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Mining activities offer clear economic benefits for mineral-rich countries. However, mining operations can produce several environmental impacts. Many of these are associated with generating and managing mining waste known as tailings, which are typically stored in surface facilities. Windblown dust emissions from tailing deposits can cause severe damage to local ecosystems and adverse health effects for the surrounding population. Microbially induced calcite precipitation (MICP) can be used for the superficial biocementation of tailings, thereby preventing such emissions. This research studied the capacity of MICP for the biocementation of tailings. The effect of applying different doses of biocementation reagents and two different methods for their application were evaluated. Results show that a relevant increase in surface strength can be achieved, especially if reagents are mechanically mixed with the tailings to induce a more homogeneous distribution of precipitates. Micrographical and mineralogical analysis by SEM, FTIR and XRD analysis showed the precipitation of calcium in the form of anorthite, calcite or vaterite. Overall results indicate that calcite precipitation can be induced in tailing by microorganisms with urease activity, providing a potential technique for the biocementation of this material.

Operations in copper sulfide flotation plants (CSFP) are complex and governed by several variables such as available technologies, reagents, and environmental conditions. However, few investigations are related to studying the microbial communities. These aspects provide a reason to compare the bacterial communities of two CSFP operated with freshwater (FwFlo) and seawater (SwFlo), and study whether indigenous bacteria could be used as pyrite bioreagents. Analyses were determined through next-generation sequencing by Illumina MiSeq System and conducted throughout the entire process: (i) minerals before and after grinding; (ii) final concentrate and concentrate thickener overflow; (iii) final tailings and tailings thickener overflow; and (iv) intake water. Bacterial strains from both plants were tested as potential bioreagents, given their tendency to adhere to pyrite after 5 min. In both CSFP, Proteobacteria (relative abundance from 45.48% to 79.22%), followed by Bacteroidetes (9.37%–44.7%), were the most abundant phyla. Regarding species, Algoriphagus olei (11.35%–43.52%) was present exclusively in FwFlo samples in contact with process water and absent in the mineral before grinding, where Cupriavidus metallidurans (16.05%) and Pseudomonas_uc (11.79%) predominated. In SwFlo samples, Marinobacter flavimaris (3.47%–41.1%), and GU061212-s (10.92%–27.63%), were the most abundant microorganisms. All of them were also detected in intake seawater. The strains with the highest adhesion rate (from 29.84% ± 0.14–100%) were phylogenetically identified as species of the genera Marinobacter, Pseudomonas, Idiomarina, Halomonas, Bacillus, Aerocuccus, and Peribacillus. Our results reveal that bacterial communities are critically dependent on process waters during mining activities, and our data depicted that indigenous bacteria could be used as potential pyrite bioreagents, evidenced by a high adhesion rate. It is thus possible to propose that different indigenous bacterial strains could be considered as new bioreagents to reduce the impact of conventional flotation reagents on health from an environment friendly perspective.

The use of seawater for mining purposes in Chile has progressively increased in recent years as fast as the interest on the negative effects of biofouling on the inner part of pipelines used to transport seawater. To prevent biofouling, chemical antifouling compounds are traditionally used, thus, causing negative environmental impacts. The aim of this research has, therefore, been to evaluate the efficiency of static magnetic fields (SMF) generators to mitigate the biofouling. Hence, experimental activities have been conducted on high density polyethylene (HDPE) pipes equipped with neodymium magnets during two experimental periods in the year of 2019, i.e., autumn–winter (A–W) and spring–summer (S–S), and under two types of SMF, i.e., continuous-type (PCS) and pulse-type (PPS). Physicochemical parameters and cell viability of microorganisms composing the biofilm were investigated. Metagenomic analyses on biofilm were conducted as well. The results showed that the cell viability was the highest, i.e., 757,780 cells/cm2, during S–S and the lowest, i.e., 349,151 cells/cm2, in A–W, both under PCS. In S–S, as well as A–W, biofilm was characterized for the most abundant eukaryotic operational taxonomic units (OTUs) under PPS conditions. The presence of OTUs, such as Articiflavibacter spp., Chaetonotida spp. and Desmodorida spp., was observed only from SMF tests., This research was funded by ANID/FONDEF/IDEA, grant number ID15I10487, and, in part, by the Programa Semilleros de Investigación: “Caracterización de una línea base para el análisis y determinación de los componentes celulares”, by the Fondo para el Desarrollo en investigación científica y/o tecnológica de actividades de titulación de pregrado 2018: “Producción de metabolitos de alto valor económico mediante exposición a un campo magnético estático tipo continuo y tipo pulso en las microalgas Scenedesmus obliquus y Nannochloropsis gaditana”, by Programa Asignación año 2021 de Asistentes de investigación de la Universidad de Antofagasta código ANT20992 and partially supported by “Antonio Panico visit at the Universidad de Antofagasta” and supported by MINEDUC-UA project code ANT1999.

