Pepsin Treatment Research Articles

Angiotensin-I converting enzyme (ACE) inhibitory bioaccessible peptides obtained from protein extracts of Macrocystis pyrifera and Chondracanthus chamissoi seaweeds

Hypertension is a paramount chronic health concern, underscoring the critical need for preventive measures in public health. In recent years, research has discovered natural anti-hypertensive agents, including those derived from macroalgae. This study focuses on enzymatically hydrolyzing protein extracts from Macrocystis pyrifera and Chondracanthus chamissoi seaweeds to yield angiotensin I-converting enzyme (ACE) inhibitory peptides, potentially applicable in both food and bioactive products. ACE inhibitory activity was evaluated for enzymatic hydrolysates generated using bromelain, papain, and alcalase. Notably, hydrolysates produced using alcalase demonstrated the highest effect, yielding 74 % ACE inhibition for M. pyrifera and 58 % for C. chamissoi protein extracts. Optimization efforts focused on hydrolysis conditions, varying hydrolysis time and substrate-to-enzyme ratio, resulting in peak ACE inhibition of 79.9 % for M. pyrifera (5.3 h, 12.7 S:E ratio) and 70.3 % for C. chamissoi (6 h, 10 S:E ratio).Further analysis explored the relationship between molecular size separation and ACE inhibitory activity in algae hydrolysates. Fractionation via ultrafiltration revealed that fractions below 3 kDa exhibited the highest ACE inhibitory potency. Additionally, in vitro digestion studies employing pepsin and pancreatin treatments demonstrated the bioaccessibility of the seaweed-derived bioactive peptides, with maintained or enhanced bioactivity post-digestion. These findings underscore the potential of protease hydrolysates from M. pyrifera and C. chamissoi as sources of ACE inhibitory activity. Consequently, they present an exciting natural source of functional ingredients or nutraceuticals for hypertension management, with the benefits of easy implementation, profitability, and sustainability in their production process.

Ultrasonication on Collagen Yield, Physiochemical and Structural Properties from Seabass (Lates Calcarifer) Scales as Affected by Pretreatment and Extraction Conditions

This research explored the use of ultrasound as a pretreatment and extraction assisted process for extraction of collagen from seabass scales. Both acid-soluble (AC) and pepsin-soluble collagens (PC) were extracted with ultrasonication at different extraction times (24 and 48 h). Ultrasound pretreatment (PU) and ultrasound-assisted extraction (UE) notably improved AC extraction yields over 48 hours, registering 2.12% and 4.62%, respectively. The highest yield for PC, 21.85%, was achieved with 48 hours of ultrasound assisted extraction. Protein analysis verified the extracted collagens as type I, indicated by the presence of specific α and β chains. Further, FTIR spectra confirmed collagen's presence in all samples through distinct amide band peaks. Interestingly, ultrasound processes marginally reduced AC's thermal stability while boosting PC's thermal stability, especially when combined with pepsin treatment. Moreover, CD spectroscopy showed the preserved native structure of collagen across all samples. The ultrasound method increased collagen extraction yields and retained its structural integrity. These outcomes are pivotal for advancing collagen extraction methods in the biomedical and food sectors. Keywords: Seabass scales, Collagen, Ultrasonication, Molecular characterization, Physicochemical properties

Effects of enzyme treatments on the functionality of commercial pea and pea blended protein ingredients

The effects of enzyme treatments on the functional properties of commercial pea protein, pea:rice protein blend (3:2), pea:oat protein blend (1:1), and pea:hemp protein blend (1:1) were investigated. Treatments were applied through hydrolysis (pepsin or papain), crosslinking (transglutaminase, TG), and their combination (pepsin + TG or papain + TG). The protein content of each protein blend increased slightly or remained unchanged under treatments involving papain but decreased after treating with pepsin or pepsin + TG. Surface hydrophobicity increased for pea, pea:rice, and pea:oat blends after all enzyme treatments. Water holding capacity decreased for all samples compared to the untreated materials. For oil holding capacity, there was only improvement in the pea:rice blend with TG and pea:hemp with papain and papain + TG. Emulsion stability of pea:rice and pea:oat blends increased after all treatments; pepsin treatment specifically improved the emulsion stability to over 90%. Foaming capacity of each protein blend increased under all enzyme treatments whereas the foaming stability improved for the pea:rice blend but decreased for the pea:hemp blend. All treatments increased protein solubility. Specific enzyme treatment can be used to tailor the functionality of commercial plant protein blends.

