By Oliver Kellhammer and Parsons Sustainable Systems
In this activity, you will learn the basic principles of maintaining a sterile protocol and inoculating feedstocks with a microbial culture as well as be challenged to envision new applications for a versatile material that has only recently come to the fore. As long as basic aseptic protocol is followed (boiling the water, making sure the kombucha culture isn’t contaminated by keeping it covered etc.) good results can be expected in about two to three weeks, depending on temperature and the vitality of the SCOBY starter culture.
i) A live SCOBY (symbiotic community of bacteria and yeast) https://www.amazon.com/gp/product/B009ZW8RP4/ref=od_aui_detailpages00?ie=UTF8&psc=1 It is quickest to start using a commercially available SCOBY though it is quite possible to start your own SCOBY from a (non-pasteurized) kombucha drink, though this will take a little more time. I purchased the initial SCOBY on Amazon but grew subsequent cultures by reusing the kombucha liquid left over after harvesting and adding more fresh brewed tea and sugar feedstock. A new SCOBY soon forms from the residual cells left in the salvaged liquid.
ii) Black or green tea in bags and granulated white sugar
iii) ONLY NEEDED IF YOUR SPACE IS COOLER THAN AVERAGE Heat Mat: I bought a Hydrofarm 9 x 19 1⁄2 “ heat mat which fits nicely under the plastic container I used, but the process will work without a heat mat provided the culture is situated in a warm location. 80 degrees F is the optimal temperature but growth will occur at room temperature, albeit slower. https://www.amazon.com/gp/product/B0001WV010/ref=od_aui_detailpages00?ie=UTF8&psc=1
iv) Translucent storage box with lid. I used a K-mart 15.8 quart storage box, as this provided a useful dimension for the finished microbial leather. Containers can be sized as needed for convenience as the finished material will grow to the size of the available surface area.
http://www.kmart.com/hefty-storage-bin-15-quart-clear/p-011W003201721000P?rrec=true v) Piece of plywood or a cutting board for drying the leather, measuring cup, disposable nitrile gloves.
i) Bring one gallon of water to a boil and add 1 cup of white sugar and 6-7 teabags (depending on how big the teabags are) of ordinary black tea (whatever is the cheapest as you won’t actually be drinking it.) Some recipes call for the addition of a little apple cider vinegar to create a more favourable pH, but I haven’t found this necessary. Allow the steeped tea and sugar mixture to cool to room temperature before pouring it into the plastic container. Remove the teabags and discard them.
ii) With nitrile gloves or very clean and freshly washed hands, add the SCOBY to the cooled liquid, put the lid on the container and place the whole thing on a heat mat and store in a dark(ish) place.
iii) Over several days a thin layer of material will begin to form on the surface of the liquid, which will gradually thicken as the SCOBY continues to feed and grow.
iv) Wait until the microbial leather layer is at least 1⁄2” thick before harvesting as the thickness will shrink down considerably during drying as it has a very high moisture content. The culture continues to add new cells from the top as it grows and this is always the youngest layer, which can (if thick enough) be peeled from the bottom layer to form a new SCOBY and inoculate more tea and sugar feedstock.
v) When thick enough remove the floating material and wash it thoroughly with cold water and a little dish soap to remove the scummy brown stuff from the surface.
vi) Lay the washed material out to dry on a wooden cutting board or a piece of plywood. Microbial leather has a very high moisture content, so drying can take several days under normal indoor conditions. This can be speeded up by putting the material next to a radiator or out in the sun.
vii) Microbial leather will maintain considerable flexibility even when dry and can be sewn, folded or formed (moulded) in a wide variety of ways as well as coloured using natural dyes, cut, embossed etc. Your imagination is the only limit and individual pieces can be joined to each other by re-wetting the edges or using conventional fastening techniques. Be advised however the finished microbial leather isn’t water resistant, which is currently one of its main drawbacks. Consider experimenting with various coatings, waterproofing treatments etc. to address this limitation.
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