Soybean Hydrolysate Research Articles

Effects of Fermentation with Tetragenococcus halophilus and Zygosaccharomyces rouxii on the Volatile Profiles of Soybean Protein Hydrolysates.

The effects of fermentation with lactic acid bacteria (LAB) and yeast on the aroma of samples were analyzed in this work. The volatile features of different soybean hydrolysates were investigated using both GC-MS and GC-IMS. Only 47 volatile flavor compounds (VFCs) were detected when using GC-IMS, while a combination of GC-MS and GC-IMS resulted in the identification of 150 compounds. LAB-yeast fermentation could significantly increase the diversity and concentrations of VFCs (p < 0.05), including alcohols, acids, esters, and sulfurs, while reduce the contents of aldehydes and ketones. Hierarchical clustering and orthogonal partial least squares analyses confirmed the impact of fermentation on the VFCs of the hydrolysates. Seven compounds were identified as significant compounds distinguishing the aromas of different groups. The partial least squares regression analysis of the 25 key VFCs (ROAV > 1) and sensory results revealed that the treatment groups positively correlated with aromatic, caramel, sour, overall aroma, and most of the key VFCs. In summary, fermentation effectively reduced the fatty and bean-like flavors of soybean hydrolysates, enhancing the overall flavor quality, with sequential inoculation proving to be more effective than simultaneous inoculation. These findings provided a theoretical basis for improving and assessing the flavor of soybean protein hydrolysates.

Production of gamma-aminobutyric acid (GABA) by Bacillus subtilis BBEL02 fermentation using nitrogen-rich industrial wastes as crude feedstocks

Industrial-scale fermentation of γ-aminobutyric acid (GABA) is often limited by high cost of the starting raw materials. Increasing commercial applications of GABA in various industries have urged the research on finding the alternative substrates for the GABA production. The effects of concentration of different types of carbon and nitrogen sources; concentration of monosodium glutamate (MSG) in the defined medium for GABA production using the newly isolated Bacillus subtilis BBEL02 were studied. The feasibility of corn steep liquor (CSL) and soybean hydrolysate (SBH) as the replacement of nitrogen sources in the fermentation media for GABA production was also investigated. Highest GABA content (10.9 gL−1) and productivity (3.7 gL−1d−1) were achieved with defined medium containing 1 % (w/v) glucose, 2 % (v/v) SBH and 5 % (w/v) MSG. Dissolved oxygen (DO) of 80 % in 2-L fermenter presented the highest productivity (4.2 gL−1d−1) and GABA concentration (12.5 gL−1), however DO of 50 % was preferred because of the lower rotation speed to prevent cells deterioration.

Differential effects of oilseed protein hydrolysates in attenuating inflammation in murine macrophages

Proteins from underutilized defatted oilseed meals have been proposed as promising sources of bioactive peptides. This study was conducted to determine the anti-inflammatory activities of five oilseed proteins (flaxseed, rapeseed, sunflower, sesame and soybean) hydrolysed via alcalase, pepsin (at pH 1.3 and pH 2.1), respectively, and to compare these against two dairy proteins (whey, casein). The potential of protein hydrolysates of three different molecular weight fractions (Mw > 10 kDa, 3–10 kDa, < 3 kDa) to modulate nuclear factor kappa B (NF-κB) signalling was screened via RAW-Blue™ reporter cells. Fractions with Mw < 3 kDa of pepsin (pH 1.3)-treated protein hydrolysates were subsequently selected to validate anti-inflammatory properties in RAW 264.7 macrophages. Rapeseed fractions showed greatest potency to attenuate inflammation, via efficiently down-regulating the expression of IL-6 (−49.1%), IL-1β (−58.6%), iNOS (−41.9%) and COX-2 (−58.7%) and up-regulating the IL-10 (+47.2%) mRNA level at 2000 μg peptides/mL. Rapeseed, sesame and casein demonstrated marked repression of NF-κB pathway, through down-regulating NF-κB1, p65 and/or IκBα mRNA levels. In addition, rapeseed, sesame and soybean reduced the expression of TLR4 and/or CD14 associated with attenuated LPS recognition. In addition, it was confirmed that rapeseed and soybean hydrolysates showed capabilities to bind 43.9 and 52.4% of LPS in solution, thereby weakening inflammatory response; an effect that could at least partially be related to the presence of hydrophobic amino acids. To summarize, current data demonstrate differing capacity of plant protein hydrolysates to interact with inflammatory signalling, indicating the need for further research into the molecular mechanisms of peptide action.

