A snapshot of microbial community structures in 20 different field-scale anaerobic bioreactors treating food waste.

This study aimed to identify significant factors shaping the microbial populations in biogas plants treating food waste (FW). Twenty full-scale anaerobic acidogenic/methanogenic bioreactors, located at 11 FW treatment facilities, were compared to find patterns in their microbial community structures and potential interactions with the process parameters. Temperature, hydraulic retention time, and organic loading rate were design parameters that systematically influenced the microbial communities. The latter two clearly separated the acidogenic and methanogenic bioreactors. Lactobacillus was the dominant (69.7 ±â€¯19.8%) bacteria in the acidogenic reactors, while hydrogen-utilizing methanogens, such as Methanoculleus (65.1 ±â€¯33.5%), were the dominant archaea in most methanogenic digesters. Defluiviitoga was the dominant (82.7 ±â€¯1.4%) bacteria in the thermophilic digesters, but was also the most abundant (33.1-33.6%) bacteria in dry mesophilic digesters. The two bioreactor categories had lower bacterial diversities, and also higher propionate concentrations (>5 g/L in 4 out of 5 cases), which may impose potential risks for the management of such digesters. The current 'snapshot' of the microbial communities suggests several bacterial and archaeal taxa as potential indicators of bioreactor categories and/or process variables.

Temporal variation in bacterial and methanogenic communities of three full-scale anaerobic digesters treating swine wastewater.

To investigate the effects of temporal variations of process parameters on microbial community structures in the two types of full-scale anaerobic digester treating swine wastewater, three full-scale anaerobic digesters were monitored. An anaerobic filter (AF)-type digester located in Gong-Ju (GJ) showed the highest COD removal among three digesters and maintained stable efficiency. A digester in Hong-Seong (HS) was of the same type as it GJ and showed improved efficiency over the sampling period. A continuously stirred tank reactor (CSTR)-type digester in Soon-Cheon (SC) showed decreasing efficiency due to a high residual concentration of VFAs and NH4+. These process efficiencies were closely correlated to the Simpson indices of the methanogenic communities. Genera Bacillus, Methanosaeta, and Methanospirillum that have filamentous morphology were dominant in both AF-type digesters, but genera Acholeplasma, Methanosarcina, and Methanoculleus that have spherical or coccoid morphology were dominantly abundant in the CSTR-type digester. Correlation between populations suggests a possible syntrophic relationship between genera Desulfobulbus and Methanosaeta in digesters GJ and HS.

Comprehensive analysis of microbial communities in full-scale mesophilic and thermophilic anaerobic digesters treating food waste-recycling wastewater.

Microbes were sampled for a year in a full-scale mesophilic anaerobic digester (MD) and a thermophilic anaerobic digester (TD) treating food waste-recycling wastewater (FRW), then microbial community structure, dynamics and diversity were quantified. In the MD, Fastidiosipila, Petrimonas, vadinBC27, Syntrophomonas, and Proteiniphilum were dominant bacterial genera; they may contribute to hydrolysis and fermentation. In the TD, Defluviitoga, Gelria and Tepidimicrobium were dominant bacteria; they may be responsible for hydrolysis and acid production. In the MD, dominant methanogens changed from Methanobacterium (17.1 ±â€¯16.9%) to Methanoculleus (67.7 ±â€¯17.8%) due to the increase in ammonium concentration. In the TD, dominant methanogens changed from Methanoculleus (42.8 ±â€¯13.6%) to Methanothermobacter (49.6 ±â€¯11.0%) due to the increase of pH. Bacteria and archaea were more diverse in the MD than in the TD. These results will guide development of microbial management methods to improve the process stability of MD and TD treating FRW.

Microbial communities underpinning mesophilic anaerobic digesters treating food wastewater or sewage sludge: A full-scale study.

