Coenzyme F420 Activities Research Articles

Unveiling the dual faces of chitosan in anaerobic digestion of waste activated sludge

In this study, the roles of chitosan (CTS) in anaerobic digestion of Waste activated sludge (WAS) were investigated. The results show that the methane production potential of WAS is positively correlated with the CTS content. The presence of 30 g/kg total suspended solids CTS increased the cumulative methane production from 215 ± 1.52 to 272 ± 1.83 mL/g volatile suspended solids. The positively charged amino groups in CTS neutralize the hydroxyl and carboxyl groups of extracellular polymeric substances, which reduces the negative charge on the surface of sludge and promotes sludge agglomeration, thereby inhibiting the release of organic matter. CTS also inhibits hydrolysis and acidification by immobilizing hydrolases and acidulase enzymes. However, CTS flocculates humus to avoid its interference with electron transfer, thereby enhancing the activity of coenzyme F420 and methanogenesis. In addition, CTS increases the abundance of methanogens, which also contributes to methane production.

Insights of enhancing methane production under high-solid anaerobic digestion of wheat straw by calcium peroxide pretreatment and zero valent iron addition

Recent investigations verified CaO2 accelerated hydrolysis of lignocellulose, but its residue caused a harmful oxidizing environment. This study therefore proposed the combined CaO2 pretreatment and zero-valent iron (ZVI) addition to enhance high-solid anaerobic digestion of wheat straw, trying to eliminate negative effect of residual oxides. Effects of CaO2 pretreatment without/with ZVI addition on digestion performance were investigated. Results showed that in non-ZVI added digesters, as CaO2 dosage increased, total production of SCOD and VFAs increased linearly, while activities of coenzyme F420 and electron transport system were negatively correlated. Pretreatment using appropriate CaO2 dosage indirectly increased biogas production by promoting hydrolysis and acidification. Comparably, initial ORP in ZVI-added digesters sharply declined below −350 mV, which was suitable for methanogen growth. ZVI significantly improved activities of cellulase, hemicellulase, acetic kinase and coenzyme F420, with the highest improvement percentages of 138%, 48%, 35% and 58%, respectively. Since ZVI could provide electrons for conversion of CO2 to CH4, compared with non-ZVI added digesters (R0-R4), methane content in ZVI-added digesters (RZ0-RZ4) increased by 8.1%, 9.0%, 11.2%, 17.0% and 18.0% successively. Consequently, 0.6 g/g VS CaO2 pretreatment combined with 0.4 g/g VS ZVI addition achieved the maximum methane production, increasing by 35.6% compared to control digester.

Effects of PES and 2,4-DCP on the Extracellular Polymeric Substances and Microbial Community of Anaerobic Granular Sludge

The effects of polyether sulfone (PES) microplastics and 2,4-dichlorophenol (2,4-DCP) on the loosely-bound extracellular polymeric substances (LB-EPS) and tightly-bound EPS (TB-EPS) of anaerobic granular sludge were investigated. In addition, high-throughput sequencing technology was used to analyze the changes in the microbial community and gene functions in the anaerobic granular sludge. The results revealed that the chemical oxygen demand (COD) removal rates of the 2,4-DCP and PES+2,4-DCP experimental groups were 35% and 37%, which were 57% and 55% lower than that of the blank control group, while the COD removal rates of the PES experimental group remained around 90%. After the addition of the PES microplastics and 2,4-DCP, the protein and polysaccharide contents in the LB-EPS decreased compared with the control group, and the polysaccharide content in TB-EPS increased the least. In presence of the PES microplastics and 2,4-DCP, the activity of coenzyme F420 was inhibited. Through high-throughput sequencing, the microbial richness and diversity of the anaerobic granular sludge in the experimental group were reduced with the addition of the PES microplastics or 2,4-DCP. In the control group and the experimental group, the dominant bacteria at the phylum level were Proteobacteria (13.45%-44.47%), Firmicutes (6.86%-21.67%), and Actinobacteria (3.16%-18.11%). The abundance of β-Proteobacteria in the PES+2,4-DCP experimental group was reduced by 15.28%, while the abundance of γ-Proteobacteria increased by 28.44% compared with the control group. Based on the phylogenetic investigation of the communities using the reconstruction of unobserved states (PICRUSt) analysis, it was found that in the experimental group with the PES microplastics or 2,4-DCP, the genes related to the sludge energy metabolism function were 0.25%-0.72% more than the control group; therefore, the abundance of genes related to the transport function group decreased significantly.

