Lactic Acid pH Research Articles

Dynamics of fermentation quality, bacterial communities, and fermentation weight loss during fermentation of sweet sorghum silage

BackgroundSweet sorghum is used mainly as an energy crop and feed crop in arid and semiarid regions, and ensiling is a satisfactory method for preserving high-quality sweet sorghum. The aim of this study was to reveal the dynamics of the fermentation quality, bacterial communities, and fermentation weight loss (FWL) of sweet sorghum silage during fermentation.MethodsSweet sorghum was harvested at the first inflorescence spikelet stage and ensiled without (CK) or with lactic acid bacterial (LAB) additives (L). After ensiling, samples were collected on days 0, 1, 3, 5, 15, 40, and 100 to assess the fermentation quality, bacterial communities, and FWL.ResultsFor CK and L, on day 1, the pH was 5.77 and 5.57, respectively, and the lactic acid (LA) was 1.30 and 2.81 g/kg dry matter (DM), respectively. Compared with CK, L had a lower pH and higher LA from days 1 to 5 (P < 0.05), a lower FWL from days 5 to 100 (P < 0.05), and a greater abundance of Lactiplantibacillus from days 1 to 15 (P < 0.05). The main bacterial genera were Leuconostoc and Weissella in CK and Lactiplantibacillus, Leuconostoc, and Weissella in L on day 1; Lactiplantibacillus in all silages from days 3 to 40; and Lactiplantibacillus and Lentilactobacillus in all silages on day 100.ConclusionsSweet sorghum silage fermented relatively slowly during the first day. Moreover, inoculation with LAB accelerated fermentation and optimized bacterial communities during the initial fermentation phase. Inoculation with LAB also reduced the silage FWL, and the LAB succession relay occurred in the silage throughout the fermentation process.

Demineralized dentin characteristics after application of Mauli banana stem gel

Background: Demineralization of dentin is a condition of dissolving minerals in peritubular dentin due to exposure to acids that release hydroxyapatite ions. To prevent dentin demineralization, a therapeutic agent that can inhibit the dissolution ability of hydroxyapatite ions is needed. One therapeutic agent that can be used is the Mauli banana (MB) stem gel. Purpose: To observe the characteristics of dentin demineralization after the use of MB stem extract gel. Method: Mandibular incisor bovine teeth were demineralized with lactic acid pH 4.5 for 72 hours and then treated with 25%; 37.5%; 50%; and 62.5% MB gel and Chlorhexidine 2% for one minute. All samples were soaked in artificial saliva with 1 mg/ml saliva of collagenase enzyme for 24 hours. The characteristic of dentin demineralization was observed by using scanning electron microscope/electron dispersive X-ray spectroscopy (SEM-EDX). Results: The SEM image in the control, Chlorhexidine, 25%; 37.5%; 50%; and 62.5% MB gel groups showed dentinal tubules of about 3.67–4.94 µm; 3.55–4 µm; 4.18–5.6 µm; 2.28–2.86 µm; 3.29–3.81 µm; and 2.42–3.17 µm in size. The EDX test found carbon (C), nitrogen (N), oxygen (O), sodium (Na), phosphorous (P), chlorine (Cl), and calcium (Ca) in all groups. The one-way Analysis of Variance (ANOVA) test results showed significant differences in the levels of C, N, O, Cl, and Ca between all groups, while the Na showed no significant differences. Conclusion: The MB can inhibit the demineralization of bovine dentin based on the decrease in the size of the dentinal tubules and increasing the C, O, P, and Ca.

