As the world population increases and developing countries and emerging economies make remarkable progress, the stress resulting from human activities on the natural environment has become more serious. Pollution of air, soil, fresh water and sea water is a problem arising from the creation and development of the country; Ecosystem damage and habitat loss can lead to many hazards [1]. The results cannot be overstated: Air pollution causes 4.2 million premature deaths every year [2]. The annual cost of air pollution to gross domestic product (GDP) in low-income countries is 1.3-1.9% [3]. If no mitigation measures are taken, climate change could lead to significant loss of life and reduce global GDP by up to 7% by the end of the century [4]. In fact, a recent study from the World Economic Forum shows that more than half of global GDP is at risk, directly or indirectly, from environmental issues [5].

Private sector activities are responsible for many negative impacts on the environment. The use of fossil fuels in energy production and transportation is a significant source of the world's greenhouse gas emissions and pollutants such as particulate matter and sulfur dioxide [3]. Agriculture and industry are the cause of soil and water pollution, and agriculture is the cause of deforestation in Africa and South America [6].

There is an ongoing debate on the concept and urgency of planetary sustainability, which, amongst others, resulted in the identification of the so-called planetary boundaries [7], a conceptual approach that identifies and quantifies human impact on our natural ecosystems. The discussions about the actions that are to be taken for planetary sustainability, however, rarely deal with issues related to microbiology, microbial ecology and microbial technology. Nonetheless, microorganisms play a key role in the Earth’s biogeochemical cycles [8, 9] and, directly or indirectly, impact the unprecedented climate change that we have to face in the coming decades. A key feature towards the protection of Earth’s natural resources is that both scientists and engineers must come to more effective management of microbiomes in soils, aqueous environments, but also in relation to bodily systems, such as the rumen, the gastro-intestinal tract, the skin and even the physiological functions in the human body. For example, soils can act either as carbon source or as sink, and this relates with the activity of soil microorganisms, although knowledge on the quantitative contribution of different phylogenetic groups remains elusive [10]. To achieve proper micro-biome management, key generic ecological principles, such as microbial economics which involves the use of microorganisms to produce sustainable and biodegradable products that replace non-renewable resources and reduce environmental pollution, the Pareto distribution concept which can describe social, scientific, and geophysical phenomena in society, top predator involvements which are important drivers in shaping ecological community structure via top-down effects as these are predators at the top of a food chain, without natural predators of its own, bio stability boundary conditions which explains the conditions where the state of the community where the productivity of the ecosystem is high and constant irrespective of the change in environment conditions need to be better defined and taken into account [11-15]. These concepts enable a microbial evaluation and management of current full-scale biotechnologies and allow microbiologists and microbial ecologists to take leadership to speak out on which biotechnology practices should be downscaled and which deserve to be should provide an appropriate framework to foster practices towards microbial products with a well-balanced evaluation of economic and human health-related constrains. Overall, microbial biotechnology will play an important role in the coming years and will be the first of our goals to combat climate change. Here we highlight the important role of microbial technology not only in well-known systems such as soil and aquatic ecosystems, but also in environmental or entire energy production ecosystems, such as (waste) water purification and at least physical purification as part of the microbial ecological environment.  Herein it is explained how the information collected in these projects can help move the world towards a better future. We use information from microbial proteins to show how to overcome microbiophobia, as this is a problem that will affect the future of some important microbial technologies, especially in mitigating climate change.2.

2. Sustainable development involves diverse and complex approaches

Human stewardship of the planet, in particular its biosphere, is wanting: the trajectories of deterioration of critical features of the biosphere (loss of biodiversity, climate change, desertification, unbalanced N and P cycles, water quality and quantity) and the quality of the human condition (hunger, poverty, regional conflicts, refugees, human trafficking, rising health costs, diminishing urban security), on one hand, and the institution of effective corrective/mitigating actions, on the other, are divergent, so planet Earth and human life are becoming increasingly unsustainable. To counteract this divergence, and to reorient evolution of the biosphere towards a more sustainable trajectory, internationally accepted Sustainable Development Goals (SDGs; United Nations, 2015) have been formulated by the United Nations that take into account the fact that all key biosphere and relevant human behavioral processes are interconnected, interdependent and hence must be steered via a systems approach. As a consequence, sustainable development goals are exceptionally diverse, ranging from poverty elimination to moderation of climate change, via safe cities, sustainable use of aquatic and terrestrial systems, to adoption of renewables. As all goals encompass environmental, economic and social aspects, efforts to achieve sustainability are of necessity highly complex.

