How are microbes helping end hunger?

This article explores the potential of microbiology to positively impact all aspects of the food supply chain, improving the quantity, quality, safety, and nutritional value of food products by providing innovative ways of growing, processing, and preserving food and thus contributing to Zero Hunger, one of the Sustainable Development Goals (SDGs) of the United Nations. Hunger is a cruel reality that affects millions of people around the world and could worsen in the coming years due to the continuous growth of the population and the limitations of our planet's resources. Feeding a population that is expected to exceed 9 billion by 2050 is extremely complex and requires not only an adequate and sustainable food supply but also a collective effort from different sectors of society. This collaborative effort should involve key stakeholders, including politicians to inspire social and cultural changes and scientists to provide technological innovations. Social changes such as promoting education on proper nutrition practices or encouraging healthy lifestyles are as important as ensuring an efficient, secure and sustainable food system. The efficiency of the system can be improved by reducing lost and waste, minimizing water use and improving nutrition quality. The food system must also ensure the health of humans and animals by preventing foodborne diseases and intoxications through improved sanitary conditions. Importantly, the food supply system must be sustainable to protect not only the well-being of individuals but also the overall health of our planet. The current way of producing food is unsustainable because it requires large amounts of energy and water, contributes to climate change and degrades ecosystems. It is essential that the food supply system can operate without causing further damage to the planet and preserving its biodiversity. This can be achieved, among other actions, by reducing greenhouse gas emissions and avoiding recalcitrant contaminants and land deforestation. In addition to the growing population, climate change itself poses a significant threat to the challenge discussed. Climate change is responsible for an increase in the number of extreme weather events, changes in temperature and precipitation patterns and the frequency of droughts and floods. All of these events disrupt crop yields, compromise food security and contribute to the spread of pests and diseases. As microbiologists, we are responsible for delivering innovative solutions to these challenges, since microorganisms, although historically ignored and underestimated, have great potential for many positive contributions. Microorganisms are valuable allies that help maintain and improve ecosystems and thus counteract the adverse impacts of intensive farming and climate change, that is, reduce the environmental footprint of agriculture. In addition, they can improve the productivity and efficiency of all aspects of the food system, including production, distribution and consumption, and more importantly, food security. This article explores the potential of microbiology to positively impact all aspects of the food supply chain, improving the quantity, quality, safety and nutritional value of food products by providing innovative ways of growing, processing and preserving food and thus contributing to Zero Hunger, one of the Sustainable Development Goals (SDGs) of the United Nations. Healthy and fertile soils foster optimal conditions for the growth of crops, which is fundamental for the sustainability of the food supply chain, but many anthropogenic activities cause significant levels of soil degradation. To address the current soil crisis, different microbial tools have been developed to improve soil fertility, facilitate the decomposition of organic matter (Sáez-Sandino et al. , 2023), promote nutrient cycling, detoxify pollutants (Jayaramaiah et al. , 2022) and support the overall resilience of the ecosystems. The importance of maintaining soil health and the positive influence of microorganisms in addressing this challenge has been discussed by Timmis and Ramos (2021), who advocate for the creation of a soil health system to proactively prevent soil loss. Importantly, microorganisms can directly improve vegetable nutritional levels, which would improve nutrient intake without requiring increased consumption (Goicoechea Salwan et al. , 2023). BCAs can limit the growth of the plant pathogen by competing for the same resources (nutrient competition), and importantly for iron by using siderophores, that is, small, high-affinity iron chelating compounds. Since many pathogenic bacteria require iron for their growth, BCA-produced siderophores are a good strategy to limit their growth and virulence and reduce the incidence of plant diseases (Ahmed Durán et al. , 2021), and the same holds true for the T4BSS (Purtschert-Montenegro et al. , 2022). Similarly, predatory microorganisms have been recognized as valuable biocontrol agents (Zhang et al. , 2023). These microorganisms produce enzymes to degrade the cell walls of target organisms or use specialized structures to capture, penetrate and consume their prey. In particular, Myxobacteria and Bdellovibrio and like organisms (BALOs) exhibit a broad predation spectrum in plant pathogens, making them good candidates for biocontrol applications (Zhang et al. , 2023). Likewise, viruses that specifically infect and kill phytopathogenic microorganisms can be used in biocontrol to reduce the population of these harmful organisms. This novel approach minimizes the impact on non-target organisms and is considered a promising biocontrol strategy currently underused mostly because of regulatory obstacles (Wagemans et al. , 2022). Many phytopathogenic bacteria exhibit social