Concurrent Carbon Capture and Biocementation through the Carbonic Anhydrase (CA) activity of microorganisms ‑ a review and outlook

Biocementation, i.e., the production of biomimetic cement through the metabolic activity of microorganisms, offers exciting new prospects for various civil and environmental engineering applications. This paper presents a systematic literature review on a biocementation pathway, which uses the carbonic anhydrase (CA) activity of microorganisms that sequester CO2 to produce biocement. The aim is the future development of this technique for civil and (geo-)environmental engineering applications towards CO2-neutral or negative processes. After screening 248 potentially relevant peer-reviewed journal papers published between 2002 and 2023, 38 publications studying CA-biocementation were considered in the review. Some of these studies used pure CA enzyme rather than bacteria-produced CA. Of these studies, 7 used biocementation for self-healing concrete, 6 for CO2 sequestration, 10 for geotechnical applications, and 15 for (geo-)environmental applications. A total of 34 bacterial strains were studied, and optimal conditions for their growth and enzymatic activity were identified. The review concluded that the topic is little researched; more studies are required both in the laboratory and field (particularly long-term field experiments, which are totally lacking). No studies on the numerical modelling of CA-biocementation and the required kinetic parameters were found. The paper thus consulted the more widely researched field of CO2 sequestration using the CA-pathway, to identify other microorganisms recommended for further research and reaction kinetic parameters for numerical modelling. Finally, challenges to be addressed and future research needs were discussed

Competition of As and other Group 15 elements for surface binding sites of an extremophilic Acidomyces acidophilus isolated from a historical tin mining site

An arsenic-resistant fungal strain, designated WKC-1, was isolated from a waste roaster pile in a historical tin mine in Cornwall, UK and successfully identified to be Acidomyces acidophilus using matrix-assisted laser desorption/ionization time-of-flight/time-of-flight tandem mass spectrometry (MALDI-TOF/TOF MS) proteomic-based biotyping approach. WKC-1 showed considerable resistance to As5+ and Sb5+ where the minimal inhibitory concentration (MIC) were 22500 mg L-1 and 100 mg L-1 respectively on Czapex-Dox Agar (CDA) medium; it was substantially more resistant to As5+ than the reference strains CBS 335.97 and CCF 4251. In a modified CDA medium containing 0.02 mg L-1 phosphate, WKC-1 was able to remove 70.30 % of As5+ (100 mg L-1). Sorption experiment showed that the maximum capacity of As5+ uptake was 170.82 mg g-1 dry biomass as predicted by the Langmuir model. The presence of Sb5+ reduced the As5+ uptake by nearly 40%. Based on the Fourier-transform infrared spectroscopy (FT-IR) analysis, we propose that Sb is competing with As for these sorption sites: OH, NH, CH, SO3 and PO4 on the fungal cell surface. To our knowledge, this is the first report on the impact of other Group 15 elements on the biosorption of As5+ in Acidomyces acidophilus

Investigating arsenic resistance in fungi from tin-mining soil and the possible interaction between arsenic and tin/antimony

There is an increasing interest in the study of fungi that inhabit extreme environments that can provide new biotechnological applications in treating contaminated land. Fungi are versatile biosorbents as they can tolerate extreme levels of metal concentration, nutrient availability, pH and temperature (Gadd, 2009). In this work, heavy metals contaminated soil was collected from Geevor Tin Mine in Penzance, Cornwall. Arsenic and antimony were found in high concentration of 18970 ± 227.0 mg/kg and 196.57 ± 1.91 mg/kg respectively in an extremely acidic soil pH of 1.13. Acidomyces acidophilus strain shows promise in tolerating elevated levels of As (>20,000 mg/L) and Sb (>300 mg/L)

Identification and characterisation of a Bacillus licheniformis strain with profound keratinase activity for degradation of melanised feather

