Diatomaceous earth as a protective vehicle for bacteria applied for self-healing concrete

Crack repair is crucial since cracks are the main cause for the decreased service life of concrete structures. An original and promising way to repair cracks is to pre-incorporate healing agents inside the concrete matrix to heal cracks the moment they appear. Thus, the concrete obtains self-healing properties. The goal of our research is to apply bacterially precipitated CaCO₃ to heal cracks in concrete since the microbial calcium carbonate is more compatible with the concrete matrix and more environmentally friendly relative to the normally used polymeric materials. Diatomaceous earth (DE) was used in this study to protect bacteria from the high-pH environment of concrete. The experimental results showed that DE had a very good protective effect for bacteria. DE immobilized bacteria had much higher ureolytic activity (12–17 g/l urea was decomposed within 3 days) than that of un-immobilized bacteria (less than 1 g/l urea was decomposed within the same time span) in cement slurry. The optimal concentration of DE for immobilization was 60% (w/v, weight of DE/volume of bacterial suspension). Self-healing in cracked specimens was visualized under light microscopy. The images showed that cracks with a width ranging from 0.15 to 0.17 mm in the specimens containing DE immobilized bacteria were completely filled by the precipitation. Scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS) were used to characterize the precipitation around the crack wall, which was confirmed to be calcium carbonate. The result from a capillary water absorption test showed that the specimens with DE immobilized bacteria had the lowest water absorption (30% of the reference ones), which indicated that the precipitation inside the cracks increased the water penetration resistance of the cracked specimens.     

Mechanical properties of bio self-healing concrete containing immobilized bacteria with iron oxide nanoparticles

Applied Microbiology and Biotechnology - Concrete is arguably one of the most important and widely used materials in the world, responsible for the majority of the industrial revolution due to its...     

Optimization of bacterial sporulation using economic nutrient for self-healing concrete

Journal of Microbiology - The use of heat- and alkali-resistant bacteria is essential for the biological repair of damaged concrete. Lysinibacillus boronitolerans YS11 was isolated from the...     

Amine-modified magnetic iron oxide nanoparticle as a promising carrier for application in bio self-healing concrete

Applied Microbiology and Biotechnology - Self-healing mechanisms are a promising solution to address the concrete cracking issue. Among the investigated self-healing strategies, the...     

Engineering bacteria for production of rhamnolipid as an agent for enhanced oil recovery

Rhamnolipid as a potent natural biosurfactant has a wide range of potential applications, including enhanced oil recovery (EOR), biodegradation, and bioremediation. Rhamnolipid is composed of rhamnose sugar molecule and beta-hydroxyalkanoic acid. The rhamnosyltransferase 1 complex (RhlAB) is the key enzyme responsible for transferring the rhamnose moiety to the beta-hydroxyalkanoic acid moiety to biosynthesize rhamnolipid. Through transposome-mediated chromosome integration, the RhlAB gene was inserted into the chromosome of the Pseudomonas aeruginosa PAO1-rhlA(-) and Escherichia coli BL21 (DE3), neither of which could produce rhamnolipid. After chromosome integration of the RhlAB gene, the constitute strains P. aeruginosa PEER02 and E. coli TnERAB did produce rhamnolipid. The HPLC/MS spectrum showed that the structure of purified rhamnolipid from P. aeruginosa PEER02 was similar to that from other P. aeruginosa strains, but with different percentage for each of the several congeners. The main congener (near 60%) of purified rhamnolipid from E. coli TnERAB was 3-(3-hydroxydecanoyloxy) decanoate (C(10)-C(10)) with mono-rhamnose. The surfactant performance of rhamnolipid was evaluated by measurement of interfacial tension (IFT) and oil recovery via sand-pack flooding tests. As expected, pH and salt concentration of the rhamnolipid solution significantly affected the IFT properties. With just 250 mg/L rhamnolipid (from P. aeruginosa PEER02 with soybean oil as substrate) in citrate-Na(2)HPO(4), pH 5, 2% NaCl, 42% of oil otherwise trapped was recovered from a sand pack. This result suggests rhamnolipid might be considered for EOR applications.     

Allelopathy as a new strategy for sustainable ecosystems development.

Natural products involved in plant-plant and plant-microorganism ecological interaction (Allelochemicals) are an important potential source for alternative agrochemicals and pharmaceuticals, in order to solve the many problems derived from inadequate culture practices and abuse of synthetic herbicides. Isolation, structural determination, bioassay techniques and applicability for these compounds in crop protection and pharmaceutical research are discussed, and future trends on Allelochemicals applications are examined. The new strategies for sustainable ecosystems controlled by allelochemicals offer a particular interest for the development of human bases in space, since these products can stimulate or inhibit plant germination and growth, and permit to develop crops with low residue amounts in water, facilitating wastewater treatment and recycling.     