Ten mesophilic full-scale anaerobic digesters treating food wastewater (FW-digesters) or sewage sludge (SL-digesters) were monitored for 1 year to investigate: (1) microbial communities underpinning FW-digesters and SL-digesters, (2) the effects of total ammonia-nitrogen concentration [TAN] and Na+ concentration [Na+] on variations of these communities. [TAN] and [Na+] in the digester varied among digesters: 1.7-6.5 g TAN/L and 1.0-3.6 g Na+/L for the FW-digesters, and 0.1-2.2 g TAN/L and 0.1-1.2 g Na+/L for the SL-digesters; [TAN] negatively correlated with the process efficiency of the FW-digesters. Microbial communities were less diverse in the FW-digesters than in the SL-digesters. The FW- and SL-digesters formed very distinct microbial community structures; [TAN] and [Na+] in the digester were the critical factors shaping these structures. Immigrant bacteria from influent sludge significantly influence the bacterial communities of the SL-digesters. Methanoculleus might be tolerant to high ammonia in AD of such organic wastewater.

A comparative study on the process efficiencies and microbial community structures of six full-scale wet and semi-dry anaerobic digesters treating food wastes.

The purpose of this study was to investigate the effect of different types of food wastes on the process efficiency and microbial community structures in full-scale anaerobic digesters and to identify parameters that affect these criteria. Six full-scale anaerobic digesters were investigated; three were operated under "wet" condition (total solids TS≤10%), and three were run under "semi-dry" condition (10%≤TS≤20%). Removal efficiency of volatile solids was much higher in the wet digesters (75.2±3.8%) than in the semi-dry digesters (42.6±5.5%). The bacterial and archaeal communities were distinctly characterized by families Porphyromonadaceae, Sphingobacteriaceae, Syntrophomonadaceae, and Methanobacteriaceae in the wet digesters; and of Clostridiaceae, Patulibacteraceae, Pseudonocardiaceae, Lachnospiraceae, Rikenellaceae, and Methanomicrobiaceae in the semi-dry digesters. The discriminant parameters identified were TS content of influent, concentration of total ammonia nitrogen and the ratio of soluble chemical oxygen demand (COD) to COD in the digester.

Bacteria and archaea communities in full-scale thermophilic and mesophilic anaerobic digesters treating food wastewater: Key process parameters and microbial indicators of process instability.

In this study, four different mesophilic and thermophilic full-scale anaerobic digesters treating food wastewater (FWW) were monitored for 1-2years in order to investigate: 1) microbial communities underpinning anaerobic digestion of FWW, 2) significant factors shaping microbial community structures, and 3) potential microbial indicators of process instability. Twenty-seven bacterial genera were identified as abundant bacteria underpinning the anaerobic digestion of FWW. Methanosaeta harundinacea, M. concilii, Methanoculleus bourgensis, M. thermophilus, and Methanobacterium beijingense were revealed as dominant methanogens. Bacterial community structures were clearly differentiated by digesters; archaeal community structures of each digester were dominated by one or two methanogen species. Temperature, ammonia, propionate, Na+, and acetate in the digester were significant factors shaping microbial community structures. The total microbial populations, microbial diversity, and specific bacteria genera showed potential as indicators of process instability in the anaerobic digestion of FWW.

Identifying methanogen community structures and their correlations with performance parameters in four full-scale anaerobic sludge digesters.

Four full-scale mesophilic anaerobic digesters treating waste sludge were monitored to characterize methanogen communities and their relationship with process parameters. The performance of the four digesters were dissimilar with the average chemical oxygen demand removal efficiencies between 24 and 45% and differing pH. Real-time quantitative PCR showed that archaeal 16S rRNA gene concentration ([ARC]) and, more pronouncedly, its ratio to bacterial counterpart ([ARC]/[BAC]) correlated positively with the performance parameters, including the lipid removal efficiency. Pyrosequencing identified 12 methanogen genera, of which Methanolinea, Methansaeta, and Methanospirillum collectively accounted for 79.2% of total archaeal reads. However, Methanoculleus, a numerically minor (1.9±2.6%) taxa, was the most promising biomarker for positive performance, while Methanoregula was abundant in samples with poor performance. These results could be useful for the control and management of anaerobic sludge digestion.

Use of Swine Wastewater as Alternative Substrate for Mycelial Bioconversion of White Rot Fungi.

