Actual pH Values Research Articles

Reinforcement of Different Sands by Low-pH Bio-Mineralization.

Different sands have significant influences on MICP reinforcement effects. Using calcium carbonate production and bioflocculation lag period as evaluation criteria, this study investigates the optimal theoretical pH values of bacterial solutions with different concentrations. We reinforced four different sands using MICP at the optimal theoretical pH, and based on permeability, moisture retention, raindrop erosion, wind erosion, penetration, and SEM tests, the influence of sand properties on low-pH MICP reinforcement was analyzed and the low-pH MICP mechanism was revealed. The results indicate the following: (1) The optimal theoretical pH values for bacterial solutions with concentrations of 0.67 × 108 cells/mL, 3 × 108 cells/mL, and 10 × 108 cells/mL are 4.5, 3, and 4, respectively. (2) With 0.67 × 108, 3 × 108, and 10 × 108 cells/mL bacterial solutions, the strength of tailings sand containing calcium salt was 21.15%, 44.42%, and 13.61% higher than that of quartz sand, respectively. The effective reinforcement depth of alkaline reclaimed sand was 10, 8, and 6 mm lower than that of neutral calcareous sand, respectively. The strength of fine tailings sand was 70.41%, 58.04%, and 22.6% higher than that of coarse reclaimed sand. The effective reinforcement depth of fine quartz sand was 6, 4, and 4 mm lower than that of coarse calcareous sand. (3) Low pH temporarily suppresses urease activity, delaying calcium carbonate flocculation and enhancing reinforcement uniformity. To achieve optimal reinforcement effects, adjusting the actual optimal pH values of bacterial solution based on sand properties is essential in engineering applications.

반응표면법에 의한 Lactiplantibacillus plantarum K79를 이용한 ACE(Angiotensin Converting Enzyme) 억제활성 향상을 위한 탈지유 발효조건 최적화

This study was conducted using response surface methodology (RSM) to elucidate fermentation conditions that will optimize ACE inhibitory activity using Lactiplantibacillus plantarum K79. Four independent variables [skim milk (with 1% added glucose) concentration (6%–14%), incubation temperature (32°C–42°C), incubation time (8–24 h), and amount of added starter (0.02%–0.2%)] were evaluated using five-level central composite design and response surface methodology to determine the optimum fermentation condition. The dependent variables were angiotensin converting enzyme (ACE) inhibitory activity (the value obtained from 102 diluted supernatant), and pH. The respective coefficients of determinations (R2) were 0.791 and 0.905 for ACE inhibitory activity and pH. The maximum ACE inhibitory activity was 90% under the following conditions: 10% skim milk (with 1% added glucose) concentration, 37°C incubation temperature, 17.8 h incubation time, and 0.2% added starter. Based on the RSM, using predicted best ACE conditions for fermentation of 13.49% skim milk (with 1% added glucose) with 0.0578% starter at 33.4°C for 21.5 h, the predicted ACE inhibitory activity and pH values were 86.69% and 4.6, respectively. Actual ACE inhibitory activity and pH values were 85.5% and 4.58, respectively.

Artificial Neural Network and Near Infrared Light in Water pH and Total Ammonia Nitrogen Prediction

Water quality plays an important role in aquaculture. The operation of a freshwater aquaculture fish farming is highly dependent on the ability to understand, monitor, and control the physical and chemical constituents of the water. pH and total ammonia nitrogen (TAN) levels are two critical water quality parameters that affect fish growth rate and health. However, pH and TAN levels are affected by uncontrollable factorse.g.weather, temperature, and biological processes occurring in the water. Therefore, it is important to monitor changes in pH and TAN levels frequently to maintain optimal conditions for freshwater habitats. Near infrared spectroscopy (NIR) has been extensively investigated as an alternative measurement approach for rapid quality control without sample preparation. Therefore, this research aims to evaluate the feasibility of machine learning combined with NIR light in predicting the water pH and TAN values of a fish farming system. The proposed system contains three main components i.e.a multi-wavelength light emitting diode (LED), a light sensing element, and a machine learning model i.e.artificial neural network (ANN). First, the transmitted NIR light with different wavelengths of water samples was measured using the proposed system. Then, the actual pH and TAN values of the water samples were quantified using conventional methods. Next, ANN was used to correlate the measured NIR transmittance with the pH and TAN values. The results show that ANN with four hidden neurons achieved the best prediction performance with a mean square error (MSE) of 0.1466 and 0.3136 and a correlation coefficient (R) of 0.8398 and 0.9560 for the pH and TAN predictions, respectively. These results show that ANNcoupled with NIR light can be promisingly developed for in situ water quality prediction without sample preparation.