Influence of polyether sulfone microplastics and bisphenol A on anaerobic granular sludge: Performance evaluation and microbial community characterization

The retention of polyether sulfone (PES) and bisphenol A (BPA) in wastewater has received extensive attention. The effects of PES and BPA on the removal of organic matter by anaerobic granular sludge were investigated. We also analyzed the changes in the electron transport system and the effects on the composition of extracellular polymeric substances (EPS), as well as alternations of the microbial community in the anaerobic granular sludge. In the experimental groups which received BPA, the removal of the chemical oxygen demand (COD) were significantly suppressed, which an average removal efficiency of less than 65%, 30% lower than that of the control group. In the loosely-bound EPS (LB-EPS) excitation-emission matrix (EEM) spectra, the absorption peak of tryptophan disappeared when the BPA pollutants was added, which it was present in the control group without added pollutants. The addition of PES and BPA also affected protease, acetate kinase, and coenzyme F420 activities in the anaerobic granular sludge. Especially, the coenzyme F420 reduced from 0.0045 to 0.0017 μmol/L in the presence of PES and BPA. The relative abundance of Spirochaetes decreased in the presence of PES and BPA, while the relative abundance of Bacteroidetes increased from 12.98% to 22.87%. At the genus level, in the presence of PES and BPA, the relative abundance of Acinetobacter increased from 2.20% to 9.64% and Hydrogenophaga decreased sharply from 15.58% to 0.12%.

Effect of liquid digestate recirculation on biogas production and enzyme activities for anaerobic digestion of corn straw

To accelerate the degradation of substrate, 50% liquid digestate recirculation (LDR) was used in the anaerobic digestion (AD) of corn straw. The effects of recirculation on the enzyme activities and biogas production were investigated by comparing with control reactor (ReactorCK). During the AD process, the fermentation system with 50% LDR was more stable. The average biogas and methane production in ReactorLDR were 7,891 mL·d-1 and 347 mL CH4·g-1 VSadded·d-1 respectively. The total volatile fatty acids (TVFAs) concentration in the two reactors both increased at first and then decreased with time. The LDR made the VFAs accumulation significant, especially propionic acid accumulation in 4 ∼ 16 days. The maximum peak value of cellulase, xylanase, dehydrogenase and coenzyme F420 activities in ReactorLDR were 0.51 mg·g-1·h-1, 0.29 mg·g-1·h-1, 4.88 mL·g-1·h-1 and 6.69 μmol·L-1, respectively, which were higher than that in ReactorCK. With or without recirculation, the concentration of TVFAs was positively correlated with cellulase, xylanase and dehydrogenase activities, while was negatively correlated with coenzyme F420 activity. Besides, a very significant correlation existed between hydrolase and dehydrogenase activities and daily biogas production in ReactorCK. And the peaks of cellulase, xylanase and dehydrogenase activities appeared ahead of the peak of daily biogas production with the LDR.

Octylphenol facilitates fermentative volatile fatty acids recovery from waste activated sludge

The presence of endocrine disruptor compounds (EDCs) in wastewater treatment plants has attracted widespread attention, but their potential impact on anaerobic fermentation of waste activated sludge (WAS) remains unclear. Therefore, this study aims to reveal the effect of typical EDC octylphenol (OP) on the recovery of volatile fatty acids (VFAs) in anaerobic fermentation. The results show that OP has a positive effect on the recovery of VFAs from WAS. The presence of 200 mg/kg dry sludge of OP increased the cumulative amount of VFAs from 3245 in the control (without OP) to 6828 mg COD/L. The increase in VFA production was mainly attributed to the accumulation of acetic acid, which rose from 1511 to 4425 mg COD/L, almost tripled. Further research found that OP promoted solubilization and hydrolysis by improving the biodegradability of WAS, and severely inhibited the methanogenesis process by inhibiting the activity of coenzyme F420, thereby significantly increasing the accumulation of acetic acid. These findings are of great significance to clarify the role of OP in anaerobic fermentation, and provide theoretical basis and guidance for the selection of target products in anaerobic fermentation of WAS containing OP.

