Physicochemical properties and biological activities of ovine caseinate hydrolysates

Two-Step Purification and Partial Characterization of Keratinolytic Proteases from Feather Meal Bioconversion by Bacillus sp. P45

This study aimed to purify and partially characterize a keratinolytic protease produced by Bacillus sp. P45 through bioconversion of feather meal. Crude protease extract was purified using a sequence of an aqueous two-phase system (ATPS) in large volume systems (10, 50, and 500 g) to increase obtaining purified enzyme, followed by a diafiltration (DF) step. Purified protease was characterized in terms of protein profile analysis by SDS-PAGE, optimum temperature and pH, thermal deactivation kinetics at different temperatures and pH, and performance in the presence of several salts (NaCl, CaCl2, MnCl2, CaO, C8H5KO4, MgSO4, CuSO4, ZnSO4, and FeCl3) and organic solvents (acetone, ethanol, methanol, acetic acid, diethyl ether, and formaldehyde). ATPS with high capacities resulted in purer protease extract without compromising purity and yields, reaching a purification factor up to 2.6-fold and 6.7-fold in first and second ATPS, respectively, and 4.0-fold in the DF process. Recoveries were up to 79% in both ATPS and reached 84.3% after the DF step. The electrophoretic analysis demonstrated a 25–28 kDa band related to keratinolytic protease. The purified protease’s optimum temperature and pH were 55 °C and 7.5, respectively. The deactivation energy (Ed) value was 118.0 kJ/mol, while D (decimal reduction time) and z (temperature interval required to reduce the D value in one log cycle) values ranged from 6.7 to 237.3 min and from 13.6 to 18.8 °C, respectively. Salts such as CaCl2, CaO, C8H5KO4, and MgSO4 increased the protease activity, while all organic solvents caused its decrease. The results are useful for future studies about ATPS scale-up for enzyme purification and protease application in different industrial processes.

Unconventional microbial proteases as promising tools for the production of bioactive protein hydrolysates

Enzymatic hydrolysis is the most prominent strategy to release bioactive peptides from different food proteins and protein-rich by-products. Unconventional microbial proteases (UMPs) have gaining increased attention for such purposes, particularly from the 2010s. In this review, we present and discuss aspects related to UMPs production, and their use to obtain bioactive protein hydrolysates. Antioxidant and anti-hypertensive potentials, commonly evaluated through in vitro testing, are mainly reported. The in vivo bioactivities of protein hydrolysates and peptides produced through UMPs action are highlighted. In addition to bioactivities, enzymatic hydrolysis acts by modulating the functional properties of proteins for potential food uses. The compiled literature indicates that UMPs are promising biocatalysts to generate bioactive protein hydrolysates, adding up to commercially available enzymes. From the recent interest on this topic, continuous and in-depth research is needed to advance toward the applicability and commercial utility of both UMPs and obtained hydrolysates.

Optimization of fermentation conditions for production of neutral metalloprotease by Bacillus subtilis SCK6 and its application in goatskin-dehairing

In this study, a high protease-producing strain was screened by spread plate method and identified by molecular biology and morphological identification. It was identified as Bacillus sp. LCB14. A neutral protease gene was cloned and heterologous expressed by B. subtilis SCK6. Then, the recombinant protease was used to dehair the goat skins. The fermentation conditions of neutral protease production by B. subtilis SCK6 were optimized. The single factor experiments, Plackett-Burma experiment, and response surface method were conducted to determine fermentation medium and culture conditions. The optimized medium contained corn meal 49 g/L, soluble starch 28 g/L, soybean meal 17 g/L, corn steep liquor powder 8 g/L, yeast extract 10 g/L, Na₂HPO₄ 2.3 g/L, KH₂PO₄ 1.9 g/L, MgSO₄ 0.5 g/L, MnCl₂ 0.1 g/L and ZnSO₄ 0.05 g/L. The optimized culture conditions were 35 °C and pH 7.0. Under the optimum conditions, the recombinant strain reached 33467.28 U/mL after 72 hr ferment. Moreover, by fed batch in 30 L fermenters, neutral protease production reached 39,440.78 U/mL and shortened fermentation time from 72 hr to 46 hr. Finally, the crude enzyme was utilized to replace sodium sulfide for dehairing of goatskins. The enzymatic dehaired pelts were white, smooth, and soft; the grain side of enzymatic dehaired pelts were clear; there was no obvious damage to the grain side of enzymatic dehaired pelts by visual observation and tactile test. Furthermore, there were no hair roots, hair follicles and other glands in enzymatic dehaired belts, and the collagen fibers of enzymatic dehaired belt were dispersed well by histological analysis.