Effect of Thermal Processing on the Conformational and Digestive Properties of Myosin

Heat treatment affects the structural properties of meat proteins, which in turn leads to changes in their sensitivity to digestive enzymes, further affecting the nutritional value of meat and meat products. The mechanism of changes in the structure and digestive properties of myosin under different heating conditions were studied. An increase in heating temperature led to the exposure of internal groups to a polar environment, but to a decrease in the sturdy α-helix structure of myosin (p < 0.05). The results of tryptophan fluorescence verified that the tertiary structure of the protein seemed to be unfolded at 70 °C. Higher protein denaturation after overheating, as proven by the sulfhydryl contents and turbidity, caused irregular aggregate generation. The excessive heating mode of treatment at 100 °C for 30 min caused myosin to exhibit a lower degree of pepsin digestion, which increased the Michaelis constant (Km value) of pepsin during the digestion, but induced the production of new peptides with longer peptide sequences. This study elucidates the effects of cooking temperature on the conformation of myosin and the change in digestibility of pepsin treatment during heating.

Pepsin and Trypsin Treatment Combined with Carvacrol: An Efficient Strategy to Fight Pseudomonas aeruginosa and Enterococcus faecalis Biofilms.

Biofilms consist of microbial communities enclosed in a self-produced extracellular matrix which is mainly responsible of biofilm virulence. Targeting this matrix could be an effective strategy to control biofilms. In this work, we examined the efficacy of two proteolytic enzymes, pepsin and trypsin, to degrade P. aeruginosa and E. faecalis biofilms and their synergistic effect when combined with carvacrol. The minimum dispersive concentrations (MDCs) and the contact times of enzymes, as well as the minimal inhibitory concentrations (MICs) and contact times of carvacrol, were determined against biofilms grown on polystyrene surfaces. For biofilms grown on stainless steel surfaces, the combined pepsin or trypsin with carvacrol treatment showed more significant reduction of both biofilms compared with carvacrol treatment alone. This reduction was more substantial after sequential treatment of both enzymes, followed by carvacrol with the greatest reduction of 4.7 log CFU mL-1 (p &lt; 0.05) for P. aeruginosa biofilm and 3.3 log CFU mL-1 (p &lt; 0.05) for E. faecalis biofilm. Such improved efficiency was also obvious in the epifluorescence microscopy analysis. These findings demonstrate that the combined effect of the protease-dispersing activity and the carvacrol antimicrobial activity could be a prospective approach for controlling P. aeruginosa and E. faecalis biofilms.

Proteolysis-driven proliferation and rigidification of pepsin-resistant amyloid fibrils

Proteolysis of amyloids is related to prevention and treatment of amyloidosis. What if the conditions for proteolysis were the same to those for amyloid formation? For example, pepsin, a gastric protease is activated in an acidic environment, which, interestingly, is also a condition that induces the amyloid formation. Here, we investigate the competition reactions between proteolysis and synthesis of amyloid under pepsin-activated conditions. The changes in the quantities and nanomechanical properties of amyloids after pepsin treatment were examined by fluorescence assay, circular dichroism and atomic force microscopy. We found that, in the case of pepsin-resistant amyloid, a secondary reaction can be accelerated, thereby proliferating amyloids. Moreover, after this reaction, the amyloid became 32.4 % thicker and 24.2 % stiffer than the original one. Our results suggest a new insight into the proteolysis-driven proliferation and rigidification of pepsin-resistant amyloids.

