Drop In pH Research Articles

PH dependencies of glycolytic enzymes of yeast under in vivo-like assay conditions.

Under carbon source transitions, the intracellular pH of Saccharomyces cerevisiae is subject to change. Dynamics in pH modulate the activity of the glycolytic enzymes, resulting in a change in glycolytic flux and ultimately cell growth. To understand how pH affects the global behavior of glycolysis and ethanol fermentation, we measured the activity of the glycolytic and fermentative enzymes in S. cerevisiae under in vivo-like conditions at different pH. We demonstrate that glycolytic enzymes exhibit differential pH dependencies, and optima, in the pH range observed during carbon source transitions. The forward reaction of GAPDH shows the highest decrease in activity, 83%, during a simulated feast/famine regime upon glucose removal (cytosolic pH drop from 7.1 to 6.4). We complement our biochemical characterization of the glycolytic enzymes by fitting the Vmax to the progression curves of product formation or decay over time. The fitting analysis shows that the observed changes in enzyme activities require changes in Vmax , but changes in Km cannot be excluded. Our study highlights the relevance of pH as a key player in metabolic regulation and provides a large set of quantitative data that can be explored to improve our understanding of metabolism in dynamic environments.

Synergistic Effect of Static Magnetic Field and Modified Atmosphere Packaging in Controlling Blown Pack Spoilage in Meatballs.

This study aimed to compare the microbial diversity in meatballs with or without blown pack spoilage (BPS) to determine the cause of BPS and to assess the synergistic effect of static magnetic field (SMF) and modified atmosphere packaging (MAP) to reduce the phenomenon of BPS. Results showed that the BPS group with a 2.26-fold larger volume and packaging containing 71.85% CO2 had Klebsiella spp. (46.05%) and Escherichia spp. (39.96%) as the dominant bacteria, which was different from the spoilage group. The results of isolation and identification of strains from the BPS group and their inoculation test confirmed that Klebsiella pneumoniae was the major strain-inducing BPS in meatballs due to its pack-swelling ability. SMF (5 mT) treatment combined with MAP (40%CO2 + 60%N2), which did not influence the sensory quality of meatballs, had a significant synergistic effect on preventing the increase in pack volume. Compared with the control group, this synergistic treatment effectively delayed bacterial growth, drop in pH, and the increase of TBARS. The findings of this study will provide further guidance for meatball manufacturers to adopt effective strategies to reduce the BPS of meatballs.

Toxoplasma gondii excretion of glycolytic products is associated with acidification of the parasitophorous vacuole during parasite egress.

The Toxoplasma gondii lytic cycle is a repetition of host cell invasion, replication, egress, and re-invasion into the next host cell. While the molecular players involved in egress have been studied in greater detail in recent years, the signals and pathways for triggering egress from the host cell have not been fully elucidated. A perforin-like protein, PLP1, has been shown to be necessary for permeabilizing the parasitophorous vacuole (PV) membrane or exit from the host cell. In vitro studies indicated that PLP1 is most active in acidic conditions, and indirect evidence using superecliptic pHluorin indicated that the PV pH drops prior to parasite egress. Using ratiometric pHluorin, a GFP variant that responds to changes in pH with changes in its bimodal excitation spectrum peaks, allowed us to directly measure the pH in the PV prior to and during egress by live-imaging microscopy. A statistically significant change was observed in PV pH during ionomycin or zaprinast induced egress in both wild-type RH and Δplp1 vacuoles compared to DMSO-treated vacuoles. Interestingly, if parasites are chemically paralyzed, a pH drop is still observed in RH but not in Δplp1 tachyzoites. This indicates that the pH drop is dependent on the presence of PLP1 or motility. Efforts to determine transporters, exchangers, or pumps that could contribute to the drop in PV pH identified two formate-nitrite transporters (FNTs). Auxin induced conditional knockdown and knockouts of FNT1 and FNT2 reduced the levels of lactate and pyruvate released by the parasites and lead to an abatement of vacuolar acidification. While additional transporters and molecules are undoubtedly involved, we provide evidence of a definitive reduction in vacuolar pH associated with induced and natural egress and characterize two transporters that contribute to the acidification.

Influence of Viscosity and Thickener on the Effects of Bleaching Gels.