A Newly Isolated Bacillus subtilis Strain Named WS-1 Inhibited Diarrhea and Death Caused by Pathogenic Escherichia coli in Newborn Piglets

Bacillus subtilis is recognized as a safe and reliable human and animal probiotic and is associated with bioactivities such as production of vitamin and immune stimulation. Additionally, it has great potential to be used as an alternative to antimicrobial drugs, which is significant in the context of antibiotic abuse in food animal production. In this study, we isolated one strain of B. subtilis, named WS-1, from apparently healthy pigs growing with sick cohorts on one Escherichia coli endemic commercial pig farm in Guangdong, China. WS-1 can strongly inhibit the growth of pathogenic E. coli in vitro. The B. subtilis strain WS-1 showed typical Bacillus characteristics by endospore staining, biochemical test, enzyme activity analysis, and 16S rRNA sequence analysis. Genomic analysis showed that the B. subtilis strain WS-1 shares 100% genomic synteny with B. subtilis with a size of 4,088,167 bp. Importantly, inoculation of newborn piglets with 1.5 × 10¹⁰ CFU of B. subtilis strain WS-1 by oral feeding was able to clearly inhibit diarrhea (p < 0.05) and death (p < 0.05) caused by pathogenic E. coli in piglets. Furthermore, histopathological results showed that the WS-1 strain could protect small intestine from lesions caused by E. coli infection. Collectively, these findings suggest that the probiotic B. subtilis strain WS-1 acts as a potential biocontrol agent protecting pigs from pathogenic E. coli infection.

Importance: In this work, one B. subtilis strain (WS-1) was successfully isolated from apparently healthy pigs growing with sick cohorts on one E. coli endemic commercial pig farm in Guangdong, China. The B. subtilis strain WS-1 was identified to inhibit the growth of pathogenic E. coli both in vitro and in vivo, indicating its potential application in protecting newborn piglets from diarrhea caused by E. coli infections. The isolation and characterization will help better understand this bacterium, and the strain WS-1 can be further explored as an alternative to antimicrobial drugs to protect human and animal health.

Antioxidant and antimicrobial activity of protein hydrolysate extracted from porcine liver

Protein hydrolysates were extracted from porcine liver using commercial proteases viz. alcalase, trypsin and papain. Porcine liver revealed appreciable amounts of protein (20.62%). Enzymatic hydrolysis of porcine liver hydrolysate (PLH) resulted in 23.56, 26.82 and 19.12% of degree of hydrolysis, respectively. Antioxidant activity such as 2–2 diphenyl–1-picrylhydrazyl (DPPH) and 2, 2-azino-bis-3-ethyl-benzthiazoline-6-sulphonic acid (ABTS) and ferric ion reducing power (FRAP) radicals were determined for PLH. All PLH samples showed slight decrease in the pH during hydrolysis while, they scavenged 42.27, 57.49 and 40.32% of DPPH radicals, respectively at sixth hour of hydrolysis. Trypsin hydrolysed PLH exhibited highest ABTS radical scavenging activity (86.79%) than alcalase hydrolysed PLH (74.62%) and papain hydrolysed PLH (70.63%). FRAP of PLH samples were found to be 13.69, 14.92 and 12.65% for alcalase, trypsin and papain extracted PLH samples, respectively. PLH obtained from trypsin hydrolysis showed highest antimicrobial activity followed by papain and alcalase PLH, respectively. However, all PLH have the potential to be a protein rich ingredient for use in formulated meat products and possible help in reduction of oxidative and microbial deterioration.

