Hollow fiber membrane based H2 diffusion for efficient in situ biogas upgrading in an anaerobic reactor

Bubbleless gas transfer through a hollow fiber membrane (HFM) module was used to supply H₂ to an anaerobic reactor for in situ biogas upgrading, and it creates a novel system that could achieve a CH₄ content higher than 90 % in the biogas. The increase of CH₄ content and pH, and the decrease of bicarbonate concentration were related with the increase of the H₂ flow rate. The CH₄ content increased from 78.4 % to 90.2 % with the increase of the H₂ flow rate from 930 to 1,440 ml/(l?day), while the pH in the reactor remained below 8.0. An even higher CH₄ content (96.1 %) was achieved when the H₂ flow rate was increased to 1,760 ml/(l?day); however, the pH increased to around 8.3 due to bicarbonate consumption which hampered the anaerobic process. The biofilm formed on the HFM was found not to be beneficial for the process since it increased the resistance of H₂ diffusion to the liquid. The study also demonstrated that the biofilm formed on the membrane only contributed 22–36 % to the H₂ consumption, while most of the H₂ was consumed by the microorganisms in the liquid phase.     

Development of a pilot scale anaerobic digester for biogas production from cow manure and whey mix

This paper presents results from anaerobic digestion of cow manure and whey mix. A pilot scale anaerobic digester, 128 l in volume, has been developed, to operate under batch and fed-batch conditions. The versatile and unique characteristics of the instrument allowed testing the methane production directly in the farm. The digester performance was evaluated with two calibration tests, the main for a period of 56 days. The study test was divided into three phases, one for each type of feeding operation (batch, fed-batch, batch). The initial phase of digestion resulted in 57 l-CH₄/kg-VS, the second phase had a yield of 86.6 l-CH₄/kg-VS and the third one had a production of 67 l-CH₄/kg-VS. The total methane yield was equal to 211.4 l-CH₄/kg-VS. Using the obtained pilot plant results to a real scale diary production cycle, it was possible to evaluate an electricity production equal to 8.86 kwh per 1 t/d. The conducted tests did show that there is a good potential to the use of a cow manure and whey biomass mix for biogas production.     

Salmonella reduction in manure by the addition of urea and ammonia

Animal manure may contain pathogenic microorganisms and disinfection is suggested to avoid reinfection of animal herds and introduction of zoonotic disease into the food chain. Ammonia and urea were tested for disinfection of bovine manure and Salmonella was found to be rapidly eliminated by the addition of 0.5% aqueous ammonia or 2% w/w urea (s). Treatments (2% urea and 0.5% ammonia), temperature (4 degrees C or 14 degrees C) and combinations of these factors significantly affected the inactivation rate. Decimal values (T(90)) were reduced from 8.3 days in the control to 2.0 days and 0.4 days at 14 degrees C after the addition of urea and ammonia, respectively. At 4 degrees C, the decimal values were reduced from 34 to 4.8 and 1.1 days, respectively. Recommended treatments of bovine manure based on Monte Carlo simulations are 0.5% ammonia followed by storage for one week or 2% urea followed by storage for two weeks at 14 degrees C, one month at 4 degrees C. Storage without additives should include at least one summer in temperate regions. Enterococci were evaluated as indicators for Salmonella but significantly slower decay rate and different behaviour in the material made them unsuitable as indicators for Salmonella in manure disinfected by ammonia or urea. Free ammonia treatment of Salmonella-contaminated manure disinfects the material and raises its fertilizer value.     