behaviour that promotes infections, including the formation of biofilms that allow these bacteria to adhere to biological surfaces as the first step of infection. Some BCAs can disrupt the formation of biofilms by producing compounds that interfere with their adhesive properties, making it difficult for pathogens to cause infections. Pathogenic bacteria can coordinate the gene expression of these 'social' virulence factors, for example, biofilm formation or T3SS, at the population level by using a Quorum Sensing (QS) communication system. Some BCAs can interfere with pathogen's QS by a mechanism known as Quorum Quenching (QQ) (Liu et al. , 2023) that inhibits the coordinated expression of virulence factors. Other signalling molecules that can be released by biocontrol agents are volatile organic compounds (VOCs). These molecules can interfere with spore germination, inhibit pathogen growth or induce systemic resistance in plants, and therefore could be exploited for pest control in sustainable agriculture (Almeida et al. , 2023). All these mechanisms contribute to the diverse arsenal of strategies employed by PGPMs and BCAs. Research in these fields continues to uncover new insights into our understanding of microbial interactions with plants, offering opportunities to optimize these relationships for the benefit of crop production, disease management practices and ecosystem health. A recent example of the new technologies that are being developed in this field is the seed biopriming system. This novel microbial inoculant technique combines effective BCAs and physiological aspects of the seed, such as hydration, to improve metabolism activity and mitigate the common limitations of bioinoculants (Singh, Vaishnav, et al. , 2023). In fact, seed biopriming has been shown to increase the protection of seeds against soil-borne pathogens and soil pollutants, for example, salts and heavy metals, while promoting germination rate and uniformity, improving not only the primary productivity but also soil health (Singh, Vaishnav, et al. , 2023). In the last decade, the promising application of these novel practices in agriculture has gained attention as sustainable and environmentally friendly approaches to improve crop productivity and its importance is expected to continue to grow in the future. Fungi that form fruiting bodies such as mushrooms and others alike are an excellent source of direct microbial food that is easily cultivated and cooked. In addition, in recent years, microbial products from fungi mycelium, such as Mycoprotein or Quorn (brand), have hit the market. Quorn is a protein-rich food ingredient produced from Fusarium venenatum that is often used as the primary component of vegetarian 'meat' because it offers a meaty texture and a suitable protein content (Banks et al. , 2022). Fungi mycelia from species such as Pleurotus ostreatus (oyster mushroom) and Ganoderma lucidum (reishi mushroom) are also used in the production of meat alternatives or snack products, such as mushroom chips or mushroom jerky. Furthermore, fungal mycelium extracts are also used in the production of functional beverages, including teas and elixirs, with potential health benefits. In recent decades, photosynthetic microorganisms like the cyanobacterium Spirulina have been cultivated for their nutritional value containing essential amino acids, vitamins and antioxidants. These bacteria hold the promise of becoming a major food source in the future (García et al. , 2017) as an alternative to animal protein. Moreover, some species of filamentous cyanobacterium Nostoc are commonly consumed in certain Asian cultures, particularly in China, and it is also a good food source due to its high protein content. The cultivation of fungi or photosynthetic microbes typically requires less land, water and resources compared to traditional agriculture, making them a great sustainable food source. However, the taste and acceptance of these products in new cultures can be a challenge, and many efforts are ongoing to improve palatability. Microorganisms are also essential for various processes directly involved in food production, especially fermentation, a traditional method that has been used for centuries. Biochemically speaking, it is a metabolic process in which microorganisms break down complex compounds into simpler ones, producing by-products that contribute to the taste, texture, nutritional content and bioactive properties of foods (Kiczorowski et al. , 2022). Examples include the fermentation of milk to produce yoghurt, cheese or kefir; the fermentation of cabbage to produce sauerkraut; the fermentation of cereals for the production of bread or beer or the fermentation of grapes to produce wine, vinegar, champagne or spirits such as brandy or grappa. The fermentation of plant-based dairy is a growing field that has emerged as an important alternative to the fermentation of animal products (Harper et al. , 2022). Conscious manipulation of the microorganisms involved in these processes could improve not only consistency but, more importantly, flavour quality. Given the extensive list of microorganisms involved in fermentation and food products resulting from this process, presenting them all here would be impractical, and readers can refer to fantastic reviews including (Tamang et al. , 2020). Instead, we highlight key food products and producer microorganisms of great interest to humans, due to their nutritional value and profound impact on human culture. Saccharomyces cerevisiae, also known as baker's yeast, is a fungus commonly used in baking and brewing. Saccharomyces in Greek means 'sugar fungus' since during fermentation, this fungus uses sugars and, as a by-product, produces alcohol. Alcohol is a molecule without biological function and is extremely