Stenotrophomonas maltophilia is an emerging multidrug-resistant global opportunistic pathogen. The increasing incidence of nosocomial and community-acquired S. maltophilia infections is of particular concern for immunocompromised individuals, as this bacterial pathogen is associated with a significant fatality/case ratio. S. maltophilia is an environmental bacterium found in aqueous habitats, including plant rhizospheres, animals, foods, and water sources. Infections of S. maltophilia can occur in a range of organs and tissues; the organism is commonly found in respiratory tract infections. This review summarizes the current literature and presents S. maltophilia as an organism with various molecular mechanisms used for colonization and infection. S. maltophilia can be recovered from polymicrobial infections, most notably from the respiratory tract of cystic fibrosis patients, as a cocolonizer with Pseudomonas aeruginosa. Recent evidence of cell-cell communication between these pathogens has implications for the development of novel pharmacological therapies. Animal models of S. maltophilia infection have provided useful information about the type of host immune response induced by this opportunistic pathogen. Current and emerging treatments for patients infected with S. maltophilia are discussed.

Stenotrophomonas maltophilia: an Emerging Global Opportunistic Pathogen

Microbial Geotechnology is a new branch of geotechnical engineering that deals with the applications of microbiological methods to geological materials used in engineering. The aim of these applications is to improve the mechanical properties of soil so that it will be more suitable for construction or environmental purposes. Two notable applications, bioclogging and biocementation, have been explored. Bioclogging is the production of pore-filling materials through microbial means so that the porosity and hydraulic conductivity of soil can be reduced. Biocementation is the generation of particle-binding materials through microbial processes in situ so that the shear strength of soil can be increased. The most suitable microorganisms for soil bioclogging or biocementation are facultative anaerobic and microaerophilic bacteria, although anaerobic fermenting bacteria, anaerobic respiring bacteria, and obligate aerobic bacteria may also be suitable to be used in geotechnical engineering. The majority of the studies on Microbial Geotechnology at present are at the laboratory stage. Due to the complexity, the applications of Microbial Geotechnology would require an integration of microbiology, ecology, geochemistry, and geotechnical engineering knowledge.

Applications of microorganisms to geotechnical engineering for bioclogging and biocementation of soil in situ

Consideration of soil as a living ecosystem offers the potential for innovative and sustainable solutions to geotechnical problems. This is a new paradigm for many in geotechnical engineering. Realising the potential of this paradigm requires a multidisciplinary approach that embraces biology and geochemistry to develop techniques for beneficial ground modification. This paper assesses the progress, opportunities, and challenges in this emerging field. Biomediated geochemical processes, which consist of a geochemical reaction regulated by subsurface microbiology, currently being explored include mineral precipitation, gas generation, biofilm formation and biopolymer generation. For each of these processes, subsurface microbial processes are employed to create an environment conducive to the desired geochemical reactions among the minerals, organic matter, pore fluids, and gases that constitute soil. Geotechnical applications currently being explored include cementation of sands to enhance bearing capacity and liquefaction resistance, sequestration of carbon, soil erosion control, groundwater flow control, and remediation of soil and groundwater impacted by metals and radionuclides. Challenges in biomediated ground modification include upscaling processes from the laboratory to the field, in situ monitoring of reactions, reaction products and properties, developing integrated biogeochemical and geotechnical models, management of treatment by-products, establishing the durability and longevity/reversibility of the process, and education of engineers and researchers.

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Biogeochemical processes and geotechnical applications: progress, opportunities and challenges

Microbially induced calcium carbonate precipitation (MICCP) is a naturally occurring biological process in which microbes produce inorganic materials as part of their basic metabolic activities. This technology has been widely explored and promising with potential in various technical applications. In the present review, the detailed mechanism of production of calcium carbonate biominerals via ureolytic bacteria has been discussed along with role of bacteria and the sectors where these biominerals are being used. The review discusses the applications of bacterially produced carbonate biominerals for improving the durability of buildings, remediation of environment (water and soil), sequestration of atmospheric CO2, filler material in rubbers and plastics etc. The study also sheds light on benefits of bacterial biominerals over traditional agents and also the issues that lie in the path of successful commercialization of the technology of Microbially induced calcium carbonate precipitation from lab to field scale.

/pdf/biomineralization-of-calcium-carbonates-and-their-engineered-elsofi30be.pdf

Biomineralization of calcium carbonates and their engineered applications: a review

The availability of trace metals as micro-nutrients plays a very significant role on the performance and stability of agricultural biogas digesters, which are operated with energy crops, animal excreta, crop residues, organic fraction of municipal solid wastes or any other type of organic waste. The unavailability of these elements in biogas digesters is probably the first reason of poor process efficiency without any other obvious reason, despite proper management and control of other operational and environmental parameters. However, trace metal requirements of biogas digesters operated with solid biomass are not often reported in literature. Therefore, the aim of this article is to review the previous and current literature about the trace metal requirements of anaerobic biogas digesters operated with solid organic substrates for production of methane.