Responses of the biogas process to pulses of oleate in reactors treating mixtures of cattle and pig manure

The effect of oleate on the anaerobic digestion process was investigated. Two thermophilic continuously stirred tank reactors (CSTR) were fed with mixtures of cattle and pig manure with different total solid (TS) and volatile solid (VS) content. The reactors were subjected to increasing pulses of oleate. Following pulses of 0.5 and 1.0 g oleate/L, the most distinct increase in volatile fatty acid (VFA) concentrations were observed in the reactor with the lowest TS/VS content. This suggests a higher adsorption of oleate on the surfaces of biofibers in the reactor with the highest TS/VS and a less pronounced inhibition of the anaerobic digestion process. On the other hand, addition of 2.0 g oleate/L severely inhibited the process in both reactors, and a significant increase in all VFA concentrations combined with an immediate drop in methane production was noticed. However, 20 days after the reactors had been exposed to oleate both reactors showed a lower VFA concentration along with a higher methane production than before the pulses. This indicates that oleate had a stimulating effect on the overall process. The improved acetogenic and methanogenic activity in the reactors was confirmed in batch activity tests. In addition to this, toxicity tests revealed that the oleate pulses induced an increase in the tolerance level of acetotrophic methanogens towards oleate. When evaluating the usability of different process parameters (i.e., VFA and methane production) as indicators of process recovery, following the inhibition by oleate, propionate was found to be most suitable.     

Co-substrate composition is critical for enrichment of functional key species and for process efficiency during biogas production from cattle manure

Cattle manure has a low energy content and high fibre and water content, limiting its value for biogas production. Co-digestion with a more energy-dense material can improve the output, but the co-substrate composition that gives the best results in terms of degree of degradation, gas production and digestate quality has not yet been identified. This study examined the effects of carbohydrate, protein and fat as co-substrates for biogas production from cattle manure. Laboratory-scale semi-continuous mesophilic reactors were operated with manure in mono-digestion or in co-digestion with egg albumin, rapeseed oil, potato starch or a mixture of these, and chemical and microbiological parameters were analysed. The results showed increased gas yield for all co-digestion reactors, but only the reactor supplemented with rapeseed oil showed synergistic effects on methane yield. The reactor receiving potato starch indicated improved fibre degradation, suggesting a priming effect by the easily accessible carbon. Both these reactors showed increased species richness and enrichment of key microbial species, such as fat-degrading Syntrophomonadaceae and families known to include cellulolytic bacteria. The addition of albumin promoted enrichment of known ammonia-tolerant syntrophic acetate- and potential propionate-degrading bacteria, but still caused slight process inhibition and less efficient overall degradation of organic matter in general, and of cellulose in particular.     

Investigation of the microbial community in a microbiological additive used in a manure composting process

The objectives of this study were to investigate the fate of microorganisms by using cultivation methods as well as DNA analyses in a commercial microbiological additive (MA) in the course of the composting. Almost all the predominant species in the microbial succession during composting process determined by polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) were in disagreement with those determined by the clone library method. None of the microbial species in the composting stages corresponded to the microorganisms identified in the MA either by the cultivation method or DNA analysis. The results in regard to predominant microorganisms of the MA detected from the liquid medium by the PCR-DGGE did not correspond with those detected from the MA itself and composting processes. Although no evidence was found that predominant species in the MA itself dominate in the composting process, predominant species diversity in the MA itself was markedly changed after culturing at different thermophilic temperatures. These results suggested that cultivable microorganisms in the MA did not become predominant in the composting process: however, some microorganisms that are detected from the MA itself by the DNA analysis may act effectively in the composting process.     