Particle Swarm Optimization (PSO) Model for Hydroponics pH Control System

Nutrients are essential to optimise plant growth. However, adding fertiliser changes the pH of the nutrition solution. This would impact plant growth as each plant types requires a specific pH range to thrive. Due to the nonlinearity characteristics, pH neutralisation adjustment is difficult but essential. In addition, alkaline solutions are not completely dissociated due to the presence of acid. For these reasons, a mathematical model to estimate the solution's pH would help improve the alkaline and acidic delivery accuracy. This study represents a pH water neutralisation behaviour using Particle Swarm Optimisation algorithm (PSO). The project begins with input and output data acquisition leading to the development of the PSO model. The model fit and residual distribution have also been analysed for this model. The model's performance was accepted based on a correlation test because the lag signal exceeded 95% of the confidence interval. The model also recorded a very minimal error, and this proved that a good agreement is established between the predicted and actual pH values.

Chemistry and microbiology in sugar extraction

The stability of the sucrose molecule and the firmness of the tissue structure in the cossettes are of major concern when optimizing the operating conditions for the extraction system. For a given extraction system the retention time is more or less fixed, but the actual pH values and temperatures to be set across the system largely determine the extent to which both sugar gets lost by hydrolysis and the cossette structure deteriorates, particularly by dissolution of pectin. Furthermore, potential sugar loss by microbial infection in the extraction system needs to be controlled too. The influence of the pH value and temperature on these undesirable chemical and microbial reactions will be outlined in this paper, including the consequences for the subsequent processing steps. It can be concluded that the recommended optimal pH values and temperatures for operating the extraction system are a compromise between good and bad.

Seasonal changes in kinetic parameters of trypsin in gastric and agastric fish

The objective of the present study was to assess if trypsin, a key enzyme involved in protein digestion, presents some kind of functional adaptations to seasonal changes in water temperature in freshwater fish. In order to test this hypothesis, individuals of two fish species Carassius gibelio (agastric) and Perca fluviatilis (gastric) were sampled in the basin of Chany Lake (Siberia, Russia) at two different seasons (spring and summer). Apparent kinetic parameters (Km and Vmax) were determined for both species and seasons at the actual pH values in fish guts, and at actual temperatures. Results showed a significant effect of both the species and sampling season on the apparent kinetic parameters of trypsin. In the case of Prussian carp, Km and Vmax were lower for each assayed temperature (for 5 and 15°C the differences were significant) for fish sampled in summer when compared to those sampled in spring. In contrast, values of Km in perch tended to be lower in spring at 5 and 25°C but these differences were not significant, while Vmax showed a significant decrease in summer samples. This suggests a sort of functional adaptation of the same trypsin enzymes to seasonal changes, oriented to maximize protein digestion under variable conditions.

Spatiotemporal Quantification of Cytosolic pH in Arabidopsis Pollen Tubes.

Ion-specific probes and fluorescent indicators have been key in establishing the role of ion signaling, namely calcium, protons, and anions, in plant development, providing a robust approach for monitoring spatiotemporal changes in intracellular ion dynamics. The integration of protons/pH in signaling mechanisms is especially important as reports of their biological functions continue to expand; however, attaining quantitative estimates with high spatiotemporal resolution in single cells poses a major research challenge. Here, we detail the use of the genetically encoded pH-sensitive pHluorin reporter expressed in Arabidopsis thaliana pollen tubes to assess cytosolic measurements with calibration to provide actual pH values. This technique enabled us to identify critical phenotypes and establish the importance of tip-focused pH gradient for pollen tube growth, although it can be adapted to other experimental systems.