Effects of Different Cutting Stages and Additives on the Fermentation Quality and Microbial Community of Sudangrass (Sorghum sudanense Stapf.) Silages

(1) Background: Previous studies have indicated that ferulic acid esterase (FAE), cellulase and xylanase have synergistic effects in lignocellulose degradation, and the cutting stage has a major impact on silages. Whether these additives affect the silages at different cutting stages is unclear. (2) Methods: Sudangrass height at the tested cutting stages was 1.8 m (S1) and 2.0 m (S2). The silage from the two cutting stages was treated with FAE-producing Lactobacillus plantarum (LP), cellulase and xylanase (CX) and a combination of LP and CX (LP+CX) for 30 and 60 days. (3) Results: Compared with CK, adding LP+CX significantly decreased the pH and the content of neutral detergent fiber (NDF) and acidic detergent fiber (ADF) (p &lt; 0.05) and increased the lactic acid (LA) concentration (p &lt; 0.05), dry matter (DM) content and crude protein content. Adding LP+CX effectively degraded lignocellulose in sudangrass, and the NDF and ADF degradation rates at the two stages were all more than 30%. In comparison, cutting at the S2 stage led to a lower pH and higher LA and DM contents (p &lt; 0.05). Additives and the cutting stage exerted a strong effect on the silage microbial community, and Firmicutes and Lactiplantibacillus became the most dominant bacterial phyla and genera, especially at the S2 stage. (4) Conclusions: The results suggest that FAE-producing L. plantarum, cellulase and xylanase had synergistic effects on sudangrass silages, especially at the S2 stage, and their use can thus serve as an efficient method for ensiling.

Novel eugenol‐based antimicrobial coatings on aluminium substrates for food packaging applications

AbstractActive packaging systems, interacting directly with the enclosed food, can delay or inhibit those phenomena responsible for food quality decay, contributing to the food shelf‐life extension. In this work a vinyl resin‐based coating containing free or loaded eugenol (EG) in Santa Barbara Amorphous (SBA)15 mesoporous silica nanoparticles is designed to coat flexible aluminium foils to obtain an antimicrobial material. Thermogravimetric analysis shows a good loading capacity of eugenol in SBA15 (48% wt/wt). SEM analysis shows a good dispersion of free EG in the hosting polymeric matrix, whereas some EG/SBA15 particles aggregations are observed in the material. Water contact angle highlights a higher hydrophobicity of the eugenol based‐materials (&gt;90°) compared to the pristine vinyl coating (85°). Electrochemical impedance spectroscopy highlights no corrosion phenomena of the VIN/5%(EG/SBA15EG) coating and corrosion phenomena of the VIN/5%EG coating after 7 days of exposure to lactic acid pH = 4. Finally, the two active coatings are studied to evaluate their antibacterial activity using the ISO 22196. Interestingly, results demonstrate that when eugenol is loaded in the SBA15 mesoporous silica nanoparticles the antimicrobial activity of the material significantly increases against both foodborne pathogens and food spoilage bacteria, achieving the highest microbial growth reduction on S. aureus (R = 3.62 log).

Two novel screened microbial consortia and their application in combination with Lactobacillus plantarum for improving fermentation quality of high-moisture alfalfa.

To enrich lignocellulolytic microbial consortia and evaluate whether a combination of these consortia and Lactobacillus plantarum can facilitate degradation of structural carbohydrates and improve fermentation quality of high-moisture alfalfa silage. Two novel microbial consortia (CL and YL) with high lignocellulolytic potential were enriched, and had higher enzyme activities at slightly acidic conditions (pH 3.5-6.5). Two consortia were inoculated with and without combined L. plantarum (LP) to alfalfa for up to 120days of ensiling. The two consortia alone or combined with LP significantly (p<0.05) increased lactic-to-acetic acid ratios and decreased contents of volatile organic acids and NH3 -N as compared to the control. Treatments that combining microbial consortia and LP further resulted in the higher contents of lactic acid (LA), water soluble carbohydrates (WSC) and crude protein, dry matter (DM) recovery, and lower neutral detergent fibre, acid detergent lignin and cellulose contents, with YLP silage showing the lowest pH (4.41) and highest LA content (76.72gkg-1 DM) and the conversion of WSC into LA (184.03%). The addition of lignocellulolytic microbial consortia (CL or YL) to alfalfa silages as attractive silage inoculants could improve fermentation quality, and that their combination with L. plantarum appeared more effective on the degradation of structural carbohydrates and conversion of soluble carbohydrates into LA. High-moisture alfalfa is difficult to ensile due to its high buffering capacity and low readily fermentable carbohydrate contents. Microbial consortia (CL and YL) can encode a broad selection of multi-functional CAZymes, and their combination with LP could be promising for the degradation of structural carbohydrates simultaneously with improvement fermentation quality, with high performance in LA production.