接种微生物菌剂对猪粪堆肥过程中细菌群落多样性的影响

利用PCR-DGGE方法研究了接种外源微生物菌剂对鲜猪粪高温好氧堆肥过程中细菌群落多样性的影响.结果表明：接种外源微生物菌剂可以促进堆肥的顺利进行,比不接种处理的高温期提前2 d.DGGE图谱分析表明,堆肥中优势细菌群落组成发生了明显的更迭现象,不同堆肥时期细菌群落的Shannon-Wiener指数呈显著差异.目的条带克隆测序结果表明,整个堆肥过程Clostridium stercorarium subsp. thermolacticum sp.一直是优势菌属,不经培养细菌、Bacillus coagulans sp.、Clostridium thermocellum sp.在接种外源微生物菌剂处理的第10、16天成为优势菌属,不经培养的Firmicutes sp.和不经培养的 delta proteobacterium分别在未接种外源微生物菌剂处理堆肥发酵的第5天和第16天成为优势菌属.非优势菌属Ureibacillus thermosphaericus、不经培养的Silvimonas sp.出现在堆肥腐熟后期,不经培养的土壤细菌主要出现在堆肥初期和高温初期.UPGMC聚类分析表明,接种外源微生物菌剂明显影响了堆肥不同时期的细菌群落结构组成.堆肥化过程中细菌DGGE图谱主成分分析表明,细菌群落变化主要受外源接种微生物菌剂的影响.     

Anaerobic digestion of swine manure under natural zeolite addition: VFA evolution, cation variation, and related microbial diversity

Batch experiments were carried out on anaerobic digestion of swine manure under 10 % of total solids and 60 g/L of zeolite addition at 35 °C. Four distinctive volatile fatty acid (VFAs) evolution stages were observed during the anaerobic process, i.e., VFA accumulation, acetic acid (HAc) and butyric acid (HBu) utilization, propionic acid (HPr) and valeric acid (HVa) degradation, and VFA depletion. Large decreases in HAc/HBu and HPr/HVa occurred respectively at the first and second biogas peaks. Biogas yield increased by 20 % after zeolite addition, about 356 mL/g VS_added with accelerated soluble chemical oxygen demand degradation and VFA (especially HPr and HBu) consumption in addition to a shortened lag phase between the two biogas peaks. Compared with Ca²⁺ and Mg²⁺ (100–300 mg/L) released from zeolite, simultaneous K⁺ and NH₄ ⁺ (580–600 mg/L) adsorptions onto zeolite particles contributed more to the enhanced biogasification, resulting in alleviated inhibition effects of ammonium on acidogenesis and methanogenesis, respectively. All the identified anaerobes could be grouped into Bacteroidetes and Firmicutes, and zeolite addition had no significant influence on the microbial biodiversity in this study.     

The replacement of skim milk by dried microbial cells and whey in milk diets for calves

In two experiments, the performance and health of calves fed on diets containing dried microbial cells (DMC) was monitored. In the first experiment 32 seven-day-old British Friesian bull calves, reared on a conventional early weaning system to 8 weeks of age, were given milk replacers in which 5, 10 and 20% spray-dried DMC and whey replaced 14–55% of skim milk protein. All DMC diets contained 36 g/kg of non-nucleic acid nitrogen. In Experiment 2, 38 two-day-old Ayrshire bull calves were fed for 63 days solely on one of two milk diets containing 0 or 10% DMC at 5 levels of intake designed to produce body gains of 0–1 kg/day. While the inclusion of up to 10% DMC in both experiments had little effect on performance or health, 20% DMC was associated with severe diarrhoea, loss of appetite and growth retardation, and impaired clotting of the milk in vitro. In Experiment 2 the response, in gain, by calves given increasing intakes of milk dry matter was linear and was unaffected by the type of diet offered.It was concluded that when levels of DMC in excess of 10% inclusion are used in association with maize starch, deleterious effects on performance are likely.     

Optimization of the microbial synthesis of dihydroxyacetone in a semi-continuous repeated-fed-batch process by in situ immobilization of Gluconobacter oxydans

The effect of in situ immobilization of Gluconobacter oxydans on a novel carrier material in a repeated-fed-batch operated packed-bed bubble-column bioreactor for the production of the fine chemical dihydroxyacetone was investigated experimentally. The carrier material were biocompatible, durable, coated Ralu-rings. The coating was a porous silicone matrix with satisfactory wetting characteristics. Settling of cells was relatively rapid. The cells were protected from abrasion caused by shear forces. A sufficiently high oxygen supply rate to the immobilized cells was provided due to the high oxygen permeability of the silicone matrix. The immobilized biomass was estimated to be about 65% of the total biomass contained in the bioreactor after 18 days of operation. The observed space-time yield was approx. 76% higher compared to a similar process which was performed without an optimized fermentation medium. Compared to previous experiments with a trickle-bed bioreactor, the space-time yield was approx. 3.7 times higher. A typical time course of the immobilization process was observed: after an induction phase, a transition phase followed which later on gave way to a nearly linear accumulation phase. A stationary phase with regard to the amount of immobilized active cells, however, was not reached. Hence, a higher bioreactor performance than observed could be expected at longer operation times.     