Preparation of sulfur-doped carbon quantum dots from lignin as a sensor to detect Sudan I in an acidic environment

To achieve a rapid and facile quantitative evaluation of Sudan I illegally added in ketchup, fluorescent carbon quantum dots with excellent stability in acidic environments are required as the actual pH value of ketchup is close to 4.0. In this paper, we developed a green approach to prepare sulfur-doped carbon quantum dots (SCQDs) via hydrothermal treatment of lignin, isolated from pre-hydrolysis liquor, in sulfuric acid solution. The resultant SCQDs from lignin possessed sulfur-containing groups, which exhibited excellent fluorescence with a quantum yield up to 13.5% and good stability in acidic environments with a wide pH range of 0-5.0. Therefore, the SCQDs were successfully employed as a sensor to detect Sudan I in acidic solutions with excellent selectivity and sensitivity. The linear range for Sudan I was 0-40 μM, while the limit of detection was 0.12 μM. In addition, the fluorescent indicator paper functionalized with SCQDs also showed outstanding selectivity to Sudan I. The proposed SCQD sensing system not only displayed application potential for quantitative evaluation of Sudan I dye in practical samples, but also provided a way to convert lignin-based waste into highly valued nanoscale materials.

Estimation of neonatal outcome artery pH value according to CTG interpretation of the last 60min before delivery: a retrospective study. Can the outcome pH value be predicted?

The aim of this study was to analyze whether the umbilical artery pH value can be estimated throughout CTG assessment 60min prior to delivery and if the estimated umbilical artery pH value correlates with the actual one. This includes analysis of correlation between CTG trace classification and actual umbilical artery pH value. Intra-and interobserver agreement and the impact of professional experience on visual analysis of fetal heart rate tracing were evaluated. This was a retrospective study. 300 CTG records of the last 60min before delivery were picked randomly from the computer database with the following inclusion criteria; singleton pregnancy >37weeks, no fetal anomalies, vaginal delivery either spontaneous or instrumental-assisted. Five obstetricians and two midwives of different professional experience classified 300 CTG traces according to the FIGO criteria and estimated the postnatal umbilical artery pH. The results showed a significant difference (p<0.05) in estimated and actual pH value, independent of professional experience. Analysis and correlation of CTG assessment and actual umbilical artery pH value showed significantly (p<0.05) diverging results. Intra- and interobserver variability was high. Intraobserver variability was significantly higher for the resident (p=0.001). No significant differences were detected regarding interobserver variability. An estimation of the pH value and consequently of neonatal outcome on the basis of a present CTG seems to be difficult. Therefore, not only CTG training but also clinical experience and the collaboration and consultation within the whole team is important.

Chelation-enhanced fluorescence of phosphorus doped carbon nanodots for multi-ion detection

The present paper reports on a chelation enhanced fluorescence (CHEF) effect that is observed on addition of certain metal ions to phosphorus doped carbon nanodots (P-CNDs). The effect is accompanied by a large shortwave shift of the emission peak. Highly passivated P-CNDs with sizes of around 3 nm were prepared from lactose and phosphoric acid, using a one-pot low temperature solvothermal method. The nanoparticles were purified according to polarity and size. The extent of blue shift and strength of enhancement depend on metal ions and actual pH value. For instance, the P-CND complex with Al(III) has a fluorescence that is shifted to shorter wavelengths, and the fluorescence quantum yield is enhanced from 12% (for the free P-CNDs) to almost 62% at 490 nm. The fluorescence is also enhanced and shifted by the ions Zn(II) and Cd(II). It is quenched by the ions Fe(II), Fe(III), Hg(II), Cu(II) and Sn(II), among others. The enhancement is attributed to the chelation of metal ions with the passivated surface functional groups of P-CNDs, mainly those of phosphorus. Phosphorous free CNDs (prepared via HCl instead of H3PO4) and low-passivated P-CNDs (prepared for longer period of time; typically 8 h) show no enhancement. The metal ion induced enhancement led to the design of a fluorometric assay for the detection of these ions. The detection limits are 4 nM for Al(III) and 100 nM for Zn(II). The two ions were quantified in spiked pharmaceutical formulations. Recoveries typically are 102% (for n = 7).

