Response surface methodology for process optimization in livestock wastewater treatment: A review.

With increasing demand for meat and dairy products, the volume of wastewater generated from the livestock industry has become a significant environmental concern. The treatment of livestock wastewater (LWW) is a challenging process that involves removing nutrients, organic matter, pathogens, and other pollutants from livestock manure and urine. In response to this challenge, researchers have developed and investigated different biological, physical, and chemical treatment technologies that perform better upon optimization. Optimization of LWW handling processes can help improve the efficacy and sustainability of treatment systems as well as minimize environmental impacts and associated costs. Response surface methodology (RSM) as an optimization approach can effectively optimize operational parameters that affect process performance. This review article summarizes the main steps of RSM, recent applications of RSM in LWW treatment, highlights the advantages and limitations of this technique, and provides recommendations for future research and practice, including its cost-effectiveness, accuracy, and ability to improve treatment efficiency.

Optimization of Simultaneous Nutrients and Chemical Oxygen Demand Removal from Anaerobically Digested Liquid Dairy Manure in a Two-Step Fed Sequencing Batch Reactor System Using Taguchi Method and Grey Relational Analysis.

The technological development for efficient nutrient removal from liquid dairy manure is critical to a sustainable dairy industry. A nutrient removal process using a two-step fed sequencing batch reactor (SBR) system was developed in this study to achieve the applicability of simultaneous removal of phosphorus, nitrogen, and chemical oxygen demand from anaerobically digested liquid dairy manure (ADLDM). Three operating parameters, namely anaerobic time:aerobic time (min), anaerobic DO:aerobic DO (mg L-1), and hydraulic retention time (days), were systematically investigated and optimized using the Taguchi method and grey relational analysis for maximum removal efficiencies of total phosphorus (TP), ortho-phosphate (OP), ammonia-nitrogen (NH3-N), total nitrogen (TN), and chemical oxygen demand (COD) simultaneously. The results demonstrated that the optimal mean removal efficiencies of 91.21%, 92.63%, 91.82%, 88.61%, and 90.21% were achieved for TP, OP, NH3-N, TN, and COD at operating conditions, i.e., anaerobic:aerobic time of 90:90 min, anaerobic DO:aerobic DO of 0.4:2.4 mg L-1, and HRT of 3 days. Based on analysis of variance, the percentage contributions of these operating parameters towards the mean removal efficiencies of TP and COD were ranked in the order of anaerobic DO:aerobic DO > HRT > anaerobic time:aerobic time, while HRT was the most influential parameter for the mean removal efficiencies of OP, NH3-N, and TN followed by anaerobic time:aerobic time and anaerobic DO:aerobic DO. The optimal conditions obtained in this study are beneficial to the development of pilot and full-scale systems for simultaneous biological removal of phosphorus, nitrogen, and COD from ADLDM.

Optimization and modeling of ammonia nitrogen removal from anaerobically digested liquid dairy manure using vacuum thermal stripping process.

During anaerobic digestion (AD) of liquid dairy manure, organic nitrogen converts to ammonia nitrogen (NH3-N) and subsequently escalates the NH3-N concentrations in manure. Among different available NH3-N removal processes treating anaerobically digested liquid dairy manure (ADLDM), vacuum thermal stripping is reported to be an effective technique. However, none of the studies have performed multi-parameter optimization, which is of utmost significance in maximizing process efficiency. In this study, critical operational parameters for vacuum thermal stripping of NH3-N from ADLDM were optimized and modeled for the first time via integrating grey relational analysis (GRA)-based Taguchi design, response surface methodology (RSM), and RSM-artificial neural network (ANN). The initial experimental trials conducted using the GRA coupled with Taguchi L16 orthogonal array revealed the order of influence of the process parameters on NH3-N removal as vacuum pressure (kPa) > temperature (°C) > treatment time (min) > mixing speed (rpm) > pH. The values of the first three most influential operating parameters were then further optimized and modeled using RSM and RSM-ANN models. Under the optimized conditions (temperature: 69.6 °C, vacuum pressure: 43.5 kPa, and treatment time: 87.65 min), the NH3-N removal efficiency of 93.58 ± 0.59 % was experimentally observed and was in line with the RSM and RSM-ANN models' predicted values. While the RSM-ANN model showed a better prediction potential than did the RSM model when compared statistically. Moreover, the nutrient contents (nitrogen, N and sulfur, S) of the recovered NH3-N as ammonium sulfate ((NH4)2SO4) were in reasonable agreement with the market-available (NH4)2SO4 fertilizer. The results presented in this study provide important insights into improving the treatment process performance and will help design and operate future pilot- and full-scale vacuum thermal stripping processes in dairy farms.