Trace element requirements of agricultural biogas digesters during biological conversion of renewable biomass to methane

Scientific and public concerns due to presence of microplastic debris in the marine and freshwater environment is fueling concerns of its impact on aquatic ecosystems and public health. Major sources of water-polluting microplastics are polyethylene and polypropylene, as they aggregate near the waterair interphase. Such neustonic hydrophobic cells attract spores of bacteria causing adverse impact on the environmental, health and food supply chain. The objectives of this review investigation were to (a): evaluate the concentration of microplastics with the sizes less 100 μm floating near the waterair interphase; (b): develop a phenomenological model to study fate and transport of microplastics; (c): analyze microbial coatings, and (d): assess potential impacts of biofilm-coated neustonic microplastics on environment. A thorough review of microplastic pollution in marine environment was conducted in terms of its size distribution, toxicity and toxicokinetic pathways. Since biofilms coated microplastics float near the surface, hydrophobic cells of bacteria typically concentrate within a few micrometers layer of water-air interphase. To develop a phenomenological model of neustonic floating biofilm-coated microplastics, samples with the size of less than 100 μm were collected from within a few millimeters near the water-air interphase and were subsequently concentrated using microfiltration of water samples for analysis. Results of the optical scan of hexadecane and bacterial cells formed on vertically submerged microscope slides near water-air interphase are presented. Additionally, microplastics near a thin layer of water-air interphase were investigated using scanning electron microscopy, fluorescent microscopy, flow cytometry, and particle analyzers. Since, hydrophobic and putative pathogenic bacteria are attached to water surface, which dominate near water-air interphase, biofilm-coated microplastics are more attractive for consumption by aquatic species than pure microplastics, which significantly increases negative impacts of microplastics on aquatic ecosystems and public health through foodchain supply. We conclude that it is critical to extend this investigation to include safety in terms of *e-mail: prof.vaseashta@ieee.org DOI: 10.15244/pjoes/131947 ONLINE PUBLICATION DATE: 2021-06-07 Vaseashta A., et al. 3458

http://www.pjoes.com/pdf-131947-66925?filename=Environmental Safety and.pdf

Environmental Safety and Security Investigationsof Neustonic Microplastic Aggregates NearWater-Air Interphase

Construction Biotechnology can be used for ground surface fixation of soil particles to control water and wind erosion of soil, to control dust and dispersion of radioactive, chemical, and bacteriological pollutants in atmosphere, to mitigate the dune movement and dust storms in sand deserts, and to seal the surface of ponds, channels, reservoirs, and landfills to diminish seepage of water. After biotreatment of the fine sand with the dosage of precipitated Ca 15.6 g/m2, the release of the sand dust and its artificial pollutants to atmosphere decreased in comparison with control by 99.8 % for dust, 92.7 % for phenantherene, 94.4 % for led nitrate, and 99.8 % for bacterial cells of Bacillus megaterium. The calculated consumption of calcium during construction of model pond was 0.7 kg Ca/m2 for biocementation by spraying, 1.2 kg Ca/m2 for biocementation through precipitation of calcite from the covering solution, and 0.2 kg Ca/m2 was used for the biocementation of the small cracks in the dried model pond.

Soil Surface Biotreatment

Plastics that are used in the construction industry produce hazardous nonbiodegradable wastes after demolition of the buildings or temporal constructions. Recent investigations on bioplastic reveal a new and sustainable construction bioplastics made from the renewable organic sources that can be left in soil or composted after demolition because of their biodegradability. Bioplastics also have the potential to lead to the rise of new building materials with low embodied energy thus contributing to energy building efficiency. Cheap raw materials, continuous, and nonaseptic cultivation of mixed bacterial culture, and production of crude composite bioplastic as construction material with low embodied energy has to be used to enhance bioplastic cost-efficiency. Bioplastic can be produced as by-product of biorefinery using acidogenic fermentation or pyrolysis of lignocellulosic biomass, as well as by-product of biotreatment of solid or liquid municipal wastes.

Construction Biotechnological Plastics

Soil, surface water, groundwater, and atmosphere on the construction sites are often contaminated by pollutants, which are toxic substances for human, animals, and plants. There are known physical and chemical methods of the remediation of polluted soil but biological methods are often most cost effective but usually much slower than physical and chemical methods. Bioremediation of the polluted construction site can be performed in situ, on site or off site. Bioaggregation of soil particles using microbially induced calcium carbonate precipitation (MICP) can be used to control water erosion of sand and the release of the sand-associated pollutants to environment. Small dosage of precipitated calcium, 6.4 g/m2 of sand or 9 g Ca/kg of sand can diminish erosion of sand as well as release of chemical pollutants by three times and release of bacteriological pollutant by 10 times. Dosage of precipitated calcium by MCP of 0.8 g/kg of coarse sand decreased the content of lead in the removed coarse sand by 50 % of initial content. MICP co-precipitate radionuclides 90Sr, 60Co, and metal contaminants such as Cd and this can be used to prevent their dispersion in environment. Specific case of ground improvement is partial soil biodesaturation that diminishes the risk of soil liquefaction and accompanying damages of infrastructure during the earthquake. Biogas bubbles produced by denitrifying bacteria decrease water saturation of sand and risk of saturated sand liquefaction. MICP can be used to stabilize the biogas bubbles in the sand pores. However, the biogas bubbles can be removed from sand by water flow, while the biosealed biogas bubbles became stable. The sequential biogas production in saturated sand and biosealing of the gas bubbles in sand pores could be useful for sustainable mitigation of sand liquefaction in case of groundwater upflow through saturated sand.

Viktor Stabnikov

Papers

Environmental Safety and Security Investigationsof Neustonic Microplastic Aggregates NearWater-Air Interphase

Soil Surface Biotreatment

Construction Biotechnological Plastics

Bioremediation and Biodesaturation of Soil

Sustainable and Safe Construction Biomaterials: Biocements and Biogrouts