The Hydrolytic Peptides of Soybean Protein Induce Cell Cycle Arrest and Apoptosis on Human Oral Cancer Cell Line HSC-3.

Protein hydrolysates from various sources, including tuna cooking juice, soy protein isolate, sodium caseinate, wheat gluten and skin gelatin from porcine, tilapia, halibut and milkfish were analyzed to screen their antiproliferative activities against the human oral squamous carcinoma cell line, HSC-3. The soy protein isolate was selected for further investigations based on its hydrolysates with bromelain (SB) and thermolysin (ST), showing the greatest inhibition of cell growth. The SB and ST hydrolysates showed antiproliferative activities up to 35.45–76.39% against HSC-3 cells at 72 h, and their IC50 values were 0.74 and 0.60 mg/mL, respectively. SB and ST induced cell cycle arrest in the S phase through a pathway independent of p21 and p27 protein expression. Further, ST induced the apoptosis of HSC-3 cells by downregulating expression of Bcl-2, PARP, caspase 3 and caspase 9, but an upregulating expression of p53 and cleaved caspase 3. Unlike ST, SB may induce necrosis on HSC-3 cells. Thus, soybean hydrolysates may be a good source for providing antiproliferative peptides against HSC-3, while SB and ST may have the potential to be developed as functional foods.

Soybean-Derived Peptides Attenuate Hyperlipidemia by Regulating Trans-Intestinal Cholesterol Excretion and Bile Acid Synthesis.

Increased triglyceride, cholesterol, and low-density lipoprotein (LDL) levels cause hyperlipidemia. Despite the availability of statin-based drugs to reduce LDL levels, additional effective treatments for reducing blood lipid concentrations are required. Herein, soybean hydrolysate prepared via peptic and tryptic hydrolysis promoted trans-intestinal cholesterol excretion (TICE) by increasing ATP-binding cassette subfamily G member 5 (ABCG5) and ABCG8 expression. The peptide sequence capable of promoting TICE was determined via HPLC and LC-MS/MS. Based on this, pure artificial peptides were synthesized, and the efficacy of the selected peptides was verified using cellular and hyperlipidemic mouse models. Soybean hydrolysates, including two bioactive peptides (ALEPDHRVESEGGL and SLVNNDDRDSYRLQSGDAL), promoted TICE via the expression of ABCG5 and ABCG8 in enterocytes. They downregulated expression of hepatic cytochrome P450 family 7 subfamily A member 1 (CYP7A1) and CYP8B1 via expression of fibroblast growth factor 19 (FGF19) in a liver X receptor α (LXRa)-dependent pathway. Administration of bioactive peptides to hyperlipidemic mouse models by oral gavage reduced cholesterol levels in serum via upregulation of ABCG5 and ABCG8 expression in the proximal intestine and through fecal cholesterol excretion, upregulated FGF 15/19 expression, and suppressed hepatic bile acid synthesis. Oral administration of soybean-derived bioactive peptides elicited hypolipidemic effects by increasing TICE and decreasing hepatic cholesterol synthesis.