Chemically Enhanced Primary Sludge as an Anaerobic Co-Digestion Additive for Biogas Production from Food Waste

In order to overcome process instability and buffer deficiency in the anaerobic digestion of mono food waste (FW), chemically enhanced primary sludge (CEPS) was selected as a co-substrate for FW treatment. In this study, batch tests were conducted to study the effects of CEPS/FW ratios on anaerobic co-digestion (coAD) performances. Both soluble chemical oxygen demand (SCOD) and protease activity were decreased, with the CEPS/FW mass ratio increasing from 0:5 to 5:0. However, it was also found that the accumulation of volatile fatty acids (VFAs) was eliminated by increasing the CEPS/FW ratio, and that corresponding VFAs concentrations decreased from 13,872.97 to 1789.98 mg chemical oxygen demand per L (mg COD/L). In addition, the maximum value of cumulative biogas yield (446.39 mL per g volatile solids removal (mL/g VSsremoval)) was observed at a CEPS/FW ratio of 4:1, and that the tendency of coenzyme F420 activity was similar to biogas production. The mechanism analysis indicated that Fe-based CEPS relived the VFAs accumulation caused by FW, and Fe(III) induced by Fe-based CEPS enhanced the activity of F420. Therefore, the addition of Fe-based CEPS provided an alternative method for FW treatment.

Process Analysis of Anaerobic Fermentation Exposure to Metal Mixtures

Anaerobic fermentation is a cost-effective biowaste disposal approach. During fermentation, microorganisms require a trace amount of metals for optimal growth and performance. This study investigated the effects of metal mixtures on biogas properties, process stability, substrate degradation, enzyme activity, and microbial communities during anaerobic fermentation. The addition of iron (Fe), nickel (Ni), and zinc (Zn) into a copper (Cu)-stressed fermentation system resulted in higher cumulative biogas yields, ammonia nitrogen (NH4+-N) concentrations and coenzyme F420 activities. Ni and Zn addition enhanced process stability and acetate utilization. The addition of these metals also improved and brought forward the peak daily biogas yields as well as increased CH4 content to 88.94 and 86.58%, respectively. Adding Zn into the Cu-stressed system improved the abundance of Defluviitoga, Fibrobacter and Methanothermobacter, the degradation of cellulose, and the transformation of CO2 to CH4. The bacterial and archaeal communities were responsible for the degradation of lignocelluloses and CH4 production during the fermentation process. This study supports the reutilization of heavy metal-contaminated biowaste and provides references for further research on heavy metals impacted anaerobic fermentation.

Cadmium Addition Effects on Anaerobic Digestion with Elevated Temperatures

Anaerobic fermentation with biogas as an energy source is influenced by the presence of heavy metals. However, the availability of the heavy metals is dependent on the digestion temperature. In this study, the impacts of Cd on the characteristics of biogas, substrate biodegradation, and enzyme activity during anaerobic co-digestion were investigated under varying digestion temperatures. The results showed that 1 mg/L initial Cd concentration improved cumulative biogas yields by 404.96%, 16.93%, and 5.56% at 55 °C, 45 °C, and 35 °C, respectively. In contrast, at low temperatures (25 °C), the yield decreased by 0.77%. In the 55 °C group, Cd addition improved the activity of cellulase (p < 0.05) and coenzyme F420 (p < 0.01). The total chemical oxygen demand (COD) during the peak period and the transformation of hydrolytic organic components into volatile fatty acids (VFAs) influenced the CH4 and biogas yields. There were no significant differences in cellulase, dehydrogenase, and coenzyme F420 activities with or without Cd addition when the digestion temperature was 45 °C, 35 °C, and 25 °C. Therefore, thermophilic digestion is recommended for the efficient degradation of Cd-contaminated biowaste. Moreover, the impact of metals on the performance of anaerobic digestion should be considered together with temperature conditions in future research and practice.

Nitrate addition improves hydrogen production from acidic fermentation of waste activated sludge

In this work, a low-cost alternative method (i.e., adding nitrate into WAS) to significantly enhance hydrogen production was reported. Experimental results showed that with an increase of nitrate addition from 0 to 362 mg/L, the maximal hydrogen production from acidic (pH 5.5) fermentation of WAS obviously increased from 12.6 ± 0.5 to 19.3 ± 0.9 mL per gram volatile suspended solids (VSS). The mechanism investigations illustrated more substrates were provided for subsequent hydrogen production. Although the nitrate added inhibited all the biological processes, its inhibition to the hydrogen consumption processes was much severer than that to the hydrogen production processes. The enzyme analyses on the long-term semi-continuous fermenters showed that the nitrate addition slightly inhibited the relative activities of protease, butyrate kinase, acetate kinase, CoA-transferase, and [FeFe] hydrogenase but largely suppressed the relative activities of coenzyme F420, carbon monoxide dehydrogenase, and adenylyl sulfate reductase.

