ABSTRACT
This work characterized the bovine ruminal content excluding stomach tissue obtained from a slaughterhouse plant located in Cordoba, Colombia. The goal is to establish possible energetic uses and valorization potential instead of risky local current contaminant practices. Samples of ruminal content (RC) were collected under two conditions as-fresh and dry. Microbiological and bromatological quality, density, proximate and elemental analysis, and calorific power values were measured. There were complemented with optical microscopy, SEM, XEDS, FTIR, TGA, and TGA-MS analysis for both conditions. Ashes of combustion products from mixtures of natural gas and RC were studied, using XRD and XRF techniques. Results showed that fresh-state RC has an important microbiological quality without some human risk pathogens, such as Salmonella sp, E. coli, and vegetable risk pathogens, such as nematodes. Dry and sieved state RC is lignin-cellulosic heterogeneous biomass, with a real density of 164 kg/m3, a calorific power between 12 and 15 kJ/kg, and ashes rich in alkaline-earth elements. These results indicate that RC might have a good potential in co-combustion, gasification, and other energy processes. However, important considerations should be done about management of RC, because its direct application as fertilizer could carry out a negative effect, which was demonstratred in the growth of a model plant.
ABSTRACT
Acidithiobacillus ferrooxidans is commonly used in bioleaching operations to recover copper from sulfide ores. It is commonly accepted that A. ferrooxidans attaches to mineral surfaces by means of extracellular polymeric substances (EPS), however the role of type IV pili and tight adherence genes in this process is poorly understood. Genes related to the formation of type IV pili and tight adherence were identified in the genome of the bacterium, and in this work, we show that A. ferrooxidans actively expresses these genes, as demonstrated by quantitative real-time PCR analysis using cells incubated with chalcopyrite for 2 h. Significant differences in gene expression were observed between planktonic and adhered cells, with the level of expression being much greater in planktonic cells. These results might indicate that planktonic cells can actively adhere to the substrate. A bioinformatics analysis of interaction networks of the tight adherence and type IV pilus assembly genes revealed a strong relationship between conjugation systems (tra operon) and regulatory systems (PilR, PilS).