The Effect of Ascorbic Acid and Soybean Protein Hyrolysate to Iron Binding Capacity

The study aimed to investigate the effect of ascorbic acid and soybean protein hydrolysate to iron-binding capacity. BPPT (Agency for the Assessment and Application of Technology) developed soybean hydrolysate, which was obtained by thermal and enzymatic hydrolysis. Ascorbic acid was added in sample preparation with composition 0, 50, 75 and 100%. Soybean protein hydrolysate (SPH) was prepared by gel filtration chromatography using Sephadex G-25 to separate peptide based on molecular weight. Characterization of SPH and SPH fractions was also conducted, such as protein concentration, molecular weight, iron-binding capacity, and amino acid concentration. Iron binding capacity was determined by the colorimetric method using an ortho-phenanthroline reagent. The result showed that soybean protein hydrolysate increases iron-binding capacity 25-37 times than ascorbic acid. Arginine, aspartic acid, glutamic acid, threonine, lysine, and serine were found as amino acids responsible for iron-binding capacity in the SPH.

Exploring the additive bio-agent impacts upon ectoine production by Halomonas salina DSM5928T using corn steep liquor and soybean hydrolysate as nutrient supplement

Ectoine production using inexpensive and renewable biomass resources has attracted great interest among the researchers due to the low yields of ectoine in current fermentation approaches that complicate the large-scale production of ectoine. In this study, ectoine was produced from corn steep liquor (CSL) and soybean hydrolysate (SH) in replacement to yeast extract as the nitrogen sources for the fermentation process. To enhance the bacterial growth and ectoine production, biotin was added to the Halomonas salina fermentation media. In addition, the effects addition of surfactants such as Tween 80 and saponin on the ectoine production were also investigated. Results showed that both the CSL and SH can be used as the nitrogen source substitutes in the fermentation media. Higher amount of ectoine (1781.9 mg L-1) was produced in shake flask culture with SH-containing media as compared to CSL-containing media. A total of 2537.0 mg L-1 of ectoine was produced at pH 7 when SH-containing media was applied in the 2 L batch fermentation. Moreover, highest amount of ectoine (1802.0 mg L-1) was recorded in the SH-containing shake flask culture with addition of 0.2 μm mL-1 biotin. This study demonstrated the efficacy of industrial waste as the nutrient supplement for the fermentation of ectoine production.

The supplement of vitamin C facilitates l-lactic acid biosynthesis in Lactobacillus thermophilus A69 from sweet sorghum juice coupled with soybean hydrolysate as feedstocks

Regulating oxidative damage is an effective way to enhance cell growth and metabolite accumulation in microbial strains. However, this strategy on lactic acid production has not been systematically reported yet. In present study, the effect of antioxidant vitamin C on cell growth and l-lactic acid production was investigated in Lactobacillus thermophilus A69, and an addition of 75 mM vitamin C resulted in significant improvement in cell growth and l-lactic acid accumulation. The total antioxidant capacity (T-AOC) and key enzyme activities involving in glycolytic pathway (such as hexokinase, phosphofructokinase, pyruvate kinase, and lactate dehydrogenase) were also significantly enhanced by vitamin C addition. Finally, with the addition of optimal concentrations of vitamin C into sweet sorghum juice coupled with cheaper soybean hydrolysate as feedstocks, a final l-lactic acid titer of 118.8 g/L with the productivity of 3.71 g/L/h was achieved by A69 strain. This study provided an efficient and economical approach for enhancement of l-lactic acid fermentation efficiency using sweet sorghum juice as a feedstock.

Effect of Spray-Drying and Freeze-Drying on the Properties of Soybean Hydrolysates

The use of enzyme-assisted aqueous extraction to extract soybean oil will produce soy protein hydrolysates (SPH) that have good antioxidant properties but are bitter and hygroscopic. To microencapsulate these hydrolysates, soy protein isolate/maltodextrin mixtures were used as the carrier. The effects of spray-drying and freeze-drying on the bitterness, hygroscopicity, and antioxidant properties were compared. The properties of different dried samples were compared using solubility, hygroscopicity, moisture content, water activity, flowability, and glass transition temperature (Tg). The results showed that the spray-drying was more effective than freeze-drying. Hygroscopicity was reduced to 18.2 g/100 g, and the Tg value was raised to 80.8°C. The morphology was analyzed using scanning electron microscopy, and the antioxidant properties of the samples were measured using the ABTS˙+ radical scavenging activity. The results showed that spray-dried SPH had more carrier masking, which weakened bitterness, reduced moisture absorption, and had no significant negative impact on its oxidation resistance, solubility, and flowability, and spray-drying after carrier encapsulation of SPH improved the recovery rate.