This research focused on the evaluation of the potential use of a soil-isolated bacteria, identified as Staphylococcus equorum, for microbial-induced calcite precipitation (MICP) and copper removal. Isolated bacteria were characterized considering growth rate, urease activity, calcium carbonate precipitation, copper tolerance as minimum inhibitory concentration (MIC) and copper precipitation. Results were compared with Sporosarcina pasteurii, which is considered a model bacteria strain for MICP processes. The results indicated that the S. equorum strain had lower urease activity, calcium removal capacity and copper tolerance than the S. pasteurii strain. However, the culture conditions tested in this study did not consider the halophilic feature of the S. equorum, which could make it a promising bacterial strain to be applied in process water from mining operations when seawater is used as process water. On the other hand, copper removal was insufficient when applying any of the bacteria strains evaluated, most likely due to the formation of a copper–ammonia complex. Thus, the implementation of S. equorum for copper removal needs to be further studied, considering the optimization of culture conditions, which may promote better performance when considering calcium, copper or other metals precipitation.

Antofagasta (Chile) is an arid region, and the climate is strongly influenced by the Atacama Desert, with few sources of fresh water. The pressure to use non-conventional water sources has boosted the construction of numerous desalination plants. High concentrations of secondary ions as calcium and magnesium cause problems in reverse osmosis plants and in other industries such as copper mining and cooling system. Biomineralization process based on hydrolysis of urea has been described in a wide variety of bacterial species with diverse applications. The selection of ureolytic halotolerant bacteria from Atacama Salar and their ability to precipitate calcium and magnesium crystals in seawater is described. Besides crystal structure and morphology were determined by electron microscopy analysis and X-ray diffraction. When assessing the mineral precipitate ability, Rhodococcus erythropolis precipitates a ~ 95% soluble calcium and 8% magnesium. The analysis of crystals showed that correspond to ~ 12.69% monohydrocalcite, ~ 30.72% struvite and ~ 56.59% halite. These results demonstrate that the biomineralization by ureolytic bacteria in seawater has great potential for its application as a pretreatment to improve water quality for industrial processes.

The use of non-desalinated seawater for mining purposes is not recommendable because of the high salinity and the presence of some ions, that is, Ca2+ and Mg2+, that can hamper the mineral tailings separation process besides being responsible for scaling formation in pipelines and equipment. To remove these ions from seawater, a novel treatment involving a biomineralization process was tested using a fluidized bed bioreactor (FBB) filled with immobilized beads of the halotolerant ureolytic strain Bacillus subtilis LN8B. The FBB was operated in batch mode according to a sequence of six cycles of eight days. The highest efficiency in removing Ca2+ and Mg2+ occurred in the first cycle for both ions, achieving the removal rate of ~100% by day four for Ca2+ and ~80% by day six for Mg2+, respectively. Precipitates from FBB were mainly composed of ~70.2% of hydromagnesite, and ~17.8% of aragonite. Furthermore, the efficiency of biologically pretreated seawater (BSw) was evaluated as mineral tailings sedimentation medium and compared with three types of water: (i) tap water (Tw); (ii) seawater (Sw); and (iii) distilled water, (Dw). The results showed that the settling velocity in BSw was the highest (i.e., 6.23 ± 0.48 m h−1).

