Sticky Bacteria: Understanding the Behavior of a D-Galactose Adapted Consortium of Acidophilic Chemolithotroph Bacteria and Their Attachment on a Concentrate of Polymetallic Mineral.

Various strategies to accelerate the formation of biofilms on minerals have been studied, and one of them is the use of D-galactose as an inducer of EPS production in planktonic cells of biooxidant bacteria. With the aim to evaluate the influence on the attachment and the effect over the solubilization of a polymetallic mineral concentrate, the behavior of a microbial consortium formed by Acidithiobacillus thiooxidans DSM 14887T and Leptospirillum ferrooxidans DSM 2705T previously induced with D-galactose for the early formation of EPS was studied. These microorganisms were previously adapted to 0.15 and 0.25% of D-galactose, respectively; afterward, different proportions of both strains were put in contact with the particle surface of a concentrate of polymetallic mineral. Also, to evaluate the affinity of each bacterium to the mineral, attachment tests were carried out with one of these species acting as a pre-colonizer. The same consortia were used to evaluate the solubilization of the polymetallic mineral. The results obtained show that the induction by D-galactose increases the microbial attachment percentage to the mineral by at least 10% with respect to the control of non-adapted consortia. On the other hand, the tests carried out with pre-colonization show that the order of inoculation also affects the microbial attachment percentage. From the different proportions tested, it was determined that the use of a consortium with a proportion of 50% of each species previously adapted to D-galactose and inoculated simultaneously, present a microbial attachment percentage to the mineral greater than 95% and better solubilization of a polymetallic mineral, reaching values of 9.7 and 11.7mgL-1 h-1 of Fe3+ and SO4 2-, respectively. Therefore, the use of D-galactose in small concentrations as inducer of EPS in acidophilic cells and the selection of an adequate strategy of inoculation can be beneficial to improve biooxidation since it would allow this process to develop in a shorter time by achieving a greater number of attached cells in a shorter time accelerating the solubilization of a sulfide mineral. Graphical AbstractEPS production using D-galactose as inducer and its influence in the attachment of consortia formed by differents proportions of A. thiooxidans and L. ferrooxidans inoculated at the same time and when one of them acting as a pre-colonizer.

Kinetic model of Clostridium beijerinckii's Acetone-Butanol-Ethanol fermentation considering metabolically diverse cell types.

Clostridium beijerinckii population branches into metabolically diverse cell types in batch cultures. Here, we present a new kinetic model of C. beijerinckii's Acetone-Butanol-Ethanol fermentation that considers three cell types: producers of acids (acidogenic), consumer of acids and producers of solvents (solventogenic), and spores cells. The model accurately recapitulates batch culture data. Also, the model estimates cell type-specific kinetic parameters, which can be helpful to improve the operation of the ABE fermentation and give a framework to study acidogenic and solventogenic metabolic pathways. To exemplify the latter, we used a constraint-based model to study how the ABE pathways are used among acidogenic and solventogenic cell types. We found that among both cell types, glycolytic production of ATP and consumption of NAD+ varies widely during the fermentation, with their maximum production/consumption rates happening when acidogenic and solventogenic growth rates were at their highest. However, acidogenic cells use the ABE pathway to contribute with an extra 12.5% of the total production of ATP, whereas solventogenic cell types use the ABE pathway to supply more than 75% of the demand for NAD+, alternating between the production of lactate and butyrate, being both coupled to the production of NAD+.

Bioremediation by Cupriavidus metallidurans Strain MSR33 of Mercury-Polluted Agricultural Soil in a Rotary Drum Bioreactor and Its Effects on Nitrogen Cycle Microorganisms.