Relationship analysis of anaerobic fermentation parameters exposed to elevated chromium (VI)

Heavy metals may affect anaerobic fermentation processes, which could result in variations in anaerobic fermentation parameters. In the present study, the impact of changing hexavalent chromium (Cr6+) concentrations on different anaerobic fermentation parameters was investigated. The results showed that adding Cr6+ affected fermentation efficiency since it elicited changes in enzyme activity as well as metabolic pathways. Adding Cr6+ (30 mg/L) resulted in significant positive correlation between coenzyme F420 activities, CH4 contents, and cumulative biogas yields. The results suggested Cr6+ enhanced biogas production by promoting the activity of coenzyme F420. Increasing the concentration of Cr6+ to 100 mg/L resulted in a significant correlation (P < 0.01) between the CH4 contents and cumulative biogas yields and oxidation–reduction potential and pH. At high concentrations, Cr6+ (500 mg/L) elicited parametric relationships dissimilar to those obtained using low Cr6+ concentrations, particularly on the hydrolysis stage. This study comprehensively demonstrated the influence of Cr6+ stress during the anaerobic fermentation process from a new insight and could provide critical references for further experimental design and data monitoring investigations. © 2019 American Institute of Chemical Engineers Environ Prog, 38: e13212, 2019

In-situ biogas upgrading by a stepwise addition of ash additives: Methanogen adaption and CO2 sequestration

Biogas from anaerobic digestion (AD) of waste activated sludge (WAS) limited its utilization due to low value-added. In this study, an innovative addition mode for ash known as stepwise addition was developed to enhance methane production and improve CO2 scavenge from AD of sludge. Experimental results confirmed stepwise addition of ash improved methane content to 79.4%, compared to control group (69.1%). Compared to Pulse addition and Control, the cumulative CH4 production was promoted by 39.2% and 35.4%, respectively. Investigation of the mechanism indicated that stepwise addition of ash could decrease hydrolytic and acidifying enzyme activities but increase activity of coenzyme F420, compared to pulse addition group. Furthermore, stepwise addition of ash not only increased the abundance of Methanomassiliicoccus (34.48%), but also promoted amounts of CO2 capture. This method ameliorate utilization availability of sludge ash for sludge anaerobic digestion through promoting cumulative methane production and increasing CO2 storage capacity.

How does copper stress influence the relationships among the anaerobic co-fermentation parameters?

The presence of heavy metals influences the efficiency of anaerobic fermentation and results in the variations of the relationships among the fermentation parameters. In this study, the impacts of elevated Cu2+ concentrations on relationships among biogas properties, process stability, substrate biodegradation, and enzyme activity were analysed by Pearson correlation analysis based on the experimental data of a mesophilic anaerobic co-fermentation with mixed acid pretreated Phragmites australis straw and raw cow dung as feedstocks. The results showed that in the absence of Cu2+, the cumulative biogas yields were positively related to pH values (0.780, p < 0.05) and negatively related to oxidation-reduction potential values (−0.909, p < 0.01) and cellulase activity (−0.937, p < 0.01). The coenzyme F420 activity was negatively related to volatile fatty acid (VFA) concentrations (−0.756, p < 0.05). In the presence of 30 mg/l Cu2+, correlation coefficients between the cumulative biogas yields and pH values, ammonia nitrogen (NH4+-N), VFA, chemical oxygen demand, hemicellulose, and cellulose were higher than the control group, indicating the efficient hydrolysis, acidogenesis, and acetogenesis stages. High Cu2+ concentrations (500 mg/l) resulted in almost completely different impacts on these relationships from the low Cu2+ concentrations, especially on the hydrolysis stage.

Process analysis of anaerobic fermentation of Phragmites australis straw and cow dung exposing to elevated chromium (VI) concentrations

