Search

Plant cell wall structures represent a barrier in the biodegradation process to produce biogas for combustion and energy production. Consequently, approaches concerning a more efficient de-polymerisation of cellulose and hemicellulose to monomeric sugars are required. Here, we show that natural activated zeolites (i.e. trace metal activated zeolites) represent eminently suitable mineral microhabitats and potential carriers for immobilisation of microorganisms responsible for anaerobic hydrolysis of biopolymers stabilising related bacterial and methanogenic communities. A strategy for comprehensive analysis of immobilised anaerobic populations was developed that includes the visualisation of biofilm formation via scanning electron microscopy and confocal laser scanning microscopy, community and fingerprint analysis as well as enzyme activity and identification analyses. Using SDS polyacrylamide gel electrophoresis, hydrolytical active protein bands were traced by congo red staining. Liquid chromatography/mass spectroscopy revealed cellulolytical endo- and exoglucanase (exocellobiohydrolase) as well as hemicellulolytical xylanase/mannase after proteolytic digestion. Relations to hydrolytic/fermentative zeolite colonisers were obtained by using single-strand conformation polymorphism analysis (SSCP) based on amplification of bacterial and archaeal 16S rRNA fragments. Thereby, dominant colonisers were affiliated to the genera Clostridium, Pseudomonas and Methanoculleus. The specific immobilisation on natural zeolites with functional microbes already colonising naturally during the fermentation offers a strategy to systematically supply the biogas formation process responsive to population dynamics and process requirements. [ABSTRACT FROM AUTHOR]

An industrial wastewater containing a total Kjeldahl nitrogen (TKN) of 12.80 g l–1 was treated in a continuously fed activated sludge reactor. The main contaminant was urea (21.52 g l–1), together with minor amounts of the nitrification inhibitor dicyandiamide (0.46 g l–1) and free ammonia (0.56 g l–1). The wastewater was diluted 1:1 with water and treated under alkaline conditions (pH 9.4), enabling the simultaneous hydrolysis of urea and stripping of free ammonia in one aerobic reactor. Experiments were conducted to eliminate the remaining ammonia in a separate treatment unit by nitrification/denitrification. An adapted nitrifying bacterial population was isolated which was able to nitrify at a rate of 0.1 g nitrogen l–1 day–1 at a dicyandiamide concentration of 0.22 g l–1. However, this was found to be too slow for an industrial-scale operation. Therefore, separate stripping with air or steam after pH adjustment to ≥10.5 is proposed. The diluted wastewater was treated with a hydraulic retention time of 6 days, corresponding to a volumetric nitrogen loading rate of 1.1 g nitrogen l–1 day–1 with an overall TKN reduction of 78.0%. [ABSTRACT FROM AUTHOR]