Effect of sorbic acid and dual‐purpose inoculants on the fermentation quality and aerobic stability of high dry matter rice straw silage

This study aimed to evaluate the feasibility of sorbic acid (SA) as a silage additive and its effects on fermentation quality and aerobic stability of high dry matter (DM) silage. High DM rice straw was ensiled with distilled water (C), 1×106 CFU per gram fresh weight (FW) Lactobacillus plantarum and 1×106 CFU per gram FW Lactobacillus buchneri (LP+LB) or SA for 45days with a subsequent aerobic stability test. After ensiling, LP+LB silage had the highest lactic acid (LA) content and the lowest pH value, whereas SA silage had the highest DM and water-soluble carbohydrate (WSC) contents, and the lowest ethanol and ammonia nitrogen (NH3 -N) contents among all silages (P<0·001). Compared to C silage, SA significantly (P<0·01) reduced the counts of yeasts but not lactic acid bacteria (LAB). During 6-day aerobic exposure, the continuous pH increase and LA decrease were observed in C and LP+LB silages, and there was no significant change in pH, DM, NH3 -N and WSC contents of SA silage over the whole aerobic exposure. The SA addition slowed the decline of LA and acetic acid (AA) contents as well as the growth of yeasts and aerobic bacteria under aerobic exposure. In this study, L. buchneri could not function in high DM rice straw silage while SA effectively improved both the fermentation quality and aerobic stability. The SA was more effective than dual-purpose inoculants to improve the aerobic stability of high DM rice straw silage. Thus, SA can be served as a potential antifungal additive for silage with high DM.

Kajian Terhadap Migrasi Plastik Hasil Induksi Panas pada Beberapa pH dan Jenis Asam Organik

In Indonesian street food vendor, most of hot acidic food and drinks are served with plastic packaging and plastic cutlery. This research is aimed to study about the presence of plastic’s component migration as a result of heat induction in the presence of various pHs and organic acid, and to identify the types of migrated plastic components through its functional groups. In this research, the samples were 10 plastic packaging and cutlery made from LDPE, HDPE, PP, PE, and PS plastic. Acetic acid, citric acid, and lactic acid and three levels of pH which were pH 4, 5, and 6. Temperatures of 80 and 100 ? were used as representation of food and drinks served warm. Each samples were conditioned in each organic acids solutions with different pH (pH 4, 5, and 6) and thermal treatments were carried out for 1 hour in each temperature. The plastic migrations were detected using UV-Visible spectroscopy, followed by FTIR spectroscopy to identify functional groups of the migrated plastic components, followed by prediction of the migrated compound. The results suggested that plastic component migration were detected in all samples, and using lactic acid pH 4, 5, and 6 an antistatic diethanolamides was ruled plausible released from white plastic glass sample.&#x0D; Keywords : plastic migration, organic acids, pH, spectroscopy, temperature.

Fermentation quality, in vitro digestibility and aerobic stability of total mixed ration silages prepared with whole-plant corn (Zea mays L.) and hulless barley (Hordeum vulgare L.) straw