Summary A microalgal strain was established from Cepsa's refinery wastewater treatment plant in Huelva (southwest of Spain). Genetic analysis of the chloroplastic rbcL gene encoding for the large subunit of the ribulose bisphosphate carboxylase enzyme (Rubisco) showed the strain had high homology with other known rbcL sequences of the genus Chlorella. The strain grows well autotrophically in minimum mineral medium, with a growth rate of 0.28 ± 0.012 day−1 and a biomass productivity of 138.9 ± 6.7 mg L−1 day−1. N-starvation and/or over illumination with 650 µmol photons m−2 s−1 of PAR light on the cultures induced a significant increase in the intracellular content of lipids in this microalga. Total lipids were extracted from the strain biomass with 2:1 chloroform-methanol, and they accounted for approximately 50% of the dry biomass. Polyunsaturated fatty acids (PUFAs) represented 60.4% of the total fatty acids found in the strain, thus making this biomass attractive as a high added-value product source. The strain was able to grow efficiently in the refinery treated wastewater from which it was isolated, providing an attractive advantage for further development of more sustainable algal biomass production processes at reduced costs close to a petrol refinery area.

Anaerobic digestion effluents contain nitrogen and phosphorous which require reduction to accomplish the corresponding discharge legislation. Microalgae can be used as an alternative treatment to reach the required effluent quality. However, only robust and fast growing microalgae species are required in order to ensure stable and efficient nutrient removal under the conditions existing in wastewater treatment plants. Consequently, maintaining a stable microalgae community adapted to this environment becomes a key issue. In this work, a local microalgal strain was isolated from an anaerobic digester effluent (ADE). Microalgal growth was defined as the isolation criteria. The isolated microalgae were identified by molecular techniques as Chlorella sorokiniana (strain S12/S13/S16). Nutrient removal capacity from the ADE was assessed for the isolated strain by cultivation on ADE in repeated batch mode. Growth was limited by phosphorus, which reached removal efficiencies close to 100%. Under such conditions, biomass productivity and growth rate were barely enhanced with CO -enriched air not compensating the extra cost of CO addition. Finally, in order to close the process scheme, the methane potential of the isolated C. sorokiniana was assessed. The methane production capacity was 376 mL CH g volatile solids, similar to values reported for other microalgae species. The novelty of this work lies in the isolation of a robust local microalgal strain that ensures a high nutrient removal capacity from ADE. The efficiency and stability of the nutrient removal process might be enhanced by isolation and controlled growth of local, robust, and also fast-growth microalgae species., This work was supported by the 7th Framework Programme of European Union, under the framework of the Algaenet Project (Grant number PIRSES-GA-2011-295165).

Antofagasta the second region of Chile is known worldwide for its extensive mining activity, mainly in the production of copper, molybdenum, iodine and lithium. It is also one of the driest areas of the world with few sources of fresh water that in addition to the current increase in the development of mining projects, it has generated a strong necessity for sea water uses in industrial processes. Recently some mining companies are evaluating the use of seawater in various processes, including mineral flotation. However, they have determined a low metallurgical recovery mainly of Mo, due to the effect of secondary ions as calcium, magnesium, sulfate and bicarbonate present in sea water, which precipitate at alkaline pH and produce colloids that interfere in flotation.As a biotechnology alternative to increase the recovery of valuable species by flotation in seawater, it has been isolated and characterized selected native halophilic bacteria in the Atacama Desert, which used urea as a source of energy to produce ammonia and CO2. The ammonia increases the pH of carbonate generating means, which provides favorable conditions for the formation and precipitation of Ca and Mg carbonates and secondary ions presented in high concentration in seawater.The results show that from the total isolates, 22% has proven urease activity by the method of Christensen and phenolphthalein. Furthermore, isolates were evaluated for their ability to precipitate these ions by biocementation assay. Those bacterial isolates that precipitate these ions faster were identified phylogenetically and urease activity and microbial kinetics were quantified. Finally the obtained crystals were subjected to electron scanning microscopy and X-ray diffraction determining the morphology of the crystals production and mineralogical composition.