Antioxidant activity of soybean peptides on human hepatic HepG2 cells

Soybean is an interesting source of bioactive peptides useful for the development of functional foods and nutraceuticals. In this study, the antioxidant activity of peptic (P) and tryptic (T) soybean hydrolysates was characterized. Results suggest that both hydrolysates are able to scavenge DPPH radical. Moreover, after induction of oxidative stress by using H2O2, either Soybean P or T pre-treatment reduces the ROS, lipid peroxidation, and NO levels in human hepatic HepG2 cells. HepG2 cells, exposed to H2O2 alone, produce a significant augmentation of intracellular reactive oxygen species (ROS) levels by 29.5%, with the consequence of an augmentation of cellular lipid peroxidation levels up to 112.4±0.5%. The pre-treatment with soybean hydrolysates restores the basal level of ROS and induces a reduction of cellular lipid peroxidation. The antioxidant ability of Soybean P and T are also confirmed by their ability to reduce the H2O2-induced NO levels in HepG2 cells.

Fermentative production of chiral acetoin by wild-type Bacillus strains

In recent years, there have been many studies on producing acetoin by microbial fermentation, while only a few studies have focused on chiral acetoin biosynthesis. The weight assignment method was first applied to balance the chiral purity (expressed as the enantiomeric excess value) and the titer of acetoin. Bacillus sp. H-18W, a thermophile, was selected from seven Bacillus strains for chiral acetoin production. To lower the cost of the fermentation medium, soybean meal was used as a feedstock. Four kinds of frequently used commercial proteinases with different active sites were tested for the hydrolyzation of the soybean meal, and the combination of the acidic proteinase and the neutral proteinase showed the best results. In a fermentation medium containing 100 g L−1 glucose and 200 g L−1 hydrolysate, Bacillus sp. H-18W produced 21.84 g L−1 acetoin with an ee value of 96.25% at 60 h. This is the first report of using a thermophilic strain to produce chiral acetoin by microbial fermentation. Thermophilic fermentation can reduce the risk of bacterial contamination and can save cooling water. Using soybean meal hydrolysate and glucose as feedstocks, this work provides an economical and alternative method for the production of chiral pure acetoin.

The variation of two extracellular enzymes and soybean meal bitterness during solid-state fermentation of Bacillus subtilis

The debittering effect of extracellular enzymes from Bacillus subtilis ACCC 01746 was studied using soybean meal as a substrate for solid-state fermentation (SSF). Results showed that B. subtilis produces proteases and carboxypeptidase in the early stage of SSF (0–8 h). Proteases are dominant and can hydrolyze the soybean protein into long-chain peptides with mild bitterness. Carboxypeptidase production is dominant at 8–16 h SSF, at which point soybean protein is further hydrolyzed and bitterness is enhanced. The strain then produces additional carboxypeptidase after 16 h, and bitterness is reduced. We compared the amino acid composition of the hydrolysates from soybean protein isolates to that of the fermented liquid of SSF. In the hydrolysates from soybean protein isolates that exhibit strong bitterness, 62.81% of amino acids are hydrophobic and occur in the form of peptides. In the fermented liquid from soybean meal, 16.22% of amino acids are hydrophobic and are mainly present in the form of free amino acids. The bitterness of fermented soybean hydrolysate is reduced from 5 to 0 when fermented for 24 h, suggesting that B. subtilis can effectively reduce bitterness, possibly due to the carboxypeptidase. Enzyme analysis shows that B. subtilis excretes carboxypeptidase during growth. The amino acids phenylalanine, alanine, tyrosine, and leucine at the C-terminal of the soybean bitter peptides in hydrolysates are cleaved in the presence of carboxypeptidase, resulting in complete debitterness.