Seven white rot fungal species were tested for growth as mycelia using swine wastewater (SW), an agro-waste with tremendous environmental footprint, as the sole nutrient source. The SW contained high concentrations of carbon and nitrogen components, which could support nutritional requirements for mycelial growth. Out of the seven species, Pleurotus ostreatus and Hericium erinaceus were successfully cultivated on the SW medium using solid-state fermentation. Response surface methodology was employed to determine the combination of pH, temperature (T), and substrate concentration (C) that maximizes mycelial growth rate (Kr) for the two species. The optimum condition was estimated as pH = 5.8, T = 28.8 °C, and C = 11.2 g chemical oxygen demand (COD)/L for P. ostreatus to yield Kr of 11.0 mm/day, whereas the greatest Kr (3.1 mm/day) was anticipated at pH = 4.6, T = 25.5 °C, and C = 11.9 g COD/L for H. erinaceus. These Kr values were comparable to growth rates obtained using other substrates in the literature. These results demonstrate that SW can be used as an effective substrate for mycelial cultivation of the two white rot fungal species, suggesting an alternative method to manage SW with the production of potentially valuable biomass.

Mesophilic Acidogenesis of Food Waste-Recycling Wastewater: Effects of Hydraulic Retention Time, pH, and Temperature.

The effects of hydraulic retention time (HRT), pH, and operating temperature (T OP) on the degradation of food waste-recycling wastewater (FRW) were investigated in laboratory-scale hydrolysis/acidogenesis reactors. Response surface analysis was used to approximate the production of volatile organic acids and degradation of volatile suspended solids (VSS), carbohydrate, protein, and lipid with regard to the independent variables (1 ≤ HRT ≤ 3 days, 4 ≤ pH ≤ 6, 25 ≤ T OP ≤ 45 °C). Partial cubic models adequately approximated the corresponding response surfaces at α < 5 %. The physiological conditions for maximum acidification (0.4 g TVFA + EtOH/g VSadded) and the maximal degradation of VSS (47.5 %), carbohydrate (92.0 %), protein (17.7 %), and lipid (73.7 %) were different. Analysis of variance suggested that pH had a great effect on the responses in most cases, while T OP and HRT, and their interaction, were significant in some cases. Denaturing gradient gel electrophoresis analysis revealed that Sporanaerobacter acetigenes, Lactobacillus sp., and Eubacterium pyruvivorans-like microorganisms might be main contributors to the hydrolysis and acidogenesis of FRW. Biochemical methane potential test confirmed higher methane yield (538.2 mL CH4/g VSadded) from an acidogenic effluent than from raw FRW.

Nutrient Recovery of Starch Processing Waste to Cordyceps militaris: Solid State Cultivation and Submerged Liquid Cultivation.

This study demonstrated the potential for managing starch processing waste (SPW) by bioconversion to Cordyceps militaris mycelia using solid state cultivation (SSC) and submerged liquid cultivation (SLC). The growth characteristics of C. militaris mycelium were accessed and compared for SSC and SLC systems on SPW under various conditions of initial SPW concentration, pH, and operating temperature. To quantify the mycelial biomass in SLC, original primer sets targeting the 18S rRNA gene of C. militaris were developed. In SSC, a maximum mycelial growth rate (543.1 mm(2)/day) was predicted to occur at 25.6 g SPW/L, pH 5.5, and 23.8 °C. In SLC, a maximum mycelial growth rate (1918.6 mg/L/day) was predicted to occur at 35.5 g SPW/L, pH 5.5, and 22.0 °C. Temperature was suggested as the most significant factor in both systems. The higher optimum substrate concentration observed for SLC than for SSC was likely due to difference in mycelial morphology and mixing effect.

Correlations between bacterial populations and process parameters in four full-scale anaerobic digesters treating sewage sludge.

Process parameters and bacterial populations were investigated in four full-scale anaerobic digesters treating sewage sludge. Although the four digesters were operated under similar conditions, digesters A and B had higher pH (7.2-7.4) and lipid removal efficiencies (>50%) than C and D (pH 6.1-6.4; average lipid removal <16%). Bacterial richness, diversity, and evenness were higher in digesters C and D. Among the top-populated genera, ten (group I) were more abundant in digesters A and/or B; they were putative syntrophic fatty acid or protein/amino acid-utilizers. In contrast, fifteen others (group II) were less abundant in A and/or B and included potentially dormant/dead cells originated from activated sludge. Despite the overall richness trend, the presence of the 25 genera in groups I/II was greater in digesters A and B (24) than in C and D (17); this observation suggests that group I bacteria might be essential in AD of sewage sludge.