2.1Microbes are (also) biological stewards of planetary health and sustainability

Microorganisms are the main form of life on Earth, both in terms of number and total biomass. They evolved as the oldest life on Earth and exhibit a wide range of adaptations, functions, and metabolic characteristics that exceed those of all other organisms on the tree of life. Some organisms can survive in harsh environments that are incompatible with most life; this means that their habitat determines the extent of the biosphere and demarcates the barrier between the biosphere and the geosphere. And because microbes can survive in highly stressful environments, they may allow life and the biosphere to recover after catastrophic events that cause major disasters on Earth (for example, deep-sea organisms may be protected from heat damage) or cold weather can remain airborne and survive without light for long periods of time). Microbes are largely our past and our future.

Their ubiquity throughout the biosphere and the diversity of their activities make microorganisms important in planetary and ecosystem studies: they regulate and regulate biogeochemical cycles and the recycling of biological products and wastes, forming a large greenhouse design and pool. Gases, which are an important determinant of gases and therefore climate change, play an important role in the quality and productivity of soil, sea, lakes and rivers, as well as soil structure and fertility. Therefore, microorganisms are also important members of the health and safety team.

2.2Microbes provide a wide range of services to humans, animals and plants: microbiomes

Microbes cover the surfaces of all other organisms (and occupy internal and even intracellular niches, in some) and influence diverse physiological activities of their hosts, including nutrition, health–disease status and hence well‐being. The microbial flora of an organism is designated its microbiome. The microbiomes of food animals and crop plants regulate productivity, and thus global food production and quality. The human microbiome, which has been termed a human organ, in particular the intestinal microbiota, provides a host of metabolic and physiological services, and thereby has a pervasive positive influence on our well‐being, as we discover when their ordinarily benign networked activities become disrupted, e.g. by antibiotic treatment. Our intestinal flora helps digest our food and extract its nutritional content, and additionally provides us with essential nutrients we neither make ourselves nor take in via our diet. It also plays an important role in the development of our immune system and, once established, affects its function (as in other animals and plants). The disadvantage is that small bacteria can be pathogenic and cause disease. However, the initial thought that infection was due to acquired microbial infections has now been tempered by the recognition that many microbial diseases are part of our normal, more benign flora and usually only occur when we or our microbiome are disrupted in a way that can cause problems. The microbiome is a key regulator of the growth success of individual microbial and functional microbial groups and thus the success of colonization prior to disease. The colonization/population growth of microbial pathogens and their subsequent interaction with tissues and the immune system may or may not lead to serious diseases and is therefore an ecological process, classical, nothing more, nothing less. Therefore, a good understanding of the ecology of diseases, especially those with other lifestyles in the environment, is important for effective control of diseases. This is in view of the current explosion of research on bacterial ecology. Recent findings suggest that the gut microbiota may also influence brain function and stimulate research at the intersection of microbiology, neurobiology, and mental health. This research is expected to lead to entirely new concepts in understanding brain development and aging, as well as the causes and management of mental disorders.

2.3Innovation and innovative solutions: harnessing microbes for an enormous spectrum of applications

Microbial activities and products have been used to serve humans since the beginning of civilization (making beer, cheese and fermented milk products, bread, wine, etc.). Although the scope of microbial technology continues to expand over time, the genetic revolution in the 1970s represented a significant leap in quantity and quality. Accelerating the diversity of new microbial species, especially through research on our biosphere, the development of (meta) genomic methods, and the discovery and testing of new metabolism and metabolism, will lead to further advances in the current and future years. Quantum evolution, continuous development and use of systems and synthetic materials, as well as new developments in methods, analytical methods, instrumentation and microfluidics  Innovation arises not only from technological progress, but also from business, medical and social needs for new and improved products and services, processes related to food production and safety, environmental protection and sustainable energy use. Studying the microbiome and its impact on human health, nutrition, and disease is encouraging the development of new models for microbial use in the prevention and treatment of disease. Studies on plants and the plant microbiome are generating new knowledge that may be of interest in nutrition and disease control, as well as in improving agriculture and achieving benefits as shown in Figure 1.