This study was carried out to assess the effects of adding Lactobacillus plantarum, molasses or/and ethanol on the fermentation quality, in vitro digestibility and aerobic stability of total mixed ration (TMR) silage, which is well accepted in small-scale dairy farms in Tibet. Total mixed ration were ensiled in laboratory silos (1 L) and treated with (1) no additive (Control), (2) ethanol (E, 25 ml/kg fresh weight (FW)), (3) molasses (M, 30 g/kg FW); (4) Lactobacillus plantarum (L, 106cfu/g FW); (5) ethanol + molasses (EM); and (6) ethanol + Lactobacillus plantarum (EL). After 45 days of ensiling, six silos per treatment were opened for the fermentation quality and in vitro digestibility analyses, whereas 18 silos were used for the aerobic stability test for the following 9 days. All TMR silages were well preserved with dominant lactic acid (LA), low pH and ammonia nitrogen, and negligible propionic and butyric acid. The L and EL silages had the lowest pH and highest LA concentrations. The addition of ethanol did not inhibit silage fermentation as there were no significant differences for the pH, LA, acetic acid, negligible propionic acid or ammonia nitrogen content, lactic acid bacteria and yeast counts between Control and the E silage. During the aerobic stability test, pH increased by 1.39, 1.67, 1.69 and 0.74 for the Control, M, L and EM silages, but only 0.40 and 0.34 for E and EL silages, respectively. Upon exposure to air, the LA concentration in the L silage was evidently (P &lt; 0.05) decreased, whereas LA concentration in the EL silage remained the highest value after the third day of aerobic exposure. Mean populations of aerobic bacteria and yeast in the E and EL silages were lower (P &lt; 0.05) than those of the Control. These findings suggested that L. plantarum is effective in improving fermentation quality of TMR silages. Although the addition of ethanol in our study did not depress the fermentation of the TMR silages, it showed potential to inhibit the aerobic spoilage of TMR silages, either alone or in combination with the L. plantarum. It is concluded that L. plantarum combined with ethanol not only ensures better fermentation but also could improve aerobic stability.

Probing the neutralization behavior of zwitterionic monomer-containing dental adhesive

ObjectiveTo investigate the polymerization kinetics, neutralization behavior, and mechanical properties of amine-functionalized dental adhesive cured in the presence of zwitterionic monomer, methacryloyloxyethyl phosphorylcholine (MPC). MethodsThe control adhesive was a mixture based on HEMA/BisGMA/2-N-morpholinoethyl methacrylate (MEMA) (40/30/30, w/w/w). The control and experimental formulations containing MPC were characterized with regard to water miscibility of liquid resins, photopolymerization kinetics, water sorption and solubility, dynamic mechanical properties and leachables from the polymers (aged in ethanol). The neutralization behavior of the adhesives was determined by monitoring the pH of lactic acid (LA) solution. ResultsThe water miscibility decreased with increasing MPC amount. The water sorption of experimental copolymer specimen was greater than the control. The addition of 8wt% water led to improved photo-polymerization efficiency for experimental formulations at MPC of 2.5 and 5wt%, and significant reduction in the cumulative amounts of leached HEMA, BisGMA, and MEMA, i.e. 90, 60 and 50% reduction, respectively. The neutralization rate of MPC-containing adhesive was faster than control. The optimal MPC concentration in the formulations was 5wt%. SignificanceIncompatibility between MEMA and MPC led to a decrease in water miscibility of the liquid resins. Water (at 8wt%) in the MPC-containing formulations (2.5–5wt% MPC) led to higher DC, faster RPmax and significant reduction in leached HEMA, BisGMA, and MEMA. The neutralization rate was enhanced with the addition of MPC in the amine-containing formulation. Promoting the neutralization capability of dentin adhesives could play an important role in reducing recurrent decay at the composite/tooth interface.

Synthesized mesoporous silica and calcium aluminate cement fillers increased the fluoride recharge and lactic acid neutralizing ability of a resin-based pit and fissure sealant.

This study evaluated the effect of different types of filler in a resin-based pit and fissure sealant on fluoride release, recharge, and lactic acid neutralization. Resin-based sealant was incorporated with 5% w/w of the following fillers: calcium aluminate cement (CAC), synthesized mesoporous silica (SI), a CAC and SI mixture (CAC+SI), glass-ionomer powder (GIC), and acetic acid-treated GIC (GICA). Sealant without filler served as control. The samples were immersed in deionized water or a lactic acid solution and the concentration of fluoride in the water, before and after fluoride recharge, and the lactic acid pH change, respectively, were determined. The CAC+SI group demonstrated the highest fluoride release after being recharged with fluoride gel. The CAC+SI group also demonstrated increased lactic acid pH. These findings suggest that a resin-based sealant containing synthesized mesoporous silica and calcium aluminate cement may enhance remineralization due to fluoride release and higher pH.