Nutritional properties and osteogenic activity of simulated digestion components and peptides from Larimichthys crocea

Fish provides a range of health benefits due to its nutritional and bioactive components. However, the bioactive peptides derived from Larimichthys crocea proteins were not fully investigated, especially the beneficial effects related to bone growth in vitro. In this study, the water extract protein was subjected to the simulated in vitro digestion process, and the osteogenic effect of enzymatic hydrolysate at different digestion stages was evaluated by the proliferation of osteoblast. The protein hydrolyzates of group pepsin treatment for 1 h and pepsin treatment for 2 h showed higher osteogenic activity in vitro. Two peptides including IERGDVVVQDSPSD from pepsin treatment for 1 h and RGDLGIEIPTEK from pepsin treatment for 2 h were identified, which revealed eminent effects in terms of promoting osteoblast proliferation and enhancing ALP activity. Moreover, the available nutrients in the proteins were determined by the molecular weight distribution and free amino acid composition. Those peptides also showed stronger interaction with RGD than integrins. Therefore, the peptides from Larimichthys crocea can be used as an effective ingredient for promoting bone growth in the future.

Truncated Pleurocidin Derivative with High Pepsin Hydrolysis Resistance to Combat Multidrug-Resistant Pathogens.

The global prevalence of antimicrobial resistance calls for the development of novel antimicrobial agents, particularly for these orally available drugs. Structural modifications of the natural antimicrobial peptides (AMPs) provide a straightforward approach to develop potent antimicrobial agents with high specificity and low toxicity. In this study, we truncated 11-amino-acids at the C-terminus of Pleurocidin, an AMP produced by Pleuronectes americanus, and obtained four peptide analogues termed GK-1, GK-2, GK-3 and GK-4. Minimum inhibitory concentration (MIC) tests showed that GK-1 obtained by direct truncation of Pleurocidin has no antibacterial activity, while GK-2, GK-3 and GK-4 show considerable antibacterial activity with Pleurocidin. Notably, GK-4 displays rapid bacteriostatic activity, great stability and low hemolysis, as well as enhanced hydrolytic resistance to pepsin treatment. Mechanistic studies showed that GK-4 induces membrane damage by interacting with bacterial membrane-specific components, dissipates bacterial membrane potential and promotes the generation of ROS. SEM and CD analysis further confirmed the ability of GK-4 to resist pepsin hydrolysis, which may be attributed to its stable helicity structure. Collectively, our findings reveal that GK-4 is a potential orally available candidate to treat infections caused by multidrug-resistant pathogens.

The antimicrobial peptide LI14 combats multidrug-resistant bacterial infections

The prevalence of multidrug-resistant (MDR) pathogens raises public fears of untreatable infections and represents a huge health risk. There is an urgent need to exploit novel antimicrobial agents. Due to the unique mechanisms, antimicrobial peptides (AMPs) with a low probability to achieve resistance are regarded as potential antibiotic alternatives to address this issue. Herein, we develop a panel of synthetic peptide compounds with novel structures based on the database filters technology (DFT), and the lead peptide LI14 shows potent antibacterial activity against all tested drug-resistant bacteria. LI14 exhibits rapid bactericidal activity and excellent anti-biofilm and -persisters activity, simultaneously showing a low propensity to induce resistance. Moreover, LI14 shows tolerance against pH, temperatures, and pepsin treatment, and no detectable toxicity both in vitro and in vivo. Mechanistic studies revealed that LI14 induces membrane damage by targeting bacterial-specific membrane components and dissipates the proton motive force (PMF), thereby resulting in metabolic perturbations and the accumulation of toxic metabolic products. Furthermore, LI14 sensitizes clinically relevant antibiotics against MDR bacteria. In animal models of infection, LI14 or combined with antibiotics are effective against drug-resistant pathogens. These findings suggest that LI14 is a promising antibiotic candidate to tackle MDR bacterial infections.