Figure: 1 Contributions of micro-organisms for sustainable development [109]

The passion for large amounts of untapped microbial diversity and health has recently led to a major expansion in environmental microbiology research led. Despite these efforts, over 90% of microbial diversity has yet to be seen. This new biodiversity represents an asset for the development and use of new and advanced biotechnologies in the chemical industry, medicine, energy, mining, materials, agriculture, food and defense. In addition, much of the genomic information still needs to be determined functionally (genomic dark matter), which also represents rich applications such as “silencing” determinants of the success of secondary metabolites. Many applications that emerge from this discovery will be both old and new, as research on microbial diversity and diversity of genetic space will reveal new catalytic reactions, metabolic activities, and products. In particular, microbial life at the interface between the biosphere and the geosphere has experienced physicochemical conditions and is expected to exhibit unusual metabolic features that would open important possibilities for evolutionary catalytic activities. Furthermore, natural microbial communities participate in metabolic processes in synergistic ways and involve multiple spatial organizations, interactions, and functional partners. What is important is that the coordination of the disease and the distribution of the reaction among different members of the society differs from the drug and ensures the coordination of these activities, differences that are thought to work in conflict.

2.4Microbial technologies contribute towards sustainable development in a broad range of key areas

The main and almost unique feature of microbial systems is the diversity of applications they can address and the needs for many specific human activities and uses (chemistry is another example). Because the sustainable development goal has many different characteristics and needs, microbial technologies have the potential to contribute to global efforts to achieve sustainable development at different levels and in different areas. In fact, microbial technology can be seen as an integral part of our journey towards sustainability.

However, many areas of action in various sustainability efforts and many areas of microbial practices are often viewed in isolation rather than as interconnected and interdependent areas within a continuous landscape.  Special issue of microbial technology and sustainability for integrating fragmented areas into a coherent landscape. However, we must humbly say that the field of microbial biotechnology is quite dynamic, with new applications being discovered and developed almost every week; so the situation is interesting, leaving this particular issue as just one example of the potential sustainable development concepts. However,  itisbelieved that it offers useful new ideas for planning and future policies, and we hope that it will encourage young people to participate in the use of microbiology for stable development.

3. Effective abilities of mixed microbial communities for engineering our direct environment

The When dealing with natural microbial communities, one should consider the concept that not only humans but also microorganisms implement a certain form of market economy [20]. Microorganisms have been shown to participate in collaborative behavior, both with other (micro)organisms and with the host  of which the human (and virtually all (in)vertebrates) gut ecosystem can be considered a key example [21, 22]. The similarity between economics and microbial behaviour even goes further, as trading of essential resources between microorganisms can accelerate the total growth of the microbial community [23]. In an open system, in which immigration of new microorganism can influence microbial assembly and function in the receiving engineered or natural ecosystem [24, 25], the complete process is carried out with more accuracy and a higher efficiency by multiple species than on an individual basis, as for example illustrated in anode biofilm assembly in microbial fuel cells [26].

Overall, using mixed microbial communities allow achieving more effective and efficient microbial processes, because the most suitable species/community combinations will be selected and become operational. Microbial biotechnologists, particularly in the framework of reaching the United Nations Sustainable Development Goals, need to explore with great priority how to optimize and manage such cooperative communities, i.e. the microbiomes as they occur in soils, aquatic environments, and engineered reactor systems and even in bodily systems. To this end, it is our role as scientists, to develop a set of pragmatic tools/answers, allowing practitioners and policymakers to select the most appropriate microbial biotechnology. An example of this program is rewilding with invertebrates and microorganisms to restore ecosystems [27].

Figure 2: Soil-water ecosystems that are essentially associated to microbial communities

3.1Essential Guidelines for Soil Microbial Resources Management Problems and Opportunities in Soil Ecosystems.

There is a lot of information about soil microbiology, but there are no strategies to modify soil microbial communities or direct them to achieve specific properties. Some soil services, such as the exchange of greenhouse gases, carbon dioxide, methane and nitrogen oxides, are well documented and depend on microbial activities and their interaction with the soil environment and land use [28-30]. Soil ecosystems contribute significantly to ecosystem services; It intercepts rain, cleans groundwater, and promotes plant growth for energy and yield by providing nutrients appropriately as seen in Figure 1. The economic value of ecosystem services is estimated to equal 50% of global gross domestic product by 2021 [31, 32].

