Influence of Hydrogen and Ethanol Addition in Methanogen-Free Mixed Culture Syngas Fermentations in Trickle Bed Reactors.

The use of mixed cultures in gas fermentations could reduce operating costs in the production of liquid chemicals such as alcohols or carboxylic acids. However, directing reducing equivalents towards the desired products presents the challenge of co-existing competing pathways. In this study, two trickle bed reactors were operated at acetogenic and chain elongating conditions to explore the fate of electron equivalents (ethanol, H, and CO) and test pH oscillations as a strategy to target chain-elongated products.

High performance removal of chlorophenols from an aqueous solution using an enzymatic membrane bioreactor.

Organochlorides and particularly chlorophenols are environmental pollutants that deserve special attention. Enzymatic membrane bioreactors may be alternatives for efficiently removing such hazardous organochlorides from aqueous solutions. We propose here a novel enzymatic membrane bioreactor comprising an ultrafiltration membrane GR81PP, electrospun fibers made of cellulose acetate, and laccase immobilized using an incubation and a fouling approach.

Microbial Enrichment Techniques on Syngas and CO Targeting Production of Higher Acids and Alcohols.

(1) Background: Microbial conversion of gaseous molecules, such as CO, CO and H to valuable compounds, has come to the forefront since the beginning of the 21st century due to increasing environmental concerns and the necessity to develop alternative technologies that contribute to a fast transition to a more sustainable era. Research efforts so far have focused on C1-C2 molecules, i.e.

Prediction of methane yield and pretreatment efficiency of lignocellulosic biomass based on composition.

Lignocellulosic biomass is considered a key resource for the future expansion of biogas production through anaerobic digestion (AD), and research on the development of pretreatment technologies for improving biomass conversion is an intensive and fast-growing field. Consequently, there is a need for creating tools able to predict the efficiency of a certain pretreatment on different biomass types, fast and accurately, and to assist in selecting a pretreatment technology for a specific biomass. In this study, seven different types of raw lignocellulosic biomass of industrial relevance were systematically analyzed regarding their composition (carbohydrates, lignin, lipids, ash, extractives, etc.

Variables and Mechanisms Affecting Electro-Membrane Extraction of Bio-Succinic Acid from Fermentation Broth.

The production of succinic acid from fermentation is a promising approach for obtaining building-block chemicals from renewable sources. However, the limited bio-succinic yield from fermentation and the complexity of purification has been making the bio-succinic acid production not competitive with petroleum-based succinic acid. Membrane electrolysis has been identified to be a promising technology in both production and separation stages of fermentation processes.

Biofouling Mitigation Approaches during Water Recovery from Fermented Broth via Forward Osmosis.

Forward Osmosis (FO) is a promising technology that can offer sustainable solutions in the biorefinery wastewater and desalination fields, via low energy water recovery. However, microbial biomass and organic matter accumulation on membrane surfaces can hinder the water recovery and potentially lead to total membrane blockage. Biofouling development is a rather complex process and can be affected by several factors such as nutrient availability, chemical composition of the solutions, and hydrodynamic conditions.

Cryopreservation and fast recovery of enriched syngas-converting microbial communities.

Over the last decades, the use of mixed microbial communities has attracted increasing scientific attention due to their potential biotechnological applications in several emerging technological platforms such as the carboxylate, bioplastic, syngas and bio-electrochemical synthesis platforms. However, this increasing interest has not been accompanied by a parallel development of suitable cryopreservation techniques for microbial communities. While cryopreservation methods for the long-term storage of axenic cultures are well established, their effectiveness in preserving the microbial diversity and functionality of microbial communities has rarely been studied.

On the Effect of Aqueous Ammonia Soaking Pre-Treatment on Continuous Anaerobic Digestion of Digested Swine Manure Fibers.

(1) Background: The continuously increasing demand for renewable energy sources renders anaerobic digestion as one of the most promising technologies for renewable energy production. Due to the animal production intensification, manure is being used as the primary feedstock for most biogas plants. Their economical profitable operation, however, relies on increasing the methane yield from the solid fraction of manure, which is not so easily degradable.

Enrichment of syngas-converting mixed microbial consortia for ethanol production and thermodynamics-based design of enrichment strategies.

Background: The production of ethanol through the biochemical conversion of syngas, a mixture of H, CO and CO, has been typically studied using pure cultures. However, mixed microbial consortia may offer a series of benefits such as higher resilience and adaptive capacity, and non-sterile operation, all of which contribute to reducing the utility consumption when compared to pure culture-based processes. This work focuses on the study of strategies for the enrichment of mixed microbial consortia with high ethanologenic potential, investigating the effect of the operational conditions (pH and yeast extract addition) on both the ethanol yield and evolution of the microbial community along the enrichment process.

Combined polyhydroxyalkanoates (PHA) and 1,3-propanediol production from crude glycerol: Selective conversion of volatile fatty acids into PHA by mixed microbial consortia.

Crude glycerol is an important by-product of the biodiesel industry, which can be converted into volatile fatty acids (VFA) and/or 1,3-propanediol (1,3-PDO) by fermentation. In this study, a selective conversion of VFA to polyhydroxyalkanoates (PHA) was attained while leaving 1,3-PDO in the supernatant by means of mixed microbial consortia selection strategies. The process showed highly reproducible results in terms of PHA yield, 0.

Polyhydroxyalkanoates (PHA) production from fermented crude glycerol: Study on the conversion of 1,3-propanediol to PHA in mixed microbial consortia.

