I quit sugar: making biofactories that run on waste

(Nanowerk News) Scientists at Macquarie University have found a way to use waste products as yeast feed.
This exciting discovery opens up the possibility of fuelling biofactories without devoting arable land to producing sugars for them, but also because of the larger role methylotrophic organisms play in the environment.
For thousands of years, humans have been using yeast for brewing and baking. More recently, we’ve taken our relationship with one particular yeast, Saccharomyces cerevisiae (S. cereivisiae), to the next level, using it to produce food, fuels, chemicals and pharmaceuticals. Yeast based biomanufacturing is more sustainable than petrochemical refining, but there’s a catch. It needs food – specifically, sugars – to grow. And that means using farmland to feed biofactories instead of to feed people.
Ideally, a biomanufacturing yeast would thrive on something that humans can’t eat. In a paper just published in Nature Communications ("Adaptive laboratory evolution of native methanol assimilation in Saccharomyces cerevisiae"), Dr Monica Espinosa Gomez, and her colleagues have shown that – with help from bioengineering – it can.
Espinosa says, “Microorganisms are being engineered to partially replace petrochemicals; fossil fuels; plant and animal-based food; and even produce entirely new materials such as spider silk, animal-free leather and milk, all using fermentation.
“However, yeast requires sugars from corn or sugarcane to grow and make products.
“This not only makes fermentation expensive and uncompetitive with oil refining, but it also means that production of these next generation bio-products competes with the human food supply by taking up arable land.”
Dr Espinosa was awarded her PhD from Macquarie for this research, as part of a team led by Dr Thomas Williams, a Research Fellow at the ARC Centre of Excellence in Synthetic Biology at Macquarie University, which has engineered the evolution of a previously unknown metabolic network in yeast that allows it to metabolise methanol.
This is particularly appealing, because methanol can be extracted from waste products. It can be produced from natural gas, coal and renewable sources such as municipal waste, biomass and agricultural waste. Because it is a liquid, it is also compatible with the existing fermentation, storage, and transportation infrastructure.
Williams stresses the importance of this. “Our current dependence on fossil fuels is not sustainable. We have finite reserves and there are negative environmental impacts from extraction and use.
“By-products from fossil fuel combustion include a myriad of toxic air pollutants and CO2, which is the main anthropogenic contributor to climate change.
“These complex environmental problems call for a global effort to move towards bio-economy in which microbial metabolism is used for the conversion of renewable materials into useful products.”
This discovery marks the first step towards engineering methylotrophy in S. cerevisiae. It is also the first time that the yeast’s native ability to metabolise methanol has been observed.
Source: Macquarie University
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