De novo assisted AFB1-Specific monoclonal antibody sequence assembly and comprehensive molecular characterization

Despite their widely used and access as biological reagents in analytical methods, the detailed structural features for most of the antibodies were rarely known. Here, a new antibody for AFB1 with high specificity in constructing ELISA was studied in detail. The molecular structure and modification were elucidated mainly by nano-electrospray ionization mass spectrometry. The mass experiments, including MALDI-TOF MS, revealed complete and specific fragments, including antibody molecular weight, peptides, glycopeptide, and N-glycoform. By proteolytic treatment of pepsin and trypsin and high-resolution tandem-MS, the primary structure of the newly developed anti-AFB1 antibody was assembled by several rounds of Database search process assisted with the de novo results. The antibody CDR annotation and constraint-based multiple alignment tool were used to differentiate and align the sequences. The method uses only two proteases to generate numerous peptides for de novo sequencing. This artificial assembled AFB1-specific monoclonal antibody sequence was validated by comparison with the sequencing results of the immunoglobulin gene. The results showed that this method achieves full sequence coverage of anti-AFB1 monoclonal antibody, with an accuracy of 100% in the CDR regions of light chain and four amino acid mismatch in heavy chain. This simple and low-cost method was confirmed by treating a public dataset. The secondary structure information of intact antibody was also elucidated from the results of circular dichroism spectrum.

Comparison of Physicochemical and Structural Properties of Acid-Soluble and Pepsin-Soluble Collagens from Blacktip Reef Shark Skin.

Fish collagen has been widely used in tissue engineering (TE) applications as an implant, which is generally transplanted into target tissue with stem cells for better regeneration ability. In this case, the success rate of this research depends on the fundamental components of fish collagen such as amino acid composition, structural and rheological properties. Therefore, researchers have been trying to find an innovative raw material from marine origins for tissue engineering applications. Based on this concept, collagens such as acid-soluble (ASC) and pepsin-soluble (PSC) were extracted from a new type of cartilaginous fish, the blacktip reef shark, for the first time, and were further investigated for physicochemical, protein pattern, microstructural and peptide mapping. The study results confirmed that the extracted collagens resemble the protein pattern of type-I collagen comprising the α1, α2, β and γ chains. The hydrophobic amino acids were dominant in both collagens with glycine and hydroxyproline as major amino acids. From the FTIR spectra, α helix (27.72 and 26.32%), β-sheet (22.24 and 23.35%), β-turn (21.34 and 22.08%), triple helix (14.11 and 14.13%) and random coil (14.59 and 14.12%) structures of ASC and PSC were confirmed, respectively. Collagens retained their triple helical and secondary structure well. Both collagens had maximum solubility at 3% NaCl and pH 4, and had absorbance maxima at 234 nm, respectively. The peptide mapping was almost similar for ASC and PSC at pH 2, generating peptides ranging from 15 to 200 kDa, with 23 kDa as a major peptide fragment. The microstructural analysis confirmed the homogenous fibrillar nature of collagens with more interconnected networks. Overall, the preset study concluded that collagen can be extracted more efficiently without disturbing the secondary structure by pepsin treatment. Therefore, the blacktip reef shark skin could serve as a potential source for collagen extraction for the pharmaceutical and biomedical applications.

Effects of protein digestion on in vitro digestibility of starch in sorghum differing in endosperm hardness and flour particle size

In vitro digestibility of starch in sorghum grains differing in endosperm hardness and flour particle size was investigated. The starch digestibility increased as the particle size of flour decreased, but no clear trend was observed in digestibility of starch in sorghum flours milled from grains with different hardness. The protein matrix affected the digestion of starch. The pH value (2.0 vs. 1.3) was a critical factor affecting protein digestion. Optimum pH (pH 2.0 for pepsin) digested more protein, resulting in a greater digestion of starch. Resistant starch (RS) content was 8.5–26.3% in isolated sorghum starch but higher (10.6–29.5%) in sorghum flours. Protein digestibility decreased after cooking while starch digestibility increased compared to native sorghum flours; disulfide bonds formed between protein molecules. RS content of cooked sorghum flour was much higher without pepsin treatment (16.93–23.99%) than that of cooked sorghum flour with pepsin treatment (4.86–12.53%).