Simultaneous production of proteases and antioxidant compounds from agro-industrial by-products

The use of processes for simultaneous production of bioproducts as enzymes and bioactive compounds is an interesting alternative to reduce environmental impacts. Thus, the aim of this study was to produce simultaneously, using the biorefinery concept, both proteases and bioactive compounds with antioxidant activity from Bacillus sp. P45 cultivation by using different by-products. The integrated process developed in this study enabled to obtain enzymes with proteolytic and keratinolytic properties in a process with alternate substrates from agro-industrial by-products (feather meal, residual feather meal and biomass), thus, creating an interesting alternative to managing them. The residual biomass provided the highest protease activity (1306.6U/mL) and the reused feather meal reached the highest keratinolytic activity (89U/mL), both at 32h of cultivation. Moreover, hydrolysates produced in cultivation using feather meal and residual biomass had high antioxidant activity, they have great potential as natural antioxidants.

Hydrolysates of sheep cheese whey as a source of bioactive peptides with antioxidant and angiotensin-converting enzyme inhibitory activities

Enzymatic proteolysis may be employed to release bioactive peptides, which have been investigated for potential benefits from both technological and human health perspectives. In this study, sheep cheese whey (SCW) was hydrolyzed with a protease preparation from Bacillus sp. P7, and the hydrolysates were evaluated for antioxidant and angiotensin I-converting enzyme (ACE)-inhibitory activities. Soluble protein and free amino acids increased during hydrolysis of SCW for up to 4h. Antioxidant activity of hydrolysates, evaluated by the 2,2'azino-bis-(3-ethylbenzothiazoline)-6-sulfonic acid radical scavenging method, increased 3.2-fold from 0 h (15.9%) to 6h of hydrolysis (51.3%). Maximum Fe(2+) chelation was reached in 3h hydrolysates, and the reducing power peaked at 1h of hydrolysis, representing 6.2 and 2.1-fold increase, respectively, when compared to that of non-hydrolyzed SCW. ACE inhibition by SCW (12%) was improved through hydrolysis, reaching maximal values (55% inhibition) in 4h, although 42% inhibition was already observed after 1h hydrolysis. The peptide LAFNPTQLEGQCHV, derived from β-lactoglobulin, was identified from 4-h hydrolysates. Such a biotechnological approach might be an interesting strategy for SCW processing, potentially contributing to the management and valorization of this abundant dairy byproduct.

Production of feather hydrolysates with antioxidant, angiotensin-I converting enzyme- and dipeptidyl peptidase-IV-inhibitory activities

The antioxidant and antihypertensive activities of feather hydrolysates obtained with the bacterium Chryseobacterium sp. kr6 were investigated. Keratin hydrolysates were produced with different concentrations of thermally denatured feathers (10-75 g l(-1)) and initial pH values (6.0-9.0). Soluble proteins accumulated in high amounts in media with 50 and 75 g l(-1) of feathers, reaching values of 18.5 and 22 mg ml(-1), respectively, after 48 hours of cultivation. In media with 50 g l(-1) of feathers, initial pH had minimal effect after 48 hours. Maximal protease production was observed after 24 hours of cultivation, and feather concentration and initial pH values showed no significant effect on enzyme yields at this time. Feather hydrolysates displayed in vitro antioxidant properties, and optimal antioxidant activities were observed in cultures with 50 g l(-1) feathers, at initial pH 8.0, after 48 hours growth at 30°C. Also, feather hydrolysates were demonstrated to inhibit the angiotesin I-converting enzyme by 65% and dipeptidyl peptidase-IV by 44%. The bioconversion of an abundant agroindustrial waste such as chicken feathers can be utilized as a strategy to obtain hydrolysates with antioxidant and antihypertensive activities. Feather hydrolysates might be employed as supplements in animal feed, and also as a potential source of bioactive molecules for feed, food and drug development.