This study investigated the influence of the viscosity and kind of thickener of 35% hydrogen peroxide bleaching gels on the tooth (color change, demineralization of enamel, and permeation) and on the gel [reactive oxygen species (ROS), pH, and peroxide concentration]. Two hundred forty specimens were divided into groups of bleaching gels with different thickeners (CAR, carbomer; ASE, alkali swellable emulsion; MSA, modified sulfonic acid polymer; SSP, semisynthetic polysaccharide; PAC, particulate colloids) in three viscosities (low: 50,000 cP; medium: 250,000 cP; high: 1,000,000 cP). Color change (ΔEab), demineralization of enamel by Knoop microhardness (KHN) reduction analysis, and peroxide permeation (PP) were analyzed in the specimens, while pH, peroxide concentration (PC), and ROS were evaluated in the gels. Data were analyzed by two-way ANOVA (α=0.05). The higher viscosity gels reduced ΔEab, PP, enamel softening, and ROS in relation to the lower viscosity gels. However, the drop in pH and PC were higher in the more viscous gels. Gels with MSA produced higher ΔEab compared with SSP and ASE. The PP was higher for PAC, and smaller for SSP and CAR. The KHN reduction was higher for CAR and smaller for PAC. The higher pH reduction was seen for ASE and CAR, and the smaller for SSP. The PC reduction was higher for SSP and smaller for CAR. More ROS were observed for MSA and fewer for ASE. Increased gel viscosity was associated with reduced color change, permeation, demineralization of enamel, and ROS, and led to increased peroxide decomposition and pH alteration during the treatment. The kind of thickener significantly interfered with the treatment effects.

Evaluation of the efficacy of some preventive measures on their ability to restrict fall in salivary pH after consumption of carbonated drinks

Introduction and Aim: Salivary pH is important for healthy enamel of the teeth. Consumption of carbonated beverages leads to a drop in salivary pH which favors the growth of microorganisms, leading to dental caries. This study evaluates the efficacy of preventive measures in resisting change of salivary pH after consumption of carbonated drink. Materials and Methods: The study consisted of four experiments (1 to 4), conducted with thirty-seven participants: consumption of drink, 1) directly from the glass, 2) Using a straw. Preventive measures post consumption of carbonated drink, 3) rinsing the mouth with water, and 4) chewing sugar free gum. The salivary pH was measured using pH paper narrow range at the basal level, and at <1, and 5 to 30 min post consumption of the drink. The data was analysed by descriptive statistics and the intergroup comparisons were done using ANOVA and Tukey test. Results: In all the four experiments there was an increase in salivary pH at the <1 min and a significant decrease in salivary pH at 5-20 min (p<0.001). There was no significant difference in the salivary pH between the two modes of drink consumption (p>0.05). Post consumption of drink, chewing gum resisted the fall in pH for a longer duration of 5-20 min than rinsing the mouth with water 5-10 min (p<0.000). Conclusion: Post consumption of the carbonated beverages, preventive measures such as rinsing the mouth with water and chewing gum resist the fall in pH of saliva. Chewing gum is more effective than rinsing the mouth with water.

Early postmortem degradation of actin muscle protein in Algerian Sahraoui dromedaries.

The present study aimed to evaluate actin degradation during the early postmortem time in Longissimus Lumborum muscle according to Sahraoui dromedary's age. A sample of eight males, young (2 years old) and adult (8 years old) dromedaries, was used to investigate meat quality traits and actin proteolysis during the conversion of muscle to meat. Results demonstrated higher pH values in young compared to adult with a polyphasic pH drop profile. While, age did not affect drip loss (DL) and the values at 72 h postmortem varied from 5 to 9%. Western blot revealed that actin proteolysis occurred since 1 h postmortem and that it was affected by age and postmortem time. In particular, the 32 and 25 kDa actin fragments could be potential markers of ongoing meat tenderization.

Effect of lactic acid fermentation on the nutritional quality and consumer acceptability of African nightshade.