Structures of microbial communities found in anaerobic batch runs that produce methane from propionic acid--Seeded from full-scale anaerobic digesters above a certain threshold.

The volatile fatty acid propionate inhibits anaerobic digestion during organic waste treatments. To examine potential microbial interactions that accelerate propionate oxidation, anaerobic digestion systems seeded with various types of anaerobic sludge were analyzed. Seed samples were collected from 10 different full-scale anaerobic reactors in South Korea. Propionate oxidation was estimated as the methane production rate per gram of propionate used per day. Two domestic sewage sludge showed the highest methane production rate values, 109.1 ± 4.2 and 74.5 ± 8.6 mL CH4/(g propionate ∙ d). A food waste recycling wastewater source exhibited the lowest methane production rate, 33.2 ± 2.6 mL CH4/(g propionate ∙ d). To investigate how the microbial community structure affected propionate oxidation, qualitative molecular analyses were carried out using denaturing gradient gel electrophoresis. Methanosaeta concilii, an aceticlastic methanogen, was detected in most batch runs. Smithella propionica, a unique propionate oxidizer and simultaneous producer of acetate, was found in domestic sewage sludge sources showing the highest methane production rate; in contrast, Desulfobulbus rhabdoformis, a sulfate reducer coupled with the consumption of acetate to be used as a precursor of methane, was observed in food waste recycling wastewater sludge source showing the lowest methane production rate. Thus, we propose that S. propionica, a syntrophic acetate producer using propionate, might cooperate with aceticlastic methanogens for high methane production during anaerobic digestion that included propionate.

Anaerobic digestion of cattle offal: protein and lipid-rich substrate degradation and population dynamics of acidogens and methanogens.

Anaerobic digestion of cattle offal was investigated in batch reactors at 35 °C to determine the feasibility of using cattle offal as a feedstock. The organic content [i.e., volatile solids (VS)] of the cattle offal was mainly composed of protein (33.9%) and lipids (46.1%). Hydrolysis along with acidogenesis was monitored to investigate the substrate degradation and generation of intermediate products (e.g., volatile fatty acids, ammonia). Acetate (2.03 g/L), propionate (0.60 g/L), n-butyrate (0.39 g/L), and iso-valerate (0.37 g/L) were major acidogenesis products (91% of total volatile fatty acid concentration). Overall protein and lipid degradation were 82.9 and 81.8%, respectively. Protein degraded first, and four times faster (0.28 day(-1)) than lipid (0.07 day(-1)). Methane yields were 0.52 L CH4/g VSadded and 0.65 L CH4/g VSremoved, indicating that anaerobic digestion of the offal was feasible. A quantitative QPCR assay was conducted to understand the microbial dynamics. The variation patt erns in the gene concentrations successfully indicated the population dynamics of proteolytic and lipolytic acidogens. A fourth-order Runge-Kutta approximation was used to determine the kinetics of the acidogens. The molecular biotechnology approach was appropriate for the evaluation of the acidogenic biokinetics. The maximum growth rate, µ m, halfsaturation coefficients, K s, microbial yield coefficient, Y, cell mass decay rate coefficient, k d, of the proteolytic acidogens were 9.9 day(-1), 37.8 g protein/L, 1.1 × 10(10) copies/g protein, and 3.8 × 10(-1), respectively. Those for the lipolytic acidogens were 1.2 × 10(-1) day(-1), 8.3 g lipid/L, 1.5 × 10(9) copies/g lipid, and 9.9 × 10(-3) day(-1), respectively.

Characterization of food waste-recycling wastewater as biogas feedstock.