Technologies to recover nitrogen from livestock manure - A review.

Today, the livestock industry is considered to be one of the biggest emitters of ammonia in the world. The nitrogen present in livestock manure has been linked to the contamination of water bodies. Livestock manures contain a significant quantity of recoverable nitrogen. Recovering nitrogen from livestock manure can minimize negative environmental consequences. This also presents an opportunity to generate some revenue by converting the captured nitrogen to marketable nitrogenous fertilizers. Substantial research efforts have been made toward recovering nitrogen from raw as well as digested livestock manures over the last decade. Many novel technologies as well as ones that have already been implemented to recover nitrogen from municipal wastewaters have been studied for their use in the livestock sector. This paper reviews the common manure nitrogen-recovery technologies reported in the literature, summarizes their efficiencies, discusses their pros and cons, and identifies the areas for future research. Owing to their higher ammonia recovery efficiencies, relatively fewer drawbacks, lower costs, and ability to produce ammonium fertilizers, air stripping by direct aeration, thermal vacuum stripping, and gas-permeable membrane stripping appear to be the most viable choices for livestock farmers. Further studies should focus on the economic feasibility, long-term performance on the manure of varying strengths, and the quality of recovered nitrogenous products.

Nutrient starvation and light deprivation effects on starch accumulation in Landoltia punctata cultivated on anaerobically digested dairy manure.

Duckweed has been recognized for its potential of producing biomass on nutrients from waste streams. Our research has shown that strains of duckweed can be successfully cultivated on anaerobically digested (AD) dairy manure under controlled levels of nitrogen (N) and phosphorus (P). The objective of this study was to explore the maximization of starch accumulation in Landoltia punctata (Mey.) Les & Crawford strain 0128 under different cultivation conditions using AD dairy manure as the nutrient source. Experimental results have shown that the most influential factors for starch accumulation in L. punctata were the nutrient concentration and the appropriate scheduling of nutrient starvation at the right growth stages. In our study, nutrient starvation for starch accumulation in L. punctata was achieved by incorporating nutrient addition of appropriately diluted AD dairy manure sequentially in a controlled manner under a constant light intensity of 3,000 lx. It was observed that a starch concentration of 30% (w/w) within the L. punctata biomass was achieved with an initial total N of 57.1 mg L-1 and a total P of 6.7 mg L-1 after a 30-d cultivation. Under the abovementioned cultivation conditions, the duckweed L. punctata recovered 16.3% (±4.0%) of total N and 25.9% (±6.6%) of total P from AD manure into its biomass. It is concluded that L. punctata can be successfully cultivated on nutrients from dairy manure for starch production, which would achieve well-being for dairy farmers by producing a feedstock for biofuels while treating dairy wastewater in an environmentally friendly manner.

Author Correction: Dairy Manure Wastewater Remediation Using Non-airtight Digestion Pretreatment Followed by Microalgae Cultivation.

The original version of this article unfortunately contained a mistake.

Dairy Manure Wastewater Remediation Using Non-airtight Digestion Pretreatment Followed by Microalgae Cultivation.