Purification and Characterization of Antioxidant Peptides from Alcalase-Hydrolyzed Soybean ( Glycine max L.) Hydrolysate and Their Cytoprotective Effects in Human Intestinal Caco-2 Cells.

This study aimed to purify and identify antioxidant peptides from the low-molecular-weight fraction (SPH-I, MW < 3 kDa) of Alcalase-hydrolyzed soybean ( Glycine max L.) hydrolysate and further evaluate the cytoprotective effects of synthesized peptides against oxidative stress in human intestinal Caco-2 cells. After purification by gel filtration chromatography and reversed-phase HPLC, four major peptides were sequenced by nano-LC-ESI-MS/MS as VVFVDRL (847 Da, SPH-IA), VIYVVDLR (976 Da, SPH-IB), IYVVDLR (877 Da, SPH-IC), and IYVFVR (795 Da, SPH-ID). The antioxidant peptides were synthesized and displayed desirable DPPH radical-scavenging activity (from 16.5 ± 0.5 to 20.3 ± 1.0 μM Trolox equivalent (TE)/μM), ABTS•+ radical-scavenging activity (from 3.42 ± 0.2 to 4.24 ± 0.4 mM TE/μM), ORAC (from 143 ± 2.1 to 171 ± 4.8 μM TE/μM), and FRAP (from 54.7 ± 1.2 to 79.0 ± 0.6 mM Fe2+/μM). Moreover, the synthesized peptides protected Caco-2 cells against H2O2-induced oxidative damage via significantly downregulating intracellular ROS generation and lipid peroxidation ( p < 0.05). Additionally, SPH-IC and SPH-ID statistically upregulated total reduced glutathione synthesis, enhanced activities of catalase and glutathione reductase, and suppressed ROS-mediated inflammatory responses via inhibiting interleukin-8 secretion ( p < 0.05).

Soybean Peptides Exert Multifunctional Bioactivity Modulating 3-Hydroxy-3-Methylglutaryl-CoA Reductase and Dipeptidyl Peptidase-IV Targets in Vitro.

This study was aimed at evaluating the cellular mechanism through which peptic (P) and tryptic (T) soybean hydrolysates modulate the targets involved in hypocholesterolemic pathways in HepG2 and antidiabetic pathways in Caco-2 cells. Both hydrolysates (tested in the concentration range of 0.5-2.5 mg/mL) inhibited the 3-hydroxy-3-methylglutaryl-CoA reductase activity in HepG2 cells. In addition, Soybean P increased LDLR protein levels on HepG2 membranes by 51.5 ± 11.6% and 63.0 ± 6.9% (0.5-1.0 mg/mL) whereas Soybean T increased them by 55.2 ± 9.7% and 85.8 ± 21.5% (0.5-1.0 mg/mL) vs the control, with a final improved HepG2 capacity in the uptake of extracellular LDL. Soybean P reduced in vitro the dipeptidyl peptidase-IV activity by 16.3 ± 3.0% and 31.4 ± 0.12% (1.0 and 2.5 mg/mL), whereas Soybean T reduced it by 15.3 ± 11.0% and 11.0 ± 0.30% (1.0 and 2.5 mg/mL) vs the control. Finally, both hydrolysates inhibited dipeptidyl peptidase-IV activity in situ in human intestinal Caco-2 cells. This investigation may help to explain the activities observed in experimental and clinical studies.

Production optimisation and characterisation of extracellular protease secreted by newly isolated Bacillus subtilis AU-2 strain obtained from Tribolium castaneum gut