When adjusted for the current global population is over few billions, ecosystem services represent a monetary value of approximately EUR 5,000 per person per year [33]. Therefore we must ask ourselves the standards and tools needed to maintain and increase theses services. We need to investigate how the microbial community in the soil ecosystem can develop without being disrupted. Because the diversity and biomass of soil microbial communities are important regulators of ecosystem processes such as organic matter decomposition, nutrient cycling, and gas flux which contribute to sustainability. The need to control anthropogenic greenhouse gas emissions is clear, but we must take into account the fact that carbon dioxide emissions from the world's ecosystems are estimated to be equal to anthropogenic carbon dioxide emissions [34]. The main difference is that greenhouse gas emissions and sinks are equal, while anthropogenic emissions cause an increase in greenhouse gases in the atmosphere. Proper agricultural land management allows us to achieve carbon sequestration at a rate of 0.3–1.0 tonnes of carbon per hectare per year [35]. Therefore, if we consider all agricultural land in the world as pasture, which was approximately 4.8 billion hectares in 2018, global anthropogenic greenhouse gas emissions were 36.2 g CO2eq in 2016 and the sequestration rate was 36.2 g CO2eq. in 1.0 tons [34]. The amount of carbon per hectare per year accounts for up to 50% of all human-caused greenhouse gas emissions. However, more conservative estimates of the carbon sequestration potential of agricultural soils account for 5–20% of total carbon emissions [36]. Although this is difficult in practice, it shows that proper management of agricultural land can reduce greenhouse gas emissions. Going back to the excessive release of reactive nitrogenous fertilizers into the soil [7, 37], which is one of the other most important factors for the world; the management of soil nitrogen is not sufficient. Approximately 60% of fertilized nitrogen is at least partially leached into water, causing eutrophication [38-40]. It appears to be directly related to uncontrolled microbial processes in agricultural ecosystems, such as nitrification and denitrification. Therefore, better studies are needed to solve microbial-based inefficiencies. In areas with very intensive agriculture, such as Flanders and the Netherlands, the release of ammonia and its subsequent release into the natural environment has become a major problem, as the release of reactive nitrogen will reduce vegetation cover variations [41].

This led to these regions being legally banned from ammonia and nitrate emissions from agriculture for the first time in history. These measures are very important since the accumulation of tens of kilograms of ammonia per hectare per year in natural ecosystems is related to plant ecology, soil microbiology and the environment.

3.2Managing the soil microbiome

To manage open microbial communities, their functions need to be understood. Fortunately, we can once again rely on the analogy between ecological and economic systems. According to Italian economist Pareto described in 1897, choice and competition in an open competitive environment lead to a 20/80 distribution pattern and yes, 20% of the population received 80% of products [42]. However, the other 80% of the population works to be productive, thus continuing to drive the entire population to be productive. This concept also applies to microbial communities [43]. Essentially, when measuring the relative abundance of taxonomy according to their role in changing biological processes, a Pareto distribution can often be seen, although not the 20/80 distribution that is always met [44]. This also applies to energy sources such as anaerobic digestion. This parameter therefore allows the assessment of the entire ecology, viability and cooperative quality of the microbial community by integrating information from multiple listed species presence or absence [45].

Another important concept is the role of apex predators in public health and diving management [46]. In soil ecosystems, nematodes feed on organisms such as bacteria and archaea, thus promoting biomass conversion and nutrient release [47]. The extensive spatial and physical heterogeneity of soil results in a variety of surface types, aggregates, pore sizes, and microclimates that allow different animals to occupy it in place and over time [48].

The fact that microbial processes in soil are rarely related to the total microbiota configuration is insufficient and reduces performance. Soil microbiology must be studied in the context of nutrients, including metabolic interactions, and further efforts are needed to create diverse biotas, including creating the best animals. For example, fatty acid profile signatures of nematodes and fungi can be used to identify specific tropical soil disturbances [49]. Direct interaction between soil microbiota and higher organisms such as plants is also an important factor in soil ecosystem management for many purposes. Greater plant diversity can increase carbon sequestration in degraded and abandoned agricultural soils [50]. The relationship between bacteria and plants in the rhizosphere and phyllosphere can be achieved by using these plants to remove soil and pollutants [51]. Recent studies have shown that by using weak electrical energy to pollute soil, electrokinetic technology can increase the number of plants interacting with microbial organisms and improve the degradation of hydrocarbon pollutants in soil [52]. The formation of this slowly decomposing organic matter in the soil requires depending on the type of plants (crops), soil and type of fertilizer used  [53, 54]. The return of organic fertilizers can be considered as good soil fertility and diversity [55, 56]. Therefore, this approach should be encouraged and supported, such as microbial biomass production with new methods such as microbial proteins to produce necrotrophs in soil [57].

