1. Introduction

By using microorganisms to produce biodegradable and sustainable products, the microbial bioeconomy offers a viable alternative to traditional production methods, which are based on the global economy principles. With continued advances and innovations, the microbial bioeconomy will likely become an increasingly important part of the global economy [7]. Genetically modified organisms (GMOs) are vital for a sustainable bioeconomy; they are employed in the creation of food and feed additives, pharmaceuticals, biomedicine, bioenergy, biofuels, bioplastics, environmental remediation and waste management, building and transportation system, forestry and agriculture, and other recyclable bio-based materials and products [7,16,17,18,19,20,21].

2. Applications of the Microbial Bioeconomy for Economic, Environmental, and Social Sustainability

2.1. Principles of the Microbial Bioeconomy

Seven (7) Key Principles Central to the Microbial Bioeconomy

• Use of renewable resources: The microbial bioeconomy relies on renewable resource utilisation, such as plant biomass, organic materials, and agricultural waste, as feedstocks for the production of products of high value. This approach helps to not only reduce reliance on non-renewable resources, such as fossil fuels, but also create a more sustainable and efficient economy [32]
• Sustainable production: The microbial bioeconomy produces products and services that are environmentally friendly and sustainable. This involves using renewable resources, converting waste materials into valuable products, and optimising production processes to minimise waste and reduce greenhouse gas emissions [33].
• Efficient utilisation of resources: The microbial bioeconomy seeks to use resources efficiently to minimise waste and reduce the environmental impact of production. This involves closed-loop systems where waste from one process is used as a resource [5].
• Adaptability: The microbial bioeconomy technologies should be adaptable to different environments and conditions and should be able to be easily modified or scaled up as needed [34].
• Innovation: The microbial bioeconomy should be driven by the development of new technologies and approaches along with a focus on innovation [35].
• Collaboration: The development and implementation of the microbial bioeconomy technologies often require collaboration between researchers, industry, and government [36].
• Transparency: The microbial bioeconomy should be transparent and open with information about processes and products and make this information readily available to stakeholders [33].

Figure 1. Principles of the Microbial Bioeconomy.

2.2. The Microbial Bioeconomy Current State

Based on a report by the [37] the global microbial market is worth €250 billion, with an annual growth of 5.6%. By 2030, it is predicted to reach €700 billion due to the rising demand for sustainable products, biotechnology advancements, and supportive policies. The European Union (EU) bioeconomy generated €2.29 trillion turnover in 2015 [38] However, the COVID-19 pandemic caused a 2% decrease in 2019 and a 0.4% decrease in 2020 in employment and gross value addition [38].

One of the key trends in the microbial bioeconomy is the growing demand for renewable and sustainable products and services driven by a growing awareness of the social and environmental impacts of non-renewable resources such as fossil fuels. Additionally, an improved public understanding of climate change and the devastations caused by non-renewable products have changed consumer preferences and resulted in more robust regulatory policies [37]. This trend creates new products and processes that rely on microorganisms, such as biofuels, biomaterials, and bioplastics [7].

Another significant trend is the increasing focus on waste management and resource recovery. Microorganisms are expected to play a critical role in this area by using anaerobic digestion and other processes to convert waste into valuable products, such as biogas, fertilisers, and biochemicals [39].

The microbial bioeconomy contributes to economic sustainability through biocatalysis, biotransformations, anaerobic digestion, and bioremediation processes. Biocatalysis has advantages over traditional chemical processes due to its improved selectivity and specificity [40,41].

2.3. Recent Advances and Innovations in the Microbial Bioeconomy

Recent advances in biotechnology have led to significant progress, particularly in the development and application of microorganisms for producing goods and services. Advances in metabolic engineering and synthetic biology have made significant progress in creating new microbial strains with improved productivity and efficiency. The Penicillium chrysogenum X-1612 strain was genetically modified using X-ray mutagenesis for enhanced genetic expression [45] (These advances have also paved the way for developing sustainable products and processes, including the production of biofuels from waste materials and using microorganisms to remove pollutants from water and air [46,47].

In addition to technical advances, there have also been significant innovations in commercialising microbial products and services. For example, the rise of biotechnology start-ups and the increasing availability of venture capital have facilitated the development and growth of the microbial bioeconomy with greater availability in some countries than others. The most common way through which start-ups are commercialising microbial products and services is the repurposing of biomass from agricultural products, consultancy, and training [48].

