WEEK 3 at BioHack Waag Amsterdam

I. FERMENTATION with Margherita Soldati

“Endosymbiosis. Homage to Lynn Margulis” (2012),
Shoshanah Dubiner, animation by David Domingo”

Lactic acid fermentation is a metabolic process by which glucose or other six-carbon sugars (also, disaccharides of six-carbon sugars, e.g. sucrose or lactose) are converted into cellular energy and the metabolite lactate, which is lactic acid in solution.

It is an anaerobic fermentation reaction that occurs in some bacteria and animal cells, such as muscle cells.

If oxygen is present in the cell, many organisms will bypass fermentation and undergo cellular respiration; however, facultative anaerobic organisms will both ferment and undergo respiration in the presence of oxygen. Sometimes even when oxygen is present and aerobic metabolism is happening in the mitochondria, if pyruvate is building up faster than it can be metabolized, the fermentation will happen anyway.

The Art of Fermentation by Sandor Ellix Katz (click the link)


Step-by-Step Guide to Pear Fermentation Using a Vacuum Machine

  • Prepare the Pears:
    • Select ripe, unblemished pears. The ripeness of the pears will affect the sugar content and the final taste of the fermented product.
    • Wash the pears thoroughly to remove any dirt or debris.
    • Cut the pears into slices or cubes, depending on your preference. Removing the core and seeds is recommended to avoid any bitter flavors.
    • 2% SALT 
  • Sugar Addition (Optional):
    • If you’re aiming for a higher alcohol content or a sweeter end product, you may add sugar to the pears. 
    • Vacuum Sealing:
    • Place the prepared pears (and sugar, if used) into vacuum seal bags. Try not to overcrowd the bags to allow for some expansion during fermentation.
    • Use the vacuum machine to seal the bags, ensuring that as much air as possible is removed from the bags. This anaerobic environment is crucial for fermentation.
  • Fermentation:
    • Store the vacuum-sealed bags in a dark, cool place. The ideal temperature for fermentation is around 55°F to 75°F (13°C to 24°C).
    • The fermentation process can take anywhere from a few days to a few weeks, depending on the temperature and the desired level of fermentation.
  • Monitoring:
    • Check the bags periodically for signs of fermentation, such as the bag puffing up due to the production of carbon dioxide.
    • Be cautious of over-fermentation, which can cause bags to burst. If a bag appears too bloated, you may need to release some gas and reseal it.
  • Finishing:
    • Once the fermentation process is complete to your satisfaction, remove the pears from the vacuum bags.
    • The fermented pears can be consumed as is, or used in various recipes.
    • Storage:
    • Store the fermented pears in a refrigerator or process them for longer storage. Fermented products can be preserved through canning, freezing, or refrigeration.

Safety and Quality Tips:

  • Always ensure your equipment is sterilized properly to avoid contamination.
  • If any of the bags show signs of mold or have an off smell, discard them immediately.



– a big, wide-mouthed jar

– Pour some beer 

-add a vinegar mother (acetobacter)

-Once you drop the mother into the jar, cover it with a cheese cloth  to protect your composition from the Fruit flies, and set it in a dark place at room temperature or warmer. 

-Vinegar needs air, so don’t seal the  jar.

-It takes a month or two for the vinegar to really be ready, depending on how large a batch you are making. Taste after a month. 



  • 1 liter of pure, unsweetened apple juice (preferably organic)
  • 1 teaspoon of brewer’s yeast or active dry yeast
  • Distilled water (if needed, to adjust sugar concentration)
  • Sugar (optional, if additional fermentation feed is needed)


  • A large glass fermenting jar or a container
  • Cheesecloth or a clean dish towel
  • A rubber band or string
  • A fermentation airlock (optional)


a. Prepare the Mixture:

  • Start by assessing the sweetness of your apple juice. If it’s very sweet or concentrated, you may want to dilute it with distilled water. A good ratio to start with is 3 parts apple juice to 1 part distilled water, but this can be adjusted based on the initial sugar content of the juice.
  • If you’re adding sugar to provide additional feed for the yeast (which can be helpful if your apple juice is less sweet or if you’ve diluted it significantly), dissolve about 1 tablespoon of sugar per liter of liquid in a small amount of warm distilled water before adding it to the mixture.

b. Activate the Yeast:

  • Warm a small portion of the apple juice to about 95°F (35°C)—warm enough to activate the yeast without killing it.
  • Dissolve the teaspoon of yeast into the warm juice. Wait for 10 to 15 minutes until it starts to foam, indicating that the yeast is active.

c. Combine and Ferment:

