Biomineralization processes of calcite induced by bacteria isolated from marine sediments

Biomineralization is a known natural phenomenon associated with a wide range of bacterial species. Bacterial-induced calcium carbonate precipitation by marine isolates was investigated in this study. Three genera of ureolytic bacteria, Sporosarcina sp., Bacillus sp. and Brevundimonas sp. were observed to precipitate calcium carbonate minerals. Of these species, Sporosarcina sp. dominated the cultured isolates. B. lentus CP28 generated higher urease activity and facilitated more efficient precipitation of calcium carbonate at 3.24 ± 0.25 × 10−4 mg/cell. X-ray diffraction indicated that the dominant calcium carbonate phase was calcite. Scanning electron microscopy showed that morphologies of the minerals were dominated by cubic, rhombic and polygonal plate-like crystals. The dynamic process of microbial calcium carbonate precipitation revealed that B. lentus CP28 precipitated calcite crystals through the enzymatic hydrolysis of urea, and that when ammonium ion concentrations reached 746 mM and the pH reached 9.6, that favored calcite precipitation at a higher level of 96 mg/L. The results of this research provide evidence that a variety of marine bacteria can induce calcium carbonate precipitation, and may influence the marine carbonate cycle in natural environments.

Bio-filtration capacity, oxygen consumption and ammonium excretion of Dosinia ponderosa and Chione gnidia (Veneroida: Veneridae) from areas impacted and non-impacted by shrimp aquaculture effluents / Bio-filtración, consumo de oxígeno y excreción amoniacal de Dosinia ponderosa y Chione gnidia (veneroida: veneridae), en áreas impactadas y no impactadas por efluentes de granjas camaroneras

Mollusks are some of the most important, abundant and diverse organisms inhabiting not only aquatic ecosystems, but also terrestrial environments. Recently, they have been used for bioremediation of aquaculture effluents; nevertheless, for that purpose it is necessary to analyze the capacity of a particular species. In this context, an experimental investigation was developed to evaluate the performance of two bivalves C. gnidia and D. ponderosa, collected from areas with or without shrimp aquaculture effluents. For this, the filtration capacity (as clearance rate) as well as the oxygen consumption and ammonia excretion rates were measured following standard methods. The clearance rate was significantly higher for D. ponderosa from impacted areas, when com- pared to C. gnidia, from both areas. Contrarily, the oxygen consumption was greater for C. gnidia from impacted areas compared to D. ponderosa from both areas. The same tendency was observed for the ammonia excretion with the highest rates observed for C. gnidia from impacted areas, whereas no differences were observed among D. ponderosa from both areas. The results suggest that both species developed different strategies to thrive and survive under the impacted conditions; D. ponderosa improved its filtration efficiency, while C. gnidia modified its oxygen consumption and ammonia excretion. We concluded that both species, and particularly D. ponderosa, can be used for bioremediation purposes.

Los moluscos son algunos de los organismos más importantes, abundantes y diversos que habitan no solo ecosistemas acuáticos sino también terrestres. Recientemente ellos han sido utilizados para la biorremediación de efluentes acuícolas; para este propósito, es necesario conocer la capacidad de especies particulares que funcionan como biorremediadores. En este contexto, se evaluó la eficiencia de filtración (medida como tasa de clarificación), así como las tasas de consumo de oxígeno y excreción amoniacal en los bivalvos D. pon- derosa y C. gnidia recolectados en áreas impactadas y no impactadas por efluentes de granjas camaroneras. La tasa de clarificación fue mayor para D. ponderosa procedente de áreas impactadas, comparada con la de C. fluctifraga en las dos áreas de recolecta. Contrariamente, la tasa de consumo de oxígeno fue superior en C. gnidia en las áreas impactadas al compararla con organismos de áreas no impactadas y con D. ponderosa de las dos áreas de recolecta. La tasa de excreción amoniacal siguió una tendencia similar con valores más altos para C. gnidia en áreas impactadas, mientras que no se observaron diferencias para D. ponderosa entre las áreas de recolecta. Los resultados sugieren que ambas especies desarrollan diferentes estrategias para adaptarse y sobrevivir bajo condiciones de impacto; D. ponderosa mejora su eficiencia de filtración y C. gnidia modifica su consumo de oxígeno y excreción amoniacal. Se concluye que ambas especies, pero sobre todo D. ponderosa pueden ser utilizadas con propósitos de biorremediación.

Growth kinetics, effect of carbon substrate in biosynthesis of mcl-PHA by Pseudomonas putida Bet001

Growth associated biosynthesis of medium chain length poly-3-hydroxyalkanoates (mcl-PHA) in Pseudomonas putida Bet001 isolated from palm oil mill effluent was studied. Models with substrate inhibition terms described well the kinetics of its growth. Selected fatty acids (C8:0 to C18:1) and ammonium were used as carbon and nitrogen sources during growth and PHA biosynthesis, resulting in PHA accumulation of about 50 to 69% (w/w) and PHA yields ranging from 10.12 g L-1 to 15.45 g L-1, respectively. The monomer composition of the PHA ranges from C4 to C14, and was strongly influenced by the type of carbon substrate fed. Interestingly, an odd carbon chain length (C7) monomer was also detected when C18:1 was fed. Polymer showed melting temperature (Tm) of 42.0 (± 0.2) °C, glass transition temperature (Tg) of -1.0 (± 0.2) °C and endothermic melting enthalpy of fusion (ΔHf) of 110.3 (± 0.1) J g-1. The molecular weight (Mw) range of the polymer was relatively narrow between 55 to 77 kDa.