Nitrogen cycle microorganisms are essential in agricultural soils and may be affected by mercury pollution. The aims of this study are to evaluate the bioremediation of mercury-polluted agricultural soil using Cupriavidus metallidurans MSR33 in a rotary drum bioreactor (RDB) and to characterize the effects of mercury pollution and bioremediation on nitrogen cycle microorganisms. An agricultural soil was contaminated with mercury (II) (20-30 ppm) and subjected to bioremediation using strain MSR33 in a custom-made RDB. The effects of mercury and bioremediation on nitrogen cycle microorganisms were studied by qPCR. Bioremediation in the RDB removed 82% mercury. MSR33 cell concentrations, thioglycolate, and mercury concentrations influence mercury removal. Mercury pollution strongly decreased nitrogen-fixing and nitrifying bacterial communities in agricultural soils. Notably, after soil bioremediation process nitrogen-fixing and nitrifying bacteria significantly increased. Diverse mercury-tolerant strains were isolated from the bioremediated soil. The isolates Glutamicibacter sp. SB1a, Brevundimonas sp. SB3b, and Ochrobactrum sp. SB4b possessed the merG gene associated with the plasmid pTP6, suggesting the horizontal transfer of this plasmid to native gram-positive and gram-negative bacteria. Bioremediation by strain MSR33 in an RDB is an attractive and innovative technology for the clean-up of mercury-polluted agricultural soils and the recovery of nitrogen cycle microbial communities.

Biooxidation of Iron by Acidithiobacillus ferrooxidans in the Presence of D-Galactose: Understanding Its Influence on the Production of EPS and Cell Tolerance to High Concentrations of Iron.

Acidithiobacillus ferrooxidans, together with other microorganisms, has an important role on biohydrometallurgical processes. Such bacterium gets its energy from the oxidation of ferrous ion and reduced sulfur; in the first case, the accumulation of ferric ion as a product can cause its inhibition. It is known that the extracellular polymeric substances (EPS) may have an important role in the adaptation and tolerance to diverse inhibiting conditions. In the present study, it was tested how D-galactose can influence the production of extracellular polymeric substances (EPS) on At. ferrooxidans by evaluating at the same time its biooxidant activity and capacity to tolerate high concentrations of ferric ion. The visualization and quantification of EPS was done through a confocal laser scanning microscope (CLSM). The results show that at low cellular concentrations, the D-galactose inhibits the microbial growth and the biooxidation of ferrous ion; however, when the quantity of microorganisms is high enough, the inhibition is not present. By means of chemostat tests, several concentrations of D-galactose (0; 0.15; 0.25; and 0.35%) were evaluated, thus reaching the highest production of EPS when using 0.35% of this sugar. In cultures with such concentration of D-galactose, the tolerance of the bacterium was tested at high concentrations of ferric ion and it was compared with cultures in which sugar was not added. The results show that cultures with D-galactose reached a higher tolerance to ferric ion (48.15 ± 1.9 g L-1) compare to cultures without adding D-galactose (38.7 ± 0.47 g L-1 ferric ion). Also it was observed a higher amount of EPS on cells growing in the presence of D-galactose suggesting its influence on the greater tolerance of At. ferrooxidans to ferric ion. Therefore, according to the results, the bases of a strategy are considered to overproduce EPS by means of At. ferrooxidans in planktonic state, so that, it can be used as a pre-treatment to increase its resistance and tolerance to high concentrations of ferric ion and improve the efficiency of At. ferrooxidans when acting in biohydrometallurgical processes.

Survival of Spray-Dried Rhodotorula mucilaginosa Isolated from Natural Microbiota of Murta Berries and AntagonisticEffect on Botrytis cinerea.

The aim of this study is to evaluate the survival rate and effective antagonistic activity against Botrytis cinerea, responsible for grey mould on harvested fruits and vegetables, of yeast Rhodotorula mucilaginosa, isolated and identified from the natural microbiota of murta (Chilean guava) berries, after spray drying at different inlet air temperatures, mass per volume ratio of encapsulating agent (maltodextrin) and feed flow rates. The 100% survival of the yeast was obtained after spray drying with 18% maltodextrin at 130 °C inlet temperature and a feed flow rate of 9.25 mL/min. The dried yeast obtained under such conditions had the highest antagonistic activity in vitro and in vivo on apples, which showed that spray drying is a valid method to produce active dried cells of R. mucilaginosa that can be used for biocontrol of grey mould spoilage. It was also found that the encapsulating agent maltodextrin improved the in vitro antagonistic activity of R. mucilaginosa.