2.4. Applications of the Microbial Bioeconomy in Various Sectors

The microbial bioeconomy is a fast-growing field with various commercial and industrial applications, bio-based product production, food and feed, energy recovery and composting, waste management, recycling, and cascading, as well as multi-output production chains [48].

The use of microorganisms in producing bio-based products, including food and animal feed, has been widely acknowledged for a long time. One key advantage of using microorganisms to produce bio-based products is their capacity to utilise a variety of feedstocks. For instance, microorganisms, such as yeast and bacteria, can convert plant-based feedstocks, such as corn and wheat, into valuable products, such as lactic acid and ethanol [49] This renders the use of microorganisms a more cost-effective and efficient option to produce biofuels [50] Additionally, they can produce a variety of food products, such as fermented foods including yogurt, which is made using Lactobacillus delbrueckii subsp. Bulgaricus and Streptococcus thermophilus [51].

Microorganisms are also used for energy recovery and composting by converting organic waste into a valuable soil amendment that improves its physical properties, such as drainage, water retention, structure, permeability, aeration, and water infiltration. There has been a growing interest recently in composting to recover energy from organic waste while promoting economic sustainability [54]. One of the main benefits of composting is that it decreases the quantity of waste sent to landfills, where organic waste decomposes anaerobically and produces methane, a potent greenhouse gas. In contrast, when organic waste is composted, it decomposes in the presence of oxygen and produces carbon dioxide, a less harmful greenhouse gas. 

Human activities have led to the proliferation of landfills and incineration facilities, which can be environmentally damaging and costly to maintain. Microorganisms can convert organic waste, such as food and agricultural wastes, into biofuels and biochemicals [46]. This reduces the amount of refuse that is sent to landfills and generates revenue from selling these products.

The microbial bioeconomy can also support integrated and multi-output production chains, leading to cost-effective and efficient production. This method utilises microorganisms to simultaneously produce multiple products from a single feedstock. Studies have shown how effective this method is in producing biofuels and chemicals from a single microbial strain [60,61,62,63] and in producing biofuels, animal feed, and bioplastics using microalgae [64,65]. Such integrated production can increase the industrial process efficiency and sustainability. The discovery of CRISPR/Cas9 and other genetic engineering techniques has enabled the precise modification of various strains to produce targeted products. This flexibility has facilitated rapid and efficient responses to changes in market demand [66].

3.5. Role of the Microbial Bioeconomy in Achieving Sustainability in the Economy and Environment

The microbial bioeconomy plays a significant role in achieving both economic and environmental sustainability by using renewable resources and reducing waste and pollution. By using biomass and biological knowledge to provide food, feed, industrial products, bioenergy, and ecological services, the microbial bioeconomy aligns with several sustainable development goals, such as affordable and clean energy (Goal 7), sustainable cities and communities (Goal 11), and responsible consumption and production (Goal 12) [18,67,68]. By creating a balance between sustainability and economic aspirations, the microbial bioeconomy can help address global challenges, such as climate change mitigation, global food security, and sustainable resource management, leading to a more resilient and sustainable economy that benefits both people and the planet [69,70]. It creates a more resilient and sustainable economy that benefits both people and the planet by utilising the unique capabilities of microorganisms [18].

The microbial-based bioeconomy can create jobs, drive economic growth, and contribute to achieving the Sustainable Development Goals of the United Nations, particularly No Poverty (SDG 1), Zero hunger (SDG 2), and Decent Work and Economic Growth (SDG 8) [71,72]. As biomass is widely available, the microbial bioeconomy can create modern jobs (biotechnologists and bioeconomists) in rural areas and promote social inclusion [69,73,74], For instance, in 2019, approximately 17.4 million people in the EU were working in the bioeconomy sectors, which was 8.3% of its total labour force. Bio-based employment can be generated from advances in the microbial bioeconomy as described in the following practical examples. Spirulina, a kind of blue-green algae, is an excellent source of protein and other nutrients, making it a potentially sustainable and nutritious food source. Spirulina cultivation can create jobs in the aquaculture and agriculture industries, as well as in the processing and packaging of spirulina-based products [72]. Spirulina platensis is also being explored for its potential use in animal feed production. Because of its high protein content, spirulina is used in animal feed, which can create jobs in the animal husbandry and feed manufacturing industries. Using microorganisms in waste treatment, biopesticide production, and bioremediation products can create jobs in the environmental industry and in research and development, engineering, and operations.

