sensitivity.
Correct Phrasing: "Respiration by the microorganisms releases heat. If the temperature rises too high, the enzymes in the organisms will denature, stopping growth and product formation. A water jacket removes excess heat to maintain the optimum temperature for maximum yield."
Key Phrase: 'Enzymes denature at high temperatures' is a mandatory point.