Nutritional value, total dry matter losses, effluent production and pollutant potential in Brachiaria brizantha cv. Paiaguás grass / [Valor nutricional, perdas totais de matéria seca, produção e potencial poluidor de efluentes em silagem de Brachiaria brizantha cv. Paiaguás]

The objective of the present study was to evaluate losses, production and polluting potential of the effluent, nutritional value and aerobic stability of silages of Brachiaria brizantha cv. Paiaguás grass, in different particle sizes and compaction density in silage. Three theoretical particle sizes (TTP 5; 8 and 12mm) and three compaction densities (DC 550; 600 and 650kg/m3) were evaluated, distributed in a factorial design (3 x 3), with four repetitions. The highest volume of effluent was found in silages with higher compaction densities (600 and 650kg/m3) and lower TTP (5 and 8mm). The highest chemical oxygen demand and biochemical oxygen demand were registered in the treatment with TTP of 5mm and higher DC (600 and 650kg/m3). Greater in vitro digestibility of DM was verified in the silage chopped at 5 and 8mm. There was no break in aerobic stability for 216 hours. Silage with a low compaction density 550kg/m3 and processing with a theoretical particle size of 12mm reduces effluent losses. In general, the nutritional value of Paiaguás grass was not influenced by the treatments. Different particle sizes and compaction density did not change the aerobic stability of silages.(AU)

Objetivou-se avaliar perdas, produção e potencial poluidor do efluente, valor nutricional e estabilidade aeróbia de silagens do capim Brachiaria brizantha cv. Paiaguás, em diferentes tamanhos de partícula e densidade de compactação na ensilagem. Foram avaliados três tamanhos teóricos de partícula (TTP 5; 8 e 12mm) e três densidades de compactação (DC 550; 600 e 650kg/m3), distribuídos em arranjo fatorial (3 x 3), com quatro repetições. O maior volume de efluente foi verificado nas silagens com maiores densidades de compactação (600 e 650kg/m3) e menores TTP (5 e 8mm). As maiores demanda química de oxigênio e demanda bioquímica de oxigênio foram registradas no tratamento com TTP de 5mm e nas maiores DC (600 e 650kg/m3). Maior digestibilidade in vitro da MS (média de 57,2%) foi verificada na silagem picada a 5 e 8mm. Não houve quebra da estabilidade aeróbia durante 216 horas. A ensilagem com baixa densidade de compactação (550kg/m3) e o processamento com tamanho teórico de partículas 12mm reduzem as perdas por efluente. O valor nutricional da silagem de capim-paiaguás, em geral, não foi influenciado pelos tratamentos. Diferentes tamanhos de partícula e densidade de compactação não alteraram a estabilidade aeróbia das silagens.(AU)

A Terrestrial Single Chamber Microbial Fuel Cell-based Biosensor for Biochemical Oxygen Demand of Synthetic Rice Washed Wastewater.

Microbial fuel cells represent an innovative technology which allow simultaneous waste treatment, electricity production, and environmental monitoring. This study provides a preliminary investigation of the use of terrestrial Single chamber Microbial Fuel Cells (SMFCs) as biosensors. Three cells were created using Andean soil, each one for monitoring a BOD concentration of synthetic washed rice wastewater (SRWW) of 10, 100, and 200 mg/L for SMFC1, SMFC2 and SMFC3, respectively. The results showed transient, exponential, and steady stages in the SMFCs. The maximum open circuit voltage (OCV) peaks were reached during the elapsed time of the transient stages, according to the tested BOD concentrations. A good linearity between OCV and time was observed in the increasing stage. The average OCV in this stage increased independently of the tested concentrations. SMFC1 required less time than SMFC2 to reach the steady stage, suggesting the BOD concentration is an influencing factor in SMFCs, and SMFC3 did not reach it. The OCV ratios were between 40.6-58.8 mV and 18.2-32.9 mV for SMFC1 and SMFC2. The reproducibility of the SMFCs was observed in four and three cycles for SMFC1 and SMFC2, respectively. The presented SMFCs had a good response and reproducibility as biosensor devices, and could be an alternative for environmental monitoring.

Residuos agroindustriales con potencial para la producción de metano mediante la digestión anaerobia / Agroindustrial wastes methanization and bacterial composition in anaerobic digestion

Las toneladas de residuos orgánicos que se generan anualmente en la agroindustria pueden aprovecharse como materia prima para la producción de metano. Para que los residuos orgánicos se puedan convertir a metano a gran escala, es importante que previamente se realicen sobre ellos pruebas de biodegradabilidad; un parámetro importante que conviene establecer es su potencial bioquímico de metano. En el presente trabajo se estudió la biodegradabilidad, la producción de metano y el comportamiento de poblaciones de eubacterias y arqueobacterias durante la digestión anaerobia de residuos de plátano, mango y papaya provenientes de la agroindustria, adicionando un inóculo microbiano. Los residuos de mango y plátano tenían mayor contenido de materia orgánica (94 y 75 %, respectivamente) que el residuo de papaya con base en su relación sólidos volátiles/sólidos totales. Después de 63 días de tratamiento, la mayor producción de metano se observó en la digestión anaerobia del residuo de plátano: 63,89 ml de metano por g de demanda química de oxígeno del residuo. Los resultados del potencial bioquímico de metano demostraron que el residuo de plátano tiene el mejor potencial para ser usado como materia prima en la producción de metano. A través de un análisis por PCR-DGGE con oligonucleótidos específicos se logró evaluar el tamaño y la composición de las poblaciones de eubacterias y arqueobacterias presentes en la digestión anaerobia de residuos agroindustriales a lo largo del proceso.