A set of experiments was carried out to characterize food waste-recycling wastewater (FRW) and to investigate annual and seasonal variations in composition, which is related to the process operation in different seasons. Year-round samplings (n=31) showed that FRW contained high chemical oxygen demand (COD; 148.7±30.5g/L) with carbohydrate (15.6%), protein (19.9%), lipid (41.6%), ethanol (14.0%), and volatile fatty acids (VFAs; 4.2%) as major constituents. FRW was partly (62%) solubilized, possibly due to partial fermentation of organics including carbohydrate. Biodegradable portions of carbohydrate and protein were estimated from acidogenesis test by first-order kinetics: 72.9±4.6% and 37.7±0.3%, respectively. A maximum of 50% of the initial organics were converted to three major VFAs, which were acetate, propionate, and butyrate. The methane potential was estimated as 0.562L CH4/g VSfeed, accounting for 90.0% of the theoretical maximum estimated by elemental analysis.

Resource recovery using whey permeate to cultivate Phellinus linteus mycelium: Solid-state and submerged liquid fermentation.

The growth characteristics of Phellinus linteus mycelium were assessed and compared under solid-state fermentation (SSF) and submerged liquid fermentation (SLF) systems on whey permeate medium. Response surface methodology was used to investigate the growth rates of mycelia under various conditions of operating temperature (TO), initial pH, and substrate concentration ([S]). The optimal growth conditions of P. linteus mycelium were determined to be 26.1°C, pH 4.6, and 60.3g of lactose/L in the SSF system, and 29.0°C, pH 5.0, and 65.3g of lactose/L in the SLF system. The maximum growth rates were predicted to be 1.92 ± 0.01 mm/d in SSF and 192.1 ± 0.0mg/L per day in SLF. Random trials were conducted to experimentally validate the evaluated optimal conditions. The differences between the modeled and observed values were only 5.3% in the SSF system and 6.1% in the SLF system. Significant engineering factors differed between the fermentation techniques; TO was significant in both cultivation systems, whereas initial pH was significant in SSF but [S] was significant in SLF. Our findings can be used to guide the operation of the bioconversion process for cultivating P. linteus mycelium using whey permeate wastewater.

Performance of and methanogenic communities involved in an innovative anaerobic process for the treatment of food wastewater in a pilot plant.

In this study, dual-cylindrical anaerobic digesters were designed and built on the pilot plant scale for the improvement of anaerobic digestion efficiency. The removal efficiency of organics, biogas productivity, yield, and microbial communities was evaluated as performance parameters of the digester. During the stable operational period in the continuous mode, the removal efficiencies of chemical oxygen demand and total solids were 74.1 and 65.1%, respectively. Biogas productivities of 63.9 m(3)/m(3)-FWW and 1.3 m(3)/kg-VSremoved were measured. The hydrogenotrophic methanogen orders, Methanomicrobiales and Methanobacteriales, were predominant over the aceticlastic methanogen order, Methanosarcinaceae, probably due to the tolerance of the hydrogenotrophs to environmental perturbation in the field and their faster growth rate compared with that of the aceticlastics.

Population dynamics of methanogens and methane formation associated with different loading rates of organic acids along with ammonia: redundancy analysis.

In anaerobic processes, the population dynamics of methanogens in the methanogenic stage were monitored along with hydraulic retention times (HRTs) shift. Decreasing HRTs increased the loading rates of volatile fatty acids (VFAs) and ammonia. Methanomicrobiales (MMB) began to be dominant at longer than 12.5 days HRT, Methanosarcinales (MSL) were dominant at 8, 10, and 12.5 days HRT, and Methanobacteriales (MBT) were dominant at shorter than 6 days HRT. Increased loading rates of VFAs and ammonia increased MBT, decreased MMB, and had no significant effect on MSL. Maximal daily methane production was observed at 1.57 L/L when MSL copy numbers also reached 3.60 × 10(7) copy/mL as a peak, which were expressed as positive correlation between DMA and MSL. No sooner had methane yield (MY) increased from 1.15 to 1.32 L/g VSremoved along with HRT reduction from 25 to 22.5 days, then MY gradually decreased from 1.32 to 0.04 L/g VSremoved.

Effects of temperature and pH on the biokinetic properties of thiocyanate biodegradation under autotrophic conditions.