Co‐substrate composition is critical for enrichment of functional key species and for process efficiency during biogas production from cattle manure

Cattle manure has a low energy content and high fibre and water content, limiting its value for biogas production. Co‐digestion with a more energy‐dense material can improve the output, but the co‐substrate composition that gives the best results in terms of degree of degradation, gas production and digestate quality has not yet been identified. This study examined the effects of carbohydrate, protein and fat as co‐substrates for biogas production from cattle manure. Laboratory‐scale semi‐continuous mesophilic reactors were operated with manure in mono‐digestion or in co‐digestion with egg albumin, rapeseed oil, potato starch or a mixture of these, and chemical and microbiological parameters were analysed. The results showed increased gas yield for all co‐digestion reactors, but only the reactor supplemented with rapeseed oil showed synergistic effects on methane yield. The reactor receiving potato starch indicated improved fibre degradation, suggesting a priming effect by the easily accessible carbon. Both these reactors showed increased species richness and enrichment of key microbial species, such as fat‐degrading Syntrophomonadaceae and families known to include cellulolytic bacteria. The addition of albumin promoted enrichment of known ammonia‐tolerant syntrophic acetate‐ and potential propionate‐degrading bacteria, but still caused slight process inhibition and less efficient overall degradation of organic matter in general, and of cellulose in particular.

The study investigated co‐digestion of cattle manure with different categories of co substrates, e.g. starch, albumin, rapeseed oil or a mix of these. The processes were evaluated using both chemical parameters and analysis of microbial communities. Results showed clear correlations between process efficiency and the applied co‐substrates, and enrichment key microbial taxa.     

Anammox for ammonia removal from pig manure effluents: Effect of organic matter content on process performance

The anammox process, under different organic loading rates (COD), was evaluated using a semi-continuous UASB reactor at 37 °C. Three different substrates were used: initially, synthetic wastewater, and later, two different pig manure effluents (after UASB-post-digestion and after partial oxidation) diluted with synthetic wastewater. High ammonium removal was achieved, up to 92.1 ± 4.9% for diluted UASB-post-digested effluent (95 mg COD L^?1) and up to 98.5 ± 0.8% for diluted partially oxidized effluent (121 mg COD L^?1). Mass balance clearly showed that an increase in organic loading (from 95 mg COD L^?1 to 237 mg COD L^?1 and from 121 mg COD L^?1 to 290 mg COD L^?1 for the UASB-post-digested effluent and the partially oxidized effluent, respectively) negatively affected the anammox process and facilitated heterotrophic denitrification. Partial oxidation as a pre-treatment method improved ammonium removal at high organic matter concentration. Up to threshold organic load concentration of 142 mg COD L^?1 of UASB-post-digested effluent and 242 mg COD L^?1 of partially oxidized effluent, no effect of organic loading on ammonia removal was registered (ammonium removal was above 80%). However, COD concentrations above 237 mg L^?1 (loading rate of 112 mg COD L^?1 day^?1) for post-digested effluent and above 290 mg L^?1 (loading rate of 136 mg COD L^?1 day^?1) for partially oxidized effluent resulted in complete cease of ammonium removal. Results obtained showed that, denitrification and anammox process were simultaneously occurring in the reactor. Denitrification became the dominant ammonium removal process when the COD loading was increased.     