African nightshade (ANS) is among many underexploited and neglected indigenous vegetables. This study assessed the effect of lactic acid fermentation (LAF) on nutritional and sensory quality in Solanum villosum (Sv) and Solanum scabrum (Ss). Spontaneously fermented (SF) and controlled fermented (CF) conditions using Lactobacillus plantarum LP90 and Leuconostoc mesenteroides LM58 were employed for 15 days and 120 h. From the fermented pickles, relish products were prepared using cooking oil and a variety of spices. The relish products were subjected to a consumer acceptability test. Results show a significant drop in pH to <3.5, increasing titratable acidity (TTA) to around 0.6 after 120 h and 15 days of CF and SF, respectively. LAF resulted in a 2.6–5 and 1.6–4.8‐fold significant rise in β‐carotene in pickles and their relish products. All pickles and relish products exhibited a significant decrease (p < .05) in vitamin C by 88.33%–95.90%. LAF significantly reduced total phenolic (26%– 43%) and Chlorophyll (16.45%–39.25%). On the other hand, LAF showed improvement in minerals content (P, Ca, Fe, and Zn) and reduction of tannin (76.27%–92.88%) and oxalate (77.33%–90%) levels. LAF relish products were highly preferred by the consumers, with S. villosum controlled fermented relish (SvCFR) leading. All fermented relishes were stable at ambient (27°C) and refrigeration (4°C) temperatures after 6 months of storage. Generally, LAF is an effective method for ANS preservation, with improved nutritional quality and safety. LAF can therefore be recommended to small‐scale farmers, processors, and households for ANS preservation. Ultimately, this method enhances the nutrition and sensory quality, safety, and livelihood.

In situ pH monitoring in accelerated cement pastes

The fast pH changes in ordinary Portland cement pastes (with and without C3A), caused by the addition of an Al2(SO4)3 based setting accelerator were in situ monitored by optical pH sensors. The results obtained clearly demonstrated the ability of this novel method to determine the pH with a high temporal resolution. Additionally, the distribution of the accelerator within the cement paste was assessed by fluorescence imaging with the use of a fluorescein tracer. Instantly after the addition of the accelerator and the subsequent formation of ettringite, the pH dropped from ~13 to ~10. The pH drop and recovery rate was controlled by the accelerator dosage and availability of Ca2+ and OH−. The methods presented would help to predict and assess the effects caused by chemical admixtures (e.g. setting accelerators) on the cement hydration progress.

Three-Electrode Study of Electrochemical Ionomer Degradation Relevant to Anion-Exchange-Membrane Water Electrolyzers.

Among existing water electrolysis (WE) technologies, anion-exchange-membrane water electrolyzers (AEMWEs) show promise for low-cost operation enabled by the basic solid-polymer electrolyte used to conduct hydroxide ions. The basic environment within the electrolyzer, in principle, allows the use of non-platinum-group metal catalysts and less-expensive cell components compared to acidic-membrane systems. Nevertheless, AEMWEs are still underdeveloped, and the degradation and failure modes are not well understood. To improve performance and durability, supporting electrolytes such as KOH and K2CO3 are often added to the water feed. The effect of the anion interactions with the ionomer membrane (particularly other than OH-), however, remains poorly understood. We studied three commercial anion-exchange ionomers (Aemion, Sustainion, and PiperION) during oxygen evolution (OER) at oxidizing potentials in several supporting electrolytes and characterized their chemical stability with surface-sensitive techniques. We analyzed factors including the ionomer conductivity, redox potential, and pH tolerance to determine what governs ionomer stability during OER. Specifically, we discovered that the oxidation of Aemion at the electrode surface is favored in the presence of CO32-/HCO3- anions perhaps due to the poor conductivity of that ionomer in the carbonate/bicarbonate form. Sustainion tends to lose its charge-carrying groups as a result of electrochemical degradation favored in basic electrolytes. PiperION seems to be similarly negatively affected by a pH drop and low carbonate/bicarbonate conductivity under the applied oxidizing potential. The insight into the interactions of the supporting electrolyte anions with the ionomer/membrane helps shed light on some of the degradation pathways possible inside of the AEMWE and enables the informed design of materials for water electrolysis.

Bioconversion of Terephthalic Acid and Ethylene Glycol Into Bacterial Cellulose by Komagataeibacter xylinus DSM 2004 and DSM 46604.

