The influence of the bonding form distribution of Fe, Ni, Co and Mn and their potential bioavailability during the anaerobic degradation of maize straw was investigated. Two reactors were operated over 117 days at 37°C and different dosage strategies of mineral were studied in reactor (R2). Control reactor (R1) was metal‐limited over time. mineral supplementation (1 g L−1) once a week reported the highest methane yield (257 mL g−1 VS) with 30% of increment. Ni and Co predominated in their oxidizable bonding forms and Fe mainly existed as residual and oxidizable fractions. The potential bioavailability (Mn ˃˃ Co ≈ Ni ˃ Fe) of R2 was higher comparing to R1. Metal deprivation in R1 led to depletion of both sequential extraction fractions and total metal concentrations until the end of the process. This study confirmed that the dosage strategy of mineral has a stimulatory effect on methane production from crop maize waste.

The effect of natural mineral on the mono-digestion of maize straw was evaluated in continuously stirred tank reactors (CSTRs) at 38 °C. Different strategies of mineral addition were studied. The organic loading rate (OLR) was varied from 0.5 to 2.5 g volatile solid (VS) L(-1) d(-1). A daily addition of 1 g mineral L(-1) in reactor 2 (R2) diminished the methane production by about 11 % with respect to the initial phase. However, after a gradual addition of mineral, an average methane yield of 257 NmL CH4 g VS(-1) was reached and the methane production was enhanced by 30 % with regard to R1. An increase in the frequency of mineral addition did not enhance the methane production. The archaeal community was more sensitive to the mineral than the bacterial population whose similarity stayed high between R1 and R2. Significant difference in methane yield was found for both reactors throughout the operation.

The bioavailability of Fe, Ni and Co and its impact on the mono-digestion of rice straw with addition of a natural nutrient source were assessed. The chemical forms and the degree of bioavailability of Fe, Ni and Co were investigated in two reactors during 311 days of experimentation at 37°C. The reactor (R2) was supplemented with 1 g/L of mineral once a week. The control reactor R1 was limited in mineral during the study. The greatest methane yield of 238 mL/g VS was obtained with mineral supply with an increment of 45% respect to reactor without metals (164 mL/g VS). The sequential extraction confirmed that 70, 88 and 75% of Fe, Ni and Co were mainly in bioavailable forms (interchangeable and carbonate), respectively, with mineral supply in R2. Fe and Co were mainly associated to the carbonate and oxidizable fractions (43% and 41% respectively), while the Ni concentrations were not detected during the experimentation. As a result, the methane yield in R2 increased by 45%, with a potential bioavailability (Ni ˃ Co ˃ Fe) higher compared to control reactor (Co ˃ Fe). Trace elements deficit in R1 result in the reduction of metal-binding forms until the end of experiment, with a negative impact on methanogenic community.

El comportamiento de muestras de sangre seca sobre papel de filtro S & S 903 (PF S & S 903) comparado con muestras de suero humano en el ensayo UMELISA HIV 1+2 RECOMBINANT, se estudiaron 318 muestras procedentes de donantes del banco de sangre supuestamente sanos. Se obtuvo como resultado 315 muestras negativas, dos muestras borderline y una muestra positiva. Una vez realizado el DAVIH-BLOT, se confirmó como positiva la muestra positiva obtenida por UMELISA y como negativa e indeterminada las muestras borderline. Con esto se obtuvo un 99.68% de especificidad. Con este mismo fin se estudiaron 233 muestras positivas en SH y PF S & S 903 a 45 y 55% de hematocrito, las cuales mantuvieron los mismos niveles de positividad por ambos métodos. Se obtuvo 100% de sensibilidad para ambos valores de hematocrito.

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