The tons of organic waste that are annually generated by agro-industry, can be used as raw material for methane production. For this reason, it is important to previously perform biodegradability tests to organic wastes for their full scale methanization. This paper addresses biodegradability, methane production and the behavior of populations of eubacteria and archaeabacteria during anaerobic digestion of banana, mango and papaya agroindustrial wastes. Mango and banana wastes had higher organic matter content than papaya in terms of their volatile solids and total solid rate (94 and 75 % respectively). After 63 days of treatment, the highest methane production was observed in banana waste anaerobic digestion: 63.89 ml CH4/per gram of chemical oxygen demand of the waste. In the PCR-DGGE molecular analysis, different genomic footprints with oligonucleotides for eubacteria and archeobacteria were found. Biochemical methane potential results proved that banana wastes have the best potential to be used as raw material for methane production. The result of a PCR- DGGE analysis using specific oligonucleotides enabled to identify the behavior of populations of eubacteria and archaeabacteria present during the anaerobic digestion of agroindustrial wastes throughout the process.

Analytical applications of microbial fuel cells. Part I: Biochemical oxygen demand.

Microbial fuel cells (MFCs) are bio-electrochemical devices, where usually the anode (but sometimes the cathode, or both) contains microorganisms able to generate and sustain an electrochemical gradient which is used typically to generate electrical power. In the more studied set-up, the anode contains heterotrophic bacteria in anaerobic conditions, capable to oxidize organic molecules releasing protons and electrons, as well as other by-products. Released protons could reach the cathode (through a membrane or not) whereas electrons travel across an external circuit originating an easily measurable direct current flow. MFCs have been proposed fundamentally as electric power producing devices or more recently as hydrogen producing devices. Here we will review the still incipient development of analytical uses of MFCs or related devices or set-ups, in the light of a non-restrictive MFC definition, as promising tools to asset water quality or other measurable parameters. An introduction to biological based analytical methods, including bioassays and biosensors, as well as MFCs design and operating principles, will also be included. Besides, the use of MFCs as biochemical oxygen demand sensors (perhaps the main analytical application of MFCs) is discussed. In a companion review (Part 2), other new analytical applications are reviewed used for toxicity sensors, metabolic sensors, life detectors, and other proposed applications.

Metabolism of Klebsiella pneumoniae freeze-dried cultures for the design of BOD bioassays.

AIMS: The survival rate of freeze-dried cultures is not enough information for technological applications of micro-organisms. There could be serious metabolic/structural damage in the survivors, leading to a delay time that can jeopardize the design of a rapid biochemical oxygen demand (BOD) metabolic-based bioassay. Therefore, we will study the metabolic activity (as ferricyanide reduction activity) and the survival rate (as colony-forming units, CFU) of different Klebsiella pneumoniae freeze-dried cultures looking for stable metabolic conditions after 35days of storage. METHOD AND RESULTS: Here, we tried several simple freeze-drying processes of Kl. pneumoniae. Electrochemical measurements of ferrocyanide and survival rates obtained with the different freeze-dried cultures were used to choose the best freeze-drying process that leads to a rapid metabolic-based bioassay. CONCLUSIONS: The use of milk plus monosodium glutamate was the best choice to obtain a Kl. pneumoniae freeze-dried culture with metabolic stable conditions after storage at -20°C without the need of vacuum storage and ready to use after 20min of rehydration. We also demonstrate that the viability and the metabolic activity are not always directly correlated. SIGNIFICANCE AND IMPACT OF THE STUDY: This study shows that the use of this Kl. pneumoniae freeze-dried culture is appropriate for the design of a rapid BOD bioassay.

Chromium (VI) biosorption and removal of chemical oxygen demand by Spirulina platensis from wastewater-supplemented culture medium.

The inappropriate discharge of wastewater containing high concentrations of toxic metals is a serious threat to the environment. Given that the microalga Spirulina platensis has demonstrated a capacity for chromium VI (Cr (VI) biosorption, we assessed the ideal concentration of chromium-containing wastewater required for maximum removal of Cr (VI) and chemical oxygen demand (COD) from the environment by using this microalga. The Paracas and Leb-52 strains of S. platensis, with initial wastewater concentrations of 0%, 12.5%, 25%, and 50%, were cultured in Zarrouk medium diluted to 50% under controlled air, temperature, and lighting conditions. The cultures were maintained for 28 days, and pH, biomass growth, COD, and Cr (VI) were assessed. The wastewater concentration influenced microalgal growth, especially at high concentrations. Removal of 82.19% COD and 60.92% Cr (VI) was obtained, but the COD removal was greater than the Cr (VI) removal in both strains of S. platensis.