Real-Time Optical pH Sensor With CMOS Contact Imaging and Microfluidics

An optical contact pH sensor integrated with capillary microfluidics is proposed in this paper. The complementary metal-oxide–semiconductor sensing array detects the changes of light intensity after absorption by a phenol red-doped sol-gel filter, while the level of absorbance corresponds to a pH value of the analyte. The optical signal is analyzed by image processing to compare the change in intensity of the filter following sample introduction, thereby obtaining the actual pH value. Deposition methods of sol-gel are optimized and compared. A spin-coating screen-printing process is proposed and tested for creating thin and crack-free sol-gel patterns. Two similar phenol red-doped sol-gel filters are patterned on the same sensor array to collect more precise results. This system offers the capability to perform an optical-based multi-parametric detection. Capillary microfluidics is utilized to enable a real-time flow in and out of the sample, as well as, for establishing more precise control over the sample introduction.

Effect of weathering transformations of coal combustion residuals on trace element mobility in view of the environmental safety and sustainability of their disposal and use. I. Hydrogeochemical processes controlling pH and phase stability

Coal combustion residuals (CCRs) are one of the most abundant high-volume waste materials disposed in impoundments worldwide. Some methods of CCR recycling, e.g. their use as structural fill for low lying areas or as soil amendment, also expose this material to atmospheric conditions. Combustion processes result in concentration of trace elements in CCRs at about an order of magnitude compared to coal. In order to assess an effect of long-term weathering transformations of CCRs on trace element binding/release, a study has been carried out. It is based on the chemical composition of real pore solutions extracted from the most abundant primary alkaline Class F bituminous CCRs, 0 to >40 years old, sampled from the surface layer and vertical profiles at four different impoundments. In this part of the study, results of a hydrogeochemical simulation of the saturation state of real pore solutions with respect to mineral phases of CCRs with use of the PHREEQC program, related to actual pH values reflecting the full cycle of weathering transformations, have been discussed. This study is the first geochemical proof of the general trend towards a progressive acidification up to pH < 4 of primary alkaline CCRs due to release of protons during internal processes of formation of gibbsite and aluminosilicate minerals, buffered by carbonates at the alkaline - near-neutral stages, and followed by parallel dissolution and buffering by aluminosilicates at pH < 7 after carbonate depletion, to the level up to pH∼3.5–4.0. The intrinsic geochemical changes have resulted in the different susceptibility of trace elements to release and associated changes in risk to the environment at consecutive stages of weathering.

PH values and activity of digestive enzymes in the gastrointestinal tract of fish in Lake Chany (West Siberia)

Optimum pH of various digestive enzymes and physiological pH values were determined in the gastrointestinal tract of fish species, such as goldfish Carassius auratus gibelio, ide Leuciscus idus, wild carp Cyprinus carpio, perch Perca fluviatilis, and zander Sander lucioperca. Physiological values of pH in the stomach of perch and zander and in different parts of the intestine of all studied fish species range within 3.5–4.5 and 6.5–7.2, respectively. The maximum values of the activity of alkaline protease and nonspecific lipase and esterase are recorded at pH 8–9; the maximum acid protease activity is recorded at pH 2–3. The optimum pH activity of alkaline protease and nonspecific lipase and esterase do not correlate with actual pH value in the digestive tract of fish. Two peaks of α-amylase activity are observed at pH 7 and 9.

The factor time in fetal heart rate monitoring and the detection of acidosis using the WAS score.