A novel protease secreting bacterial strain was isolated from the gut of Tribolium castaneum residing in stored Glycine max (soybean) seeds. The strain was identified as Bacillus subtilis AU-2. A response surface approach using Plakett-Burman Design (PBD) was used for the screening and a Central Composite Design (CCD) was used for the optimization of production parameters. An elevated protease production (580 U/mL) was achieved in optimised medium comprised of (g/L) soy bean meal, 10 g; glucose, 7.5 g; KH2PO4, 1.0 g; CaCl2, 1.0 g and pH, 7.0 by using 3.5% inoculum at 37°C temperature in agitated (60 rpm) batch culture after 48 h. The three step enzyme purification achieved 26.81 fold purified protease which yielded a specific activity of 22773 U/mg and 34% recovery. The purified extracellular protease of B. subtilis AU-2 has molecular mass 38 kDa. The protease was documented as metallo-protease having optimum pH 7.5 and temperature 40°C. The purified protease showed appreciable endurance in presence of sodium dodecyl sulphate, Triton X-100, hydrogen peroxide and sodium per-borate. The protease efficiently digests proteinaceous substrates like casein, soybean flour, bovine serum albumin, haemoglobin, and egg albumin. The protease of newly isolated B. subtilis is now available for various food applications like soybean hydrolysate preparation, meat tenderisation, casein lysate preparation, milk clotting, and food waste treatment.

Fish meal replaced by hydrolysed soybean meal in diets increases growth and improves the antioxidant defense system of silver catfish ( Rhamdia quelen )

One of the current challenges of global fish farming is developing plant-based proteins as a feasible substitute for fishmeal in the formulation of aquafeeds. Substitution levels of fishmeal with hydrolyzed soybean meal (HSM) in diets for silver catfish (Rhamdia quelen) were evaluated for growth, protein metabolism and antioxidant activity. The experiment was carried out in a recirculation system of 20 tanks of 250 L. A total of 300 silver catfish juveniles were used to compose five treatments and four replicates per treatment. Levels of soybean hydrolysate (0%, 5%, 10%, 15% and 20%) were tested in diets (39% protein and 3,500 Kcal) for 60 days. Silver catfish growth was higher at all inclusion levels of HSM when compared to the control diet. No change was shown for body protein deposition. The production of nitrogenous compounds in the liver and muscle was also unaffected by any of the diets. The diet containing 20% HSM promoted an increase in the amounts of non-protein thiols in the gills and brain. The HSM substitution levels of up to 20% of fishmeal in the diet increases growth and contributes to silver catfish antioxidant activity.

Efficient l‐lactic acid production from purified sweet sorghum juice coupled with soybean hydrolysate as nitrogen source by Lactobacillus thermophilus A69 strain

AbstractBACKGROUNDHigh‐efficiency utilization of sweet sorghum juice can bring significant economic feasibility of l‐lactic acid production. However, an expensive nitrogen source increases the capital cost, and the complex composition of sweet sorghum juice could limit the yield.RESULTSIn the present study, a bioprocess was developed to enhance the efficiency of l‐lactic acid production using purified sweet sorghum juice and cheap nitrogen supply strategies. It was first demonstrated that cheaper soybean hydrolysate could be used as a low‐cost nitrogen source for efficient l‐lactic acid production by Lactobacillus thermophilus A69, the optimal soybean hydrolysate concentration being 25 g L−1. It was then proved that the efficiency of l‐lactic acid production was significantly boosted using sweet sorghum juice purified via clarification treatment. Finally, on combining the cheap nitrogen source and the clarification strategy, 114.6 g L−1 l‐lactic acid with a productivity of 2.61 g L−1 h−1 was produced by A69 strain in a 5 L bioreactor.CONCLUSIONThis study provides a simple, practical and economic approach to promote l‐lactic acid production using sweet sorghum juice as feedstock. © 2019 Society of Chemical Industry

Anti-hyperuricemic peptides derived from bonito hydrolysates based on in vivo hyperuricemic model and in vitro xanthine oxidase inhibitory activity