Komagataeibacter xylinus strains DSM 2004 and DSM 46604 were evaluated for their ability to grow and produce bacterial cellulose (BC) upon cultivation on terephthalic acid (TA) and ethylene glycol (EG), which are monomers of the petrochemical-derived plastic polyethylene terephthalate (PET). Both strains were able to utilize TA, EG, and their mixtures for BC synthesis, with different performances. K. xylinus DSM 2004 achieved higher BC production from TA (0.81 ± 0.01 g/L), EG (0.64 ± 0.02 g/L), and TA + EG mixtures (0.6 ± 0.1 g/L) than strain DSM 46604. The latter was unable to utilize EG as the sole carbon source and reached a BC production of 0.16 ± 0.01 g/L and 0.23 ± 0.1 g/L from TA alone or TA + EG mixtures, respectively. Further supplementing the media with glucose enhanced BC production by both strains. During cultivation on media containing TA and EG, rapid pH drop due to metabolization of EG into acidic compounds led to some precipitation of TA that was impregnated into the BC pellicles. An adaptation of the downstream procedure involving BC dissolution in NaOH was used for the recovery of pure BC. The different medium composition tested, as well as the downstream procedure, impacted the BC pellicles’ physical properties. Although no variation in terms of the chemical structure were observed, differences in crystallinity degree and microstructure of the produced BC were observed. The BC produced by K. xylinus DSM 2004 had a higher crystallinity (19–64%) than that of the strain DSM 46604 (17–53%). Moreover, the scanning electron microscopy analysis showed a higher fiber diameter for K. xylinus DSM 2004 BC (46–56 nm) than for K. xylinus DSM 46604 (37–49 nm). Dissolution of BC in NaOH did not influence the chemical structure; however, it led to BC conversion from type I to type II, as well as a decrease in crystallinity. These results demonstrate that PET monomers, TA and EG, can be upcycled into a value-added product, BC, presenting an approach that will contribute to lessening the environmental burden caused by plastic disposal in the environment.

SODIUM BICARBONATE DEFEATS CORONAVIRUS

Scientists emphasize that the human body must maintain a pH level between 7.35-7.45 to survive and function properly. Acidosis in the blood is characterized by a drop in pH to less than 7.35. Scientists also claim that the presence of acidosis in the blood facilitates virus entry into host cells, where it then thrives and replicates. According to chemistry, when diluted in an acidosis aqueous liquid, sodium bicarbonate absorbs the H+ ions and produces water and carbon dioxide gas.As a result, it restores the liquid state to equilibrium. Based on these ndings, we propose a new strategy for combating coronavirus. Rather than using drugs or vaccination to combat the virus, this strategy involves depleting the virus's resources. We use sodium bicarbonate to achieve this by bringing the pH of the blood back to normal. Athletes use sodium bicarbonate to improve their performance in a variety of exercises, conrming the safety of sodium bicarbonate on human bodies. One important difference between sodium bicarbonate and drugs and vaccination is that sodium bicarbonate is given to covid-19 patients to cure them as well as non-patients to bring their pH level to equilibrium and thus neutralize the effects of viruses. The current work is a solid scientic discovery; we recommend putting it through a clinical trial to determine the dosage of sodium bicarbonate required to cure each case. Its success could propel us to the forefront of the ght against SARS-CoV-2 and other viruses.

Light- and pH-dependent structural changes in cyanobacteriochrome AnPixJg2

Cyanobacteriochromes (CBCRs) are phytochrome-related photosensory proteins that play an essential role in regulating phototaxis, chromatic acclimation, and cell aggregation in cyanobacteria. Here, we apply solid-state NMR spectroscopy to the red/green GAF2 domain of the CBCR AnPixJ assembled in vitro with a uniformly 13C- and 15N-labeled bilin chromophore, tracking changes in electronic structure, geometry, and structural heterogeneity of the chromophore as well as intimate contacts between the chromophore and protein residues in the photocycle. Our data confirm that the bilin ring D is strongly twisted with respect to the B–C plane in both dark and photoproduct states. We also identify a greater structural heterogeneity of the bilin chromophore in the photoproduct than in the dark state. In addition, the binding pocket is more hydrated in the photoproduct. Observation of interfacial 1H contacts of the photoproduct chromophore, together with quantum mechanics/molecular mechanics (QM/MM)-based structural models for this photoproduct, clearly suggests the presence of a biprotonated (cationic) imidazolium side-chain for a conserved histidine residue (322) at a distance of ~2.7 Å, generalizing the recent theoretical findings that explicitly link the structural heterogeneity of the dark-state chromophore to the protonation of this specific residue. Moreover, we examine pH effects on this in vitro assembled holoprotein, showing a substantially altered electronic structure and protonation of the photoproduct chromophore even with a small pH drop from 7.8 to 7.2. Our studies provide further information regarding the light- and pH-induced changes of the chromophore and the rearrangements of the hydrogen-bonding and electrostatic interaction network around it. Possible correlations between structural heterogeneity of the chromophore, protonation of the histidine residue nearby, and hydration of the pocket in both photostates are discussed.Graphical abstract