Using the naked eye evaluation of fetal heart rate (fhr) patterns remains difficult and is not complete. Computer-aided analysis of the fhr offers the opportunity to analyze fhr patterns completely and to detect all changes due to hypoxia and acidosis. It was the goal of this study to analyze the factor time in fetal monitoring and to evaluate the association between the fhr and the actual pH values in arterial umbilical blood. During a period of 11 years the FHR signals (i. e., the R-R interval of the F-ECG) of 646 fetuses were recorded with a CTG and simultaneously by a computer. The computer files were analyzed thereafter, i. e., the results did not influence our clinical management. To enter the study, all fetuses must have been delivered by the vaginal route--in consequence without a significant loss of fhr signals. During forceps and/or vacuum deliveries recordings were continued. If necessary a new electrode was inserted. In this study recordings of fetuses with chorioamnionitis, tracings of malformed neonates and tracings shorter than 30 min were excluded. Thus 484 recordings were left. We used our own computer programs written in MATLAB (USA). 3 parameters were determined electronically: 1) the mean fetal frequency [fhf, (bpm)], 2) the number of turning points (N/min) in the fhr, which we called 'microfluctuation' (micro) and 3) the oscillation amplitude, oamp (bpm). Measurements of the acid-base variables from arterial (UA) and venous (UV) blood were performed using RADIOMETER equipment (ABL500) and trained personnel. However, only the actual pHUA values were used in this study. To detect the influence of hypoxia and acidosis, all 484 cases were separated into 7 groups according to the actual pH(UA) value: 55 fetuses lying in a small non-acidotic "pH-window" (pH(UA)=7.290-7.310, mean=7.300±0.008) were used as 'controls'. In humans fhf, micro and the oamp behave differently during the last 30 min of delivery and with different fetal pHUA values: micro is early (at 0 min) decreased with fetal acidemia and is steadily deceasing (68-40 N/min) during vaginal delivery; the oamp--mainly due to decelerations--is increased from 35 up to 70 bpm during the last 30 min. Hypoxia and acidosis increase the amplitude and duration of decelerations; finally fhf shows only an insignificant reaction to acidemia but is decreased (from 135 to 110 bpm) overall with the course of time. Therefore the 3 characteristics of the fhr might be ranged according to their decreasing sensitivity to acidemia as follows: 1) fetal microfluctuation, 2) oscillation amplitude and 3) mean frequency. The 3 components of the fhr were used to invent and apply a score named the WAS score. This score increases the association between the actual pHUA values and the activity of the fetal heart. The 3 variables of the fhr mentioned above were rated differently; the 3 factors necessary to achieve this were computed electronically using an optimization program. The result is the WAS score: WAS=mean [frq*f(f)(v(j)) * micro*f(m)(v(j))/oamp*f(a)(v(j))](j=1,30). Using the last 30 min of delivery the correlation coefficient r of this score with pH(UA) reaches 0.645, P<< 0.001. The regression is linear in our 484 cases. Microfluctuation is the most sensible variable of the fetal heart followed by the oscillation amplitude and mean frequency. The WAS score offers the best correlation with the actual pH values measured in arterial umbilical blood.

In Vivo Determination of Organellar pH Using a Universal Wavelength-Based Confocal Microscopy Approach

Many essential cellular processes are affected by transmembrane H+ gradients and intracellular pH (pHi). The research of such metabolic events calls for a non-invasive method to monitor pHi within individual subcellular compartments. We present a novel confocal microscopy approach for the determination of organellar pHi in living cells expressing pH-dependent ratiometric fluorescent proteins. Unlike conventional intensity-based fluorometry, our method relies on emission wavelength scans at single-organelle resolution to produce wavelength-based pH estimates both accurate and robust to low-signal artifacts. Analyses of Ato1p-pHluorin and Ato1p-mCherry yeast cells revealed previously unreported wavelength shifts in pHluorin emission which, together with ratiometric mCherry, allowed for high-precision quantification of actual physiological pH values and evidenced dynamic pHi changes throughout the different stages of yeast colony development. Additionally, comparative pH quantification of Ato1p-pHluorin and Met17p-pHluorin cells implied the existence of a significant pHi gradient between peripheral and internal cytoplasm of cells from colonies occurring in the ammonia-producing alkali developmental phase. Results represent a step forward in the study of pHi regulation and subcellular metabolic functions beyond the scope of this study.