  • Combine the yeast mixture with the rest of the apple juice (and diluted water, if used) in the fermenting jar. If you’ve added extra sugar, make sure it’s dissolved and mixed in well.
  • Cover the mouth of the jar with cheesecloth or a clean dish towel and secure it with a rubber band. This setup allows the mixture to breathe and release carbon dioxide while keeping out contaminants. Alternatively, you can use an airlock to allow gases to escape without letting air in.

d. First Fermentation Phase:

  • Place the jar in a dark, room-temperature spot for about 1 to 2 weeks. The mixture should start bubbling in a few days, indicating that fermentation is underway.
  • After the bubbling becomes less intense, indicating the end of the alcoholic fermentation, proceed to the next step.

e. Second Fermentation Phase:

  • After the initial fermentation, you can either transfer the liquid to a new container or continue in the same one. Replace the cloth or reattach the airlock.
  • Let the liquid sit for another 4 to 6 weeks, stirring it every few days to incorporate air, which helps the acetic acid bacteria convert the alcohol into vinegar.
  • Taste the vinegar periodically. Once it reaches the desired acidity level, it’s ready for the next step.

f. Strain and Store:

  • Strain the vinegar through a fine mesh sieve or cheesecloth to remove any sediment.
  • Transfer the vinegar into clean, sterilized bottles. Seal the bottles tightly to stop the fermentation process.

g. Mature:

  • Store your vinegar in a cool, dark place. It will continue to mature and develop flavor over time. There’s no need to refrigerate it.


  • The Mother: Over time, your vinegar may develop a gelatinous mass known as “the mother.” This is a sign of a healthy vinegar and can be used to start future batches.



  • 1-2 kg of cucumbers (small to medium-sized are preferred for pickling)
  • 4 cups of water
  • 2 cups of white vinegar
  • 2 tablespoons of salt (use pickling or canning salt for best results, as table salt can make the brine cloudy)
  • bay leaves
  • 1-2 tablespoons of sugar (optional, for a slightly sweet brine)
  • Garlic cloves (to taste, usually 1-2 cloves per jar)
  • Fresh dill (to taste, a few sprigs per jar)
  • Mustard seeds (1 teaspoon per jar)
  • Black peppercorns (1/2 teaspoon per jar)
  • Red pepper flakes (optional, for a spicy kick)


  • jars with lids (sterilized)

a. Prepare the Cucumbers:

  • Wash the cucumbers thoroughly.
  • Cut off the blossom end of the cucumbers to prevent them from becoming soft during pickling. You can leave them whole, slice them into spears, or cut them into rounds, depending on your preference.

b. Sterilize the Jars:

  • Place the jars in a large pot, cover them with water, and bring to a boil. Boil for 10 minutes to sterilize or other sterilisation methods.

c. Prepare the Brine:

  • In a small pot, combine water, vinegar, salt, and sugar (if using).

d. Pack the Jars:

  • optional: Place a couple of dill sprigs, bay leaves, 1-2 garlic cloves, mustard seeds, black peppercorns, and red pepper flakes (if using) into the bottom of each jar.
  • Pack the cucumbers tightly into the jars. It’s important that they are snug to prevent floating.

e. Add the Brine:

  • Pour the brine over the cucumbers in the jars, leaving about a 1/2 inch of headspace at the top.

f. Cool and Store:

  • Allow the jars to cool completely at room temperature. Check the seals; the lids should be sucked down and not flex when you press the center.
  • Store the pickles in a cool, dark place for at least 48 hours before eating to allow the flavors to develop. For the best flavor, wait about two weeks.

part II


Mycelium is a root-like structure of a fungus consisting of a mass of branching, thread-like hyphae.

 Its normal form is that of branched, slender, entangled, anastomosing, hyaline threads.

 Fungal colonies composed of mycelium are found in and on soil and many other substrates

A typical single spore germinates into a monokaryotic mycelium,which cannot reproduce sexually; when two compatible monokaryotic mycelia join and form a dikaryotic mycelium, that mycelium may form fruiting bodies such as mushrooms.

Through the mycelium, a fungus absorbs nutrients from its environment,  in a two-stage process. First, the hyphae secrete enzymes onto or into the food source, which break down biological polymers into smaller units such as monomers. These monomers are then absorbed into the mycelium by facilitated diffusion and active transport.