Anaerobic fermentation is considered as a cost-effective way of biomass waste disposal. Chromium (Cr) is one of the heavy metals that often been blamed for unsatisfactory operation or failure of anaerobic fermentation. The impact of Cr (added as K2Cr2O7) on mesophilic anaerobic fermentation of Phragmites australis straw and cow dung was demonstrated by investigating the biogas properties, process stability, substrate degradation and enzyme activities during the fermentation process. The results showed that 30, 100 and 500 mg/L Cr6+ addition increased the cumulative biogas yields by up to 19.00%, 14.85% and 7.68% respectively, and brought forward the daily biogas yield peak. Meanwhile, the methane (CH4) content in the 30 (52.47%) and 100 (40.57%) mg/L Cr6+-added groups were generally higher than the control group (37.70%). Higher pH values (close to pH 7) and lower oxidation-reduction potential (ORP) values in the Cr6+-added groups after the 15th day indicated the better process stability compared to the control group. Taking the whole fermentation process into account, the promoting effect of Cr6+ addition on biogas yields was mainly attributable to better process stability, the enhanced degradation of lignin and hemicellulose, the transformation of intermediates into VFA, the higher coenzyme F420 activities and the efficient generation of CH4. These results demonstrate that an appropriate addition of Cr6+ could enhance the anaerobic fermentation which support the regulations utilizing of the Cr6+ contaminated biowaste.

Comparing the mechanisms of ZVI and Fe3O4 for promoting waste-activated sludge digestion

Anaerobic digestion is one of the most promising technologies to stabilize waste-activated sludge (WAS) and recover energy. However, the low efficiency of anaerobic digestion of WAS constrains its application. Supplementing zero valent iron (ZVI) and Fe3O4 in digesters could improve the sludge digestion performance, which has recently been extensively studied. However, the mechanisms behind this improvement remain unclear. In this study, the effects of ZVI and Fe3O4 on the four stages of anaerobic digestion of WAS (solubilization, hydrolysis, acidification and methanogenesis) were investigated. Results showed that ZVI had only a slight effect on the solubilization, hydrolysis and acidification processes, while ZVI significantly promoted the hydrogenotrophic methanogenesis, increasing methane production by 70%. Further investigation indicated that coenzyme F420 activity in the ZVI added reactor was 32.3% higher than in the blank. These results indicate that ZVI promoted anaerobic digestion of WAS through promoting hydrogenotrophic methanogenesis. On the other hand, Fe3O4 obviously promoted the solubilization, hydrolysis and acidification of sludge. Vast Fe2+ was detected in the aqueous phase of the Fe3O4 digester which was a result of dissimilatory iron reduction that can utilize complicated matter as a substrate. This was in agreement with the acceleration of the solubilization, hydrolysis and acidification of the sludge. However, the acetoclastic and hydrogenotrophic methanogenesis with Fe3O4 decreased by 27% and 22% compared to the Fe3O4-free digester, respectively. Further study indicated that Fe3O4 competed with CH3▪S▪CoM for electrons and thus inhibited the methanogenesis process.

Free ammonia enhances dark fermentative hydrogen production from waste activated sludge

Ammonium and/or free ammonia (the unionized form of ammonium) are generally thought to inhibit the activities of microbes involved in anaerobic digestion of waste activated sludge. It was found in this work, however, that the presence of ammonium (NH4+-N) largely enhanced dark fermentative hydrogen production from alkaline pretreated-sludge. With the increase of initial NH4+-N level from 36 to 266 mg/L, the maximal hydrogen production from alkaline (pH 9.5) pretreated-sludge increased from 7.3 to 15.6 mL per gram volatile suspended solids (VSS) under the standard condition. Further increase of NH4+-N to 308 mg/L caused a slight decrease of hydrogen yield (15.0 mL/g VSS). Experimental results demonstrated that free ammonia instead of NH4+-N was the true contributor to the enhancement of hydrogen production. It was found that the presence of free ammonia facilitated the releases of both extracellular and intracellular constituents, which thereby provided more substrates for subsequent hydrogen production. The free ammonia at the tested levels (i.e., 0–444 mg/L) did not affect acetogenesis significantly. Although free ammonia inhibited all other bio-processes, its inhibition to the hydrogen consumption processes (i.e., homoacetogenesis, methanogenesis, and sulfate-reducing process) was much severer than that to the hydrolysis and acidogenesis processes. Further investigations with enzyme analyses showed that free ammonia posed slight impacts on protease, butyrate kinase, acetate kinase, CoA-transferase, and [FeFe] hydrogenase activities but largely suppressed the activities of coenzyme F420, carbon monoxide dehydrogenase, and adenylyl sulfate reductase, which were consistent with the chemical analyses performed above.