The non-airtight digestion technology is emerging to be applied in the acidogenic phase for two-stage methane production. However, in this study, it was used to pretreat screened dairy manure (SDM) in order to provide microalgae cultivation with a substrate that might be more suitable for nutrient reduction, especially phosphorus. SDM was firstly underwent non-airtight digestion applying different dilution folds, i.e., blank (no dilution), 5-fold, 10-fold, and 15-fold. Total solids (TS), total dissolved solids (TDS), and chemical oxygen demand (COD) of the SDM were mostly reduced when there was no dilution applied. Five-fold dilution is the most beneficial one for ammonia reduction. Total phosphorus (TP) was reduced the most efficiently in the blank SDM. After the non-airtight digestion, 5-fold diluted original SDM, 5-fold diluted digested original SDM, and digested 5-fold diluted SDM were used to grow microalgae for 8 days. Microalgae grown in 5-fold diluted digested original SDM and digested 5-fold diluted SDM had better removal efficiencies in COD and NH4-N. From the monitoring of pH and TP during the 8-day culture period, it is found that pHs were peaked on the 4th day for microalgae grown in 5-fold diluted digested original SDM and digested 5-fold diluted SDM, corresponding to the maximal TP removal. Non-airtight digestion of SDM could help achieve better nutrient removal by microalgal cultivation in a shorter time span.

Microalgae Cultivation Using Screened Liquid Dairy Manure Applying Different Folds of Dilution: Nutrient Reduction Analysis with Emphasis on Phosphorus Removal.

A number of dairies in southern Idaho employed stationary inclined screens to separate large solid particles out of liquid dairy manure. In this way, the total solid content of the liquid dairy manure can drop about 20%. Solids in dairy wastewater cause high turbidities, which could block the incident light, a key factor in the microalgae cultivation process using wastewaters as culture media. In this study, screened liquid dairy manure was used as the microalgae Chlorella vulgaris culture media. The aim was to optimize the dilution folds for the best growth of Chlorella vulgaris and nutrients' reduction with a special focus on phosphorus removal and recovery. Four folds of dilution, designated as 5*, 10*, 15*, 20*, were applied to the liquid dairy manure to alleviate hindrance of the high turbidity together with the high ammonium. Microalgal cultivation removed a significant amount of turbidity and major nutrients. For differently diluted liquid dairy manures, although the initial turbidities varied a lot, the final removal rates were not significantly different, falling in the range of 88.11-91.73%. Chemical oxygen demand (COD) in the 5-fold diluted liquid dairy manure dropped from 6700 to 1200 mg/L, corresponding to a removal rate of 79.81%. For the 10-fold, 15-fold, and 20-fold diluted manures, Chlorella removed around 67-69% of the initial CODs. Total Kjeldahl nitrogen (TKN) was removed at rates ranging from 70.84 to 73.99% from the four differently diluted liquid dairy manures without significant differences. NH4-N was removed most efficiently by 88.92% from the 20-fold diluted liquid dairy manure, and the least at 68.65% from the 5-fold diluted one. Although the original total phosphorus (TP) concentrations were distinctive for each group, the TP removal rates stayed in the range of 52.16 to 65.22%. Scanning electron microscopy (SEM) and energy-dispersive spectrometry (EDS) analysis of the precipitates harvested from the microalgal cultivation suggested possible phosphate precipitate forms. The chelation of Ca or Mg cations by dissolved organic matter (DOM) under alkaline conditions caused by microalgae cultivation could explain the unsatisfactory phosphorus removals observed in this study.

Non-airtight Fermentation of Dairy Manure with Waste Potato Peels and Subsequent Phosphorus Recovery via Struvite Precipitation.

Two-phase anaerobic co-digestion of lignocellulosic crop residues with animal wastes can efficiently generate more biogas compared with the digestion of animal waste alone. Non-airtight fermentation of the mixed substrates is the primary step to hydrolyze complex organics and achieve simultaneous phosphorus release. Recycling phosphorus from tremendous animal wastes is remarkably meaningful regarding non-renewable resource recovery. In this study, the feasibility of a two-step process combining non-airtight fermentation of potato peels with dairy manure and the following struvite precipitation was explored. The hydrolysis and acidification process of the 6-day non-airtight mesophilic fermentation lowered pH to 6.4 under the highest mixed solid content of 4.8%; meanwhile, the ratio of reactive phosphorus to total phosphorus increased from 49.6 to 93.7% accordingly. Struvite formation was successfully induced by adjusting pH to 8.0 and 9.5. Under these two pHs, the precipitates were dominated by struvite as characterized by X-ray diffraction (XRD). Scanning electron microscopy and energy-dispersive spectrometry (SEM-EDS) results indicated that there should exist both struvite and calcium phosphate in the precipitates obtained under the two pHs. pH 8.0 precipitate should contain around 75% struvite, while the proportion rose to about 90% for pH 9.5 precipitate, based on the calculation of respective Mg/P and Ca/P molar ratios.

