Currently, sustainable and eco-friendly technologies are a leading trend in the research field, as many resources are finite and are being constantly depleted. The chemical industry, which was expected to move more than US$5 trillion by 2020, is frequently dealing with major drawbacks, such as hazardous-substance management, extreme pressures and temperatures, and non-specificity (Clomburg et al., 2017). One promising alternative for the chemical- and petroleum-based industry is biotechnology, which uses living organisms or their derivatives to produce commodities humans need. The biotechnology area is aligned with the search for renewable resources, proper destination of residues, and ecological means of production, and new policies are investing in these concepts for societal changes for a sustainable future, such as bioeconomy, circular economy, and biorefinery (Carus and Dammer, 2018; Patermann and Aguilar, 2018; Ronzon et al., 2020).

The three concepts are deeply connected with eco-friendly perspectives, yet they differ slightly in their definitions. The term “bioeconomy” refers to the use of renewable biological resources, including crops, forests, animals, microorganisms, and their waste, and converting them into value-added products, such as bioactive compounds, bio-based products, and bioenergy (McCormick and Kautto, 2013; Patermann and Aguilar, 2018). On the other hand, the circular-economy approach focuses on maintaining as long as possible all the materials and resources in the production chain, turning the waste into resources and “recirculating” it to produce other products and reducing residue generation as much as possible (Carus and Dammer, 2018). Biorefineries blend the two strategies into a productive process. For instance, an industry that is classified as biorefinery has a proper endpoint for all its residues along the production line and is characterized by extremely reduced emissions, enhanced use of bio-renewable sources, and great environmental care (Schroedter et al., 2021).

In this aspect, one of the main tools of biotechnology is the use of microorganisms as cell factories, which can be coupled with strategies for greener chemical and energy production. The use of bacteria, fungi, yeasts, and microalgae is being studied as an expressive alternative, especially with recent advances in metabolic engineering (Liu et al., 2013; Shiue and Prather, 2012). Among bacteria, Bacillus is one of the main genera applied for industrial purposes. It is generally associated with some advantages, such as superior protein secretion capacity (Zweers et al., 2008), robustness for growth in several substrates (Khardziani et al., 2017b), endurance for resisting extreme pH and temperatures (Abhyankar et al., 2016), and safe consumption (Kimura and Yokoyama, 2019). The utilization of this genus in industrial processes includes a large variety of compounds and products, such as enzymes, proteins, peptide antibiotics, surfactant agents, biofertilizers, chemicals, biopolymers, pharmaceuticals, and nutraceuticals (Gu et al., 2018; Park et al., 2021). With its great versatility, Bacillus spp. are promising bacteria for application in sustainable and ecological technologies, as this concept can be implemented in the majority of their products.

Although the Bacillus genus is broadly applied in industry and large-scale production, the current information regarding bioeconomy and circular economy indicators for these bacteria is scarce, even regarding specific products. These indicators are numbers often associated with environmental aspects and provide an overview of the process as a whole, including life cycle assessments, carbon and water footprint analysis, energy and fuel consumption, and other related criteria (Carus and Dammer, 2018; Ronzon et al., 2020). Recently, the literature has presented a tendency to focus on genetic engineering tools applied for modifying Bacillus spp., the variety of new compounds they can produce, and their general application (Elshaghabee et al., 2017; Gu et al., 2018; Liu et al., 2013; Park et al., 2021; Schallmey et al., 2004). However, they do not gather several products simultaneously, provide a critical overview of them, or recover or update the genus characteristics besides the lack of bioeconomy and circular-economy data.

In this review, we aim to provide information about industrial applications of the Bacillus genus, greener alternatives for the production of each product, economic value the market offers, and technological development. The products covered in this work were mainly food, feed, probiotics, biocides, plant growth promoters, enzymes, bioactive compounds and, other products, all approached from bioeconomy and circular economy perspectives and presenting the information available in the literature. We also report the genus characteristics, genetic engineering tools applied to the bacteria, and fermentation strategies to demonstrate these microorganisms' versatility and robustness in industrial application. Additionally, we present an analysis of patents associated with the Bacillus genus main products with submission dates between 2017 and 2022, as it can indicate in which direction technologies have been recently developed. The economic and production data gathered demonstrate the potentials of and strategies towards bioeconomy and circular economy of the Bacillus, as the literature on the subject is considerably recent.