Effect of Deep Tissue Incision on pH Responses of Afferent Fibers and Dorsal Root Ganglia Innervating Muscle

Understanding the mechanisms underlying deep tissue pain in the postoperative period is critical to improve therapies. Using the in vitro plantar flexor digitorum brevis muscle-nerve preparation and patch clamp recordings from cultured dorsal root ganglia neurons innervating incised and unincised muscle, the authors investigated responses to various pH changes. Incision including the plantar flexor digitorum brevis muscle or sham operation was made in the rat hind paw. On postoperative day 1, in vitro single-fiber recording was undertaken. On the basis of previous studies, the authors recorded from at least 40 fibers per group. Also DiI-labeled dorsal root ganglia innervating muscle from rats undergoing incision and a sham operation were cultured and tested for acid responses, using whole cell patch clamp recordings. The prevalence of responsive group IV afferents to lactic acid pH 6.5 in the incision group (15 of 67; 22.3%) was greater than that in the control group (2 of 35; 5.7%; P=0.022). In dorsal root ganglia neurons innervating muscle, incision increased mean current amplitudes of acid-evoked currents; the acid-sensing ion channel blocker, amiloride 300 μM, inhibited more than 75% of the acid-evoked current, whereas, the transient receptor vanilloid receptor 1 blocker (AMG9810 1 μM) did not cause significant inhibition. The authors' experiments demonstrated that incision increases the responses of flexor digitorum brevis muscle afferent fibers to weak acid solutions, and increased acid-evoked currents in dorsal root ganglia innervating muscle. The authors' data suggest that up-regulation of acid-sensing ion channels might underlie this increased chemosensitivity caused by surgery.

Rosmarinus officinalis L. Essential Oil and Its Majority Compound 1,8-Cineole at Sublethal Amounts Induce No Direct and Cross Protection in Staphylococcus aureus ATCC 6538

In this study, the inhibitory efficacy of Rosmarinus officinalis essential L. (ROEO) and 1,8-cineole (CIN) in inhibiting the growth and survival of Staphylococcus aureus ATCC 6538 and the induction of direct and bacterial cross protection (lactic acid pH 5.2; NaCl 100 g/L; high temperature 45°C) were evaluated following exposure to sublethal and increasing amounts of these treatments in meat broth. All of the concentrations of the ROEO and CIN examined in this study (minimum inhibitory concentration [MIC], 1/2 MIC, and 1/4 MIC) inhibited the viability of S. aureus throughout the 120 min of exposure. The overnight exposure of S. aureus to sublethal amounts of both ROEO or CIN in meat broth did not result in direct or cross protection. Cells progressively subcultured (24-h cycles) in meat broth with increasing amounts of ROEO or CIN showed no increased direct tolerance. These results reveal the antimicrobial efficacy of ROEO and CIN for use in food conservation systems as anti-S. aureus compounds given their efficacy at inhibiting bacterial growth, in addition to their lack of induction for the development of homologous and heterologous resistance.

Leaching of Ions from Materials used in Alternative Restorative Technique under Neutral and Acidic Conditions: A Comparative Evaluation

This study was undertaken to gain an insight into the interaction of conventional glass ionomers (GC Fuji II, GC Fuji IX GP and Chem Flex restorative materials) commonly used in Alternative Restorative Technique (ART) with aqueous solutions in terms of water sorption, solution buffering and ion release. Both immature and mature specimens of all materials evaluated, showed a substantial increase in mass, pH and release of Na, Ca, Sr, Al, Si, P and F following immersion in deionized water lactic acid (pH 2.7) and lactic acid (pH 5.2). However the ion release profiles were found to be greater in acidic media (Lactic Acid pH 2.7 > Lactic Acid pH 5.2) than in deionized water.