Nutrient Reduction of Dairy Manure Through Solid-Liquid Separation with Flocculation and Subsequent Microalgal Treatment.

High concentrations of dairy operations in Southern Idaho have brought up big challenges for proper manure management to alleviate the eutrophication stress. In order to explore more technologies confronting the high nutrient load in dairy manure, a sequential process combining enhanced solid-liquid separation through flocculation-centrifuge and the subsequent microalgal growth in the liquid part was studied in this study. Solid-liquid separation by flocculation-centrifuge process, using a natural flocculant chitosan and a flocculation aid kaolin, was optimized through response surface methodology (RSM) technique using central composite design (CCD) method. Under the optimal flocculation-centrifuge pretreatment, i.e., the maximal total suspended solid (turbidity) removal group, turbidity, COD, TKN, and TP have been removed by 92.7%, 72.6%, 58.7%, and 43.0%, respectively. Applying 2-fold dilution, the supernatant from this treatment was further used for microalgae Chlorella vulgaris cultivation. COD, TKN, and TP were further reduced by 82.2%, 90.1%, and 83.4%, respectively. Turbidity was largely removed from the original dairy manure, providing a relatively clear solution that became suitable for photo-mixotrophic culture of microalgae.

Non-airtight fermentation of sugar beet pulp with anaerobically digested dairy manure to provide acid-rich hydrolysate for mixotrophic microalgae cultivation.

Non-airtight fermentation of lignocellulosic agricultural residues with animal wastes is an emerging pretreatment method to produce acid-rich substrates in two-phase anaerobic digestion. Acid-rich hydrolysate could be an excellent feedstock for cultivating microalgae, therefore, the feasibility of a two-step process combining non-airtight fermentation of sugar beet pulp with anaerobically digested dairy manure and mixotrophic microalgae species Chlorella cultivation in the hydrolysate was explored in this study. The hydrolysis and acidification process of 8-day non-airtight fermentation produced up to 8.1 g/L volatile fatty acids under mesophilic condition. Microalgal growths in diluted hydrolysates were compared with that in diluted digested dairy manure (DDM) as a control using experimental data and fitted logistic models. Chlorella grown in the 10-fold diluted DDM showed an exponential decay, while Chlorella cultured in the 3-fold diluted hydrolysate demonstrated the best performance in terms of biomass density, which reached 2.17 g/L within a short period of time.

Pre-digestion to enhance volatile fatty acids (VFAs) concentration as a carbon source for denitrification in treatment of liquid swine manure.

Insufficient denitrification in biological treatment is often a result of the lack of a carbon source. In this study, use of the volatile fatty acids (VFAs) generated via pre-digestion as a carbon source to improve denitrification in sequencing batch reactor (SBR) treatment of liquid swine manure was investigated. The pre-digestion of swine manure was realized by storing the manure in a sealed container in room temperature and samples were taken periodically from the container to determine the VFA levels. The results showed that after 14 days of pre-digestion, the VFA level in the digested liquid was increased by 200%. A polynomial relationship for the VFA level in the digested manure with the digestion time was observed with a correlation coefficient being 0.9748. Two identical SBRs were built and operated on 8-h cycles in parallel, with one fed with pre-digested and the other raw swine manure. There were five phases included in each cycle, i.e., anaerobic (90 min), anoxic (150 min), anoxic/anaerobic (90 min), anoxic/aerobic (120 min), and settle/decant (30 min), and the feeding was split to 600 mL/200 mL and performed at the beginning of and 240 min into the cycle. The SBR fed on pre-digested swine manure achieved successful denitrification with only 0.35 mg/L nitrate left in the effluent, compared to 15.9 mg/L found in the effluent of the other SBR. Nitrite was not detected in the effluent from both SBRs. The results also indicated that there was no negative impact of feeding SBRs with the pre-digested liquid swine manure for treatment on the removal of other constituents such as total solids (TS), volatile solids (VS), suspended solids (SS), volatile suspended solids (VSS), and soluble chemical oxygen demand (COD). Therefore, anaerobic digestion as a pretreatment can be an effective way to condition liquid swine manure for SBR treatment to achieve sufficient nitrate removal.