Proteome changes in human bladder T24 cells induced by hydroquinone derived from Arctostaphylos uva-ursi herbal preparation

Ethnopharmacological relevanceArctostaphylos uva-ursi (L.) Spreng. (bearberry) is a well-known traditional herbal plant used as a urinary tract disinfectant. Its antiseptic and diuretic properties can be attributed to hydroquinone, obtained by hydrolysis of arbutin. Aim of the studyThis study aimed to determine the toxic profile of free hydroquinone on urinary bladder cells (T24) as a target of therapeutic action. Materials and methodsQuantitative and qualitative analysis of the extract and the digestive stability and bioavailability of arbutin and hydroquinone were performed by HPLC assay and simulated in vitro digestion, respectively. Cytotoxic effect, reactive oxygen species induction and proteome changes in T24 cells after hydroquinone treatment were determined using Neutral red assay, 2′,7′-dichlorofluorescein-diacetate (DCFH-DA) assay and mass spectrometry, respectively. ResultsThrough in vitro digestion, arbutin was stable, but hydroquinone increased after pepsin treatment (109.6%) and then decreased after the small intestine phase (65.38%). The recommended doses of Uva-ursi had a cytotoxic effect on T24 cells only when all hydroquinone conjugates were converted to free hydroquinone (320 and 900 μg/mL) and the toxic effect was enhanced by recovery. One cup of the therapeutic dose had a prooxidative effect after 4 h of incubation. Shorter time of cell exposure (2 h) to hydroquinone did not have any impact on reactive oxygen species induction. Proteomic analysis found 17 significantly up-regulated proteins compared to control. Hydroquinone activated proteins related to oxidative stress response, stress-adaptive signalling, heat shock response and initiation of translation. ConclusionsDespite the therapeutic properties of bearberry, up-regulated T24 cell proteins are evidence that plant compounds, although from a natural source, may exhibit negative properties.

Ultrasound treatment can increase digestibility of myofibrillar protein of pork with modified atmosphere packaging

We explored whether ultrasound treatment affected digestibility of myofibrillar protein (MP) isolated from modified atmosphere packed (MAP, 70% N2 and 30% CO2) pork. MP digestibility under pepsin and pancreatin treatments decreased significantly with storage time. Ultrasound treatment increased the digestibility and produced a greater number of smaller peptides. However, the total peptide count and unique peptide counts were significantly reduced. Moreover, active sulfhydryl, total sulfhydryl, particle size, turbidity and surface hydrophobicity of MP increased with time, while protein solubility and ATPase activity decreased. Compared with the untreated samples, ultrasound treatment increased protein solubility, surface hydrophobicity, and active sulfhydryl content, but decreased total sulfhydryl content (except 10 d), particle sizes, turbidity and ATPase activity. Ultrasound treatment resulted in a decline in β-turn and α-helix contents. Therefore, ultrasound is conducive to the digestion. Additionally, structural and functional properties of protein in MAP were less stable than those in vacuum-packed pork reported before.

The Bioactivity Prediction of Peptides from Tuna Skin Collagen Using Integrated Method Combining In Vitro and In Silico.

The hydrolysates and peptide fractions of bigeye tuna (Thunnus obesus) skin collagen have been successfully studied. The hydrolysates (HPA, HPN, HPS, HBA, HBN, HBS) were the result of the hydrolysis of collagen using alcalase, neutrase, and savinase. The peptide fractions (PPA, PPN, PPS, PBA, PBN, PBS) were the fractions obtained following ultrafiltration of the hydrolysates. The antioxidant activities of the hydrolysates and peptide fractions were studied using the DPPH method. The effects of collagen types, enzymes, and molecular sizes on the antioxidant activities were analyzed using profile plots analysis. The amino acid sequences of the peptides in the fraction with the highest antioxidant activity were analyzed using LC-MS/MS. Finally, their bioactivity and characteristics were studied using in silico analysis. The hydrolysates and peptide fractions provided antioxidant activity (6.17–135.40 µmol AAE/g protein). The lower molecular weight fraction had higher antioxidant activity. Collagen from pepsin treatment produced higher activity than that of bromelain treatment. The fraction from collagen hydrolysates by savinase treatment had the highest activity compared to neutrase and alcalase treatments. The peptides in the PBN and PPS fractions of <3 kDa had antidiabetic, antihypertensive and antioxidant activities. In conclusion, they have the potential to be used in food and health applications.

Adsorption of Recombinant Human β-Defensin 2 and Two Mutants on Mesoporous Silica Nanoparticles and Its Effect against Clavibacter michiganensis subsp. michiganensis.

