This is a peer-reviewed, accepted author manuscript of the following article: Salifu, E., Gutteridge, F., & Witte, K. (2021). Recent advances in engineered microbial technologies for the construction industry. Paper presented at Young Researchers' Forum V , Glasgow, United Kingdom. Young Researchers’ Forum V Innovation in Construction Materials 22 April 2021 Paper Number XX Recent Advances in Engineered Microbial Technologies for the Construction Industry E. Salifu1, F. Gutteridge2, K. Witte3 1Department of Civil and Environmental Engineering, University of Strathclyde, Glasgow, UK 2Department of Design, Manufacturing and Engineering Management, University of Strathclyde, Glasgow UK 3Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, UK ABSTRACT Microbial biotechnologies have received attention in the construction industry in recent times. This is partly driven by the climate change motivated transition towards the adoption of low carbon and environmentally friendly cementitious technologies in varied sectors of the construction industry. The multidisciplinary approach by researchers in the emerging area of Construction Biotechnology has led to the development of innovative low costs and low carbon microbial-based products like bio-bricks, bio concrete or self-healing concrete/bricks mediated by bacteria, fungi, and biofilms. Similar advancements are recorded in the development of microbial biocements and biogrouts, as well as the recent concepts of engineered growth of microbial living systems (e.g., using bacteria, fungal mycelia, microbial communities such as biofilms, lichens) towards applications in ground improvement, as living building materials, or as resource for production of construction materials. This paper presents a brief scoping review of the research advancements in the development of microbial-based materials/products/processes for applications in the construction industry. A description of recent breakthroughs in engineered microbial technologies which may be imminently deployed in practice are also presented. Besides providing a snapshot of the state-of-art, this paper also reveals unique insights and concepts that expose existing research gaps and propose areas of future research directions in engineered microbial biotechnologies for the construction industry. processes or modify existing ones for use in the 1. INTRODUCTION construction industry, has been evolving over the last decade (Ivanov, Chu and Stabnikov, 2015; The construction industry has come under Stabnikov, Ivanov and Chu, 2015). Conventionally, pressures to adopt innovative processes and microorganisms such as bacteria, fungi, and algae materials to meet societal challenges and are considered hazardous to structures and demands (Latham, 1994), and more importantly, building materials, known to cause staining or for environmental sustainability. Traditional discolouration, corrosion, disaggregation, processes and methods of production of weakening and dissolution of structural materials construction materials are energy-intensive and (Gaylarde et al., 2003; Bertron, 2015). But often associated with adverse environmental microorganisms are ubiquitous in natural impacts. Research has shown that the adoption of environments and highly ‘pervasive’ inbuilt novel bioprocesses and biomaterials could result in infrastructure. Researchers in construction less environmental pollution and ~10% reduction in microbial biotechnology have been exploring energy demand compared to conventional techniques for taking advantage of these abundant approaches (Ivanov and Stabnikov, 2017). With natural biological systems to provide beneficial exponential growth and development in industrial effects for structural elements, components, biotechnologies (e.g., medicine and materials, and processes in the construction pharmaceuticals, food and agriculture, industry. Table 1 presents a summary of environmental sectors) it has been predicted that developments in research activities and by 2030, one-third of materials will be derived from innovations involving microbial-based products and biological sources (Padinjakkara, 2018). To processes for application in the construction maintain its competitiveness, the construction industry. industry has been challenged to transition towards the adoption of low carbon and environmentally More recently, there has been a growing body of friendly technologies derived from biological research in the aspect of engineered growth/ sources. Construction microbial biotechnology, a modification of microorganisms for targeted new subdiscipline concerned with the use of applications in the construction industry. This is microbial systems, microorganisms, or their focused on the potential deployment of derivatives to develop new materials and microorganisms, insitu, as living functional systems 1 to enhance restoration, strengthening, and record was found for research in engineered beautification of structural components or lichens. Other studies did not fit into the criteria for construction materials. Additionally, this comes with any of the three broad classes of engineered the potential of lowering carbon emissions and microbial technologies within the scope of this construction maintenance costs as well as paper. 40 enhancing the properties and functions of Conference Review Engineered Review construction materials. This paper provides an lichen Book Chapter Conference Paper 35 overview of research developments in the aspects Article of engineered bacteria, fungi, and microbial Engineered fungi 30 communities (biofilms, lichens) in soil or ground improvement and in the production and Engineered 25 optimisation of building/structural materials. A brief bacteria 20 scoping review, that is, a descriptive style Construction microbial systematic literature review (SLR), showing biotechnology advances in research publications in engineered 15 0 20 40 60 80 100 120 microbial technologies for the construction industry Number of publications 10 Number of publications is provided, followed by a description of findings Construction microbial biotechnology from the latest relevant studies on each aspect of Engineered bacteria Engineered fungi 5 this technology, and a discussion of research gaps Engineered lichen and future directions of this novel subdiscipline. 0 1989199019911992199319941995199619971998199920002001200220032004200520062007200820092010201120122013201420152016 201720182019 Year Figure 2. Number of publications and type of publications in construction microbial biotechnology and engineered microbes (bacteria, fungi, lichens) from 1989-2019. Table 1. Journals with >6 publications in construction microbial biotechnology based on the total eligible documents used in the scoping review Journals (number of publications) Construction and Building Materials (21) Journal of Materials in Civil Engineering (9) Figure 1. Research & developments in construction Advanced Materials Research (8) biotechnology (Based on Ivanov, Chu and Stabnikov, 2015; Ecological Engineering (8) Stabnikov, Ivanov and Chu, 2015) Water Resources Research (8) Scientific Reports (7) 2. Overview of Construction Microbial Biotechnologies and Engineered Microbial Technologies for the Construction Industry Research activities in this area started gradually about two decades ago and have increased A scoping review was performed to ascertain the exponentially since 2010 to date. This increase status of research advancements in engineered may be due to the developments in a rapidly microbial technologies within the subdiscipline of emerging area of geotechnical engineering called construction biotechnology. Keywords used in the biogeotechnics, which embraced research into the literature search include the terms in Table 1 as application of microbial induced calcite well as multiple variations of construction precipitation (MICP), a biomineralisation technique biotechnology, microbes, soil, and concrete, for ground improvement (DeJong et al., 2010). among others. The review was conducted following Active researchers are drawn from multidisciplinary the procedures described by Arksey & O’Malley subject areas encompassing civil engineering, (2005) for identification of relevant studies, study material sciences, and environmental sciences, as selection, data collation, summarising and reflected in the journal titles in Table 2. reporting. Publications were obtained from a search in the Scopus database. (Details of the As shown in Table 1, microbial mediated search strings and dataset are available at the link technologies for the construction industry are in the provided in the data statement at the end of this broad areas of (i) soil modification via paper). biomineralization involving biocementation or As shown in Fig. 1, the total number of research bioclogging of soil resulting in soil particle publications, n, in the Construction Microbial aggregation, biocrusting, surface biocoating, Biotechnology applied to ground improvement or biodesaturation, bioencapsulation and construction materials/processes within the period bioremediation (Ivanov and Stabnikov, 2017); and 1990 – 2019 was 123. The research outputs (ii) production or modification of construction obtained, including those in engineered bacteria (n materials such as the manufacture of durable bio = 86) and engineered fungi (n = 6) were published cement or mortar bio bricks or bio concrete - as journal articles, review papers, book chapters concrete self-repair via bacteria-mediated