Mycelia are vital in terrestrial and aquatic ecosystems for their role in the decomposition of plant material. They contribute to the organic fraction of soil, and their growth releases carbon dioxide back into the atmosphere 

 Mycelium is an important food source for many soil invertebrates. They are vital to agriculture and are important to almost all species of plants, many species co-evolving with the fungi

b. Mycelium as a Biomaterial


Fungal-based composites are the recently implemented technology that fulfills the concept of the circular economy. It is made with the complex of fungi mycelium and organic substrates by using fungal mycelium as natural adhesive materials. The quality of the composite depends on both types of fungi and substrate. To ensure the physicochemical property of the fabricated composite, mycelium morphology, bimolecular content, density, compressive strength, thermal stability, and hydrophobicity were determined. This composite is proven to be used for different applications such as packaging, architectural designs, walls, costume design and accessories, insulation.



Grey Oyster mushroom (Pleurotus ostreatus)

is not just a culinary delight but also an organism of significant interest due to its potential in sustainable material production. This area of study explores how biological systems can be harnessed to develop new materials and products that are biodegradable, sustainable, and have a lower environmental impact compared to conventional materials. Here’s an overview of the Grey Oyster mushroom’s potential as a biomaterial:

Mycelium as a Building Material:

  • Mycelium Network: The root structure of mushrooms, known as mycelium, is being explored for its use in creating sustainable building materials. Mycelium can grow through and bind substrates like agricultural byproducts (straw, sawdust, etc.), forming a dense, fibrous network. Once it colonizes a substrate, it can be dried, stopping its growth, and resulting in a lightweight, strong, and naturally insulating material.
  • Biodegradable and Sustainable: Materials derived from mycelium are fully biodegradable and can be composted, returning nutrients to the environment. This contrasts sharply with conventional building and packaging materials, which often contribute to pollution and waste.

Applications in Packaging:

  • Alternative to Polystyrene: Mycelium-based materials are being developed as a sustainable alternative to polystyrene and other plastic-based packaging materials. These biodegradable materials can protect goods during shipping and degrade naturally once disposed of.

Textiles and Leather Alternatives:

  • Mycelium Leather: Research into mycelium also extends to the fashion industry, where it is used to create sustainable, vegan leather alternatives. This mycelium “leather” is grown in controlled conditions to produce sheets of material that can be tanned and treated much like traditional leather.

Environmental Benefits:

  • Low Resource Requirement: Growing mycelium-based materials requires significantly less water, energy, and land compared to traditional materials. Furthermore, it can utilize waste products as growth substrates, contributing to a circular economy.
  • Carbon Sequestration: Mycelium absorbs carbon as it grows, potentially making it a carbon-negative material. By locking away carbon, mycelium-based products could help mitigate climate change.

Challenges and Future Directions:

  • Scalability: While promising, scaling up mycelium production to meet large-scale demand presents challenges, including optimizing growth conditions and ensuring consistent quality of the material.
  • Research and Development: Ongoing research aims to enhance the properties of mycelium materials (strength, water resistance, durability) to widen their application range and make them competitive with conventional materials.

The Reishi mushroom (Ganoderma lucidum)

, also known as Lingzhi, has been revered in traditional medicine for centuries, particularly in East Asia. Beyond its well-documented health benefits, Reishi is gaining attention in the biomaterials field for its unique properties and potential applications. From a biomaterial perspective, Reishi mushroom presents fascinating opportunities for sustainable material development, similar to other fungi. Here’s an exploration of Reishi’s potential as a biomaterial:

Composition and Structure:

  • Chitin-Based Structure: Like other fungi, the cell walls of Reishi mushrooms are composed of chitin, a natural polymer that provides a robust framework for developing materials. Chitin is being explored as a base for creating biodegradable plastics and other sustainable materials.
  • Dense Mycelial Network: Reishi’s mycelium, the root-like structure of the fungus, forms a dense and intricate network capable of binding substrates together. This network can be harnessed to produce materials with unique properties, such as mycelium-based composites.

Potential Applications:

  • Biofabrication: Reishi mycelium can be grown into predetermined shapes and sizes by providing a mold or scaffold. This process, known as biofabrication, allows for the production of custom objects or materials with minimal waste, offering a sustainable alternative to conventional manufacturing techniques.
  • Biodegradable Products: Items made from Reishi mycelium, such as packaging, containers, and even furniture, are biodegradable and compostable, presenting a lower environmental impact compared to similar products made from plastics or other non-renewable materials.
  • Textiles and Leather Alternatives: Reishi mycelium is being explored for its potential to create sustainable textiles and leather-like materials. These alternatives are not only eco-friendly but also provide options for those seeking materials not derived from animals.

MYCELIUM MOLD/PATTERN (making a sustainable Mycelium corset, inspired by a Byzantine pattern)


how to grow your own starter culture:

2:1 raw kombucha starter with starter liquid

tea, red wine (tanin sources)

sugar 10%

filtered water

vinagre, to adjust the PH between 3.8 – 4.5

when it dries, clean it with bee wax.