Fluorescence evidence of annexin A6 translocation across membrane in model matrix vesicles during apatite formation

AbstractMatrix vesicles (MVs) are 100–300 nm spherical structures released by mineralization competent cells to initiate formation of apatite, the mineral component in bones. Among proteins present in MVs, annexin A6 (AnxA6) is thought to be ubiquitously distributed in the MVs’ lumen, on the surface of the internal and external leaflets of the membrane and also inserted in the lipid bilayer. To determine the molecular mechanism(s) that lead to the different locations of AnxA6, we hypothesized the occurrence of a pH drop during the mineralization. Such a change would induce the AnxA6 protonation, which in turn, and because of its isoelectric point of 5.41, would change the protein hydrophobicity facilitating its insertion into the MVs’ bilayer. The various distributions of AnxA6 are likely to disturb membrane phospholipid organization. To examine this possibility, we used fluorescein as pH reporter, and established that pH decreased inside MVs during apatite formation. Then, 4‐(14‐phenyldibenzo[a,c]phenazin‐9(14H)‐yl)‐phenol, a vibration‐induced emission fluorescent probe, was used as a reporter of changes in membrane organization occurring with the varying mode of AnxA6 binding. Proteoliposomes containing AnxA6 and 1,2‐Dimyristoyl‐sn‐glycero‐3phosphocholine (DMPC) or 1,2‐Dimyristoyl‐sn‐glycero‐3phosphocholine: 1,2‐Dipalmitoyl‐sn‐glycero‐3‐phosphoserine (DMPC:DPPS 9:1), to mimic the external and internal MV membrane leaflet, respectively, served as biomimetic models to investigate the nature of AnxA6 binding. Addition of Anx6 to DMPC at pH 7.4 and 5.4, or DMPC:DPPS (9:1) at pH 7.4 induced a decrease in membrane fluidity, consistent with AnxA6 interactions with the bilayer surface. In contrast, AnxA6 addition to DMPC:DPPS (9:1) at pH 5.4 increased the fluidity of the membrane. This latest result was interpreted as reflecting the insertion of AnxA6 into the bilayer. Taken together, these findings point to a possible mechanism of AnxA6 translocation in MVs from the surface of the internal leaflet into the phospholipid bilayer stimulated upon acidification of the MVs’ lumen during formation of apatite.

Role of Lysinibacillus sphaericus on aviation kerosene degradation and corrosion of 7B04 aluminum alloy

Microbial activity leads to degradation of kerosene, corrosion of pipeline and deterioration of stored products. This paper describes the use of the Fourier transform infrared spectroscopy (FT-IR), turbidimetry, pH measurements, electrochemical impedance spectroscopy (EIS), polarization curves and surface analysis to study the degradation of kerosene by Lysinibacillus sphaericus and its effect on the corrosion behavior of 7B04 aluminum alloy. A model strain was isolated from the contaminated kerosene and identified as L. sphaericus based on cloning of the 16 S rDNA gene and sequence analysis. FT-IR results showed that aliphatic protons in kerosene were degraded in the presence of L. sphaericus. SEM and EDS analysis showed that L. sphaericus colonized on the surface of aluminum alloy, formed biofilm and produced organic acids in physiological activities. Thus, the drop of pH resulted in the decrease of the cathodic depolarization, indicating the acceleration of corrosion. In addition, electrochemical measurements showed that the corrosion resistance of aluminum alloy was reduced, and the corrosion current density increased after immersion in the L. sphaericus system compared to the value in the sterile system, revealing the L. sphaericus promoted the corrosion of aluminum alloy.

Impact of simulated acid rain on the growth of three species Brassica integrifolia, Brassica rapa, Brassica juncea in Hanoi, Vietnam.