A correlation study on optimum conditions of microbial precipitation and prerequisites for self-healing concrete

Microbial induced CaCO₃ precipitation (MICP) based upon enzymatic urea hydrolysis has been verified as an effective way for crack treatment, especially for self-healing of concrete cracks. This paper aimed at correlating optimum conditions of MICP with prerequisites for self-healing concrete. Orthogonal experiments on a combination of factors contributing to the MICP process were firstly performed. Initial cell density and Ca²⁺ concentration were highly significant factor and significant factor respectively. High initial cell density (1×10⁸ cells·mL^-1) together with relatively low Ca²⁺ concentration (50 mM) favored microbial precipitation. The second part of this study was associated with dissolution tests to simulate the dissolving behavior of urea and calcium, since the dissolving of healing agents in cracks is a prerequisite of self-healing. By an addition of urea and Ca(NO₃)₂ with constant mass ratio of 2:3 in concrete, the highest values of the estimated urea concentration (345 mM) and Ca²⁺ concentration (44 mM) dissolved in cracks were close to the optimal values found by orthogonal studies. Although the addition of urea and Ca(NO₃)₂ would not have a negative impact on the mechanical properties of concrete, direct mixing is not recommended due to the low utilization efficiency of incorporating healing agents for self-healing.     

Wild and cultivated mushrooms as a model of sustainable development

The natural resources are currently overexploited and since 1992 the Conference of Rio de Janeiro has focused on sustainable development to safeguard our planet for future generations. The Fungi kingdom includes producers of goods and services for ecosystems and organisms widely used in the food industry. Besides, macrofungi are recognized as non-timber forest products and could be utilized as agents of environmental management through weed biocontrol and environmental improvement. Moreover, the cultivation of fungi, in particular truffles, can provide an important income in agroecosystems, especially in marginal areas, along with the development of new technologies to produce novel products from fungi.     

Chemical recycling of polyhydroxyalkanoates as a method towards sustainable development

Chemical recycling of bio-based polymers polyhydroxyalkanoates (PHAs) by thermal degradation was investigated from the viewpoint of biorefinery. The thermal degradation resulted in successful transformation of PHAs into vinyl monomers using alkali earth compound (AEC) catalysts. Poly(3-hydroxybutyrate-co-3-hydroxyvalerate)s (PHBVs) were smoothly and selectively depolymerized into crotonic (CA) and 2-pentenoic (2-PA) acids at lower degradation temperatures in the presence of CaO and Mg(OH)₂ as catalysts. Obtained CA from 3-hydroxybutyrate sequences in PHBV was copolymerized with acrylic acid to produce useful water-soluble copolymers, poly(crotonic acid-co-acrylic acid) that have high glass-transition temperatures. The copolymerization of CA derived from PHA pyrolysis is an example of cascade utilization of PHAs, which meets the idea of sustainable development.     

Lactic acid bacteria as reducing and capping agent for the fast and efficient production of silver nanoparticles

There is a growing demand for silver-based biocides, including both ionic silver forms and metallic nanosilver. The use of metallic nanosilver, typically chemically produced, faces challenges including particle agglomeration, high costs, and upscaling difficulties . Additionally, there exists a need for the development of a more eco-friendly production of nanosilver. In this study, Gram-positive and Gram-negative bacteria were utilized in the non-enzymatic production of silver nanoparticles via the interaction of silver ions and organic compounds present on the bacterial cell. Only lactic acid bacteria, Lactobacillus spp., Pediococcus pentosaceus, Enterococcus faecium, and Lactococcus garvieae, were able to reduce silver. The nanoparticles of the five best producing Lactobacillus spp. were examined more into detail with transmission electron microscopy. Particle localization inside the cell, the mean particle size, and size distribution were species dependent, with Lactobacillus fermentum having the smallest mean particle size of 11.2 nm, the most narrow size distribution, and most nanoparticles associated with the outside of the cells. Furthermore, influence of pH on the reduction process was investigated. With increasing pH, silver recovery increased as well as the reduction rate as indicated by UV–VIS analyses. This study demonstrated that Lactobacillus spp. can be used for a rapid and efficient production of silver nanoparticles.     

