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In vitro food digestion methods are increasingly used due to standardised protocols and validation with in vivo data. Porcine pepsin is the major gastric enzyme used to replace human pepsin during the gastric phase of in vitro digestion models. Until now, limited information exists on the combined effect of the temperature and pH variations that occur during digestion on the activity of these enzymes. This study addresses gaps in the understanding of how pH (1–7) and temperature (4–60 °C) affect pepsin activity. Human pepsin exhibited broader activity retention than porcine pepsin, maintaining 80% and 46% activity at pH 3 and 4, respectively, versus 47% and 13% for porcine pepsin. Predictive models for both enzymes were developed to quantify activity under varied conditions. Porcine pepsin required heating to 75 °C for ≥ 5 min for complete inactivation, while 65 °C for 15 min proved insufficient. These findings allow direct comparison of standardised in vitro digestion results across studies, improving the translation of in vitro outcomes to in vivo human digestion. Additionally, this study clarifies optimal inactivation protocols for sample preparation. This work therefore enhances the accuracy of in vitro models, supporting their use in food research.

Objective To investigate the consistency between the reflux symptom score (RSS) and the multitemporal salivary pepsin test in screening for laryngopharyngeal reflux (LPR) and the screening value of the RSS for LPR by simultaneously administering daytime multitemporal salivary pepsin test and RSS to patients. Methods This was a single-center prospective observational study. All included patients underwent simultaneous daytime multitemporal salivary pepsin testing and RSS. A participant was considered to have LPR when one or more positive salivary pepsin test results or RSS score > 13 were obtained. The consistency between the multitemporal salivary pepsin test and the RSS was compared by the weighted Cohen’s kappa statistic. The screening value of the RSS for LPR was investigated by receiver operating characteristic (ROC) analysis. Results A total of 67 patients were included. The positivity rate of LPR was 71.64% according to the results of the multitemporal salivary pepsin test. According to RSS, the positive rate of LPR was 70.15%. The weighted Kappa value between the multitemporal salivary pepsin test and the RSS was 0.675 ( p  < 0.001). The area under curve of RSS screening for LPR was 0.843 ( p  < 0.01), and the sensitivity, specificity, positive predictive value, and negative predictive value of RSS screening for LPR were 89.58%, 78.95%, 91.49%, and 75%, respectively. Conclusion There is a good consistency between the RSS and the multitemporal salivary pepsin test, and the RSS has a good screening value for LPR, which can be applied to screen for LPR in otolaryngologic patients.

Purpose Studies on the impact of tapered-cuff tracheal tubes on rates of microaspiration and ventilator-associated pneumonia (VAP) in intubated patients have reported conflicting results. The aim of this study was to determine the influence of this shape of tracheal cuff on abundant microaspiration of gastric contents in critically ill patients. Methods All patients intubated in the intensive care unit (ICU) and requiring mechanical ventilation for at least 48 h were eligible for this multicenter cluster-randomized controlled cross-over open-label study. The primary outcome was abundant microaspiration of gastric contents, defined by the presence of pepsin at significant level in >30% of tracheal aspirates. Quantitative measurement of pepsin and salivary amylase was performed in all tracheal aspirates during the 48 h following enrollment. Results A total of 326 patients were enrolled in the ten participating ICUs (162 in the PVC tapered-cuff group and 164 in the standard-cuff group). Patient characteristics were similar in the two study groups. The proportion of patients with abundant microaspiration of gastric contents was 53.5% in the tapered-cuff and 51.0% in the standard-cuff group (odds ratio 1.14, 95% CI 0.72–1.82). While abundant microaspiration of oropharyngeal secretions was not significantly different (77.4 vs 68.6%, p  = 0.095), the proportion of patients with tracheobronchial colonization was significantly lower (29.6 vs 43.3%, p  = 0.01) in the tapered-cuff than in the standard-cuff group. No significant difference between the two groups was found for other secondary outcomes, including ventilator-associated events and VAP. Conclusions This trial showed no significant impact of tapered-cuff tracheal tubes on abundant microaspiration of gastric contents. Trial registration ClinicalTrials.gov, number NCT01948635.