Impact of fertilization by natural manure on the microbial quality of soil: Molecular approach

The quality of soil is strongly bound by several interactions between chemical and biological components, including microbial composition, which are a key importance for soil performance. Cultural activities have a huge induction on soil health, through both modification of physicochemical proprieties and changing on soil microbial communities. This usually affects the safety of soil, and then the crop production and water.In the present work, the information on bacterial community composition was determined from a set of 6 soils collected from 2 farms in agricultural land of Marrakech (Morocco), one of which used poultry manure (PM) and the other cow manure (CM) as fertilizers. To profile this structure of the bacterial community Denaturing Gradient Gel Electrophoresis (DGGE) of 16S rDNA fragments has been used.These amendments resulted in the appearance of several novel bands and different relative intensities of bands between the control station and other sites studied. The stations most affected are those receiving a supply of manure rather high, which results in an organic and bacterial load in the soil. The results showed a bacterial diversity very important indicating a fecal contamination like Bacteroides, Pseudomonas, Staphylococcus,… etc. Bacteria pertain to the phylum Firmicutes and Bacteroidetes were noted to be the dominant ribotype in amended soil.Moreover, this work demonstrates also the existence of pathogens strains in soil amended by poultry manure (PM) belonging to the Clostridiales order and Pseudomonadales. The pathogenic bacteria detected posing a hazard of human contagion when they are used for soil practice.     

In situ identification of polyphosphate- and polyhydroxyalkanoate-accumulating traits for microbial populations in a biological phosphorus removal process

Polyphosphate- and polyhydroxyalkanoate (PHA)-accumulating traits of predominant microorganisms in an efficient enhanced biological phosphorus removal (EBPR) process were investigated systematically using a suite of non-culture-dependent methods. Results of 16S rDNA clone library and fluorescence in situ hybridization (FISH) with rRNA-targeted, group-specific oligonucleotide probes indicated that the microbial community consisted mostly of the alpha- (9.5% of total cells), beta- (41.3%) and gamma- (6.8%) subclasses of the class Proteobacteria, Flexibacter-Cytophaga (4.5%) and the Gram-positive high G+C (HGC) group (17.9%). With individual phylogenetic groups or subgroups, members of Candidatus Accumulibacter phosphatis in the beta-2 subclass, a novel HGC group closely related to Tetrasphaera spp., and a novel gamma-proteobacterial group were the predominant populations. Furthermore, electron microscopy with energy-dispersive X-ray analysis was used to validate the staining specificity of 4,6-diamino-2-phenylindole (DAPI) for intracellular polyphosphate and revealed the composition of polyphosphate granules accumulated in predominant bacteria as mostly P, Ca and Na. As a result, DAPI and PHA staining procedures could be combined with FISH to identify directly the polyphosphate- and PHA-accumulating traits of different phylogenetic groups. Members of Accumulibacter phosphatis and the novel gamma-proteobacterial group were observed to accumulate both polyphosphate and PHA. In addition, one novel rod-shaped group, closely related to coccus-shaped Tetrasphaera, and one filamentous group resembling Candidatus Nostocoidia limicola in the HGC group were found to accumulate polyphosphate but not PHA. No cellular inclusions were detected in most members of the alpha-Proteobacteria and the Cytophaga-Flavobacterium group. The diversified functional traits observed suggested that different substrate metabolisms were used by predominant phylogenetic groups in EBPR processes.     

Evaluation of methods for preparing hydrogen-producing seed inocula under thermophilic condition by process performance and microbial community analysis