3.3Using the Soil Microbiome to Reduce Greenhouse Gases

Soil scientists can contribute to CO2 reduction in several ways. First, deep soil that previously stored carbon monoxide is exposed to the voluntary use of water to produce and store methane for renewable energy, as demonstrated in Austria's underground solar energy storage project [58]. This methane is produced in situ by the action of hydrogenotrophic methanogenic organisms, using more hydrogen and carbon dioxide produced by the combustion of methane during the cycle.

Figure 3: Comparison of A) the less effective ruminant method and B) the more effective method for grass cellulose fibers obtained directly from bacteria in the biorefinery

Second, soil scientists should work to support biorefineries for the production of carbohydrate-rich biomass products. For example, annual grasses not only produce grass biomass without needing large amounts of fertilizer, but they can also store approximately one tonne of organic carbon per hectare per year.

So now carbohydrate-rich biomass is largely consumed by ruminant animals. However, the overall impact on ruminants is low. Ruminants digest 60-70% of grass fiber and approximately 15% of the digested product is converted into products such as meat or milk [59, 60]. Therefore, on a dry basis, approximately 0.10 kg of milk solids is obtained from every kilogram of dry matter fiber straw as shown in Figure 3. Carbon- and nitrogen-rich crop components, such as grass are microbially “improved” for the production of products such as food, nutrients, and fatty acids [61, 62] and return energy (biomethane from biogas) deserve to be promoted. Such bio-refining can harmonize (i) terrestrial ecosystems and services (ii) with agricultural logistics and economy.

3.4Closing the Water Loop: Wastewater Recycling and Recovery Recycled Water Need for Safe Drinking Water

There is nothing more valuable than good drinking water. Given our extensive use of water in domestic and commercial applications, water scientists must consider the cost of water use, such as drinking water or process water [63, 64]. We now indirectly reuse primary water released by drinking water producers from wastewater treatment plants.

The demand for the direct use of "purified water" (i.e. effluent from wastewater treatment plants) will increase in the coming years especially during the dry season [65]. Belgium Cockside is a good example of uncontaminated water for direct water use; Since the beginning of 2000 50% of the drinking water provided to consumers in the region is water reuse [66]. The aquifer has been recharged [67]. Clearly, the high levels of removal of micro pollutants by systems such as slow sand have been well established [68], there are further questions about the sustainability of the water box. Engineers can characterize sustainability by considering the availability of nutrients and the presence of adequate and diverse microbial communities [69].

3.5Anaerobic digestion: an old technology with future potential.

Anaerobic digestion can be considered a good biotechnological process that has the potential to increase its importance in our future bio circular economy [70, 71]. In fact, a group of bacteria combines many complex molecules and produces biogas consisting mainly of CH4 and CO2, accounting for 90% or more of the energy of biogas (biodegradable) enter all its thermodynamics, biochemistry and applicability are astonishing. Various configurations have been developed over the years, from upflow anaerobic sludge bed reactor systems [72] to solid-state digesters [73] The emergence of high-throughput molecular methods in the last few years has greatly accelerated our understanding of the ecology of anaerobic digestive microorganisms [74, 75]. However, it must be acknowledged that so far, to our knowledge, no synthetic microbial groups have been created and have been created that can manage waste “entropy” with superior performance in anaerobic digestion in the natural microbiome.

Therefore there is still great potential to improve the cost and remaining metabolites that will need to be addressed in the future.

3.6Bioflocs: An example of the feces-to-food cycle in an aquatic ecosystem

A particular achievement in microbial biotechnology is biofloc technology [76]. Many years ago, at the beginning of water use, it turned out that it was difficult to convert the protein-rich fish used into target biomass (such as fish, shrimp) and 20-80% is wasted. Waste products from target organisms of aquaculture can be converted into food microbial biomass in situ by providing additional carbohydrates [77]. This biomass will grow into flocs and can be used as feed for subsequent or even the same aquaculture production animals [78]. This doubles the nutritional efficiency of heavy aquaculture systems while cleaning up other large wastes. In fact the example vividly demonstrates how the circular economy concept can be achieved. Fixation of fecal matter to food can be easily used and accepted by consumers.

