Recovery of purple non-sulfur bacteria-mediated single-cell protein from domestic wastewater in two-stage treatment using high rate digester and raceway pond.

Wastewater resources can be used to produce microbial protein for animal feed or organic fertiliser, conserving food chain resources. This investigation hasemployed thefermented sewage to photoheterotrophically grown purple non-sulfur bacteria (PNSB) in a 2.5 m pilot-scaleraceway-pond with infrared light to produce proteinaceous biomass.

High nitrite accumulation in hydrogenotrophic denitrification at low temperature: Transcriptional regulation and microbial community succession.

High Pressure Hydrogenotrophic Denitrification (HPHD) provided a promising alternative for efficient and clean nitrate removal. In particular, the denitrification rates at low temperature could be compensated by elevated H partial pressure. However, nitrite reduction was strongly inhibited while nitrate reduction was barely affected at low temperature.

Effects of Low Oxygen Dosages on an Anaerobic Membrane Bioreactor, Simulating the Oxygen Load in an Anaerobic Digester-Dissolved Air Flotation (AD-DAF) System.

This study reports the effects of microaeration on a laboratory-scale AnMBR (MA-AnMBR) fed with synthetic concentrated domestic sewage. The imposed oxygen load mimics the oxygen load coming from a dissolved air flotation (DAF) unit, establishing an anaerobic digester-DAF (AD-DAF) combination with sludge recycling. Results showed a reduced COD concentration in the MA-AnMBR permeate compared with the AnMBR permeate, from 90 to 74 mgCOD L, and a concomitant 27% decrease in biogas production.

The fate of sulfamethoxazole and trimethoprim in a micro-aerated anaerobic membrane bioreactor and the occurrence of antibiotic resistance in the permeate.

This study investigates the effects, conversions, and resistance induction, following the addition of 150 μg·L of two antibiotics, sulfamethoxazole (SMX) and trimethoprim (TMP), in a laboratory-scale micro-aerated anaerobic membrane bioreactor (MA-AnMBR). TMP and SMX were removed at 97 and 86%, indicating that micro-aeration did not hamper their removal. These antibiotics only affected the pH and biogas composition of the process, with a significant change in pH from 7.

A novel mechanistic modelling approach for microbial selection dynamics: Towards improved design and control of raceway reactors for purple bacteria.

Purple phototrophic bacteria (PPB) show an underexplored potential for resource recovery from wastewater. Raceway reactors offer a more affordable full-scale solution on wastewater and enable useful additional aerobic processes. Current mathematical models of PPB systems provide useful mechanistic insights, but do not represent the full metabolic versatility of PPB and thus require further advancement to simulate the process for technology development and control.

Steering the product spectrum in high-pressure anaerobic processes: CO partial pressure as a novel tool in biorefinery concepts.

Background: Elevated CO partial pressure (pCO) has been proposed as a potential steering parameter for selective carboxylate production in mixed culture fermentation. It is anticipated that intermediate product spectrum and production rates, as well as changes in the microbial community, are (in)directly influenced by elevated pCO. However, it remains unclear how pCO interacts with other operational conditions, namely substrate specificity, substrate-to-biomass (S/X) ratio and the presence of an additional electron donor, and what effect pCO has on the exact composition of fermentation products.

Modelling of autogenerative high-pressure anaerobic digestion in a batch reactor for the production of pressurised biogas.

Background: Pressurised anaerobic digestion allows the production of biogas with a high content of methane and, at the same time, avoid the energy costs for the biogas upgrading and injection into the distribution grid. The technology carries potential, but the research faces practical constraints by a.o.

Pre-incubation conditions determine the fermentation pattern and microbial community structure in fermenters at mild hydrostatic pressure.

Fermentation at elevated hydrostatic pressure is a novel strategy targeting product selectivity. However, the role of inoculum history and cross-resistance, that is, acquired tolerance from incubation under distinctive environmental stress, remains unclear in high-pressure operation. In our here presented work, we studied fermentation and microbial community responses of halotolerant marine sediment inoculum (MSI) and anaerobic digester inoculum (ADI), pre-incubated in serum bottles at different temperatures and subsequently exposed to mild hydrostatic pressure (MHP; < 10 MPa) in stainless steel reactors.

Directional Selection of Microbial Community Reduces Propionate Accumulation in Glycerol and Glucose Anaerobic Bioconversion Under Elevated pCO.

Volatile fatty acid accumulation is a sign of digester perturbation. Previous work showed the thermodynamic limitations of hydrogen and CO in syntrophic propionate oxidation under elevated partial pressure of CO (pCO). Here we study the effect of directional selection under increasing substrate load as a strategy to restructure the microbial community and induce cross-protection mechanisms to improve glucose and glycerol conversion performance under elevated pCO.