Botryococcus braunii race A is a green microalga that produces alkadienes and alkatrienes, fatty acids, and other compounds with commercial applications. A simple, effective, and reliable genetic transformation method for B. braunii would accelerate the development of a large-scale production method. We propose here a transformation method based on the treatment of B. braunii with a cellulolytic enzyme that transiently weakens its cell wall, facilitating its ability to incorporate foreign DNA. To test the method’s effectiveness, B. braunii cells were treated with cellulase. Weakening of the cell wall was confirmed using confocal and epifluorescence microscopy. Treated cells were transformed with plasmid pSI103, which contains the selective marker AphVIII, a gene that confers resistance to the antibiotic paromomycin (Par). Transformants were obtained on a selection medium containing Par, with a transformation efficiency of 80 transformants μg−1 of plasmid DNA. A PCR analysis showed the presence of the Par gene in the resistant transformants and its maintenance through the sixth generation, after 6 months with antibiotic selection. The availability of an efficient and simple transformation method for B. braunii will make its use more feasible in a wide range of biotechnological applications.

The use of photosynthetic CO2 reduction capacity of microalgae can be used for biogas upgrading. Such process would convert CO2 contained in the biogas into microalgal biomass, generating two products: upgraded biogas and biomass. Growth rate of Nannochloropsis gaditana was determined in atmospheres containing different levels of CH4 and CO2. Results showed no effect of CH4 rich atmosphere over microalgal development. CO2 inhibition was observed only when microalgae culture was exposed to atmospheres containing 9% of CO2. Direct contact of the biogas and the microalgal culture is not a feasible way to upgrade biogas, due to oxygen desorption to the gas phase. A two-stage process, involving a photobioreactor connected with a gas/liquid mass transfer unit showed to be an efficient way to remove CO2 from the biogas, keeping low levels of oxygen in the upgraded biogas.

Copper contamination in watercourses is a recent issue in countries where mining operations are prevalent. In this study, the application of copper precipitation through microbe-induced carbonate precipitation (MICP) was analyzed using urea hydrolysis by bacteria to evaluate precipitated copper carbonates. This article demonstrates the application of a copper precipitation assay involving Sporosarcina pasteurii (in 0.5 mM Cu2+ and 333 mM urea) and analyzes the resultant low removal (10%). The analysis indicates that the low removal was a consequence of Cu2+ complexation with the ammonia resulting from the hydrolysis of urea. However, the results indicate that there should be a positive correlation between the initial urea concentration and the bacterial tolerance to copper. This identifies a challenge in the industrial application of the process, wherein a minimum consumption of urea represents an economic advantage. Therefore, it is necessary to design a sequential process that decouples bacterial growth and copper precipitation, thereby decreasing the urea requirement.

In the last decade, there has been a remarkable advance in the development of biodiesel from raw materials, highlighting various studies on the use of microorganisms such as bacteria, yeast and microalgae. A process flow sheet for biodiesel production from microalgae Botryococcus braunii under alkaline conditions on a commercial scale was developed. Detailed operating conditions and equipment designs for this process were obtained. A technological assessment of this process was conducted to evaluate the technical benefits and limitations. Parameters investigated in the sensitivity analysis were the selling price of biodiesel, oil prices fed, credit glycerin and discount rate, which proved to be the most significant variables affecting the economic viability of the process. These parameters were analyzed using statistical analysis with an experimental design. Economic evaluation of the transesterification process with a base catalysis from microalgae (75,000 tons/year) was performed. The net present value of the process is MUS $ 159.12, the positive value of the net income, for a number of periods equal to 15 years, and a discount rate of 12%, indicated that the project is profitable. The alkali-catalyzed transesterification process using microalgae proved to be technically feasible, thereby making it a competitive alternative to current commercial productions of biodiesel.