Gut pH as a limiting factor for digestive proteolysis in cultured juveniles of the gilthead sea bream (Sparus aurata)

After the development of the gastric function in juvenile fish, dietary proteins enter a two-phase digestive process comprising an acidic gastric phase followed by an alkaline intestinal phase. However, the main gastric protease, pepsin, is strictly dependent on the existence of a low-enough environmental pH. In 20-g gilthead sea bream, Sparus aurata, the mean minimal gastric pH is close to 4.5, while the mean pH in the duodenal portion of the intestine was nearly fixed at 6.5. The mean maximal gastric content of HCl was approximately 20microEq for a low-buffering diet. Gastric proteases were more severely affected than intestinal proteases when assayed at actual sub-optimal pH values, 4.5 and 6.5, respectively. When the gastric proteases of juvenile fish were pre-incubated with a citric acid buffer at pH 6.0, the activity at pH 4.5 was very low, whereas when they were pre-incubated with the same buffer at pH 3.0, the activity at pH 4.5 was significantly increased; this fact suggests a deficient activation of zymogens during the gastric digestion and points to a potential approach to improve protein digestion in juvenile gilthead sea bream.

Fenton oxidation treatment of tannery wastewater and tanning agents: synthetic tannin and nonylphenol ethoxylate based degreasing agent

In the present experimental work, the degradation and detoxification of two commercially important products being widely used in the tannery industry as synthetic tannin (ST) and degreasing agent (EP) containing 0.1% of nonylphenol ethoxylate (NPE) as well as degreasing wastewater from re-tanning was investigated using Fenton (FO) and Photo-Fenton (PFC) oxidation processes. FO and PFC oxidation experiments were performed in batch reactors for 30 min at pH 3 ± 0.2 and 40–45°C, considering the actual temperature and pH values of retanning bath effluents. For the FO experiments the effect of varying Fe2+ and H2O2 concentrations and UV-C light irradiation on oxidation measured by the parameters COD, UV254 and UV280 absorbancies was studied. Toxicity of untreated and FO, PFC-treated synthetic solutions to the freshwater cladoceran Daphnia magna was also tested. PFC provided appreciably high COD (>80%) and UV254 and UV280 (>90%) removals for ST. The toxicity could be drastically reduced in the PFC-treated ST sa...

Novel milk-based oral formulations: Proof of concept

The aim of this study is to develop milk-based formulations for ionized and unionized lipophilic drugs. Solubility studies of the following non-steroidal anti-inflammatory drugs (NSAIDs): mefenamic acid, tolfenamic acid, ketoprofen, meloxicam, tenoxicam and nimesulide in phosphate– and glycine–NaOH buffers at nominal pH 8–12, were performed. The solubilities of cyclosporine and danazol in water–ethanol solutions were studied. NSAIDs–, cyclosporine–, danazol–, aspirin–milk oral liquid formulations were prepared by adding the appropriate volume of (i) NSAIDs–alkaline buffer solutions, (ii) water–ethanol solutions of cyclosporine and danazol and (iii) aspirin aqueous solution to 150–200 ml of milk. All the non-steroidal anti-inflammatory drugs exhibited increased solubility in the alkaline buffers. The actual pH values (range 6.7–7.7) of the final NSAIDs–milk formulations were very close to milk pH. The higher ethanol content in ethanol–water mixtures increased the solubility of danazol and cyclosporine. A 15 mg meloxicam–, a 100 mg cyclosporine– and a 500 mg aspirin–milk formulation was administered orally to healthy volunteers. All these formulations showed a satisfactory in vivo performance. The strong buffering capacity of milk that was observed and the high solubility of unionized drugs in ethanol allow the preparation of drug–milk formulations with enhanced pharmacokinetic properties.

