Bread 'trash' is microbial treasure

Tonnes of bread end up in landfill every year, but researchers have now found a way to repurpose this discarded bread and dough. Research published in Frontiers in Microbiology has revealed that old bread can be used as a medium for cultivating microbial fermentation starters, which could have applications in food industries like bakeries, dairy and winemaking.

“We believe that the introduction of innovative bioprocessing technologies might be the key to unravel the burden of food waste [and] improving sustainability of the agro-food system,” said Dr Carlo G Rizzello, team coordinator at the University of Bari Also Moro in Italy.

Researchers experimented with more than 40 different kinds of growing conditions to determine the best combination for various bacteria, yeast and other microorganisms used in food fermentation. This included finding the correct recipe of bread amount, enzymes and supplemental ingredients, as well as the ideal time and temperature for incubation. Researchers wanted to create a wasted bread medium (WBM) that could surpass current production methods that rely on raw materials; they achieved this by using 50% waste bread that was appetising to a variety of microorganisms, including bacteria used in yoghurt production. Researchers also estimated that the production cost of WBM is considerably lower than that of conventional media.

“The protocol we were able to set up combines both the need for disposing of the huge amount of bread waste with that of cheap sources for media production, while fitting for the cultivation of several food industry starters, and it is patent pending,” said Dr Rizzello.

WBM protocols could be adapted by bakers who currently rely on other companies to provide the starters. Bakeries could use their own waste to produce the medium and propagate the cultures, without modifying their existing technology.

“The strength of our study strictly relies on how easily applicable the protocol is, and proof of its feasibility is indeed the fact that the process is already scaled up at industrial level. Nevertheless, WBM offers a possibility for sustainable starter production to all the food industries working in the field of fermented foods and beverages,” said Michela Verni, lead author.

WBM has applications beyond microbial cultivation; a few changes to the WBM recipe could enable it to be used as a food ingredient or as fermentation with different starters. It could also serve as a substrate to feed microbes that produce compounds used in food supplements or cosmetics.

While WBM appears to be an effective medium for growing lactic acid bacteria and yeasts, Dr Rizzello said further study is needed to determine if certain components or lack of some micronutrients might affect microbial metabolism in some significant way.

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