Microorganisms play a vital role in mitigating and achieving climate neutrality, as they are used in various industrial processes that can help reduce greenhouse gas emissions and promote environmental sustainability. Using biological resources for food, feed, bio-based products, and bioenergy can align with the United Nations’ Sustainable Development Goals (SDGs), such as Affordable and Clean Energy (SDG 7); Industry, Innovation, and Infrastructure (SDG 9); and Responsible Consumption and Production (SDG 12) [7]. Microorganisms, such as yeast and algae, can produce biofuels, such as ethanol and biodiesel, as alternatives for fossil fuels. The production of biofuels using microorganisms can reduce lifecycle greenhouse gas emissions, as biofuels have a lower net GHG emission compared to fossil fuels [77].

Microbes play a crucial role in ecosystem and biodiversity restoration in several ways. For example, certain bacteria can break down pollutants and waste products, making them less harmful to the environment [78]. This process, known as bioremediation, can help clean up contaminated soil and water, making it safer for plants, animals, and humans. One example of a bacterium that can be used in bioremediation is Pseudomonas cepacia. This bacterium secretes a bio-surfactant that cleans up hydrocarbon contamination [79]. Microorganisms, such as bacteria and fungi, can degrade organic waste and pollutants, aiding in wastewater treatment and soil remediation. Specific examples of microorganisms that are used in the bioremediation of crude oil include Pseudomonas cepacian [79,80]. Bacillus cereus [81], Aspergillus oryzae [82], Bacillus coagulans [80], Citrobacter koseri [80] and Serratia ficariam [83]. These microorganisms can degrade pollutant hydrocarbons, heavy metals, and pesticides and are also used in the bioremediation of dyes in textile industry wastewater. Specific examples of microorganisms effective in dye bioremediation include Exiguobacterium indicum [84] (Exiguobacterium aurantiacums [85] Bacillus cereus [86] and Acinetobacter baumanii [87].

Penicillium, which is known for breaking down cellulose, a major component of plant cell walls [88] can help release nutrients into the soil, making them more available to plants. Additionally, Penicillium can produce antibiotics that can kill or inhibit the growth of other microbes, which can help control soil-borne diseases. Other fungi involved in this process include Trichoderma, Rhizopus, and Fusarium.

Trichoderma is a diverse genus of fungi. Some can break down varieties of organic compounds, including lignin, cellulose, and hemicellulose [89]. This renders it an effective tool for improving soil health and supporting the growth of plants. Rhizopus is another fungus in which most group members can help decompose organic matter and release nutrients into the soil, and it is known for its ability to break down starch and other complex sugars. One of the most well-known is Rhizopus stolonifer (the common bread mould), making it an essential contributor to the soil nutrient cycle [90].

2.6. Barriers to the Development of the Microbial Bioeconomy

Several limitations must be considered when using microorganisms in the bioeconomy [92]. One of the main limitations is the complexity of the microorganisms themselves. The genetic makeup of microorganisms can vary significantly, even within the same species, making it challenging to standardise the production process. Major advances are required, including genome sequencing and the creation of systems that can facilitate multitrophic and multi-layered production of microorganisms [93]. In addition, the process of genetically modifying microorganisms, an important component of the microbial bioeconomy, is complex and expensive, making it difficult to scale up production for commercial viability [93]. The use of these organisms raises ethical and safety concerns as they could escape into the environment and potentially cause harm to other organisms and could also spread to wild populations. Addressing these limitations is important for the successful implementation of the microbial bioeconomy.

To ensure sustainable production and prevent environmental harm, the microbial bioeconomy must consider resource availability and feedstocks. It involves developing microbial-based products and services while addressing bottlenecks through scientific policy and economic approaches. Policy recommendations include increasing research investments, incentivising microbial-based products, and facilitating public–private partnerships. Multi-disciplinary research from microbiologists, chemists, economists, and farmers is necessary, as in the case of biogas production, to evaluate the innovations’ scientific and societal impacts. Clear communication and close engagement with society are also crucial [94].

Another barrier lies in combining biodiversity with synthetic biotechnology for industrial-scale CO₂ capture. The CO₂ emission from fossil fuels and increased global warming are major challenges that will have significant and lasting implications for future generations. The first indicators of artificial climate change are the rising frequency of droughts, wildfires, heat waves in southern nations, excessive rainfall, and flooding [95,96].

This entry is adapted from the peer-reviewed paper 10.3390/su15097251