Influence of metal ions and organic carbons on denitrification activity of the halotolerant bacterium, Paracoccus pantotrophus P16 a strain from shrimp pond

The effect of metal ions, ferric ion (Fe3+) and molybdenum ion (Mo6+) on the denitrification process of Paracoccus pantotrophus P16 grown under saline conditions was investigated. Results revealed that the dosages of added Fe3+ and Mo6+ significantly accelerated nitrate utilization and nitrite accumulation. Enzymatic studies revealed that the membrane-bound nitrate reductase and the periplasmic nitrite reductase had activities of 998 \ub1 28 and 373 \ub1 18 nmol (mg protein)-1 min-1, respectively after growing Paracoccus pantotrophus P16 in medium supplemented with 1.5 \u3bcM Fe3+. If provided with 1.5 \u3bcM Fe3+ and 2.4 \u3bcM Mo6+, the membrane-bound nitrate reductase activity increased to 6,223 \ub1 502 nmol (mg protein)-1 min-1 and the periplasmic nitrite reductase was 344 \ub1 20 nmol (mg protein)-1 min-1. The results indicated that an addition of Fe3+ and Mo6+ led to an overstimulation of nitrate reductase activity as compared with nitrite reductase activity. When glucose was supplied, the minimal ratio of carbon per nitrate (C/N) was 2.31 mg C/mg NO3 --N with denitrification yield of 0.45 g NO3 --N/g C. Addition of ethanol instead of glucose, the minimal ratio of C/N was 1.15 mg C/mg NO3 --N with denitrification yield of 1.08 g NO3 --N/g C

Cultivating conditions optimization of the anaerobic digestion of corn ethanol distillery residuals using response surface methodology

AbstractThis study investigated the individual and interactive effects of three factors — temperature, inoculum/substrate ratio (ISR) and inoculum typology — on the anaerobic digestion of corn ethanol distillery wastewater. Biochemical methane potential assays planned with factorial design with two independent quantitative variables on three levels (ISR: 1:1, 2:1 and 3:1; temperature: 30°C, 33.5°C, 37°C) and one independent qualitative variable (inoculum type: suspended, granular, mixed) have been performed. Response Surface Methodology has been used to study the effect of the factors with the aim of maximizing the specific methane yields (YCH4) obtainable with this substrate. The results show that all three investigated factors influence in a significant matter the YCH4, the ISR having the strongest effect on it. The temperature has significant influence on the YCH4 only in combination with high ISR values. The optimal conditions for the maximum YCH4 (551 mL CH4 g−1 VSadded) have been found at 37°C operating temperature, ISR=3:1 and using granular inoculum. These conditions gave rise to a 4-fold increase of YCH4 with respect to the worst combination of factors (YCH4=129 mL g−1 VSadded for the suspended inoculum type, at 30°C and ISR=1:1). The results improve the knowledge on the digestion of this substrate, providing information for successful process up-scaling