Significant amount of keratins in the form of feather, hair, hoof and horn are generated annually by the livestock industry. Keratinases are increasingly important in the reprocessing and environmental pollution control of keratin wastes. The aim of this study is to isolate a microbial strain of high keratinase activity and to evaluate its feather degrading potential. Thirty-two keratin degrading microbial strains from farmyard wastes and primary effluent were isolated using a selective medium containing feather meal at 30, 37 and 50 °C. One of the isolates, which demonstrated the highest keratinolytic activity (11.00 ± 0.71 Uml-1) was identified as a species of Bacillus licheniformis based on the 16S rDNA analysis, designated as strain N22 and deposited in a culture collection. Optimum keratinase production by this bacterium was achieved in 32 h using a minimum growth medium containing 1.1% (w/v) feather meal at 50 °C and pH 8.5. The molecular weight of the keratinase was ≈ 28 KDa as determined sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) analysis and confirmed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). The keratinase reported here significantly degraded melanised feather in 48 h in the absence of reducing agents. There are few reports on the evaluation of feather degrading ability of keratinases using highly resistant melanised feather. The efficient degradation of melanised feathers by this keratinase may offer an environmentally friendly solution to the degradation of feather waste and other organic matter of similar molecular composition

A critical review of household recycling barriers in the United Kingdom

The UK recycling rate fluctuates between 45% and 47% and has consistently failed to meet the 65% target set by the post-Brexit Resource and Waste Strategy. Understanding the issues surrounding the low recycling rate in metropolitan cities in the UK will help to overcome these recycling challenges. The review examines the current situation with regards to the recycling rate and tonnage of waste produced in the UK based on available secondary waste flow data and explores different barriers related to household recycling. Many areas giving rise to the recycling challenges have been identified, including waste policy constraints, lack of effective communication, public engagement, physical barriers, service constraints, human factors, and socio-economic barriers. The literature review reveals factors such as waste policy, communication, and physical factors were the most important aspects in influencing recycling rate or output. It is concluded that a multi-dimension intervention is required, which includes a thorough review of waste policy, a more stringent enforcement, an improved communication strategy, and a more integrated planning development policy to mitigate issues affecting the UK’s low recycling rate or output. This approach will propel the local authorities to launch or initiate effective recycling management and to put in place the required infrastructure to facilitate effective recycling activities

Chemistry and the environment

A report on three symposia in the ‘Energy, Water and Environmental Science’ programme at the International Union of Pure and Applied Chemistry (IUPAC) 46th World Chemistry Congress (in Sao Paulo, Brazil, 9-14 July, 2017). The symposia presented the latest advances concerning the environmental impact of emerging technologies and the fate of pollutants in the environment

Combining phytoremediation with bioenergy production: developing a multi‑criteria decision matrix for plant species selection

The use of plants to extract metal contaminants from soils has been proposed as a cost-effective means of remediation, and utilizing energy crops for this phytoextraction process is a useful way of attaining added value from the process. To simultaneously attain both these objectives successfully, selection of an appropriate plant species is crucial to satisfy a number of important criteria including translocation index, metal and drought tolerance, fast growth rate, high lignocellulosic content, good biomass production, adequate calorific value, second generation attribute, and a good rooting system. In this study, we proposed a multi-criteria decision analysis (MCDA) to aid decision-making on plant species based on information generated from a systematic review survey. Eight species Helianthus annuus (sunflower), Brassica juncea (Indian mustard), Glycine max (soybean), Salix spp. (willow), Populus spp. (poplar), Panicum virgatum (switchgrass), Typha latifolia (cattails), and Miscanthus sinensis (silvergrass) were examined based on the amount of hits on a number of scientific search databases. The data was normalized by estimating their min–max values and their suitability. These criteria/indicators were weighted based on stipulated research objectives/priorities to form the basis of a final overall utility scoring. Using the MCDA, sunflower and silvergrass emerged as the top two candidates for both phytoremediation and bioenergy production. The multi-criteria matrix scores assist the process of making decisions because they compile plant species options quantitatively for all relevant criteria and key performance indicators (KPIs) and its weighing process helps incorporate stakeholder priorities to the selection process