Making sticky cells: effect of galactose and ferrous iron on the attachment of Leptospirillum ferrooxidans to mineral surfaces.

The purpose of this study was to compare the efficacy of galactose and high initial ferrous iron concentrations as inducers for extracellular polymeric substances (EPS) production in planktonic cells of Leptospirillum ferrooxidans and to study cell attachment to a mineral surface in comparison to cells not exposed to such substances. L. ferrooxidans was successfully adapted to grow in a modified 9K medium at different concentrations of galactose (0.15, 0.25, 0.35%) and also at different initial ferrous iron concentrations (18, 27, 36 g/L), which are higher than 9K medium (9 g/L). The experiments were done in shake flasks using ferrous iron as energy source. A comparison of growth kinetics showed a decreasing of maximum specific growth rate of L. ferrooxidans with increasing concentrations of galactose and initial ferrous iron. The EPS content increased and the EPS chemical composition (relative abundance of carbohydrates, proteins and ferric iron) changed with increasing concentrations of galactose and initial ferrous iron. Results revealed that the increase of the bacterial adhesion rather depended on the chemical composition, i.e. relative abundance of the constituents of the EPS, than on the total amount of EPS. The EPS induced by galactose seemed to be "stickier" than the one induced by ferrous iron. Based on the results of this study it is proposed that galactose might enhance biooxidation processes which needs to be tested in future studies.

Biofiltration of trimethylamine in biotrickling filter inoculated with Aminobacter aminovorans

Background: Trimethylamine (TMA) is the main responsible for the odor associated with rotting fish and other annoying odors generated in many industrial activities. Biofiltration has proved to be efficient for treating odorous gaseous emissions. The main objective of this work was to determine the removal capacity of TMA of a biotrickling filter inoculated with Aminobacter aminovorans and to evaluate the effect of H2S on its performance. Results: The maximumspecific growth rate ofA. aminovorans in a liquid culture was 0.15 h -1 , witha TMAto biomass yield of 0.10 (g g -1) and a specific consumption rate of 0.062 g·g-1·h-1 . The initial specific consumption rate of TMA was highly influenced by the presence of H2S in liquid culture at concentrations of 20 and 69 ppm in heading space oftheflasks.ABTF inoculatedwithA. aminovorans showedremoval efficiencieshigher than98%ina range ofloading rate of 0.2 to 8 g·m-3·h-1 at empty bed residence time (EBRT) of 85 and 180 s. No effect on the elimination capacity and efficiency was detected when H2S was added at 20 and 50 ppm to the inlet gaseous emission, though the fraction of A. aminovorans measured by qPCR in the biofilm decreased. Conclusions:Abiotrickling filter inoculated with A. aminovorans can remove efficiently the TMA in a gaseous stream. The elimination capacity of TMA can be negatively affected by H2S, but its effect is not notorious when it is forming part of a biofilm, due to its high specific consumption rate of TMA.

p-Coumaric acid reduces high glucose-mediated impairment of endothelium-dependent relaxation in rat aorta / Ácido p-cumárico reduce el deterioro mediado por alta glucosa de la relajación dependiente de endotelio en aorta de rata

p-Coumaric acid (p-CA) is an ubiquitous plant metabolite with antioxidant, anti-inflammatory, and anticancer properties. The present study was designed to evaluate the preventive effects of p-CA on endothelium-dependent impairment produced by high glucose (HG) (D-Glucose 25 mM) in isolated rat thoracic aorta. Aortic rings obtained from male Sprague-Dawley rats were mounted in an organ bath and pretreated for 3 h with D-Glucose 5 mM, HG and HG plus p-CA (1, 10 and 100 uM). After this period of time endothelium-dependent relaxation was tested by cumulative addition of acetylcholine (ACh) in pre-contracted rings with phenylephrine (PE) (0.1 μM). p-CA elicited a moderate endothelium-dependent vasodilatory effect (Emax= 29.28 +/- 1.89 percent, N=6; pD2= 6.075 +/- 0.184, N=6). When aortic rings were pre-incubated for 3 h with HG, Emax for ACh decreased dramatically from 87.69 +/- 2.59 percent (N=6) to 40.54 +/- 1.78 percent (N=6). The negative effect of HG was partially reverted in rings co-incubated with p-CA in a concentration-dependent manner as shown for Emax values to each p-CA concentration: 1 uM (48.57 +/- 1.82 percent), 10 uM (60.81 +/- 1.80 percent) and 100 uM (64.51 +/- 1.80 percent). The action of p-CA was associated with a significant change in Emax. No statistical difference in pD2 was observed. Our results clearly show that p-CA protect ACh-induced endothelial-dependent relaxation affected by HG in isolated rat aortic rings.