Direct and Indirect Effects of Increased CO Partial Pressure on the Bioenergetics of Syntrophic Propionate and Butyrate Conversion.

Simultaneous digestion and in situ biogas upgrading in high-pressure bioreactors will result in elevated CO partial pressure (pCO). With the concomitant increase in dissolved CO, microbial conversion processes may be affected beyond the impact of increased acidity. Elevated pCO was reported to affect the kinetics and thermodynamics of biochemical conversions because CO is an intermediate and end-product of the digestion process and modifies the carbonate equilibrium.

Reactivation of Microbial Strains and Synthetic Communities After a Spaceflight to the International Space Station: Corroborating the Feasibility of Essential Conversions in the MELiSSA Loop.

To sustain human deep space exploration or extra-terrestrial settlements where no resupply from the Earth or other planets is possible, technologies for food production, water, air, and waste recovery need to be developed. The Micro-Ecological Life Support System Alternative (MELiSSA) is such a Regenerative Life Support System (RLSS) and it builds on several bacterial bioprocesses. However, alterations in gravity, temperature, and radiation associated with the space environment can affect survival and functionality of the microorganisms.

Nitrogen cycle microorganisms can be reactivated after Space exposure.

Long-term human Space missions depend on regenerative life support systems (RLSS) to produce food, water and oxygen from waste and metabolic products. Microbial biotechnology is efficient for nitrogen conversion, with nitrate or nitrogen gas as desirable products. A prerequisite to bioreactor operation in Space is the feasibility to reactivate cells exposed to microgravity and radiation.

Refinery and concentration of nutrients from urine with electrodialysis enabled by upstream precipitation and nitrification.

Human urine is a valuable resource for nutrient recovery, given its high levels of nitrogen, phosphorus and potassium, but the compositional complexity of urine presents a challenge for an energy-efficient concentration and refinery of nutrients. In this study, a pilot installation combining precipitation, nitrification and electrodialysis (ED), designed for one person equivalent (1.2 L d), was continuously operated for ∼7 months.

Piezo-tolerant natural gas-producing microbes under accumulating CO.

Background: It is known that a part of natural gas is produced by biogenic degradation of organic matter, but the microbial pathways resulting in the formation of pressurized gas fields remain unknown. Autogeneration of biogas pressure of up to 20 bar has been shown to improve the quality of biogas to the level of biogenic natural gas as the fraction of CO decreased. Still, the CO is higher compared to atmospheric digestion and this may affect the process in several ways.

Nitrification and microalgae cultivation for two-stage biological nutrient valorization from source separated urine.

Urine contains the majority of nutrients in urban wastewaters and is an ideal nutrient recovery target. In this study, stabilization of real undiluted urine through nitrification and subsequent microalgae cultivation were explored as strategy for biological nutrient recovery. A nitrifying inoculum screening revealed a commercial aquaculture inoculum to have the highest halotolerance.

Effect of substrate and cation requirement on anaerobic volatile fatty acid conversion rates at elevated biogas pressure.

This work studied the anaerobic conversion of neutralized volatile fatty acids (VFA) into biogas under Autogenerative High Pressure Digestion (AHPD) conditions. The effects of the operating conditions on the biogas quality, and the substrate utilisation rates were evaluated using 3 AHPD reactors (0.6 L); feeding a concentration of acetate and VFA (1-10 g COD/L) corresponding to an expected pressure increase of 1-20 bar.

Silicate minerals for CO2 scavenging from biogas in Autogenerative High Pressure Digestion.

Autogenerative High Pressure Digestion (AHPD) is a novel concept that integrates gas upgrading with anaerobic digestion by selective dissolution of CO2 at elevated biogas pressure. However, accumulation of CO2 and fatty acids after anaerobic digestion of glucose resulted in pH 3-5, which is incompatible with the commonly applied high-rate methanogenic processes. Therefore, we studied the use of wollastonite, olivine and anorthosite, with measured composition of CaSi1.

High-calorific biogas production by selective CO₂ retention at autogenerated biogas pressures up to 20 bar.

Autogenerative high pressure digestion (AHPD) is a novel configuration of anaerobic digestion, in which micro-organisms produce autogenerated biogas pressures up to 90 bar with >90% CH(4)-content in a single step reactor. (1) The less than 10% CO(2)-content was postulated to be resulting from proportionally more CO(2) dissolution relative to CH(4) at increasing pressure. However, at 90 bar of total pressure Henry's law also predicts dissolution of 81% of produced CH(4).