Solanum lycopersicum L. is affected among other pests and diseases, by the actinomycete Clavibacter michiganensis subsp. michiganensis (Cmm), causing important economic losses worldwide. Antimicrobial peptides (AMPs) are amphipathic cationic oligopeptides with which the development of pathogenic microorganisms has been inhibited. Therefore, in this study, we evaluate antimicrobial activity of mesoporous silica nanoparticles (MSN5.4) loaded with human β-defensin-2 (hβD2) and two mutants (TRX-hβD2-M and hβD2-M) against Cmm. hβD2, TRX-hβD2-M and hβD2-M presented a half-maximum inhibitory concentration (IC50) of 3.64, 1.56 and 6.17 μg/mL, respectively. MSNs had average particle sizes of 140 nm (SEM) and a tunable pore diameter of 4.8 up to 5.4 nm (BJH). AMPs were adsorbed more than 99% into MSN and a first release after 24 h was observed. The MSN loaded with the AMPs inhibited the growth of Cmm in solid and liquid media. It was also determined that MSNs protect AMPs from enzymatic degradation when the MSN/AMPs complexes were exposed to a pepsin treatment. An improved AMP performance was registered when it was adsorbed in the mesoporous matrix. The present study could expand the applications of MSNs loaded with AMPs as a biological control and provide new tools for the management of phytopathogenic microorganisms.

Plant-derived secretory component gives protease-resistance to Shiga toxin 1-specific dimeric IgA.

A plant-derived secretory component conferred protease-resistance to Shiga toxin-specific mammalian immunoglobulin A. The protease-resistance was functionally demonstrated by a toxin neutralization assay. Secretory component (SC) is believed to play roles in such as the protease-resistance of secretory immunoglobulin A (SIgA), allowing it to function on mucosae. Although the use of a plant expression system for SIgA production has been increasing, it has not been sufficiently assessed as to whether heterologously expressed SC could functionally contribute to the protease-resistance of SIgA. Here, we reconstituted SIgA using plant-derived SC and tested for changes in vulnerability to protease challenge. With glutathione redox buffers, plant-derived SC and mammalian cell-derived dimeric IgA (dIgA) specific for Shiga toxin 1 (Stx1) efficiently formed SIgA. Prior ammonium sulfate precipitation of dIgA was also shown to be useful to enhance the formation of SIgA. The reconstituted SIgA was treated with two gastrointestinal proteases, pepsin and trypsin. After 2-h pepsin treatment, the signal from SIgA remained at 42% with plant-derived SC-reconstitution while that from dIgA remained at 12% without SC-reconstitution on western blot analysis. Similarly, the signal from SIgA remained at 74% with SC but that from dIgA remained at 36% without SC after 4-h trypsin treatment. Furthermore, an effect of SC-reconstitution of dIgA on pepsin-resistance was observed in a toxin neutralization assay involving Vero cells. These results indicated that the plant-derived SC could contribute to the production of orally applicable SIgA.

The improvement of the functional properties of a chickpea protein isolate through proteolysis with three proteases

AbstractBackground and objectivesEnzymatic hydrolysis has previously been shown to have beneficial influences on the protein functionality of pulse protein isolates. To apply and optimize these benefits in chickpeas, a chickpea protein isolate (CPI) was hydrolyzed with three different proteases (trypsin, pepsin, and papain), to three different degrees of hydrolysis (DH): 5%, 10%, and 15%. Changes to zeta potential, hydrophobicity, water and oil holding capacity (WHC and OHC), as well as solubility, emulsifying, and foaming properties at pH 4.0, 7.0, and 10.0 of the various hydrolysates were then quantified and compared with one another in order to determine optimal hydrolytic conditions.FindingsIncreasing length of enzymatic treatments led to a gradual increase in zeta potential, and a rise in protein hydrophobicity. The solubility of trypsin and papain hydrolyzed CPI proteins increased at pH 10.0, while minor decreases in solubility were noted at pH 7.0. Increasing length of pepsin and papain treatment was noted to improve the water holding capacity (WHC), whereas hydrolysis with all three enzymes led to decreases in oil holding capacity (OHC). The emulsifying activity index (EAI) of the CPI increased following hydrolysis with all enzymes at pH 4.0 and 10.0, while at pH 7.0 no changes were observed. The emulsifying stability index (ESI) of the CPI increased following trypsin treatment at pH 4.0; at pH 10.0 emulsions appeared stable, exhibiting no separation over a 30‐min period. Foaming capacity (FC) increased following enzyme treatments at pH 4.0, pH 7.0, and more dramatically at pH 10.0. Foaming stability (FS) worsened at pH 10.0 following higher levels of trypsin hydrolysis (DH &gt; 10%).ConclusionsApproximately 15% hydrolysis with papain was shown as the best conditions to augment the emulsifying, foaming and water holding properties of a CPI material, potentially allowing for the generation of specialized chickpea protein ingredients.Significance and noveltyA total of nine distinct CPI hydrolysates were generated and compared with one another to determine optimal hydrolytic conditions with respect to the functional properties of the CPI.