toxic to most microorganisms, except for this resistant fungus that uses it as a chemical weapon to eliminate competitors. This fungus has been widely studied for decades due to its involvement in food production, and many revisions are available in the literature (Gänzle, 2022). The role of Saccharomyces and other yeasts is also essential in the first steps of cocoa fermentation and is directly involved in the development of the cocoa flavour. Cocoa beans are very bitter and acidic and must go through a correct fermentation process to lose bad taste and obtain good quality chocolate. Up to 45 yeast genera have been identified in cocoa fermentation in different countries including Saccharomyces, Pichia, Candida, Hanseniaspora, Torulaspora, Issatchenkia and Saccharomycopsis (Schwan et al. , 2023). Saccharomyces have also been involved in the spontaneous fermentation of coffee beans together with other microorganisms that are part of a complex microbiota present in the fruit. This complex microbiota formed by yeasts, filamentous fungi and bacteria can vary depending on the environmental conditions, coffee varieties, fruit maturation, season, altitude, temperature and processing methods affecting the quality of this beverage (Schwan et al. , 2023). Similarly, Saccharomyces cerevisiae and other fungi, including Penicillium roqueforti, Penicillium camemberti and Geotrichum candidum, have been used for centuries to produce cheese and Penicillium nalgiovense and Penicillium salami to dry-cure meat, such as salami (Ropars Tesfaye et al. , 2019). In addition to dairy products fermentation, LAB including several species of Leuconostoc, Lactobacillus, and Weissella are used to ferment vegetables such as napa cabbage or Korean radish to produce traditional Korean kimchi. Similarly, the fermentation of raw cabbages by LAB produce sauerkraut, cucumbers are transformed into cucumber pickles and olives are fermented by yeasts and LAB to remove bitterness and make them palatable. In recent years, a fermented tea beverage known as kombucha has become a fashionable and healthier alternative to carbonated beverages and can be found in many supermarkets around the world. The fermentation occurs by a symbiotic culture of bacteria and yeast (SCOBY) consisting of LAB, acetic acid bacteria (AAB) and yeast, which metabolize the sugar and tea components. This process results in a naturally carbonated beverage, with a flavour that combines sweet and sour, antioxidants and vitamins and with trace amounts of alcohol (Diez-Ozaeta that is, BCAs can help prevent food spoilage by inhibiting the growth of pathogens or toxins-producing microorganisms during the phases of production, processing and distribution, extending the shelf life of perishable items. Similarly, microorganisms responsible for fermentation processes preserve food products, reducing perishability and contamination with pathogens and mycotoxins (Adebo et al. , 2019) due to the inhibitory effect of toxic compounds produced as by-products such as alcohol or acids (Guo et al. , 2023). An interesting example of animal food (forage) preservation is silage made from green crops, such as grass or corn, that are stored and fermented under airtight conditions. The absence of oxygen promotes fermentation by lactic acid bacteria, which produce an acidic environment that helps preserve forage for months, preventing spoilage and decay. Furthermore, current knowledge about the use of LAB in crop silage indicates that the fermentation process improves the digestibility of the silage by livestock, and is a vehicle for the delivery of probiotic substances that can expand animal health (Guo et al. , 2023). On a different line, microbes can be directly involved in waste management within the food industry. They can be used in processes such as composting and anaerobic digestion to convert organic waste into valuable products such as fertilizers and biogas, promoting sustainability and reducing environmental impact (Rastogi Zhang et al. , 2022). In conclusion, microbes are indispensable allies in the intricate web of food production and their importance is expected to continue increasing. They enhance manufacturing, improve food properties, prevent spoilage and pathogenicity and contribute to human health. In this way, they are crucial to ensuring the sustainability and efficiency of the entire food supply chain. Importantly, recognizing and harnessing the power of microbes in food production is the key to addressing global food security challenges and promoting a more sustainable and resilient food system. Patricia Bernal conceived the idea for this article, conducted all the necessary literature review, and wrote the entire manuscript. Figure 1 has been crafted using Canva (canva. com) and a Freya Saad-designed template titled "Green and Blue Playful Illustrative Mind Map". P. B. is supported by the MCIN/AEI/10. 13039/501100011033 Spanish agency through the Ramon y Cajal RYC2019-026551-I and her laboratory is funded by three Research Grants from the State Subprogram for Knowledge Generation from the Spanish Minister of Science and Innovation (MCIN) ; MCIN/AEI/10. 13039/501100011033/FEDER, EU – PID2021, MCIN/AEI/10. 13039/501100011033/NGEU/PRTR – TED2021, MCIN/AEI/10. 13039/501100011033/NGEU/PRTR/ – CNS202, the Spanish State Research Agency (AEI) and the European Union (UE) with reference PID2021-123000OB-I00 (MCIN/AEI/10. 13039/501100011033/FEDER, UE), TED2021-130357B-I00 and CNS2022-135585 (MCIN/AEI/10. 13039/501100011033/"NextGenerationEU"/PRTR The Spanish Recovery, Transformation and Resilience Plan). P. B. is also supported by a Grant (Excellence Grant 2021) from the Andalusian Knowledge Agency (AAC), Andalusian government with reference ProyExcel₀0450. The author declares that there is no conflict of interest.