Genome-wide analysis of autophagy-related genes (ARGs) in grapevine and plant tolerance to copper stress.

MAIN CONCLUSION: Grapevine autophagy-related genes (ARGs) include 35 members that have unique evolutionary backgrounds and expression patterns, with some of them responding to abiotic stresses, including copper stress. Autophagy is one of the most crucial self-regulating phenomena in livings organisms, including animals, plants, yeasts, etc. In the genomes of plants, like Arabidopsis, rice, tobacco, and barley, more than 30 autophagy-related genes (ARGs) have been found. These ARGs are involved in plant development, programed cell death, and the stress response process. In plants, and particularly in grapevine, high copper stress results from the application of the Bordeaux mixture, a widely used fungicide. However, the function of autophagy in plant tolerance to copper stress is unknown. Accordingly, in this study, a genome-wide analysis was performed to identify Vitis vinifera ARGs (VvARGs), and 35 VvARGs were detected. A gene family analysis revealed that the tandem and segmental duplication events played significant roles in the VvARG gene family expansion. Moreover, there was more intense signature of purifying selection for the comparison between grape and rice than between grape and Arabidopsis. In response to copper treatment, both the autophagosome number and malondialdehyde concentration increased during the initial 4 h post-treatment, and reached maximal values at 24 h. An expression analysis indicated that most VvARGs responded to copper stress at 4 h post-treatment, and some VvARGs (e.g., VvATG6, VvATG8i, and VvATG18h) exhibited responses to most abiotic stresses. These results provide a detailed overview of the ARGs in grapevine and indicate multiple functions of autophagy in fruit development and abiotic stresses in grapevine. The key ARG (e.g., ATG8i) should be investigated in more detail in grapevine and other plant species.

Characterization of miR061 and its target genes in grapevine responding to exogenous gibberellic acid.

MicroRNAs (miRNAs), as an important growth regulator, are also involved in gibberellic acid (GA) signaling, revealing much relationship between miRNAs and GA in various plant responses. Grape is highly sensitive to GA3, which plays a significant regulatory role in regulation of flower development, berry expansion, berry set, berry ripening, and seedlessness induction; further, it was found that grapevine miR061 (VvmiR061) is a GA3 responsive miRNA. In this study, grapevine REV (VvREV) and HOX32 (VvHOX32), two target genes of VvmiR061, were predicted, verified, and cloned; homologous conservation was analyzed in various plants. The expression profiles of both VvmiR061 and its target genes (VvREV and VvHOX32) under GA3 treatment were detected by qRT-PCR during grapevine flower and berry development. Results revealed that GA3 treatment has upregulated the transcription of VvREV and VvHOX32, while it downregulated the expression of VvmiR061. The function of VvmiR061 in cleaving target genes VvREV and VvHOX32 was diminished by GA3 treatment during flower developmental process. The results of this study exhibited the importance of VvmiR061 in regulating flower development and GA3 signaling pathway and also contributed some to the knowledge of small RNA-mediated regulation in grape.

Feeding schemes and C/N ratio of a laboratory-scale step-fed sequencing batch reactor for liquid swine manure treatment.

This study was undertaken to investigate the effect of two split feeding schemes (600 mL/200 mL and 400 mL/400 mL, designated as FS1 and FS2, respectively) on the performance of a step-fed sequencing batch reactor (SBR) in treating liquid swine manure for nutrient removal. The SBR was run on an 8-h cycle with a repeated pattern of anaerobic/anoxic/aerobic phases in each cycle and the two feedings always occurred at the beginning of each anaerobic phase. A low-level aeration was used (1.0 L/m3.sec) for the anoxic/aerobic phase to facilitate nitrification and phosphorus uptake while reducing the energy consumption. The results showed that FS1 reduced NH4+-N by 98.7% and FS2 by 98.3%. FS1 had 12.3 mg/L NO3-N left in the effluent, while FS2 had 4.51 mg/L. For soluble phosphorus removal, FS1 achieved 95.2%, while FS2 reached only 68.5%. Both feeding schemes achieved ≥ 95% removal of COD. A good power regression was observed between total nitrogen (sum of all three nitrogen species) and the carbon to nitrogen (C/N) ratio, with the correlation coefficients of 0.9729 and 0.9542 for FS1 and FS2, respectively, based on which it was concluded that higher C/N ratios were required to achieve higher nitrogen removal efficiencies.