Crude glycerol, a by-product from the biodiesel industry, can be converted by mixed microbial consortia into 1,3-propanediol (1,3-PDO) and volatile fatty acids. In this study, further conversion of these main products into polyhydroxyalkanoates (PHA) was investigated with the focus on 1,3-PDO. Two different approaches for the enrichment of PHA accumulating microbial consortia using an aerobic dynamic feeding strategy were applied.

Optimization of Aqueous Ammonia Soaking of manure fibers by Response Surface Methodology for unlocking the methane potential of swine manure.

Swine manure mono-digestion often results to economically non-feasible processes, due to the high dilution and ammonia concentration together with the low degradation rates it presents. The effects of different parameters of Aqueous Ammonia Soaking (AAS) as a pretreatment for improving the digestion of manure fibers when coupled to an ammonia removal step were investigated in this study. Response Surface Methodology was followed and the influence and interactions of the following AAS parameters were studied: NH concentration, duration and solid-to-liquid ratio.

Effect of in situ acids removal on mixed glucose and xylose fermentation by Clostridium tyrobutyricum.

In the present study, the effect of potassium ions and increasing concentrations of glucose and xylose on the growth of a strain of Clostridium tyrobutyricum, adapted to wheat straw hydrolysate, was investigated. Application of continuous fermentation of a mixture of glucose and xylose and in situ acid removal by reverse electro enhanced dialysis (REED) was investigated as a method to alleviate potassium and end-product inhibition and consequently enhance the sugar consumption rates and butyric acid productivity. It was found that glucose and xylose were not inhibitory up to a concentration of 50 and 37 g L(-1) respectively, and that they were consumed at comparable rates when fermented alone.

Enhancement of methane yield from wheat straw, miscanthus and willow using aqueous ammonia soaking.

The increasing demand for methane production cannot be satisfied by the use of anaerobic digestion only from waste/wastewater treatment. Perennial energy crops, such as miscanthus and willow, as well as agricultural residues can be considered as options for increasing the methane production through biomass digestion, due to their high organic content and biomass yield. These materials present a great potential, which is only limited by the rigid lignocellulosic structure.

ADM1-based modeling of methane production from acidified sweet sorghum extract in a two stage process.

The present study focused on the application of the Anaerobic Digestion Model 1 on the methane production from acidified sorghum extract generated from a hydrogen producing bioreactor in a two-stage anaerobic process. The kinetic parameters for hydrogen and volatile fatty acids consumption were estimated through fitting of the model equations to the data obtained from batch experiments. The simulation of the continuous reactor performance at all HRTs tested (20, 15, and 10d) was very satisfactory.

Hydrogen and methane production through two-stage mesophilic anaerobic digestion of olive pulp.

The present study focused on the anaerobic biohydrogen production from olive pulp (two phase olive mill wastes, TPOMW) and the subsequent anaerobic treatment of the effluent for methane production under mesophilic conditions in a two-stage process. Biohydrogen production from water-diluted (1:4) olive pulp was investigated at hydraulic retention times (HRT) of 30 h, 14.5 h and 7.

Improving anaerobic sewage sludge digestion by implementation of a hyper-thermophilic prehydrolysis step.

The present study focuses on a two-step process for treatment and stabilisation of primary sludge. The process consists of a hyper-thermophilic hydrolysis step operated at 70 degrees C and a hydraulic retention time (HRT) of 2 days followed by a thermophilic (55 degrees C) anaerobic digestion step at a HRT of 13 days. A one-step anaerobic digester operated at 55 degrees C and 15 days HRT was used as a reference process.

Effect of temperature on ethanol tolerance of a thermophilic anaerobic ethanol producer Thermoanaerobacter A10: modeling and simulation.

The low ethanol tolerance of thermophilic anaerobic bacteria (<2%, v/v) is a major obstacle for their industrial exploitation for ethanol production. The ethanol tolerance of the thermophilic anaerobic ethanol-producing strain Thermoanaerobacter A10 was studied during batch tests of xylose fermentation at a temperature range of 50-70 degrees C with exogenously added ethanol up to approximately 6.4% (v/v).

Biofuels generation from sweet sorghum: fermentative hydrogen production and anaerobic digestion of the remaining biomass.

The present study focuses on the exploitation of sweet sorghum biomass as a source for hydrogen and methane. Fermentative hydrogen production from the sugars of sweet sorghum extract was investigated at different hydraulic retention times (HRT). The subsequent methane production from the effluent of the hydrogenogenic process and the methane potential of the remaining solids after the extraction process were assessed as well.

Mesophilic and thermophilic anaerobic digestion of primary and secondary sludge. Effect of pre-treatment at elevated temperature.

Anaerobic digestion is an appropriate technique for the treatment of sludge before final disposal and it is employed worldwide as the oldest and most important process for sludge stabilization. In general, mesophilic anaerobic digestion of sewage sludge is more widely used compared to thermophilic digestion. Furthermore, thermal pre-treatment is suitable for the improvement of stabilization, enhancement of dewatering of the sludge, reduction of the numbers of pathogens and could be realized at relatively low cost especially at low temperatures.

Anaerobic granular sludge and biofilm reactors.

The long retention time of the active biomass in the high-rate anaerobic digesters is the key factor for the successful application of the high rate anaerobic wastewater treatment. The long solids retention time is achieved due to the specific reactor configuration and it is enhanced by the immobilization of the biomass, which forms static biofilms, particle-supported biofilms, or granules depending on the reactor's operational conditions. The advantages of the high-rate anaerobic digestion over the conventional aerobic wastewater treatment methods has created a clear trend for the change of the role of the anaerobic digestion in the wastewater treatment plants from a pre-treatment method to the main biological treatment method.