Traditional drugs used to treat hyperuricemia have adverse effects. In this study, to identify safer anti-hyperuricemic bioactive peptides isolated from food-derived protein hydrolysates, a hyperuricemia rat model induced by potassium oxonate (PO) was used to evaluate the activity of bonito hydrolysates (BH), dephenolised walnut hydrolysates (DWH), and soybean hydrolysates (SH). The serum uric acid level of rats in the BH group (95.4 ± 27.4 μM, p < 0.01) was significantly reduced compared to that in the model group (212.00 ± 30.00 μM) to a level even lower than that in allopurinol group (114.3 ± 53.0 μM). Furthermore, BH alleviated renal impairment caused by PO in vivo and exhibited the greatest xanthine oxidase (XOD) inhibitory activity (65.5 ± 8.0%) in vitro compared to the other hydrolysates. Two peptides identified from BH bound the catalytic site of XOD, among which the hydrophobic peptide WML entered the active site of XOD more easily compared to the hydrophilic peptide PGACSN, possibly because of hydrophobic interactions. The chemically synthesized WML demonstrated high XOD inhibitory effect compared to PGACSN and a significant change in the secondary structure of XOD. Therefore, hexapeptide PGACSN and tripeptide WML are partially responsible for the anti-hyperuricemic activity of BH, and hydrophobic amino acids play important roles in the XOD inhibitory activity of peptides.

Antioxidant activity and protective effects of Alcalase-hydrolyzed soybean hydrolysate in human intestinal epithelial Caco-2 cells

Soybeans are known as a promising source of bioactive peptides. However, knowledge on the antioxidant behaviors of soybean protein hydrolysate (SPH) in the human intestinal epithelium is limited. In this study, SPH was prepared with Alcalase and subsequently ultrafiltered into four peptide fractions as SPH-I (<3 kDa), SPH-II (3–5 kDa), SPH-III (5–10 kDa) and SPH-IV (>10 kDa). The antioxidant properties of SPH and membrane fractions were investigated using different chemical assays and their protective effects against oxidative stress were evaluated using H2O2-stressed human intestinal Caco-2 cells. Results showed that SPH-I exhibited the strongest 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity (IC50 = 2.56 mg/mL) and reducing capacity while SPH-III had the best metal ion-chelating activity (IC50 = 0.29 mg/mL). Both SPH and the peptide fractions dose-dependently suppressed intracellular reactive oxygen species (ROS) accumulation induced by H2O2 in Caco-2 cells, but the strongest inhibitory effect was observed for SPH-I. Amino acid (AA) results revealed that SPH-I was rich in hydrophobic and antioxidant AAs, which could contribute to its stronger antioxidant properties. Additionally, SPH-I protected Caco-2 cells from H2O2-induced oxidative stress via inhibiting lipid peroxidation and stimulating antioxidant enzyme activities. These results suggest that SPH-I and constitutive peptides can be beneficial ingredients with antioxidant properties and protective effects against ROS-mediated intestinal injury.

Metabolic engineering of Escherichia coli to produce succinate from soybean hydrolysate under anaerobic conditions.

It is of great economic interest to produce succinate from low-grade carbon sources, which can enhance the competitiveness of the biological route. In this study, succinate producer Escherichia coli CT550/pHL413KF1 was further engineered to efficiently use the mixed sugars from non-food based soybean hydrolysate to produce succinate under anaerobic conditions. Since many common E. coli strains fail to use galactose anaerobically even if they can use it aerobically, the glucose, and galactose related sugar transporters were deactivated individually and evaluated. The PTS system was found to be important for utilization of mixed sugars, and galactose uptake was activated by deactivating ptsG. In the ptsG- strain, glucose, and galactose were used simultaneously. Glucose was assimilated mainly through the mannose PTS system while galactose was transferred mainly through GalP in a ptsG- strain. A new succinate producing strain, FZ591C which can efficiently produce succinate from the mixed sugars present in soybean hydrolysate was constructed by integration of the high succinate yield producing module and the galactose utilization module into the chromosome of the CT550 ptsG- strain. The succinate yield reached 1.64 mol/mol hexose consumed (95% of maximum theoretical yield) when a mixed sugars feedstock was used as a carbon source. Based on the three monitored sugars, a nominal succinate yield of 1.95 mol/mol was observed as the strain can apparently also use some other minor sugars in the hydrolysate. In this study, we demonstrate that FZ591C can use soybean hydrolysate as an inexpensive carbon source for high yield succinate production under anaerobic conditions, giving it the potential for industrial application.