Casein microparticles, which are gently produced by depletion flocculation and film drying, are suitable as a sustainable, biodegradable encapsulation material due to their pH-dependent swelling behaviour. However, the food protein casein is highly susceptible to degradation in the stomach due to its open, flexible conformation. In simulated gastric juice, the particles undergo different phases of shrinkage and swelling. Control experiments show that the initial two-stage shrinkage process and the subsequent swelling are due to the acidification of the particles. When pH 2 is reached, an almost exponential decay induced by pepsin takes place until a highly degraded final state is reached. The kinetic analysis of the results is based on the pH profile of the casein solubility as well as on pH- and pepsin-induced structural changes in the casein matrix, which are combined in a system-dynamic model. Data and model simulations show that microparticles can pass through the gastric environment.

This research examines the enzymatic modification of lysozyme, a glycosidic hydrolase that has restricted effectiveness against Gram-negative bacteria, in order to produce bioactive peptide fractions with improved antibacterial and physicochemical characteristics. Utilizing chicken egg lysozyme, modifications were performed in controlled settings with proteolytic enzymes, mainly pepsin, and experiments with a pepsin-trypsin ratio. The modification methods sought to improve the hydrophobic nature of lysozyme’s surface, create oligomeric and peptide forms, and decrease immunogenicity. Findings showed that raising pepsin concentration enhanced the creation of peptide fractions, increasing surface hydrophobicity while reducing hydrolytic and antioxidant activities. Increased hydrophobicity and reduced enzyme activity were linked to enhanced antibacterial effectiveness, particularly against Gram-negative bacteria, a characteristic absent in natural lysozyme. Additionally, the research noted a decrease in immunoreactivity as pepsin concentrations increased, achieving the lowest antibody response in optimized formulations. This enzymatic method offers an economical way to create lysozyme derivatives that hold considerable promise for wider applications, particularly in scenarios where lower immunoreactivity and a prolonged antibacterial spectrum are needed.

Collagen is one of the most useful biomaterials and widely applied in functional food and cosmetics. However, some consumers have paid close attention to the safety of mammalian collagens because of the outbreaks of bovine spongiform encephalopathy (BSE), foot-and-mouth disease (FMD), and other prion diseases. Therefore, there is a strong demand for developing alternative sources of collagen, with one promising source being from the process by-products of commercial fisheries. In this report, acid-soluble collagen (ASC-SB) and pepsin-soluble collagen (PSC-SB) from swim bladders of miiuy croaker (Miichthys miiuy) were isolated with yields of 1.33 ± 0.11% and 8.37 ± 0.24% of dry swim bladder weight. Glycine was the major amino acid present, with a content of 320.5 (ASC-SB) and 333.6 residues/1000 residues (PSC-SB). ASC-SB and PSC-SB had much lower denaturation temperatures compared to mammalian collagen, a consequence of low imino acid contents (196.7 and 199.5 residues/1000 residues for ASC-SB and PSC-SB, respectively). The data of amino acid composition, SDS-PAGE pattern, UV and FTIR spectra confirmed that ASC-SB and PSC-SB were mainly composed of type I collagen. FTIR spectra data indicated there were more hydrogen bonding and intermolecular crosslinks in ASC-SB. These collagens showed high solubility in the acidic pH ranges and low NaCl concentrations (less than 2%). The Zeta potential values of ASC-SB and PSC-SB were 6.74 and 6.85, respectively. ASC-SB and PSC-SB presented irregular, dense, sheet-like films linked by random-coiled filaments under scanning electron microscopy. In addition, ASC-SB and PSC-SB could scavenge DPPH radical, hydroxyl radical, superoxide anion radical, and ABTS radical in a dose-dependent manner. Overall, the results indicate that collagens from the swim bladders of miiuy croaker are a viable substitute for mammalian collagen, with potential functional food and cosmeceutical applications.

Ti-6Al-4 V titanium alloy is widely utilized in orthodontic applications due to its favorable biocompatibility and mechanical properties. However, its long-term performance can be adversely affected by the dynamic and hostile oral environment, particularly under pathological conditions such as gastroesophageal reflux disease (GERD). Herein, In vitro corrosion behavior of Ti-6Al-4 V over a 240-hour immersion period at 37 °C in artificial saliva simulating GERD, with pepsin and Candida albicans , both individually and combined. Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization revealed that pepsin significantly improved corrosion resistance, achieving a maximum inhibition efficiency (IE) of 87.4%, while C. albicans showed a time-dependent decline in protection, with lower IE 71.8%. The combined presence of both agents further reduced IE to 55.6%, indicating a complex synergistic effect accelerating corrosion. Surface characterization by scanning electron microscopy (SEM) confirmed biofilm formation and surface degradation. Response Surface Methodology (RSM) modeling identified immersion time and component interactions as key factors influencing corrosion behavior. These findings offer novel insights into the interplay among enzymatic activity and microbial colonization, highlighting clinical implications for implant stability in GERD-affected oral environments.

