Calcium ion adsorption with extracellular proteins of thermophilic bacteria isolated from geothermal sites—A feasibility study

Untargeted metabolomic analysis reveals the mechanism of Enterococcus faecium agent induced CaCO3 scale inhibition

In this study, a lactic acid bacterium, Enterococcus faecium, was found to prevent CaCO₃ precipitation through its metabolism. On analysis of all stages of E. faecium growth, static jar tests demonstrated that stationary phase E. faecium broth possessed the highest inhibition efficiency of 97.3% at a 0.4% inoculation dosage, followed by the decline and log phases with efficiencies of 90.03% and 76.07%, respectively. Biomineralization experiments indicated that E. faecium fermented the substrate to produce organic acid, which resulted in modulation of the pH and alkalinity of the environment and thus inhibited CaCO₃ precipitation. Surface characterization techniques indicated that the CaCO₃ crystals precipitated by the E. faecium broth tended to be significantly distorted and formed other organogenic calcite crystals. The scale inhibition mechanisms were revealed by untargeted metabolomic analysis on log and stationary phase E. faecium broth. In total, 264 metabolites were detected, 28 of which were differential metabolites (VIP ≥ 1 and p < 0.05). Of these, 15 metabolites were upregulated in stationary phase broth, and 13 metabolites were downregulated in log phase broth. Metabolic pathway analysis suggested that improved glycolysis and the TCA cycle were the main reasons for enhancement of the antiscaling performance of E. faecium broth. These findings have significant implications for microbial metabolism-induced CaCO₃ scale inhibition.

State of art bio-materials as scale inhibitors in recirculating cooling water system: a review article

During the operation of the circulating cooling water system, inorganic scale deposition may cause technical problems, such as reduction of heat transfer efficiency in cooling systems and obstruction of pipes. In the industry, chemicals are often used as scale inhibitors in scale deposition control, antiscalants popular in industry are generally phosphorus and nitrogen-containing chemicals, which may lead to eutrophication. However, increasing environmental concern and discharge limitations have guided antiscalants to move toward biodegradability, nontoxicity and cost-effectiveness. This paper reviews current research on the application of using bio-materials as scale inhibitors, including proteins and amino acids, polysaccharides, plant extracts, microbial reagents, and microbiological products. The non-bioaccumulation, low cost, readily biodegradability and sustainably available characters promote the development of green-scale inhibitor chemistry.

Recovery of gold from industrial wastewater by extracellular proteins obtained from a thermophilic bacterium Tepidimonas fonticaldi AT-A2

Biosorption has emerged as a promising alternative approach for treating wastewater with dilute metal contents in a green and cost effective way. In this study, extracellular proteins of an isolated thermophilic bacterium (Tepidimonas fonticaldi AT-A2) were used as biosorbent to recover precious metal (i.e., Au) from wastewater. The Au (III) adsorption capacity on the T. fonticaldi AT-A2 proteins was the highest when the pH was set at about 4.0-5.0. The adsorption capacity increased with increasing temperature from 15 to 70°C. Adsorption isotherm studies show that both Langmuir and Freundrich models could describe the adsorption equilibrium. The maximum adsorption capacity of Au (III) at 50°C and pH 5 could reach 9.7mg Au/mg protein. The protein-based biosorbent was also used for the recovery of Au from a wastewater containing 15mg/L of Au, achieving a high adsorption capacity of 1.45mg Au/mg protein and a removal efficiency of 71%.