Removal of arsenic from acidic liquors using chemical and autotrophic and mixed heterotrophic bacteria-produced biogenic schwertmannites.

Arsenic penetrates human society through a variety of geological and anthropogenic processes, posing significant health hazards. Acid mine drainage, which contains high concentrations of heavy metals and sulfate, is formed by the biological oxidation of pyrite and other metal-containing sulfidic minerals and is a significant environmental hazard. Adsorption is a simple and effective method for removing arsenic from water. In this study, co-precipitation and adsorption of arsenic with biogenic and chemically produced iron-containing settleable precipitates, i.e. schwertmannites were studied. Autotrophic Leptospirillum ferrooxidans and heterotrophic mixed culture of Alicyclobacillus tolerans and Acidiphilium cryptum oxidized iron at rates from 18 to 23 mg/(L.h) in the presence of 5 and 10 mg/L As3+, and both cultures tolerated up to 100 mg As3+/L although Fe2+ oxidation rates decreased to 3-4 mg/(L.h). At Fe/As ratios of ≥20, As removal efficiencies of ≥95% were obtained by co-precipitation with Fe3+ at pH 3.5-4.5. Because schwertmannite precipitates produced by the heterotrophic culture formed crystals, it was studied for adsorptive removals of As3+ and As5+ and compared with chemically synthesized schwertmannites. As3+ (100 mg/L) adsorption onto biogenic and chemical schwertmannite were 25 and 44%, respectively, at pH 4. At 100 mg As5+/L, adsorption capacity and efficiency onto biogenic schwertmannite were 47 mg/g and 50%, respectively. At 300 mg As5+/L, adsorption capacity and efficiency onto chemical schwertmannite were 169 mg/g and 56%, respectively. In summary, biogenic schwertmannite has potential for As removal via co-precipitation with Fe3+ at pH 3.5-4.5 and Fe/As ratios of ≥20 due to low production cost from acidic mine drainage. In contrast to the schwertmannite generation methods, which are usually performed with autotrophic acidophilic bacteria in the literature, this efficient and modular schwertmannite production process and its evaluation on arsenic adsorption is an important potential in acidic mine drainage treatment containing arsenic.

Dye decolorization of magnetically retrievable formulation of laccase with amine-functionalized microparticles.

Laccase is an important enzyme used in many industries because of its multi-substrate catalyst. New immobilization agents are excellent tools for enhancing the abilities of this enzyme. In this study, immobilization of laccase on silica microparticles with NH2 (S-NH2) surface modification to use in dye removal applications was aimed. The yield of immobilization by this method was found to be 93.93 ± 2.86% under optimum conditions. In addition, this newly created immobilized enzyme was adapted to a decolorization application with 87.56 ± 1.60% efficiency. Silica microparticles with NH2 (S-NH2) surface modification were used for laccase immobilization and this immobilized laccase had quite good potential. Besides, Random Amplified Polymorphic DNA (RAPD) analysis in evaluating the toxicity of the decolorization process was utilized. After amplification with two RAPD primers, decreased toxicity of dye in this study was observed. This study showed that RAPD analysis in toxicity testing could be accepted as an alternative and practical method that this approach will contribute to the literature in terms of providing fast and reliable results. The use of amine-modified surface silica microparticles for laccase immobilization and RAPD for toxicity testing is a crucial aspect of our investigation.

Optimization of biodegradation yield of reactive blue 49: An integrated approach using response surface methodology based marine predators algorithm.

Biodegradation involving the use of biological systems are proving to be more cost-effective, energy efficient and environmentally friendly method for treatment with dye. There are also some advantages of enzymatic degradation to remove pollutants from textile effluents. They are specific and selectable for the substrates. Moreover, the usage of enzymatic degradation with laccase has environmental and social dimensions of sustainable bio-economy when compared with commercial solutions. In this study, besides the conventional RSM (Response Surface Methodology) approaches, the performance of a new metaheuristic, MPA (Marine Predators Algorithm) integrated with RSM has also been tested. The effect of four independent variables time, enzyme amount, agitation speed, and initial dye concentration have been studied to obtain maximum decolorization. Two major techniques of RSM, namely Box Behnken Design (BBD) and Central Composite Design (CCD) have been used to determine optimal levels of parameters. The highest decolorization efficiency (%) of Reactive Blue 49 (RB49) has been achieved as 92.82% with BBD and 90.56% with CCD. Maximum efficiency for BBD based MPA as being 94.69% has been obtained at 70.96 min, 1.5 mL, 74.63 rpm, and 99.09 ppm. For CCD based MPA, the level of efficiency has been obtained as 93.1% at 39.69 min, 1 mL, 72.07 rpm, and 74.41 ppm. The results of MPA indicate that using metaheuristics combined with RSM is a suitable and sustainable way to optimize parameters of RB49% for decolorization.

A novel higher polyhydroxybutyrate producer Halomonas halmophila 18H with unique cell factory attributes.

For cost-competitive biosynthesis of polyhydroxybutyrate (PHB), the screening of efficient producers and characterization of their genomic potential is fundamental. In this study, 94 newly isolated halophilic strains from Turkish salterns were screened for their polyhydroxyalkanoates (PHAs) biosynthesis capabilities through fermentation. Halomonas halmophila 18H was found to be the highest PHB producer, yielding 63.72 % of its biomass as PHB. The PHB produced by this strain was physically and chemically characterized using various techniques. Its genome was also sequenced and found to be large (6,713,657 bp) and have a GC content of 59.9 %. Halomonas halmophila 18H was also found to have several copies of PHB biosynthesis genes, as well as 20 % more protein-coding genes and 1075 singletons compared to other high PHB producers. These unique genomic features make it a promising cell factory for the simultaneous production of PHAs and other biotechnologically important secondary metabolites.

Whole-genome sequencing and genome-scale metabolic modeling of Chromohalobacter canadensis 85B to explore its salt tolerance and biotechnological use.

Salt tolerant organisms are increasingly being used for the industrial production of high-value biomolecules due to their better adaptability compared to mesophiles. Chromohalobacter canadensis is one of the early halophiles to show promising biotechnology potential, which has not been explored to date. Advanced high throughput technologies such as whole-genome sequencing allow in-depth insight into the potential of organisms while at the frontiers of systems biology. At the same time, genome-scale metabolic models (GEMs) enable phenotype predictions through a mechanistic representation of metabolism. Here, we sequence and analyze the genome of C. canadensis 85B, and we use it to reconstruct a GEM. We then analyze the GEM using flux balance analysis and validate it against literature data on C. canadensis. We show that C. canadensis 85B is a metabolically versatile organism with many features for stress and osmotic adaptation. Pathways to produce ectoine and polyhydroxybutyrates were also predicted. The GEM reveals the ability to grow on several carbon sources in a minimal medium and reproduce osmoadaptation phenotypes. Overall, this study reveals insights from the genome of C. canadensis 85B, providing genomic data and a draft GEM that will serve as the first steps towards a better understanding of its metabolism, for novel applications in industrial biotechnology.