Early Larval Development of the Sydney Rock OysterSaccostrea glomerataUnder Near-Future Predictions of CO2-Driven Ocean Acidification

Anthropogenic emissions of carbon dioxide (CO2) from fossil fuel combustion and deforestation are rapidly increasing the atmospheric concentration of CO2 and reducing the pH of the oceans. This study shows that predicted near-future levels of ocean acidification have significant negative effects on early larval development of the Sydney rock oyster Saccostrea glomerata (Gould, 1850). CO2 was added to seawater to produce pH levels set at 8.1 (control), 7.8, and 7.6 (actual pH values were 8.11, 7.81, and 7.64, respectively). These treatments represent present-day surface ocean pH, as well as upper (Δ pH ≈ -0.3) and lower (Δ pH ≈ -0.5) pH predictions for the surface oceans in 2100. With decreasing pH, survival of S. glomerata larvae decreased, and growth and development were retarded. Larval survival decreased by 43% at pH 7.8 and by 72% at pH 7.6. Antero-posterior measurement (APM) was reduced by 6.3% at pH 7.8 and 8.7% at pH 7.6, and dorso-ventral measurement (DVM) was reduced by 5.1% atpH 7.8 and 7.5% at pH 7.6. The percentage of empty shells remaining from dead larvae decreased by 16% atpH 7.8 and by 90% at pH 7.6 indicating that the majority of empty shells dissolved within 7 days at pH 7.6. Scanning electron microscope images of 8-day-old larvae show abnormalities on the shell surface at low pH suggesting (1) problems with shell deposition, (2) retarded periostracum formation, and/or (3) increased shell dissolution. Larval life-history stages are considered particularly susceptible to climate change, and this study shows that S. glomerata larvae are sensitive to a high-CO2 world and are, specifically, negatively affected by exposure to pH conditions predicted for the world's oceans for the year 2100.

Influence of exogenous fibrolytic enzyme level and incubation pH on the in vitro ruminal fermentation of alfalfa stems

A series of in vitro experiments was carried out to examine the impact of enzyme application rate and incubation medium pH on the rate and extent of fermentation of alfalfa stems. In Experiment 1, a commercial enzyme product (Liquicell 2500, Specialty Enzyme and Biochemicals, Fresno, CA, USA) was added to alfalfa stems at six levels: 0, 0.51, 1.02, 2.55, 5.1, and 25.5 μl/g (control and L1–L5, respectively) to forage DM in a completely randomized design, with a factorial arrangement of treatments. Rate and extent of fermentation and apparent organic matter degradation (OMD) were determined in vitro, using a gas production technique. Addition of enzyme linearly increased (P<0.01) gas production for up to 12 h (68.9, 70.9, 67.6, 67.9, 71.9, and 74.9 ml/g OM for control, L1–L5, respectively) and OMD for up to 19 h incubation (0.425, 0.444, 0.433, 0.446, 0.443, and 0.451 for control, L1–L5, respectively), but no increases (P>0.05) were detected thereafter. In Experiment 2, the effect of the same enzyme as used previously (added at 0.51 μl/g forage DM, directly into the incubation medium), and buffer pH were examined using the ANKOM system, in a completely randomized design. Incubation medium pH was altered using 1 M citric acid, in order to obtain target initial pH values of 6.8 (control, no citric acid added), 6.2, 5.8, and 5.4. Actual initial pH values achieved were 6.72, 6.50, 6.20, and 5.72. Lowering the pH decreased (P<0.01) dry matter disappearance (DMD) at 18 h incubation (0.339, 0.341, 0.314, and 0.291 for 6.72, 6.50, 6.20, and 5.72, respectively), whereas enzyme addition increased (P<0.05) DMD at 24 h (0.363 versus 0.387 for control and enzyme-treated, respectively). Addition of enzyme increased (P<0.05) neutral detergent fibre (NDF), acid detergent fibre (ADF), and hemicellulose (HC) degradation at pH 6.50 (0.077 versus 0.117; 0.020 versus 0.051; 0.217 versus 0.270 for control and enzyme-treated NDF, ADF and hemicellulose degradation, respectively) and 6.72 (0.091 versus 0.134; 0.041 versus 0.079; 0.205 versus 0.261 for control and enzyme-treated NDF, ADF and HC degradation, respectively). It is concluded that the positive effects of this enzyme product were independent of the pre-treatment period, but pH influenced the responses to enzyme supplementation. Under the conditions of this experiment, exogenous fibrolytic enzymes seemed to work better at close to neutrality ruminal pH conditions.