Biotechnology in Food

The Fermentation Process

Producing mycoprotein requires a continuous culture system with carefully controlled conditions.

• Nutrients: The fungus is supplied with glucose syrup (as a carbon and energy source) and ammonia (as a nitrogen source to synthesise amino acids and proteins).
• Aerobic conditions: The fungus needs oxygen for aerobic respiration to grow. Sterile air is continuously pumped into the fermenter.
• Temperature control: Respiration is an exothermic reaction that releases heat. A water cooling jacket surrounds the fermenter to maintain an optimum temperature (around $40^\circ\text{C}$) so enzymes do not denature.
• pH control: Sensors constantly monitor and adjust the mixture to maintain an optimum pH (typically pH $6.0$).
• Mixing: Stirring paddles or air bubbles ensure that oxygen, heat, and nutrients are distributed evenly and stop the fungus from settling.
• Sterility: The fermenter and nutrients are sterilised with steam before use. This prevents contamination by competing microbes that would consume the food/oxygen, produce toxins, or be pathogenic.
• Harvesting: The fungal biomass is continuously harvested, purified to remove excess RNA/DNA, dried, and then textured to make meat substitutes.

Calculating Biomass Growth

Under optimum conditions, Fusarium can double its mass rapidly.

• Formula: Final Mass = $\text{Initial Mass} \times 2^n$ (where $n$ is the number of doublings).

Worked Example: If a fermenter starts with $10$ kg of Fusarium and it doubles every $5$ hours, how much will there be after $15$ hours?

• Step 1: Calculate the number of doublings. $15 \div 5 = 3$

• Step 2: Apply the formula. Final Mass = $10 \times 2^3$

• Step 3: Calculate the final answer. Final Mass = $80$ kg.

Genetically Modified (GM) Crops

Understanding genetic modification explains why we can now grow crops that survive weedkillers or even prevent blindness.

• GM crops have had their genome modified by inserting a gene from another organism.
• Improving Nutritional Value: Golden Rice has been engineered using genes from daffodils and bacteria. The rice produces beta-carotene, which the human body converts into Vitamin A. This prevents Vitamin A deficiency, a major cause of blindness in developing countries.
• Increasing Yield (Pest Resistance): Crops can be engineered with a gene from the bacterium Bacillus thuringiensis (Bt). The plant produces a toxin that kills insect pests (like caterpillars) when they eat it.
• Increasing Yield (Herbicide Resistance): Crops are made resistant to specific weedkillers. Farmers can spray the whole field to kill competing weeds without harming the crop, leaving more light, water, and minerals for the crop.
• Concerns: Risks include a reduction in biodiversity (fewer wild flowers and insects), the creation of "superweeds" if genes leak via cross-pollination, and fears over long-term health effects.

Calculating Crop Yield

Yield measures how much food is produced per unit area of land. GM technology is estimated to increase crop yields by an average of $22\%$.

• Formula:

$$\text{Yield} = \frac{\text{Total Mass}}{\text{Area}}$$

Worked Example: A farm harvests $32.8$ tonnes of GM crops from an area of $2$ hectares. Calculate the yield.

• Step 1: Identify the values. Total Mass = $32.8$ tonnes, Area = $2$ hectares.

• Step 2: Substitute into the equation. Yield = $32.8 \div 2$

• Step 3: Calculate the final answer. Yield = $16.4$ tonnes/hectare.

Industrial Production of Human Insulin

Before the 1980s, diabetics had to use insulin extracted from pigs, which carried a risk of allergic reactions. Today, we use genetic engineering to make bacteria produce exact copies of human insulin, which carries no risk of allergy and is suitable for vegetarians.

Here is the step-by-step mechanism:

• First, the human insulin gene is isolated from human pancreatic cells.
• Then, a restriction enzyme is used to "cut out" the insulin gene and to cut open a bacterial plasmid.
• Crucially, using the exact same restriction enzyme ensures that both pieces of DNA have complementary sticky ends (overhanging unpaired bases).
• Next, the enzyme DNA ligase joins the insulin gene and the plasmid together. This forms recombinant DNA.
• Then, the plasmid acts as a vector, carrying the foreign DNA into a host bacterium (like E. coli).
• Finally, these transgenic bacteria are grown in mass quantities in fermenters, where they express the gene and produce human insulin. The insulin is then extracted and purified for medical use.