Comparison on batch anaerobic digestion of five different livestock manures and prediction of biochemical methane potential (BMP) using different statistical models.

There is a lack of literature reporting the methane potential of several livestock manures under the same anaerobic digestion conditions (same inoculum, temperature, time, and size of the digester). To the best of our knowledge, no previous study has reported biochemical methane potential (BMP) predicting models developed and evaluated by solely using at least five different livestock manure tests results. The goal of this study was to evaluate the BMP of five different livestock manures (dairy manure (DM), horse manure (HM), goat manure (GM), chicken manure (CM) and swine manure (SM)) and to predict the BMP using different statistical models. Nutrients of the digested different manures were also monitored. The BMP tests were conducted under mesophilic temperatures with a manure loading factor of 3.5g volatile solids (VS)/L and a feed to inoculum ratio (F/I) of 0.5. Single variable and multiple variable regression models were developed using manure total carbohydrate (TC), crude protein (CP), total fat (TF), lignin (LIG) and acid detergent fiber (ADF), and measured BMP data. Three different kinetic models (first order kinetic model, modified Gompertz model and Chen and Hashimoto model) were evaluated for BMP predictions. The BMPs of DM, HM, GM, CM and SM were measured to be 204, 155, 159, 259, and 323mL/g VS, respectively and the VS removals were calculated to be 58.6%, 52.9%, 46.4%, 81.4%, 81.4%, respectively. The technical digestion time (T80-90, time required to produce 80-90% of total biogas production) for DM, HM, GM, CM and SM was calculated to be in the ranges of 19-28, 27-37, 31-44, 13-18, 12-17days, respectively. The effluents from the HM showed the lowest nitrogen, phosphorus and potassium concentrations. The effluents from the CM digesters showed highest nitrogen and phosphorus concentrations and digested SM showed highest potassium concentration. Based on the results of the regression analysis, the model using the variable of LIG showed the best (R(2)=0.851, p=0.026) for BMP prediction among the single variable models, and the model including variables of TC and TF showed the best prediction for BMPs (R(2)=0.913, p=0.068-0.075) comparing with other two-variable models, while the model including variables of CP, LIG and ADF performed the best in BMP prediction (R(2)=0.999, p=0.009-0.017) if three-variable models were compared. Among the three kinetic models used, the first order kinetic model fitted the measured BMPs data best (R(2)=0.996-0.998, rRMSE=0.171-0.381) and deviations between measured and the first order kinetic model predicted BMPs were less than 3.0%.

Field evaluation of wood bark-based down-flow biofilters for mitigation of odor, ammonia, and hydrogen sulfide emissions from confined swine nursery barns.

Two down-flow wood bark-based biofilters were evaluated for their effectiveness in treating odor, NH3 and H2S under actual swine farm conditions. The water requirement for maintaining proper media moisture contents (MC) under different ventilation rates and intervals were determined. The effect of media depth and MC on the biofilters' performance was also evaluated. The aerodynamic resistance on biofilters was studied using computational fluid dynamics (CFD) software. Water requirements for biofilters were obtained in the range of 3.8-556.0 L/m(3)/d for ventilation duration of 1-24 h/d (depending on the age of the pig and environmental conditions). The highest reductions in odor, NH3 and H2S, obtained in this study at empty bed residence times (EBRT) of 1.6-3.1 s, were 73.5-76.9%, 95.2-97.9% and 95.8-100.0%, respectively. The pressure drop was 28.8-68.8 Pa for a media depth of 381 mm at an EBRT of 1.6-3.1 s and an MC of 64-65%. The pressure drop followed a secondary order polynomial line with both airflow rate and media MC (R(2) = 0.927-0.982). The results of odor, NH3 and H2S reduction efficiency and pressure drop suggest a media depth of ≥254 mm, MC ≥ 35-50% and EBRT of 2-3 s for successful operations of the wood bark-based biofilters. A high correlation was found between the measured and predicted pressured drops obtained using CFD software (R(2) = 0.921, RMSE = 0.145).