3.7Intervention to prevent Covid-19

The pandemic has once again proven that diseases are everywhere within us and around us. Since we cannot separate or even live without them, we must cooperate with things that are beneficial to the human body. In this context, many technological issues come to mind. The rumen is a very important reactor-like system. It is well researched as it effectively converts cellulosic fibers into good products like meat and dairy.

Figure: 4 Presentation of the concept of bio-refinery

However, this fact should be evaluated according to its relationship with the environment. As previously mentioned, ruminants are not very efficient at converting cellulosic fiber into milk or meat; the overall efficiency in converting food into protein (dairy or meat) is only 10%. Additionally, the rumen converts 5-7% of the energy in the feed into the greenhouse gas methane, while 26-50% of the energy is lost in the feces [79].

Methane emissions from cattle constitute 1-2% of the total global greenhouse gas burden [80]. Many attempts have been made to reduce CH4 emissions from ruminants, such as the addition of specific chemicals such as polyunsaturated fatty acids, fragrances, or 3-nitrooxypropanol [81, 82]. Although these techniques reduce methane emissions, they only account for 5-10% of production.

Methanogen production by methanogenic archaea is important for controlling cellulose hydrolysis in the rumen; because fat removal and pH regulation are important for the maintenance of rumen biofilms [83]. Agriculture focused on ruminants therefore seems incompatible with the future climate. From this perspective, the way forward is that the development of Carbohydrate-rich fibers aims to lead biorefinery Technology, while facing the fact that the focus on fiber conversion in livestock and ruminants must be reduced as shown in Figure 4 [84].

Over the past few years, microbiologists and microbiologists have explored and investigated the human gastrointestinal microbiome both in vivo and in powerful simulators such as the Human Intestinal Simulator of Microbial Ecosystems (SHIME) [85]. Molecular methods allow the detection and identification of diseases that spread in our body and affect not only our energy balance, the absorption of amino acids, minerals and vitamins, but also our immune system and even our health our mental health [86, 87]. So far the main topic has focused on analysis, but now it's time self-management of our digestive system is not as easy and difficult as the connection between the human gut microbiome and the gut microbiome [88]. The end of the body is related to the bacteria we encounter around us every day. There are many indications that the diversity of our environment, including the diversity of microbial organisms, can reduce the incidence of allergies [89, 90]. There also appears to be a link between reduced biodiversity and increased inflammatory diseases in humans. This can be translated as the “hygiene hypothesis”, which states that an environment rich in microbial diversity protects against allergies and autoimmune diseases [89]. However, although we have now managed to use the best methods of disinfecting our environment to protect our health, the idea of our “old friends” deserves further study in the future [91]. In general, in our homes, schools, hospitals, etc there must be a good need to create atmosphere and space. We must dare to think outside the traditional box and of course we must also use the COVID-19 clearance to unblock every germ that can reach us..

4. Microbial biotechnologies to be promoted in full force: specific aspects

The decision taken so far shows that there are many applications around us that are worth listening to. Two things deserve special attention; one is business issues and the other is all customer and management issues.

4.1Microbial protein revisited: a reconsideration and future perspectives

The established practice of the biofloc technology [78] demonstrates that waste streams (even faecal waste) can be upgraded by a reliable microbial value chain to, for example in the case of the bioflocs, fish protein. The central element is the fact that microbial cells can contain up to 75–80% protein, rich in all essential amino acids and with a high digestibility [92]. The concept of single-cell or microbial protein dates back around fifty years ago, with ‘Pruteen’ as microbial protein supplement [93].

A combination of, amongst others, low prices for soy, particularly in the USA and Brazil, and fishmeal, increased oil prices and a high nucleic acid content (upto 15–16% of the dry cell weight) resulted in the temporal discontinuation [92, 94]. Currently, the further increase of soy cultivation comes to its limits, and also the harvesting of massive amounts of fish in the high seas is no longer an area where further expansion is desirable [95]. Therefore, time has come to revisit microbial protein.