A novel bacteriocin from Lactobacillus salivarius against Staphylococcus aureus: Isolation, purification, identification, antibacterial and antibiofilm activity

Bacteriocins are known to inhibit various foodborne bacteria and their biofilms; however, few bacteriocins with activity against food-derived Staphylococcus aureus have been reported. Here, a novel bacteriocin (XJS01) from the Lactobacillus salivarius strain CGMCC2070 was obtained, purified, and extensively characterized. Molecular mass and amino acid composition of XJS01 were 666.31 Da and F–S-G-L-A-G-D, respectively. XJS01 inhibited the S. aureus strain 2612:1606BL1486 (S. aureus_26), which was originally isolated from chicken meat. Also, XJS01 showed good resistance to heat treatment, and was only susceptible to pepsin treatment. The minimum inhibitory concentration of XJS01 against S. aureus_26 was 9.85 μg/mL, which is lower than previously reported levels for most described bacteriocins. Furthermore, exposure to XJS01 also decreased viability and significantly inhibited (p < 0.05) planktonic S. aureus_26 cells. Biofilm formation of S. aureus_26 was also significantly inhibited (p < 0.05). The results of electron microscopy showed that XJS01 impaired membrane permeability in S. aureus_26, caused leakage of cytoplasmic content, and led to cell deformation. In summary, this study identifies the bacteriocin XJS01 as a potentially candidate for the control of S. aureus in foods in either planktonic or biofilm states.

Effect of pepsin and SO2 treatments on the yield, physicochemical, morphological, and functional properties of pearl millet starch

Influence of enzymatic and SO2 treatments on the yield, physicochemical, functional, morphological, and colour properties of starches isolated from pearl millet (Ashana and Demby cultivars) was studied. The treatment conditions were; control (steeping for 24 h with 0.2% SO2), B (steeping for 7 h with 3 h in distilled water and 4 h in 0.1 M sodium acetate buffer pH, 4.5), S (steeping for 7 h with 3 h in distilled water and 4 h in 0.2% SO2), BE (steeping for 7 h with 3 h in distilled water and 4 h in 0.1 M sodium acetate buffer pH (4–4.5) + 250 mg pepsin) and BES (steeping for 7 h with 3 h in distilled water and 4 h in 0.1 M sodium acetate buffer pH, 4.5, + 250 mg pepsin + 0.2% SO2). The result showed that starch yield from the treatment BE, BES and S was significantly (p ≤ 0.05) higher than that of B and control treatments in both cultivars. From the micrographs studies, the hydrolytic effect of pepsin on protein matrix attached to the starch could be observed as holes created on the surface of starch granules. All treatments significantly (p ≤ 0.05) affected the amylose content and pH value of both starches, while the falling number and acidity were not affected (p ≥ 0.05) by these treatments compared to controls. Water absorption capacity and fat absorption capacity reduced significantly in all treated starches from the two pearl millet cultivars, while viscosity increased following treatments in both cultivars except treatment S (p ≤ 0.01). In conclusion, functional properties and yield of starch from both millet cultivars were improved by using a combination of enzyme and SO2 during wet milling process.