Efficient Total Nitrogen Removal in an Ammonia Gas Biofilter through High-Rate OLAND

Ammonia gas is conventionally treated in nitrifying biofilters; however, addition of organic carbon to perform post-denitrification is required to obtain total nitrogen removal. Oxygen-limited autotrophic nitrification/denitrification (OLAND), applied in full-scale for wastewater treatment, can offer a cost-effective alternative for gas treatment. In this study, the OLAND application thus was broadened toward ammonia loaded gaseous streams. A down flow, oxygen-saturated biofilter (height of 1.5 m; diameter of 0.11 m) was fed with an ammonia gas stream (248 +/- 10 ppmv) at a loading rate of 0.86 +/- 0.04 kg N m(-3) biofilter d(-1) and an empty bed residence time of 14 s. After 45 days of operation a stable nitrogen removal rate of 0.67 +/- 0.06 kg N m(-3) biofilter d(-1), an ammonia removal efficiency of 99%, a removal of 75-80% of the total nitrogen, and negligible NO/N2O productions were obtained at water flow rates of 1.3 +/- 0.4 m(3) m(-2) biofilter section d(-1). Profile measurements revealed that 91% of the total nitrogen activity was taking place in the top 36% of the filter. This study demonstrated for the first time highly effective and sustainable autotrophic ammonia removal in a gas biofilter and therefore shows the appealing potential of the OLAND process to treat streams

Optimized cryopreservation of mixed microbial communities for conserved functionality and diversity.

The use of mixed microbial communities (microbiomes) for biotechnological applications has steadily increased over the past decades. However, these microbiomes are not readily available from public culture collections, hampering their potential for widespread use. The main reason for this lack of availability is the lack of an effective cryopreservation protocol. Due to this critical need, we evaluated the functionality as well as the community structure of three different types of microbiomes before and after cryopreservation with two cryoprotective agents (CPA). Microbiomes were selected based upon relevance towards applications: (1) a methanotrophic co-culture (MOB), with potential for mitigation of greenhouse gas emissions, environmental pollutants removal and bioplastics production; (2) an oxygen limited autotrophic nitrification/denitrification (OLAND) biofilm, with enhanced economic and ecological benefits for wastewater treatment, and (3) fecal material from a human donor, with potential applications for fecal transplants and pre/probiotics research. After three months of cryopreservation at -80 °C, we found that metabolic activity, in terms of the specific activity recovery of MOB, aerobic ammonium oxidizing bacteria (AerAOB) and anaerobic AOB (AnAOB, anammox) in the OLAND mixed culture, resumes sooner when one of our selected CPA [dimethyl sulfoxide (DMSO) and DMSO plus trehalose and tryptic soy broth (DMSO+TT)] was added. However, the activity of the fecal community was not influenced by the CPA addition, although the preservation of the community structure (as determined by 16S rRNA gene sequencing) was enhanced by addition of CPA. In summary, we have evaluated a cryopreservation protocol that succeeded in preserving both community structure and functionality of value-added microbiomes. This will allow individual laboratories and culture collections to boost the use of microbiomes in biotechnological applications

Functionality of autoinducer systems in complex environments.

Cell-to-cell signalling via small diffusible molecules, usually termed quorum sensing (QS), represents a common behaviour in bacteria. This signalling regulates life style switches in many, if not most symbiotic microbial species either beneficial or pathogenic for their eukaryotic hosts, but is also involved in controlling environmental processes such as biofouling, degradation processes in sewage plants or environmental pollutions and N cycling [1–4]. Biochemically, the core of a generic system comprises a cytoplasmatic signal synthase (or several involved enzymes), a small, diffusible signal which is released into the environment, and a signal receptor located in the cell membrane or in the cytoplasma. The signal-receptor complex directly or indirectly controls the expression of target genes (Fig. 5.1). The signal was termed autoinducer (AI), because the same cells produce and react on the signal molecules. For an overview of the various chemical realizations of AI systems see, e.g. Atkinson and Williams [5]. Originally, three main types of AI molecules have been described: (a) Mainly gram-negative proteobacteria, but also some cyanobacteria and archaebacteria employ molecules of the acylhomoserine lactone (AHL) group as AIs, (b) oligopeptide AIs occur in gram-positive bacteria, and (c) AI2 has been described as a universal signal for interspecies communication. Recently, a still increasing number of AIs belonging to various chemical classes have been discovered