Five methods for preparation of hydrogen-producing seeds (base, acid, 2-bromoethanesulfonic acid (BESA), load-shock and heat shock treatments) as well as an untreated anaerobic digested sludge were compared for their hydrogen production performance and responsible microbial community structures under thermophilic condition (60 degrees C). The results showed that the load-shock treatment method was the best for enriching thermophilic hydrogen-producing seeds from mixed anaerobic cultures as it completely repressed methanogenic activity and gave the a maximum hydrogen production yield of 1.96 mol H(2) mol(-1) hexose with an hydrogen production rate of 11.2 mmol H(2) l(-1)h(-1). Load-shock and heat-shock treatments resulted in a dominance of Thermoanaerobacterium thermosaccharolyticum with acetic acid and butyric acid type of fermentation while base- and acid-treated seeds were dominated by Clostridium sp. and BESA-treated seeds were dominated by Bacillus sp. The comparative experimental results from hydrogen production performance and microbial community analysis showed that the load-shock treatment method was better than the other four methods for enriching thermophilic hydrogen-producing seeds from anaerobic digested sludge. Load-shock treated sludge was implemented in palm oil mill effluent (POME) fermentation and was found to give maximum hydrogen production rates of 13.34 mmol H(2) l(-1)h(-1) and resulted in a dominance of Thermoanaerobacterium spp. Load-shock treatment is an easy and practical method for enriching thermophilic hydrogen-producing bacteria from anaerobic digested sludge.     

In situ product removal in fermentation systems: improved process performance and rational extractant selection

The separation of inhibitory compounds as they are produced in biotransformation and fermentation systems is termed in situ product removal (ISPR). This review examines recent ISPR strategies employing several classes of extractants including liquids, solids, gases, and combined extraction systems. Improvement through the simple application of an auxiliary phase are tabulated and summarized to indicate the breadth of recent ISPR activities. Studies within the past 5 years that have highlighted and have discussed “second phase” properties, and that have an effect on fermentation performance, are particular focus of this review. ISPR, as a demonstrably effective processing strategy, continues to be widely adopted as more applications are explored; however, focus on the properties of extractants and their rational selection based on first principle considerations will likely be key to successfully applying ISPR to more challenging target molecules.     

猪粪与沼气渣对双季稻田甲烷排放的影响

随着环境温度的升高,稻田甲烷排放通量增加。早稻期间甲烷排放通量随着水稻生育期的增加而逐步加快,而晚稻甲烷排放主要集中在水稻生长的前中期,而且排放量很高。一天中甲烷排放具有很强的周期性,在6：00～8：00时,甲烷排放通量进入谷底,14：00时甲烷排放通量达到峰值。稻田甲烷排放通量与土壤5cm处的温度及土壤水溶解甲烷含量具有较高的相关性。猪粪和沼气渣的施用分别提高稻田甲烷排放量22．14％和4．40％。在早稻期间,施用猪粪和沼气渣分别提高土壤水溶解甲烷含量40．3％和11．9％,而晚稻期间仅分别提高23．9％和5．04％。     

In situ Inactivation of the Oxidase Activity of Xylem Peroxidases by H2O2 in the H2O2-Producing Xylem of Zinnia elegans

Zinnia elegans stems with 3,3′, 5, 5′-tetramethylbenzidine (TMB) in the presence and in the absence of catalase reveals the presence of xylem oxidase activities in the H₂O₂-producing lignifying xylem cells. This staining of lignifying xylem cells with TMB is the result of two independent mechanisms: one is the catalase-sensitive (H₂O₂-dependent) peroxidase-mediated oxidation of TMB, and the other the catalase-insensitive (H₂O₂-independent) oxidation of TMB, probably due to the oxidase activity of xylem peroxidases. The response of this TMB-oxidase activity of xylem peroxidases to different exogenous H₂O₂ concentrations was studied, and the results showed that H₂O₂ at high concentrations (100–1,000 mM) clearly acted as an inactivator of this xylem TMB-oxidase activity, although some inhibitory effect could still be appreciated at 10 mM H₂O₂. This xylem TMB-oxidase activity resided in a strongly basic cell wall-bound peroxidase (pl about 10.5). Given such a scenario, it may be concluded that this TMB-oxidase activity of peroxidase is located in tissues capable of sustaining H₂O₂ production, and that the in situ oxidase activity shown by this enzyme is inactivated by high H₂O₂ concentrations. Received 20 April 1999/ Accepted in revised form 16 August 1999