面向可持续城市生态系统管理的国土空间开发适宜性评价——以烟台市为例

国土空间开发适宜性评价是国土空间规划编制的基础和前提。面向可持续城市生态系统管理目标,基于生态保护红线和永久基本农田的"底线"思维,以资源环境禀赋为基础,构建了本底约束—综合限制—承载力评价-多空间适宜评价的资源环境承载力和国土空间开发适宜性评价的逻辑框架和指标体系,并以烟台为例,设置城市生态系统保护的不同情景,综合运用特尔斐法及多要素空间叠置等方法,开展了城市资源环境承载力与国土空间开发适宜性评价的实践应用。研究结果表明:①资源环境对烟台经济社会发展的阻碍与限制总体较小,高限制区面积仅占烟台国土面积的6.09%。②烟台市不同区县之间的资源环境承载力差异较大。从西北部向东南,烟台市资源环境承载力呈现出逐渐提高的变化趋势。③面向可持续城市生态系统管理情景,烟台市各县市国土空间开发建设适宜性差异显著,适宜建设区范围为2380 km²。面向城市生态系统一般保护情景,烟台市适宜建设区面积达2610 km²,不适宜建设开发区与适宜建设开发区数量结构为1.12∶1,未来国土空间开发利用潜力较大。两种情景下烟台市国土空间开发适宜性适宜建设区面积均大于现状建...     

Engineering bacteria for production of sustainable polycyclopropanated jet fuel alternatives

Replacing petroleum-based fuels in high-power sectors like aviation and rocketry is a major sustainability challenge. Polycyclopropanated hydrocarbons provide excellent fuel characteristics for these applications, but their synthesis is challenging. Cruz-Morales et al. demonstrated microbial production of a range of polycyclopropanated ‘fuelimycins’ based on an unusual iterative polyketide synthase (iPKS).     

Screening siderophore producing bacteria as potential biological control agent for fungal rice pathogens in Thailand

Rice (Oryza sativa) is a staple food in Thailand and, in addition, feeds around one half of the world’s population. Therefore, diseases of rice are of special concern. Rice is destroyed by 2 main pathogens, Fusarium oxysporum and Pyricularia oryzae the causative agents of root rot and blast in rice respectively. These pathogens result in low grain yield in Thailand and other Southeast Asian countries. Soil samples were taken from paddy fields in Northern Thailand and bacteria were isolated using the soil dilution plate method on Nutrient agar. Isolation yielded 216 bacterial isolates which were subsequently tested for their siderophore production and effectiveness in inhibiting mycelial growth in vitro of the rice pathogenic fungi; Alternaria sp., Fusarium oxysporum, Pyricularia oryzae and Sclerotium sp., the causal agent of leaf spot, root rot, blast and stem rot in rice. It was found that 23% of the bacteria isolated produced siderophore on solid plating medium and liquid medium, In dual culture technique, the siderophore producing rhizobacteria showed a strong antagonistic effect against the Alternaria (35.4%), Fusarium oxysporum (37.5%), Pyricularia oryzae (31.2%) and Sclerotium sp. (10.4%) strains tested. Streptomyces sp. strain A 130 and Pseudomonas sp. strain MW 2.6 in particular showed a significant higher antagonistic effect against Alternaria sp. while Ochrobactrum anthropi D 5.2 exhibited a good antagonistic effect against F. oxysporum. Bacillus firmus D 4.1 inhibited P. oryzae and Kocuria rhizophila 4(2.1.1) strongly inhibited Sclerotium sp. P. aureofaciens AR 1 was the best siderophore producer overall and secreted hydroxamate type siderophore. This strain exhibits an in vitro antagonistic effect against Alternaria sp., F. oxysporum and P. oryzae. Siderophore production in this isolate was maximal after 15 days and at an optimal temperature of 30°C, yielding 99.96 ± 0.46 μg ml^?1 of siderophore. The most effective isolates were identified by biochemical tests and molecular techniques as members of the Genus Bacillus, Pseudomonas and Kocuria including B. firmus D 4.1, P. aureofaciens AR1 and Kocuria rhizophila 4(2.1.1). The study demonstrated antagonistic activity towards the target pathogens discussed and are thus potential agents for biocontrol of soil borne diseases of rice in Thailand and other countries.     

Simulation and analysis for sustainable product development

Purpose

Simulation plays a critical role in the design of products, materials, and manufacturing processes. However, there are gaps in the simulation tools used by industry to provide reliable results from which effective decisions can be made about environmental impacts at different stages of product life cycle. A holistic and systems approach to predicting impacts via sustainable manufacturing planning and simulation (SMPS) is presented in an effort to incorporate sustainability aspects across a product life cycle.

Methods

Increasingly, simulation is replacing physical tests to ensure product reliability and quality, thereby facilitating steady reductions in design and manufacturing cycles. For SMPS, we propose to extend an earlier framework developed in the Systems Integration for Manufacturing Applications (SIMA) program at the National Institute of Standards and Technology. SMPS framework has four phases, viz. design product, engineer manufacturing, engineer production system, and produce products. Each phase has its inputs, outputs, phase level activities, and sustainability-related data, metrics and tools.

Results and discussion

An automotive manufacturing scenario that highlights the potential of utilizing SMPS framework to facilitate decision making across different phases of product life cycle is presented. Various research opportunities are discussed for the SMPS framework and corresponding information models.

Conclusions

The SMPS framework built on the SIMA model has potential in aiding sustainable product development.