Abstract Rationale Underinflation of the tracheal cuff frequently occurs in critically ill patients and represents a risk factor for microaspiration of contaminated oropharyngeal secretions and gastric contents that plays a major role in the pathogenesis of ventilator-associated pneumonia (VAP). Objectives To determine the impact of continuous control of tracheal cuff pressure (Pcuff) on microaspiration of gastric contents. Methods Prospective randomized controlled trial performed in a single medical intensive care unit. A total of 122 patients expected to receive mechanical ventilation for at least 48 hours through a tracheal tube were randomized to receive continuous control of Pcuff using a pneumatic device (intervention group, n = 61) or routine care of Pcuff (control group, n = 61). Measurements and Main Results The primary outcome was microaspiration of gastric contents as defined by the presence of pepsin at a significant level in tracheal secretions collected during the 48 hours after randomization. Secondary outcomes included incidence of VAP, tracheobronchial bacterial concentration, and tracheal ischemic lesions. The pneumatic device was efficient in controlling Pcuff. Pepsin was measured in 1,205 tracheal aspirates. Percentage of patients with abundant microaspiration (18 vs. 46%; P = 0.002; OR [95% confidence interval], 0.25 [0.11–0.59]), bacterial concentration in tracheal aspirates (mean ± SD 1.6 ± 2.4 vs. 3.1 ± 3.7 log10 cfu/ml, P = 0.014), and VAP rate (9.8 vs. 26.2%; P = 0.032; 0.30 [0.11–0.84]) were significantly lower in the intervention group compared with the control group. However, no significant difference was found in tracheal ischemia score between the two groups. Conclusions Continuous control of Pcuff is associated with significantly decreased microaspiration of gastric contents in critically ill patients.

Pepsin plays an important role in laryngopharyngeal reflux (LPR), a risk factor for the development of hypopharyngeal squamous cell carcinomas (HPSCC). However, the role of pepsin in HPSCC is not clear. We show by immunohistochemistry that pepsin positivity occurs in a significant proportion of human primary HPSCC specimens, and in many cases matched adjacent uninvolved epithelia are negative for pepsin. Pepsin positivity is associated with nodal involvement, suggesting that pepsin may have a role in metastasis. Treatment of FaDu cancer cells with pepsin increased cell proliferation, possibly by inducing G1/S transition. We also observed significant changes in expression of genes involved in NF-kappaB, TRAIL and Notch signaling. Our data suggest that pepsin plays an important role in HPSCC and that targeting pepsin could have potential therapeutic benefits.

In this paper we studied the antioxidant and antiproliferative activities of the heated pepsin hydrolysate from a marine fish half-fin anchovy (HAHp-H). Furthermore, we compared the chemical profiles including the amino acid composition, the browning intensity, the IR and UV-visible spectra, and the molecular weight distribution between the half-fin anchovy pepsin hydrolysate (HAHp) and HAHp-H. Results showed that heat sterilization on HAHp improved the 1,1-diphenyl-2-picryl-hydrazil (DPPH) radical-scavenging activity and reducing power. In addition, the antiproliferative activities were all increased for HAHp-H on DU-145 human prostate cancer cell line, 1299 human lung cancer cell line and 109 human esophagus cancer cell line. The contents of free amino acid and reducing sugar of HAHp-H were decreased (P < 0.05). However, hydrophobic amino acid residues and the browning intensity of HAHp-H were increased. FT-IR spectroscopy indicated that amide I and amide III bands of HAHp-H were slightly modified, whereas band intensity of amide II was reduced dramatically. Thermal sterilization resulted in the increased fractions of HAHp-H with molecular weight of 3000–5000 Da and below 500 Da. The enhanced antioxidant and antiproliferative activities of HAHp-H might be attributed to the Maillard reaction.