The simultaneous effects of temperature and pH on the biokinetic properties of thiocyanate biodegradation under mixed-culture, autotrophic conditions were investigated using response surface analysis (RSA) combined with biokinetic modeling. A partial cubic model, based on substrate inhibition biokinetics, was constructed for each kinetic coefficient in Andrew model (i.e., maximum specific growth rate (µ(m)), saturation coefficient (K(S)), and substrate inhibition coefficient (K(SI))). Each model proved statistically reliable to approximate the responses of the kinetic coefficients to temperature and pH changes (r(2) > 0.8, p < 0.05). The response surface plots demonstrated that the biokinetic coefficients change with respect to temperature and pH significantly and in different ways. The model response surfaces were substantially different to each other, indicating distinct correlations between the independent (temperature and pH) and dependent (model response) variables in the models. Based on the estimated response surface models, temperature was shown to have significant effects on all biokinetic coefficients tested. A dominant influence of temperature on µ(m) response was observed while the interdependence of temperature and pH was apparent in the K(S) and K(SI) models. Specific growth rate (µ) versus substrate (i.e., thiocyanate) concentration plots simulating using the obtained response surface models confirmed the significant effects of temperature and pH on the microbial growth rate and therefore on the thiocyanate degradation rate. Overall, the response surface models able to describe the biokinetic effects of temperature and pH on thiocyanate biodegradation within the explored region (20-30 °C and pH 6.0-9.0) were successfully constructed and validated, providing fundamental information for better process control in thiocyanate treatment.

Common key acidogen populations in anaerobic reactors treating different wastewaters: molecular identification and quantitative monitoring.

Bacterial population dynamics during the start-up of three lab-scale anaerobic reactors treating different wastewaters, i.e., synthetic glucose wastewater, whey permeate, and liquefied sewage sludge, were assessed using a combination of denaturing gradient gel electrophoresis (DGGE) and real-time PCR techniques. The DGGE results showed that bacterial populations related to Aeromonas spp. and Clostridium sticklandii emerged as common and prominent acidogens in all reactors. Two real-time PCR primer/probe sets targeting Aeromonas or C. sticklandii were developed, and successfully applied to quantitatively investigate their dynamics in relation to changes in reactor performance. Quantitative analysis demonstrated that both Aeromonas- and C. sticklandii-related populations were highly abundant for acidogenic period in all reactors. Aeromonas populations accounted for up to 86.6-95.3% of total bacterial 16S rRNA genes during start-up, suggesting that, given its capability of utilizing carbohydrate, Aeromonas is likely the major acidogen group responsible for the rapid initial fermentation of carbohydrate. C. sticklandii, able to utilize specific amino acids only, occupied up to 8.5-55.2% of total bacterial 16S rRNA genes in the reactors tested. Growth of this population is inferred to be supported, at least in part, by non-substrate amino acid sources like cell debris or extracellular excretions, particularly in the reactor fed on synthetic glucose wastewater with no amino acid source. The quantitative dynamics of the two acidogen groups of interest, together with their putative functions, suggest that Aeromonas and C. sticklandii populations were numerically as well as functionally important in all reactors tested, regardless of the differences in substrate composition. Particularly, the members of Aeromonas supposedly play vital roles in anaerobic digesters treating various substrates under acidogenic, fermentative start-up conditions.

A comprehensive microbial insight into two-stage anaerobic digestion of food waste-recycling wastewater.

Microbial community structures were assessed in a two-stage anaerobic digestion system treating food waste-recycling wastewater. The reactors were operated for 390 d at 10 different hydraulic retention times (HRTs) ranging from 25 to 4 d. Stable operation was achieved with the overall chemical oxygen demand (COD) removal efficiency of 73.0-85.9% at organic loading rate of up to 35.6 g COD/L·d. Performance of the acidogenic reactors, however, changed significantly during operation. This change coincided with transition of the bacterial community from one dominated by Aeriscardovia- and Lactobacillus amylovorus-related species to one dominated by Lactobacillus acetotolerans- and Lactobacillus kefiri-like organisms. In methanogenic reactors, the microbial community structures also changed at this stage along with the shift from Methanoculleus- to Methanosarcina-like organisms. This trend was confirmed by the non-metric multidimensional scaling joint plot of microbial shifts along with performance parameters. These results indicated that the overall process performance was relatively stable compared to the dynamic changes in the microbial structures and the acidogenic performance.