Dosing with pyrite significantly increases anammox performance: Its role in the electron transfer enhancement and the functions of the Fe-N-S cycle.

Anaerobic ammonium oxidation (anammox) represents an energy-efficient process for biological nitrogen removal from ammonium-rich wastewater. However, there are mechanistic issues unsolved regarding the low microbial electron transfer and undesired accumulation of nitrate in treated water, limiting its widespread engineering applications. We found that the addition of pyrite (1 g L-1 reactor), an earth-abundant iron-bearing sulfide mineral, to the anammox system significantly improved the nitrogen removal rate by 52% in long-term operation at a high substrate shock loading (3.86 kg N m-3 d-1). Two lines of evidence were presented to unravel the underlying mechanisms of the pyrite-induced enhancement. Physiochemical evidence indicated that an increase of cytochromes c and Fe-S protein was responsible for the accelerated electron transfer among metabolic enzymes. Multi-omics evidence showed that the depletion of nitrate was attributed to the Fe-N-S cycle driven by nitrate-dependent Fe(II) oxidation and S-based denitrification. This study deepens our understanding of the roles of electron transfer and the Fe-N-S cycle in anammox systems, providing a fundamental basis for the development of mediators in the anammox process for practical implications.

Simultaneous reduction of perchlorate and nitrate in a combined heterotrophic-sulfur-autotrophic system: Secondary pollution control, pH balance and microbial community analysis.

A combined heterotrophic-sulfur-autotrophic system (CHSAS) was established to simultaneously reduce perchlorate and nitrate in water. In this system, the OH- produced by the acetate heterotrophic part (H-part) could be neutralized with the H+ produced by the sulfur autotrophic part (S-part); thus, the pH of the final effluent could keep neutral. In addition, the S-part could further reduce the pollutants and residual carbon from the H-part to achieve a high performance. For 19.62 ±â€¯0.30 mg/L ClO4- and 21.56 ±â€¯0.83 mg/L NO3--N in the influent, the operating parameters were optimal at a hydraulic retention time (HRT) of 1.0 h and an acetate concentration of 70 mg/L. The removal efficiency of ClO4- and NO3- reached 95.43% and 99.23%, without secondary pollution caused by residual organic carbon. It was also revealed that sulfur (S0) disproportionation can be inhibited by shortening the HRT and reducing the acetate dosage. The dominant heterotrophic and autotrophic bacteria were Thauera and Ferritrophicum, respectively, while Chlorobaculum was related to S0 disproportionation.

Micropropagación de plantas de lechosa en recipientes de inmersión temporal a partir de brotes axilares / Micropropagation of papaya plants in temporary immersion recipients from axilary shoots

Se estandarizaron las condiciones de iniciación, multiplicación, enraizamiento y aclimatización de plantas hermafroditas de lechosa cv Maradol provenientes de brotes axilares, producidos en recipientes de inmersión temporal RITA®. En cada envase, contentivo de 200 ml de medio de cultivo líquido de Fitch, se colocaron cuatro brotes de 2 a 3 cm de longitud. Los biorreactores se conectaron a tres líneas de inmersión de 5, 2 y 1 min cada 4h y se colocaron 6 envases en promedio por línea, en condiciones de fotoperíodo de 16 h. Transcurridos 30 a 45 días, se cuantificaron los brotes y se clasificaron de acuerdo al tamaño: < 2 cm (pequeños), entre 2 a 3 cm (medianos), > 3 cm con y sin raíz (grandes). Los dos primeros tipos de brotes se continuaron multiplicando en los mismos medios; y los más elongados se aclimatizaron utilizando el Sistema Autotrófico Hidropónico (SAH). Se determinó la sanidad y la fidelidad de las plantas producidas mediante pruebas de ELISA y RAPD, respectivamente. Durante un periodo de 6 meses se reciclaron un total de 47 recipientes, los cuales produjeron 1.091 brotes: 377 pequeños; 482 medianos; 175 grandes sin raíz y 57 con raíz. Usando el SAH se obtuvo 89,5% de plantas aclimatizadas cuando se usaron brotes enraizados, y 41,6% a partir de brotes sin raíces. Con la combinación de las técnicas RITA y SAH se logró un sistema continuo y eficiente de producción de plantas sanas y fieles al tipo, en comparación con los métodos convencionales de micropropagación y aclimatización.

We standardized initiation, multiplication, rooting and acclimatization conditions of papaya cv Maradol hermaphrodite plants from axillary buds produced in temporary immersion reactor RITA®. Recipients contained 200 ml of Fitch liquid culture medium, and four shoots of 2 to 3 cm. in length were placed in each. The bioreactors were connected to three different immersion lines of 5, 2, and 1 min each 4h, with 6 containers per line on average, in 16 h photoperiod. After 30 to 45 days, the shoots produced were quantified and classified according to size: <2 cm (small), from 2 to 3 cm (medium), >3 cm with or without roots (large). The first two types of shoots were multiplied in the same culture media, and more elongated shoots were acclimatized using Autotrophic Hydroponic System (AHS). The sanity and fidelity of the produced plants were determined using ELISA and RAPD, respectively. For a period of six months 47 vessels were recycled and 1,091 shoots were produced: 377 small; 482 medium; 175 large without roots and 57 rooted shoots. Using AHS, 89.5% acclimatized plants were obtained when rooted shoots were used, and 41.6% from rootless shoots. With the combination of RITA and AHS techniques we achieved a continuous and efficient production of healthy and true to type papaya plants, in comparison to conventional micropropagation and acclimatization procedures.

Trophic functioning and nutrient flux in a highly productive tropical lagoon.

Chiku Lagoon is a highly productive tropical lagoon with high fishery yields. Trophic networks and stoichiometrically linked water-salt-nutrient budgets were constructed to relate the functioning of the food web to nonconservative behavior of nutrients in the lagoon. Network analysis showed that the lagoon is more dependent on phytoplankton than detritus and periphyton to generate food sources for consumers. Nevertheless, detritivory is more important than herbivory in the food web. Transfer efficiency is high at low trophic levels, but declines at higher levels due to the high fishery pressure. Thus, only a small fraction of organic matter (15%) is recycled, and this all through detrital pathways, most of which involve only two compartments. Summation of individual rate measurements for primary production and respiration yielded an estimate of +249 g C m-2 year-1, suggesting an autotrophic ecosystem. An alternative biogeochemical approach demonstrated that the lagoon is a large sink for total dissolved nitrogen and phosphorus, and the net system metabolism was calculated to be +144 g C m-2 year-1, thus providing a biogeochemical explanation for the high productivity of Chiku Lagoon. Our results suggest that the high fishery yield in Chiku Lagoon can be attributed to high planktonic productivity induced by the high rate of nutrient loading, and the straight-through pathways of the food web.