Interaction between GIC and S. sanguis biofilms: Antibacterial properties and changes of surface hardness

The aim of this study was to investigate the interaction of Streptococcus sanguis with two glass-ionomer formulations (GIC:A containing fluoride and GIC:B without fluoride) with particular reference to bacterial growth and changes in hardness of the cement with respect to time. Discs of two water activated glass-ionomer cements were prepared according to the manufacturer's instruction. Hydroxyapatite discs (HA) were used as controls. 3D laser scanning technique was used to characterize surface roughness and area of the substrate prior to growing biofilms. Surface hardness was evaluated before and after biofilm growth. A constant depth film fermenter system (CDFF) was used to grow S. sanguis biofilms on the specimens in a similar manner to that described previously by Wilson et al. in 1995. For susceptibility measurement, specimens were removed from CDFF aseptically over periods up to 14d after the first colonization with bacteria. Counts of viable bacterial in the accumulating biofilm layer on each surface were measured and converted to colony forming units per unit surface area. To determine the effect of storage media, hardness discs were exposed to distilled water, lactic acid pH 4, lactic acid pH 5, citric acid pH 5, artificial saliva and S. sanguis biofilms. Twenty-four hours after preparing and subsequent autoclaving, specimens were transferred to a vessel containing 40 ml storage medium. The specimens were investigated for periods up to 7d. The viable counts of S. sanguis per mm2 on GIC:A were significantly less than those on HA and GIC:B during the first 5d (p<0.05). The viable counts of bacteria on the surface of GIC:B were lower during the initial 5d when compared to HA. Exposure of GIC:A and GIC:B to different medium produced softening to the surface of cement. It is apparent that the effects of the biofilms are significantly greater than storage in water but similar to storage in lactic acid pH 5. This investigation showed that the growth of S. sanguis biofilms were significantly affected by both glass-ionomer formulations, the greater reduction being noted on the surface of the fluoride containing GIC. S. sanguis biofilms produced reduction on the surface hardness of the cement equivalent to that seen after immersion in lactic acid at pH 5. This indicates that while S. sanguis biofilm is affected by the GIC, there is also a decrease in hardness of the cement indicating some cement degradation.

The rate of change of pH of lactic acid exposed to glass-ionomer dental cements

The rate of change of pH of aqueous lactic acid at pH 4.2–4.5 (i.e. a little below that of active caries in vivo) in contact with disks of various commercial glass-ionomer cements has been determined in two configurations. In the first of them, a thin film set-up, 20 μl of solution was spread across the surface of a cement disk (diameter: 13 mm), and its pH determined by pressing a flat-ended electrode against the film at varying time intervals. In the second, a similar disk was immersed in 1.5 ml of solution, removed after varying time intervals, after which the pH of the solution was measured using a round-ended electrode. The latter measurement was more reliable, in that the pH electrode had time to equilibrate, whereas the former was more realistic because the film was approximately the same thickness as that of saliva on a tooth surface. Both series of experiments showed measurable differences in pH after only 30 s, with the thin-film configuration showing a range of pH changes of 0.5–1.2 units depending on the cement and the small volume configuration showing a range of 0.1–0.5 units, also depending on the cement. After 10 min, in the small volume experiments, the pH had generally increased further. The extent and speed of the change in pH led to the conclusion that ability of glass-ionomers to increase pH is likely to be an important mechanism of caries protection under clinical conditions.

A Method of Screening for Highly Inhibitory Lactic Acid Bacteria

A rapid method of screening for lactic acid bacteria with high inhibitory power was developed. The methodology employed was the agar-diffusion assay, which was standardized for the indicator strain, medium composition, and incubation conditions. The assay was performed in nutrient agar at 30°C with 108 spores of Bacillus subtilis per plate as indicator strain. The inhibition produced by supernatants of lactic acid bacteria cultures harvested at stationary phase was determined. The inhibitory powers of different strains were compared with a standard curve obtained with racemic lactic acid. Results obtained with lactic acid and supernatants of bacterial cultures demonstrate that the diameter of the inhibition zone (d) was related to the pH by the exponential relation d = a exp (− b pH). Results obtained with strains that produced inhibitory substances other than lactic acid could not be fitted into the standard linear curves obtained in the plot of ln d versus pH of lactic acid.