THANKS to an internal AgResearch “curiosity fund”, Dr Seth Laurenson and his colleagues gained some funding to explore the possibility of turning kombucha SCOBY (symbiotic culture of bacteria and yeast) into a bioplastic product.
The SCOBY is the active fermented culture often found sitting snot-like in a bottle of commercial tea-brewed kombucha.
The researchers figured that if a kombucha type SCOBY could be grown to a reasonable size, it could then be dried and moulded into a bioplastic application.
“We grew them in big tubs of nutrient broth, to the point you could pick it up and hold it in your hands and shake it, not unlike a towel,” Laurenson said.
The researchers were looking at the potential the resulting bioplastic, while crude, may have for an application where low-grade plastics are used, such as for baleage wrap.
They achieved what they set out to do, creating a bioplastic, moulded protective guard out of the SCOBY. But they also found further work was needed to ensure it was impermeable to moisture, which tended to cause it to soften.
“But we also found that in the tubs, the pH dropped to four (acid) quite quickly when the SCOBYs were introduced, often within a day or so,” he said.
“We figured that could be enough to kill any microbial population, so a logical step was to see what effect it would have on killing bacteria in effluent.”
Growing a SCOBY in farm fresh dairy effluent resulted in E.coli bacteria levels dropping within 48 hours, along with the decline in pH.
Initially the researchers figured the drop in pH the SCOBY was causing was prompting bacteria to die as their environment became more acid.
But comparing E.coli numbers in the SCOBY tubs against E.coli numbers in effluent, with its pH lowered by dosing with added acid, soon had the scientists looking at other possibilities for SCOBY’s bacteria-killing effectiveness.
“The SCOBY tubs experienced a more effective bacteria kill, suggesting there is something more complex going on than just a change in pH with the SCOBY there,” he said.
After eight days they could not detect any E.coli bacteria in the SCOBY treated effluent.
Revisiting some of the literature on SCOBY science, the researchers believe it may be alcohol produced by the SCOBY fermentation that is adding to its bacteria cleansing ability.
Commercial kombucha is often sold with the note that it contains about 1% alcohol, due to the natural fermentation process that uses tea, rather than effluent.
“The big elephant in the room though was that we were left with this treated effluent that had a low pH (4) and was not suitable to put onto paddocks,” he said.
If the work were to be taken further in the future this could be countered, possibly by combining treated and untreated effluent to buffer the pH back up, making it suitable for application.
Laurenson attributes the curiosity fund to helping the researchers explore a little known or understood area of research, and the opportunity to enable some good scientific minds to “blue sky” their research options.
The same fund has provided Laurenson and his team the opportunity to trial 3D printing soil, with one eye on how to emulate the key properties of a growing medium that could be applied in less than ideal growing situations, including Mars.
“The challenge has been to try and maintain biological life within the manufactured soil, which is proving quite hard,” he said.
In the meantime, the learnings about SCOBY application have been valuable.
“We were extremely surprised to learn that if you put a SCOBY into effluent, we thought the effluent bacteria would overpower the SCOBY and kill it off, but that was not the case,” he said.
“Literature suggests the SCOBY can actually protect the biome community within the environment, it has a competitive advantage.”
They also learnt how quickly the SCOBY adjusts to the environment it is placed in.
“We thought it would be four days, but it was biologically active almost immediately,” he said.
Laurenson says the team was pleased to have a proof of concept, with the potential now there for parties to pick it up and look at practical applications on-farm.
“We were looking at a micro-circular system on-farm, where you could produce the SCOBY, provide a treatment to the effluent and produce a bio-plastic, all in one place,” he said.
