Chromatographic determination of phosphine (PH3) and hydrogen sulfide (H2S) in the headspace of anaerobic bacterial enrichments using flame photometric detection

Effects of segmented aerobic and anaerobic fermentation assisted with chemical treatment on comprehensive properties and composition of wheat straw

Traditional aerobic composting used for straw treatment shows limited regulation effects and unstable properties, and it is necessary to introduce some co-processing methods to optimize its performance. Herein, segmented aerobic/anaerobic fermentation, combined with chemical treatment with wood vinegar/NaOH, was used to treat wheat straw. The results showed that anaerobic fermentation when used as the first stage could stabilize the wheat straw pH between 5.19 and 6.13 and improve nutrient contents. All treatments had greater effects on substrate aeration porosities (range of 14%) than on total porosity (range of 6%), and the water-holding porosities were improved to a greater extent by NaOH than by wood vinegar. The hemicellulose degradation rate of aerobic-anaerobic treatment was higher than that achieved with anaerobic-aerobic treatment, while the latter method was more effective at removing the neutral detergent-soluble as well as remaining organic matter, which was generated due to a higher KCl content in the ash.

The htx and ptx operons of Pseudomonas stutzeri WM88 are new members of the pho regulon

The htx and ptx operons of Pseudomonas stutzeri WM88 allow for the use of the inorganic reduced phosphorus (P) compounds hypophosphite (P valence, +1) and phosphite (P valence, +3) as sole P sources. To support the proposed in vivo role for the htx and ptx operons, namely the use of phosphite and hypophosphite as alternative P sources, we used reporter gene fusions to examine their expression levels with respect to various P conditions. Expression of the htx and ptx operons was induced up to 17- and 22-fold, respectively, in cultures grown under phosphate starvation conditions relative to expression in medium with excess phosphate (Pi). However, the presence of the reduced P substrate hypophosphite, phosphite, or methylphosphonate, in addition to excess Pi, did not result in an increase in the expression of either operon. To provide further support for a role of the htx and ptx operons in Pi acquisition, we identified P. stutzeri phoBR homologs and constructed deletion mutants. Induction of the htx and ptx reporter gene fusions in response to growth on limiting Pi was abolished in DeltaphoB, DeltaphoR, and DeltaphoBR mutants, demonstrating that htx and ptx expression is phoBR dependent. The putative LysR-type regulator encoded by ptxE has no apparent role in the expression of the htx and ptx operons, as no effect was observed on the level of induction of either operon in a DeltaptxE mutant.

Determination of phosphine in biogas and sludge at ppt-levels with gas chromatography-thermionic specific detection

A gas chromatographic (GC) system to measure free phosphine in biogas and matrix bound phosphine in manure and sludge is presented. The system consists of a sample preconcentration trap filled with glass beads, connected with a capillary GC equipped with a thermionic specific detector. With a trap temperature as low as -155 degrees C, a sampling flow of 20 ml/min and a typical total sample volume of 100 ml, free phosphine concentrations in the low ng/m3 range and matrix bound phosphine in the low ng/kg dry matter range, can be accurately and reproducibly determined.

Phosphine generation by mixed- and monoseptic-cultures of anaerobic bacteria

A microbial basis for bioreductive generation of phosphine is proposed, which could account at least in part for the presence of this toxic gas in natural anaerobic environments and in sewage and landfill gases. Phosphine generation under anaerobic growth conditions was dependent upon both the culture inoculum source (animal faeces) and enrichment culture conditions. Phosphine was detected in headspace gases from mixed cultures under conditions promoting fermentative growth of mixed acid and butyric acid bacteria, either in the presence or absence of methane generation. Monoseptic cultures of certain mixed acid fermentors (Escherichia coli, Salmonella gallinarum, and Salmonella arizonae) and solvent fermentors (Clostridium sporogenes, Clostridium acetobutyricum and Clostridium cochliarium) also generated phosphine. Such fermentative bacteria participate in the multi-stage process of methanogenesis in nature. Generation of phosphine by these bacteria, rather than by methanoarchaea themselves, could explain the apparent correlation between methanogenesis and the formation of phosphine in nature.