Over the past decade, the extent and magnitude of acid rain in Vietnam and other Asian countries have become more apparent. In this study, the effect of simulated acid rain (pH 5.0, 4.0, and 3.0) and control treatment (pH 6.0) are observed for three species Brassica integrifolia, Brassica rapa, and Brassica juncea in Hanoi. The pot experiment was conducted for 42days and arranged according to a randomized complete block design (RCBD), replicated 3 times with acid rain exposure being supplied every 4days. The results show that acid rain causes direct damage to leaves. Observations reveal white spots on leaves; leaves getting discolored and gradually turning yellow, curling leaf marginals, and turning dark blue, with the most severe symptoms being necrotic leaves. Parameters of the shoot and root length, leaf area, biomass, and chlorophyll content all decrease as pH drops. However, the accumulation of proline content in leaves tends to increase with greater acidity. In conclusion, Brassica rara has the highest resistance capability to acid rain compared with Brassica integrifolia and Brassica juncea, especially its proline content is the highest at pH 3.0 in three Brassicaceae species.

Contrasting intensity of aragonite dissolution and dolomite cementation in glacial versus interglacial intervals of a subtropical carbonate succession

AbstractAragonite and high‐Mg calcite are abundant in modern, neritic carbonate systems but almost absent in their fossil counterparts. Dissolution of these metastable mineral phases commonly leaves no visible trace in the sedimentary record, compromising the derivation of palaeoenvironmental information from the rock record. The upper 25 m of Integrated Ocean Drilling Program (IODP) Site U1460 on the outer ramp of the western Australian Shelf were investigated to study shallow burial (tens of metres) marine diagenesis in organic‐carbon poor sediments using microscopic, total organic carbon, biomarkers and mineralogical analysis in combination with porewater geochemistry. Aragonite dissolution is negligible at the seafloor but intensifies ca 5 m below, even though bulk porewaters are supersaturated for aragonite. This apparent contradiction likely results from dissolution in undersaturated microenvironments. Aragonite dissolution below 5 to 6 m is on average more intense in interglacial compared to glacial intervals. The presence of disseminated framboidal pyrite and porewater results indicate that minor sulphate reduction is active at IODP Site U1460. Sulphate reduction is probably limited by the low organic matter content (ca 0.2%). It is well‐known from the literature that incipient sulphate reduction can lead to a drop in pH and consequently to carbonate dissolution. It is therefore assumed that the slightly higher concentration of organic matter in the interglacial intervals allowed increased aragonite dissolution during sulphate reduction compared to glacial beds. Low amounts of dolomite cement (&lt;15%) start to form at the same depth (5 to 6 m) as aragonite dissolution intensifies. Dolomite formation and aragonite dissolution also show covariance on a metre‐scale below 5 to 6 m, indicating that a low carbonate saturation state might enhance dolomite formation. This mechanism provides an indirect link between dolomite formation, aragonite dissolution and orbital cycles. The outcome of this study, therefore, contributes to a better understanding of differential diagenesis in marine carbonates.

Effects of Lactic Acid Bacteria and Molasses Additives on Dynamic Fermentation Quality and Microbial Community of Native Grass Silage.

Ensiling native grass is an effective method to protect the nutritional quality of forage and alleviate feed shortages in the cold winter of the Inner Mongolian Plateau. To improve the usability of native grass resources as feed in China, the effects of lactic acid bacteria and molasses additions on the microbial population, fermentation quality, and nutritional quality of native grass during silage were investigated. Treatments were a control treatment with no additive (CK), lactic acid bacteria (L), molasses (M), and lactic acid bacteria in combination with molasses (L+M), all of which were stored at ambient temperature (17–28°C) for 7, 14, 30, and 60 days. The results showed that all additives improved nutritional value and fermentation quality with low pH and ammonia nitrogen (NH3–N) and high crude protein (CP) and water soluble carbohydrate (WSC) than control silage over the ensiling period. Compared with L or M silage, the L+M silage combination improved fermentability, as evidenced by higher LA content and a faster pH drop during the first 7 days of ensiling. With prolonged ensiling time, the combined addition of L and M could increase the count of desirable Lactobacillus, decrease microbial diversity, and inhibit the growth of undesirable microorganism, such as Clostridia, Escherichia, and Enterobacter abundance compared with silage treated with CK, L. or M. Application of L together with M could further improve the silage quality of native grass by altering bacterial community structure. In summary, the addition of lactic acid bacteria and molasses increased the relative abundance of Lactobacillus of native grass silage and improved fermentation quality.

