Could Wastewater Be A Triple Solution for Food Waste, Sustainable Proteins & Green Fuels?
)
How would you like your wastewater-derived meat?
It may sound unappetising, but residual water from the food and pharmaceutical sectors could be a solution to our crippling food waste problem, while producing alternative proteins like meat and dairy analogues, as well as greener fuels.
Researchers from the Technical University of Denmark (DTU) tapped the salty residue from cheese produced by Danish dairy giant Arla to test a yeast strain called Debaryomyces hansenii. These microbes can thrive in highly saline environments, and the study found that they can be turned into valuable proteins to make meat analogues, dairy alternatives, pigments, and enzymes.
“There are businesses that create waste streams that are rich in nutrients, but also have a very high salt content, which is often a problem,” explains DTU Bioengineering assistant professor José Martinez.
“The salinity prevents utilisation of the nutrients while preventing businesses from discharging their waste streams as ordinary wastewater, which means they have to special treat, and this is costly. Why don’t we try to grow this type of yeast in these salty waste streams?” he explains.
Food waste meets pharma waste
Courtesy: Jose Ramos
In 2020, a study found that wastewater from raw cheese manufacturing – usually derived from the demineralisation of whey – was problematic, “posing severe environmental and public health problems” thanks to its acidic pH and the high amounts of phosphorus, total solids, oils and fats, and minerals involved.
Agriculture’s planetary impact is already massive – it accounts for a third of global greenhouse gas emissions. But a third of all food produced is either lost or wasted, which alone makes up 8-10% of emissions. So a solution that valorises a food industry sidestream that otherwise ends up harming the planet and our health has bags of potential.
Martinez has been researching yeast cells adapted to extreme conditions like high temperatures, low nutrient content, or high salinity for years. D. hansenii is adapted to aquatic environments, and can thrive in water up to six times as salty as seawater.
The experiment with Arla’s wastewater exceeded his expectations. The saline residue was also rich in lactose (a sugar), which the yeast cells easily metabolised. While more salt content meant more efficient growth, the yeast’s development wasn’t as efficient as it could be due to insufficient nitrogen levels.
To solve this bottleneck of the lactose-rich waste stream, Martinez met with Manuel Quirós, a cultivation specialist at Danish pharmaceutical giant Novo Nordisk. Quirós revealed that Novo Nordik had a salty residue of its own – linked to the manufacture of haemophiliacs – which was high in nitrogen.
“We simply mixed the two saline waste streams – the one with a high lactose content and the one with a high nitrogen content,” explains Martinez. “We used them as they were. We didn’t need to add fresh water, nor did we need to sterilize the fermentation tank, because the salt prevented the growth of other microorganisms. It was plug and play.”
His research team found that D. hansenii thrived in the mixture. To make the yeast a product of commercial interest, they used CRISPR technology to modify the strain into a protein as it grew.
CRISPR is a gene-editing technology that can cut the DNA of cells in specific places, allowing scientists and manufacturers to deactivate genes, insert new pieces of DNA into the genome, and change genes to get rid of mutations. It can help produce many different proteins and substances, and its potential has been explored by researchers using koji mould to make better-tasting meat analogues too.