El ácido p-cumárico (p-CA) es un metabolito ubicuo en plantas, con propiedades antioxidantes, anti-inflamatoria, y anticancerígenas. El presente estudio fue diseñado para evaluar los efectos preventivos de p-CA sobre la relajación dependiente de endotelio, deteriorada por niveles altos de glucosa (HG) (D-glucosa 25 mM) en aorta torácica aislada de rata. Los anillos aórticos obtenidos de ratas macho Sprague-Dawley se montaron en un baño de órganos y fueron pre-tratados durante 3 h con D-glucosa 5 mM, HG, y HG más de p-CA (1, 10 y 100 uM). Después de este período de tiempo se evaluó la relajación dependiente de endotelio mediante la adición acumulativa de acetilcolina (ACh) en anillos pre-contraídos con fenilefrina (PE) (0,1 uM). p-CA mostró un moderado efecto vasodilatador dependiente de endotelio (Emax = 29,28 +/- 1,89 por ciento, N = 6; pD2 = 6,075 +/- 0,184, N = 6). Cuando los anillos aórticos se pre-incubaron durante 3 h con HG, la Emax para ACh se redujo drásticamente desde 87,69 +/- 2,59 por ciento (N = 6) a 40,54 +/- 1,78 por ciento (N = 6). El efecto negativo de HG se revirtió parcialmente, de manera dependiente de concentración, en los anillos co-incubados con p-CA tal como lo muestra el valor de Emax para cada concentración de p-CA: 1 u M (48,57 +/- 1,82 por ciento), 10 uM (60,81 +/- 1,80 por ciento) y 100 uM (64,51 +/- 1,80 por ciento). La acción de p-CA se asoció con un cambio significativo en la Emax. No se observó diferencia estadísticamente significativa en el pD2. Nuestros resultados muestran claramente que p-CA protege la relajación dependiente de endotelio inducida por ACh, la cual es afectada por HG en anillos aislados de aorta de rata.

Application of bioleaching to copper mining in Chile

Background: Bioleaching of minerals is a process that allows the treatment of insoluble sulphides and insoluble oxides via hydrometallurgy, as opposed to the more traditional technology of pyrometallurgy. Bioleaching presents several technological, environmental and economic advantages as compared with pyrometallurgy, as well as some limitations. Results: In this work a general panorama of copper mining and biomining, the influence of the most relevant operating variables and their present and future situation in Chile are presented and discussed. Conclusions: Today, Chile plays an important role in the development and commercial application of bioleaching to copper ores. This background information allows predicting a brilliant future for this technology in Chile, as has been forecasted in the last years.

Bio-oxidation of H2S by Sulfolobus metallicus.

Sulfolobus metallicus is a hyperthermophilic and chemolithoautotrophic archaeon that uses elemental sulfur as an energy source. Its ability to oxidize H(2)S was measured either in the presence or absence of elemental sulphur, showing its ability for using both as an energy source. A biotrickling filter was set up and a biofilm of S. metallicus was established over the support. The maximum removal capacity of the biotrickling filter reached at 55°C was 40 g S/m(3)h for input loads higher than 70 g S/m(3)h. Thus, S. metallicus can be used in a biofiltration system for the treatment of waste gas emissions at high temperatures contaminated with H(2)S.