Comparison of nano-TiO2 immobilization approaches onto biochar: Superiorities of click chemistry strategy and self-acceleration of pollutant degradation

To overcome the recovery challenge of nanoscale photocatalysts, great endeavor has been paid to explore effective nano-TiO2 immobilization approaches, but comprehensive comparison between these methods is still lacking. Herein, four approaches, namely impregnation-calcination, sol-gel, solvothermal route and click chemistry strategy were fully compared to immobilize nano-TiO2 onto biochar from the viewpoint of properties characterization, photocatalytic activity, structure stability and pollutant degradation pathway. It was found that, compared to other three methods, product obtained by click chemistry (CC-P25/BC) showed superior adsorption-photocatalysis synergy and persistent long-term stability. These superiorities were not attributed to pore structure, crystallinity or light absorption, but predominated by the robust chemical bonds between TiO2 and biochar, which served as an effective internal channel for electrons transportation. Besides, with CC-P25/BC as photocatalyst, a unique self-acceleration period was observed during methylene orange (MO) degradation. Via investigating MO degradation pathway and solution environment, we found that it was the strong photocatalytic activity of CC-P25/BC that selectively accelerated MO demethylation, thus leading to solution pH drop and subsequent MO adsorption enhancement and then degradation acceleration. Thus, this study confirmed the superiority of click chemistry in nanoscale photocatalyst immobilization, and affirmed the importance of pollutant degradation process in governing its degradation rate.

The influence of microbial transglutaminase on camel milk yogurt

This study investigates camel milk yogurts made with microbial transglutaminase (mTGase) at two different concentrations (3 and 6 U/g protein) and three different protein sources (micellar casein, whey protein concentrate, and sodium caseinate) and assesses their physical, chemical, and sensory properties. Of thirty samples, five were selected for further testing based on their viscosity and rapid pH drop during fermentation. During fermentation, many volatile compounds were formed, namely acetaldehyde, diacetyl, acetyl propionyl, ethanol, hexanal, and methane. Acetaldehyde percentages were lower with higher mTGase concentrations. All three milk protein powders increased the diversity of volatile compounds. Electrophoresis results showed that monomer band intensity decreased with higher mTGase concentrations. Lower-intensity monomer bands were formed at higher mTGase concentrations. Among the five optimal samples, the best microstructure was obtained in the sample produced with 6 U/g mTGase and 6.2 g/100 mL whey protein concentrate. The sample with the best sensory properties was prepared with 6 U/g mTGase and micellar casein. In conclusion, mTGase improved the gel structure and sensory properties of camel yogurt.

Metagenomics and network analysis elucidating the coordination between fermentative bacteria and microalgae in a novel bacterial-algal coupling reactor (BACR) for mariculture wastewater treatment

To achieve the goal of treating mariculture wastewater economically and efficiently, a novel bacterial-algal coupling reactor (BACR) integrating acidogenic fermentation and microalgae cultivation was firstly investigated for mariculture wastewater treatment. Volatile fatty acids (VFAs) generated in the dark chamber migrated into the photo chamber for microalgal utilization, which alleviated the pH drop and feedback inhibition of the acidogenic fermentation. The maximum dry cell weight (DCW) of microalgae was 1.46 g/L, and pollutants such as chemical oxygen demand (COD), ammonium (NH4+-N) and total phosphorus (TP) in the BACR were effectively removed under the mixotrophic culture condition. Furthermore, bacterial community profiles and functional genes in the BACR and single acidogenic fermentation reactor were identified. Compared with the single acidogenic fermentation reactor, most of the fermentative bacteria (e.g., Ruminococcus, Christensenellaceae R-7 group, Exiguobacterium, Pseudomonas and Levilinea) were enriched by the BACR. From the genetic perspective, the abundances of dominant genes (ackA, acs and atoD) associated with acetic, propionic and butyric acid production were greatly enhanced in the BACR. In the fatty acid biosynthesis pathway (ko00061), three kinds of high-abundance acetyl-CoA carboxylase genes and eight kinds of downstream functional genes were up-regulated in the BACR. Finally, based on co-occurrence network analysis, the coordination between fermentative bacteria and microalgae in the BACR was revealed. This study provided a deep insight into the advantage and potential of the BACR in mariculture wastewater treatment.