Anaerobic digestion of Chinese cabbage waste silage with swine manure for biogas production: batch and continuous study.

The aim of this study was to investigate the potential for anaerobic co-digestion of Chinese cabbage waste silage (CCWS) with swine manure (SM). Batch and continuous experiments were carried out under mesophilic anaerobic conditions (36-38°C). The batch test evaluated the effect of CCWS co-digestion with SM (SM: CCWS=100:0; 25:75; 33:67; 0:100, % volatile solids (VS) basis). The continuous test evaluated the performance of a single stage completely stirred tank reactor with SM alone and with a mixture of SM and CCWS. Batch test results showed no significant difference in biogas yield up to 25-33% of CCWS; however, biogas yield was significantly decreased when CCWS contents in feed increased to 67% and 100%. When testing continuous digestion, the biogas yield at organic loading rate (OLR) of 2.0 g VSL⁻¹ d⁻¹ increased by 17% with a mixture of SM and CCWS (SM:CCWS=75:25) (423 mL g⁻¹ VS) than with SM alone (361 mL g⁻¹ VS). The continuous anaerobic digestion process (biogas production, pH, total volatile fatty acids (TVFA) and TVFA/total alkalinity ratios) was stable when co-digesting SM and CCWS (75:25) at OLR of 2.0 g VSL⁻¹ d⁻¹ and hydraulic retention time of 20 days under mesophilic conditions.

Effect of feed to microbe ratios on anaerobic digestion of Chinese cabbage waste under mesophilic and thermophilic conditions: biogas potential and kinetic study.

The objective of this study was to investigate the effect of the feed-to-microbe (F/M) ratios on anaerobic digestion of Chinese cabbage waste (CCW) generated from a kimchi factory. The batch test was conducted for 96 days under mesophilic (36.5 °C) (Experiment I) and thermophilic (55 °C) conditions (Experiment II) at F/M ratios of 0.5, 1.0 and 2.0. The first-order kinetic model was evaluated for methane yield. The biogas yield in terms of volatile solids (VS) added increased from 591 to 677 mL/g VS under mesophilic conditions and 434 to 639 mL/g VS under thermophilic conditions when the F/M ratio increased from 0.5 to 2.0. Similarly, the volumetric biogas production increased from 1.479 to 6.771 L/L under mesophilic conditions and from 1.086 to 6.384 L/L under thermophilic conditions when F/M ratio increased from 0.5 to 2.0. The VS removal increased from 59.4 to 75.6% under mesophilic conditions and from 63.5 to 78.3% under thermophilic conditions when the F/M ratio increased from 0.5 to 2.0. The first-order kinetic constant (k, 1/day) decreased under the mesophilic temperature conditions and increased under thermophilic conditions when the F/M ratio increased from 0.5 to 2.0. The difference between the experimental and predicted methane yield was in the range of 3.4-14.5% under mesophilic conditions and in the range of 1.1-3.0% under thermophilic conditions. The predicted methane yield derived from the first-order kinetic model was in good agreement with the experimental results.

microRNA, cell cycle, and human breast cancer.

The discovery of microRNAs as a novel class of gene expression regulators has led to a new strategy for disease diagnostics and therapeutics. Cell cycle, cell proliferation, and tumorigenesis are all regulated by microRNAs. Several general principles linking microRNAs and cancer have been recently reviewed; therefore, the current review focuses specifically on the perspective of microRNAs in control of cell cycle, stem cells, and heterotypic signaling, as well as the role of these processes in breast cancer. Altered abundance of cell cycle regulation proteins and aberrant expression of microRNAs frequently coexist in human breast cancers. Altered microRNA expression in breast cancer cell lines is associated with altered cell cycle progression and cell proliferation. Indeed, recent studies have demonstrated a causal role for microRNA in governing breast tumor suppression or collaborative oncogenesis. This review summarizes the current understanding of the role for microRNA in regulating the cell cycle and summarizes the evidence for aberrant microRNA expression in breast cancer. The new evidence for microRNA regulation by annotated genes and the involvement of microRNA in breast cancer metastasis are discussed, as is the potential for microRNA to improve breast cancer diagnosis and therapy.