Impact of a high ammonia-ammonium-pH system on methane-producing archaea and sulfate-reducing bacteria in mesophilic anaerobic digestion

A novel strategy for acclimation to ammonia stress was implemented by stimulating a high ammonia-ammonium-pH environment in a high-solid anaerobic digestion (AD) system in this study. Three semi-continuously stirred anaerobic reactors performed well over the whole study period under mesophilic conditions, especially in experimental group (R-2) when accommodated from acclimation period which the maximum total ammonia nitrogen (TAN) and free ammonia nitrogen (FAN) increased to 4921 and 2996mg/L, respectively. Moreover, when it accommodated the high ammonia-ammonium-pH system, the daily biogas production and methane content were similar to those in R-1 (the blank control to R-2), but the hydrogen sulfide (H2S) content lower than the blank control. Moreover, mechanistic studies showed that high ammonia stress enhanced the activity of coenzyme F420. The results of real-time fluorescent quantitative polymerase chain reaction (PCR) showed that ammonia stress decreased the abundance of sulfate-reducing bacteria and increased the abundance of methane-producing archaea.

Copper stressed anaerobic fermentation: biogas properties, process stability, biodegradation and enzyme responses.

The effect of copper (added as CuCl2) on the anaerobic co-digestion of Phragmites straw and cow dung was studied in pilot experiments by investigating the biogas properties, process stability, substrate degradation and enzyme activities at different stages of mesophilic fermentation. The results showed that 30 and 100mg/L Cu2+ addition increased the cumulative biogas yields by up to 43.62 and 20.77% respectively, and brought forward the daily biogas yield peak, while 500mg/L Cu2+ addition inhibited biogas production. Meanwhile, the CH4 content in the 30 and 100mg/L Cu2+-added groups was higher than that in the control group. Higher pH values (close to pH 7) and lower oxidation-reduction potential (ORP) values in the Cu2+-added groups after the 8th day indicated better process stability compared to the control group. In the presence of Cu2+, the degradation of volatile fatty acids (VFAs) and other organic molecules (represented by chemical oxygen demand, COD) generated from hydrolysis was enhanced, and the ammonia nitrogen (NH4+-N) concentrations were more stable than in the control group. The contents of lignin and hemicellulose in the substrate declined in the Cu2+-added groups while the cellulose contents did not. Neither the cellulase nor the coenzyme F420 activities could determine the biogas producing efficiency. Taking the whole fermentation process into account, the promoting effect of Cu2+ addition on biogas yields was mainly attributable to better process stability, the enhanced degradation of lignin and hemicellulose, the transformation of intermediates into VFA, and the generation of CH4 from VFA.

Influences of different substrates on simulated lignite biogas production

Using lignite samples, selected from Zhaotong basin, Yunnan province, China, as the parent source, simulating experiments of lignite biogas were conducted with 0.1% methanol, 5mg/L yeast extract and 0.2mol/L sodium acetate solutions as the exogenous substance respectively. Variation characteristics of gas production, gas composition, VFA content and activity of coenzyme F420 in the simulated process were analyzed to discuss the influence of different substrates on lignite biogas generation. The results show that 0.1% methanol and 5mg/L yeast extract solutions increase VFA contents in the biogas generation system (p<0.05) and inhibit coenzyme F420 and methanogen activities significantly, so they decrease both gas amounts (p<0.05) and CH4 contents (p<0.05). 0.2mol/L sodium acetate solution activates coenzyme F420 and methanogen activities and improves the efficiency of enzymatic reaction, so the gas quantity (p<0.05) and the CH4 content (p<0.01) increase significantly. Therefore, sodium acetate can be one kind of good exogenous substance for the generation of lignite biogenic gas.

Tolerance response to in situ ammonia stress in a pilot-scale anaerobic digestion reactor for alleviating ammonia inhibition

The anaerobic digestion (AD) of protein-rich substrates is generally inhibited by ammonia. In this study, ammonia-tolerant acclimation was exposed to a stepwise in situ ammonia stress during the continuous AD of solid residual kitchen waste by using a continuous stirred tank reactor with a 50L active volume. The reactor worked well during the acclimation process, with an average daily biogas production of 58L/d, an effluent soluble chemical oxygen demand of 7238mg/L, a volatile fatty acid (VFA) content of 578mg/L, and a VFA/alkalinity ratio of less than 0.4. Moreover, ammonia stress enhanced the activity of Coenzyme F420. The results of high-throughput 16S rDNA sequencing showed that ammonia stress increased the relative abundance of Firmicutes bacteria and hydrogenotrophic methanogens but decreased the abundance of acetotrophic methanogens. This microbial community shift was proposed to be an in situ response strategy for ammonia stress adaptation.