Lessons from a Loaf of Bread
Originally published in An Inkling Journal (Vol. 3)
The humble loaf. An ancient and still living craft that has sustained life for centuries, not only for human civilisations in the form of food, but also the microbial communities who are in fact behind the creation of this unique food item that is staple to many cultures. Wild yeasts and bacteria in the air feed on the mixture of cereal grains and water, forming a stable yet dynamic microbial community that is commonly known as a sourdough starter. This starter is subsequently used to leaven bread, creating the distinctive aerated texture that has captured the hearts of many. But there is a lot more to it than that.
Coexistence
The sourdough starter is a great example of a mutually beneficial coexistence amongst microorganisms. A stable equilibrium is created by the various species within the culture, whereby the yeast produces a specific protein known as amylase to break down the starch into simpler sugars, in this case maltose, for the Lactic Acid Bacteria (LAB) to ferment. The products of the fermentation process, namely glucose and lactic acid, in turn create an ideal condition for the yeast to thrive. Metabolic dependency can also arise in such communities, where amino acids produced from yeast metabolism overflow to encourage LAB growth, creating symbiotic niches [1]. This perfectly illustrates how the interaction and dependencies amongst microbial species could shape the environment that they are in, creating conditions that not only the community as a whole will thrive in, but are also dynamic and constantly evolving.
Food Durability
The production of ethanol and lactic acidic as part of the yeast and LAB metabolism, also acts as a form of natural defence for these sorts of ecological niches, preventing pathogenic microbes from disrupting the community. The idea that these communities adapt to form their own ‘immune system’ is an intriguing one, as it relates to the concept of food durability. Studies have shown that breads made using the sourdough method are less susceptible to pathogenic bacterial spoilage due to the acidic environment created by the LAB [2]. Does this mean that foods with more diverse microbial communities are more ‘resilient’ and can keep longer? And could these protective properties be transferred to different environments, thereby increasing food durability in general and reducing food waste? Whilst we currently don’t have answers to all these questions, more and more research is being done in these areas, which will hopefully result in beneficial applications for our food system in the not too distant future.
Microbial cooking
Microorganisms have the ability to transform and increase the bioavailability of various compounds, increasing the overall nutritional value of our food. A good example of this relates the main ingredient in most breads, wheat. Phytate (or phytic acid) is a compound found in the outer layer of wheat and many other cereal grains. On one hand it is an important phosphorous and energy store [3], but on the other it also has a strong affinity in binding dietary minerals including calcium, iron and zinc, and inhibits the absorption of these micronutrients in mammalian guts. Microorganisms present in sourdough have the ability to process phytic acid due to the presence of the phytase enzymes (absent in mammals), thereby alleviating this inhibition and unlocking the nutritional potential of the grains [4]. The concept of ‘microbial cooking’ is therefore an interesting one to further explore, as it provides an alternative method for harnessing nutrients from food sources, which conventionally is done via physical cooking techniques like heating, or chemical ones including acid treatment.
WHEN MICROBES MEETS SDGs
You may be wondering, what does all this have to do with sustainable development? So here are just a few examples to illustrate how microbes might be our solution to building a better and more sustainable future.
By harnessing the power of microorganisms to transform and increase the bioavailability of nutrients in different food sources, we can contribute to the efforts of reaching Zero Hunger by 2030, as highlighted in the UN’s Sustainable Development Goals (SDGs). It can also help us ensure Responsible Consumption and Production through shaping a better food system. For example, using microorganisms to pre-process phytates contained in animal feed could be one of the solutions to prevent eutrophication caused by the high phosphorous content in animal faeces, due to the inability of the mammalian digestive system to break down phytic acid.
Microbial communities can also be used as a way to model how our own microbiome may interact with the microbiome in our food and environment, working towards ensuring Good Health and Well-being across the globe. Finally, a more sustainable food system, especially with an emphasis on the agricultural part of the food chain, can have a direct impact on improving Life on Land, and contribute towards efforts in Climate Action.
OUTRO
In essence, a humble loaf of bread has led us to rethink the role that we, as humans, play in our food system and wider network. We must move away from the egocentric view of that we are at the centre of this complex ecosystem, and learn to interact with the other organisms that are also part of the system. It is important to appreciate that our world is a closed system, and hence there are only a finite amount of resource available. Therefore, as part of the sustainable development efforts, we should explore new ways to more efficiently access the nutrients in our food sources, and design more circular systems within the network to build a more sustainable future.
REFERENCES
Ponomarova, O., et al., Yeast Creates a Niche for Symbiotic Lactic Acid Bacteria through Nitrogen Overflow. Cell Syst, 2017. 5(4): p. 345-357 e6.
Katina, K., et al., Potential of Lactic Acid Bacteria to Inhibit Rope Spoilage in Wheat Sourdough Bread. LWT - Food Science and Technology, 2002. 35(1): p. 38-45.
Schlemmer, U., et al., Phytate in foods and significance for humans: food sources, intake, processing, bioavailability, protective role and analysis. Mol Nutr Food Res, 2009. 53 Suppl 2: p. S330-75.
Kikunaga, S., M. Takahashi, and H. Huzisige, Accurate and Simple Measurement of Phytic Acid Contents in Cereal Grains. Plant Cell Physiology, 1985. 26(7): p. 1323-1330.