Several lines of production of microbial protein can be envisioned, including autotrophic growth with natural sunlight [96, 97], autotrophic growth with for instance hydrogen gas produced from water electrolysis using renewable energy [98], and heterotrophic growth with organic matter, such as carbohydrates produced from conventional crops [57]. In all cases, microbial protein production in terms of energy input is at least three times higher than that of higher organisms, except phototrophic algae [98]. Phototrophs can achieve 100% of the results of transforming the medium because they utilize light-driven anabolism, while organotrophs can achieve 100% of the results of transforming the medium. 30-40%, because they consume part of the energy found in organic carbon sources in aerobic metabolism [98]. By comparison, higher organisms such as insects and other animals convert carbon into biomass only 10% efficiently. The difference between prokaryotes and eukaryotes can be explained by the fact that bacteria do not have organelles or cellular components to form and have small genomes. However, compared to higher organisms, the end product of microbial protein is "merely" protein and so far has no definition and texture.

However, microbial proteins have succeeded with the idea of the stability of the world based on the use of energy and the measurement of life [99-101]. However, identifying effective ingredients. More research is needed to identify and promote it. An essential aspect is that the quality of the input determines the quality of the recovered protein, i.e. the GIGO principle (garbage in, garbage out) also, to a certain extent, applies to microbial protein.

Depending on the characteristics of the microbial protein product, it can be used as food, feed or implemented as an organic fertilizer [58], thus, opening the potential to have more microbial necromass in the soil system or even produce commodities. It can be projected that, by 2050, substituting 10-19% of plant protein for microbial protein could liberate up to 13% of agricultural soils, which can be used for other purposes [58]. Expanding this replacement and/or directly using microbial protein as food source in the future could free up even more agricultural soils, enabling land owners to shift their focus from food production to other soil management strategies, such as the reduction of greenhouse gas emissions or promoting biodiversity.

Recently, it was even demonstrated that microbial protein, produced from starch, could serve as protein source for the production of bioplastics [102], which reflects a huge market potential. Clearly, the time has come to carefully delineate the future of microbial protein. An important aspect is that, to generate microbial protein from waste streams (e.g. sewage), either directly [103] or indirectly over methane [104], one should face the fact that the organics in these waste streams are most probably contaminated with chemicals, bacteria and viruses, which need to be avoided. By combining anaerobic digestion with thermochemical gasification, organic waste streams can be converted to clean gaseous substrates in the ‘full gas’ route [105], which can be used for the safe production of microbial protein through various routes.

4.2Overcoming microphobia for microbial products

In the free market economy, it is essential that one touches base with the consumer. The consumer is willing to accept a shift towards a circular bio-economy, provided the products generated are appealing in terms of price and, especially, safe in terms of use [106]. The aspect of safety of products generated by means of microbial biotechnology is not a minor issue and is further complicated since the consumer demands rigorous protection by the regulator. In the past, multiple products, such as drinking water using slow sand filters, sourdough, cheese using raw milk, Gueuze beer and wine have been produced by means of open, mixed microbial communities, i.e. by allowing the natural selection of microorganisms, some even with specific health benefits [107] These products are generated under particular conditions of ‘good manufacturing practices’, and a set of analyses targeting indicator organisms, for example non-tuberculous mycobacteria in drinking water [108], are demanded.

The development and implementation of the ‘omics’ in the last decade allows us to detect every species, even present in a nominal, minor concentration, in such open microbiomes. The "Omics" approach and its success If no species/species not approved on the Generally Recognized as Safe (GRAS) list are passed as a line of defense for the authorities, then turn on biotechnology Water purification (waste water), composting, mushroom production, winemaking, cheese made from raw milk, etc. Future use in areas will become ineffective and expensive.

Thoughts about studies working with the microbiome have been put forward. It is important for consumers and regulators to learn about all aspects, hazards and regulatory aspects of microbial biotechnology to minimize risk, while also recognizing that “Zero hazard” is impossible and the ability to control and treat is impossible always available. The general public should learn that to work well, we do well to work with the microbial partners we live with on Earth.

5. Conclusion

In this article, we highlight the potential of using microbial technology to improve microbial processes of important but often underestimated importance for planetary sustainability and human health. We emphasize the need for integration from analysis to theory in microbial engineering. It is believed that the regulators should trust the stochastic nature of the microbiome and rely on historical information to ensure that the microbiome and its ecosystem services the potential to further support our planet are retained. By harnessing the power of micro-organisms and working together to make the world a better place, we can help the masses become a rare resource in the world, drive innovations that support the Agenda, and make progress towards sustainability goals..