This research paper provides a brief discussion about the relevance of third generation biodiesel co-products diversification. This diversification can be performed through the utilization of residual microalgal biomass (RMB) after oil extraction process. The present work analyses the use of RMB as potential filler for biocomposite production by means of understanding the chemical composition, the thermal stability as well as the protein content of RMB. Thermogravimetric analysis revealed the processing window of the RMB for biocomposite production and its dependence on its purity, especially on residual fat content. Biocomposites of RMB and poly(butylene succinate) (PBS) were prepared by melting processing technique using extrusion followed by injection-molding. Tensile, flexural and impact properties of the processed samples were evaluated. Scanning electron microscopy of fractured sections of the biocomposites was also used to examine the dispersion of RMB in PBS matrix. Finally, this study shows a competitive alternative to produce PBS-RMB biocomposites by replacing PBS by RMB in the range between 20 and 30 %. However, further studies are necessary to improve the compatibility of RMB with PBS to obtain competitive mechanical properties, compared to neat materials through, for instance, block co-polymers.

Unicellular microalgae generally grow in the presence of bacteria, particularly when they are farmed massively. This study analyzes the bacteria associated with mass culture of Botryococcus braunii: both the planktonic bacteria in the water column and those forming biofilms adhered to the surface of the microalgal cells (∼10⁷-10⁸ culturable cells per gram microalgae). Furthermore, we identified the culturable bacteria forming a biofilm in the microalgal cells by 16S rDNA sequencing. At least eight different culturable species of bacteria were detected in the biofilm and were evaluated for the presence of quorum-sensing signals in these bacteria. Few studies have considered the implications of this phenomenon as regards the interaction between bacteria and microalgae. Production of C4-AHL and C6-AHL were detected in two species, Pseudomonas sp. and Rhizobium sp., which are present in the bacterial biofilm associated with B. braunii. This type of signal was not detected in the planktonic bacteria isolated from the water. We also noted that the bacterium, Rhizobium sp., acted as a probiotic bacterium and significantly encouraged the growth of B. braunii. A direct application of these beneficial bacteria associated with B. braunii could be, to use them like inoculants for large-scale microalgal cultures. They could optimize biomass production by enhancing growth, particularly in this microalga that has a low growth rate.

10 páginas.-- 2 figuras.-- 1 tabla.-- 26 referencias, Hydrolysis of polymers is a first and often limiting step during the degradation of plant residues. Plant biomass is generally a major component of waste residues and a major renewable resource to obtain a variety of secondary products including biofuels. Improving the performance of enzymatic hydrolysis of plant material with minimum costs and limiting the use of additional microbial biomass or hydrolytic enzymes directly influences competitiveness of these green biotechnological processes. In this study, we cloned and expressed a cellulase and two esterases recovered from environmental thermophilic soil bacterial communities and characterize their optimum activity conditions including the effect of several metal ions. Results showed that supplementing these hydrolytic reactions with Barium increases the activity of these extracellular hydrolytic enzymes. This observation represents a simple but major improvement to enhance the efficiency and competitiveness of this process within an increasingly important biotechnological sector., Support from the Spanish Ministry of Economy and Competitiveness (CONSOLIDER CSD2009-00006, CGL2014-58762-P, CTM2014-55095), the Andalusian Government (BIO288 and RNM2529), both cofinanced by FEDER funds, intramural project OEP2011 (201570I020), the mobility programme 003-ABEL-CM-2013 (NILS Science and Sustainability programme, EEA grants), the mobility and coordination European project ALGAENET (Marie Curie Actions IRSES- 295165, FP7-PEOPLE-2011) and COST Action ES1302.

Quorum sensing (QS) is a process by which bacteria communicate via the secretion and detection of chemical signaling molecules termed autoinducers. It is an important method for the regulation of population density-dependent cellular processes, such as the production of antibiotics and virulence factors, conjugation, transformation, swarming behavior, and biofilm formation (20). Several different QS systems have been discovered including the LuxIR paradigm, in which the signaling molecule is an acyl homoserine lactone (AHL), used principally by gram-negative bacteria (22, 39, 40); the furanosyl-borate diester signaling system (3); the peptide signaling systems used primarily by gram-positive bacteria (7); the LuxS/autoinducer-2 signaling used for interspecies communication; and the 3/epinephrine/norepinephrine interkingdom signaling system (36). Although QS systems have been described in a wide variety of microorganisms (26), there are few reports of the presence of QS in extremophiles. AHL-based QS has been detected in the haloalkaliphilic archaeon Natronococcus occultus (21) and in the haloalkaliphilic Halomonas genus of bacteria (17). In addition, peptide-based QS has been detected in the hyperthermophilic bacterium Thermotoga maritima (13). Little is known about QS systems in other extremophilic archaea, although a genome-wide survey indicated that a furanosyl-borate diester signaling system may be prevalent in archaea (38). The paucity of information regarding bacterial communication in extreme conditions, especially in acidic environments, prompted the present investigation. Recently, a classic LuxIR system was described in the extreme acidophile Acidithiobacillus ferrooxidans (8, 27). A. ferrooxidans is a chemolithoautotrophic, mesophilic, facultative aerobe of the gammaproteobacterium group. It obtains energy and electrons by the oxidation of hydrogen and reduced sulfur compounds to sulfate and FeII to FeIII. It grows in extremely acidic conditions (

Cyanobacteria can produce biotoxins that are significant hazards to humans. After the intoxication incident in 1996 at the city of Caruaru, Brazil, a phytoplankton-monitoring programme was established at its main water supply, the Tabocas reservoir. Data obtained during 1997 and 1998 revealed the dominant species at Tabocas to be Cylindrospermopsis raciborskii, which was responsible for a massive bloom observed in July–October 1998. Laboratory cultures of isolate ITEP-018 demonstrated highly toxic properties, mice inoculated with this strain exhibited the same symptoms as those of paralytic shellfish poisoning, with an acute lethal effect of 9.3 mouse units mg−1 of dry cells. Several saxitoxin analogues were identified in these cultures, specifically saxitoxin (3.3 mol% total toxin content), gonyautoxin 6 (6.4 mol%), decarbamoyl-saxitoxin (8.5 mol%), neosaxitoxin (17.1 mol%), and a new saxitoxin analogue, which proved to be the major product of the Tabocas strain, accounting for 64.6 mol% of the ...

In this study, we designed and evaluated a microalgal pretreatment method using cellulolytic bacteria that naturally degrades microalgae in their native habitat. Bacterial strains were isolated from each of two mollusk species in a medium containing 1% carboxymethyl cellulose agar. We selected nine bacterial strains that had endoglucanase activity: five strains from Mytilus chilensis , a Chilean mussel, and four strains from Mesodesma donacium , a clam found in the Southern Pacific. These strains were identified phylogenetically as belonging to the genera Aeromonas , Pseudomonas , Chryseobacterium , and Raoultella . The cellulase-producing capacities of these strains were characterized, and the degradation of cell walls in Botryococcus braunii and Nannochloropsis gaditana was tested with “whole-cell” cellulolytic experiments. Aeromonas bivalvium MA2, Raoultella ornithinolytica MA5, and Aeromonas salmonicida MC25 degraded B. braunii , and R. ornithinolytica MC3 and MA5 degraded N. gaditana . In addition, N. gaditana was pretreated with R. ornithinolytica strains MC3 and MA5 and was then subjected to an anaerobic digestion process, which increased the yield of methane by 140.32% and 158.68%, respectively, over that from nonpretreated microalgae. Therefore, a “whole-cell” cellulolytic pretreatment can increase the performance and efficiency of biogas production.