Antioxidant properties of Klunzinger's mullet (Liza klunzingeri) protein hydrolysates prepared with enzymatic hydrolysis using a commercial protease and microbial hydrolysis with Bacillus licheniformis

Novel microbial fermentation for the preparation of iron-chelating scallop skirts peptides-its profile, identification, and possible binding mode

Iron chelating peptides have been widely utilized as iron supplements due to their excellent absorption capacity, However, the high cost and cumbersome manufacturing process of these peptides significantly limit their industrial application. In this study, fermentation was used for the first time to prepare iron chelating peptides. Bacillus altitudinis 3*1-3 was selected as the most suitable strain from 50 strains. The hydrolysates of fermented scallop skirts showed excellent iron-chelating capacity (9.39 mg/g). Aspartic acid, glutamic acid, and histidine are crucial for the binding of peptides to ferrous ions. The heptapeptide (FEDPEFE) forms six binding bonds with ferrous irons. Compared with ferrous sulfate, peptide-ferrous chelate showed more stability in salt solution and simulated gastrointestinal juice (p < 0.05). Furthermore, the fermentation method could save >50% of the cost compared with the enzymatic method. The results can provide a theoretical basis for the preparation of ferrous-chelated peptides using the fermentation method.

Antioxidant peptide nanohybrid: a new perspective to immobilize bioactive peptides from milk industry wastewater

In this study, dairy industry wastewater was collected and used as a protein source. The proteins were converted into powder form using lyophilization. The proteins were digested using Bacillus subtilis (B. subtilis) NCIM 2724. The maximum degree of hydrolysis (DH) of protein was observed at pH of 7, 30 °C incubation temperature, 120 rpm shaking speed, and 96 h incubation. The tris-glycine sodium dodecyl sulfate-polyacrylamide (tris-glycine-SDS) gel electrophoresis showed the disappearance of large molecular weight proteins due to the proteolytic action of B. subtilis. The resulting digest was fractionated using a 3 kDa membrane filter. The antioxidant activity of the obtained fractions was evaluated. Antioxidant activity of digest and filtrate was found to be 12.78% (±0.040) and 49% (±0.025), respectively, at a concentration of 50 mg/mL. The 3 kDa filtrate was subjected to liquid chromatography-mass spectrometry (LCMS) analysis. Bioinformatics tools were used to predict the sequences of antioxidant peptides. Furthermore, the 3 kDa filtrate was used for the synthesis of antioxidant nanohybrid. Scanning electron microscopy (SEM)-energy dispersive spectroscopy (EDS) confirmed the nanohybrid formation and encapsulation of peptides. The antioxidant nanohybrid showed enhanced antioxidant activity compared to the free peptide solution. The dairy industry has a significant environmental impact due to high water use and waste generation. This study addresses an important issue of recycling protein-containing wastewater and the potential to be used for converting these proteins into antioxidant peptides. Such practices will help to reduce environmental impact and sustainably operate the industry.

Evaluation of egg white hydrolysates on the hepatoprotective effect in vitro and in vivo

The small molecule characteristics and nutritional value of egg white hydrolysates have been widely used. In the present study, in vitro and in vivo models were used to investigate the hepatoprotective effect of egg protein hydrolysate (EWH) by regulating the expression of antioxidant enzymes. The in vitro experiment results showed that 0.1, 0.5, and 1 mg/mL of EWH enhanced antioxidant activity in HepG2 cells by increased glutathione peroxidase (GPx) activity and reduced glutathione (GSH) levels. The in vivo experiment results showed that EWH (L) (38.5 mg/kg BW) and EWH (H) (385 mg/kg BW) alleviated carbon tetrachloride (CCl4)-induced hepatotoxicity in SD rats through reduced levels of serum aspartate aminotransferase (AST) alanine aminotransferase (ALT), and lipid peroxidation products malondialdehyde (MDA). In addition, EWH also ameliorates CCl4-induced hepatotoxicity in SD rats by increasing the antioxidant activity of GSH levels with a decrease in oxidized glutathione (GSSG) levels. Besides, EWH ameliorates liver tissue injuries by CCl4-induction. EWH has the highest glutamic acid in free amino acid composition, the second highest was aspartic acid, and the third was cystine, 204, 141, and 125 mg/100 g, respectively. These results suggest EWH has hepatoprotective potential through reduced lipid peroxidation products and enhanced antioxidant activity.

Investigation of the optimal production conditions for egg white hydrolysates and physicochemical characteristics

This study aimed to investigate the potential of egg white protein hydrolysate (EWH) as a functional food by identifying the optimum production conditions for EWH with response surface methodology (the results of the sensory evaluation were considered as an essential quality indicator). At the same time, its physicochemical and biological activity was also evaluated. The optimal economic production conditions were selected: substrate concentration of 12.5%, enzyme content of 7.5%, and hydrolysis time at 100 min. The degree of hydrolysis (DH %) was 13.51%. In addition, to the better acceptance of the evaluation, it also helps to reduce the production cost of the protein hydrolysate, which is beneficial to future processing and applications. The antioxidant capacity experiments showed that EWH has good antioxidant activity, which presents a dose-dependent relationship. Hence, this study provides a theoretical basis for future research and application of EWH for processing applications, including dietary supplementation.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13197-023-05708-0.

Screening, characterization, and kinetic studies of a serine alkaline protease from kitchen wastewater bacteria P2S1An and evaluation of its application in nutraceutical production

This present investigation aimed at characterizing the biochemical potential and kinetic study of the protease isolated from kitchen wastewater bacteria, P2S1An. The enzymatic activity was optimum when incubated for 96 h, at 30°C and pH 9.0. The enzymatic activity of the purified protease (PrA) was 10.47-folds that of crude protease (S1). PrA was about 35 kDa in molecular weight. The broad pH and thermal stability, chelators, surfactants and solvent tolerance, and favorable thermodynamics suggested the potentiality of the extracted protease PrA. Thermal activity and stability were enhanced in presence of 1-mM Ca²⁺ ion at high temperatures. The protease was a serine one as its activity was completely diminished in presence of 1-mM PMSF. The V_max , K_m , and K_cat /K_m suggested stability and catalytic efficiency of the protease. PrA hydrolyzes fish protein with 26.61 ± 0.16% of peptide bond cleavage after 240 min, comparable to Alcalase 2.4L (27.13 ± 0.31%). PRACTITIONER POINTS: A serine alkaline protease PrA was extracted from kitchen wastewater bacteria Bacillus tropicus Y14. Protease PrA showed significant activity and stability in a wide temperature and pH range. Protease showed great stability towards additives like metal ions, solvents, surfactants, polyols, and inhibitors. Kinetic study showed that the protease PrA had a prominent affinity and catalytic efficiency for the substrates. PrA hydrolysed fish proteins into short bioactive peptides which signify its potential in the formation of functional food ingredients.

Protein hydrolysates derived from aquaculture and marine byproducts through autolytic hydrolysis

Autolysis technology has shown potential for protein hydrolysates production from marine and aquaculture byproducts. Viscera are a source of cheap proteolytic enzymes for producing protein hydrolysates from the whole fish or processing byproducts of the most valuable commercial species by applying autolysis technology. The use of autolysis allows economical production of protein hydrolysate and provides an opportunity to valorize downstream fish and shellfish processing byproducts at a lower cost. As a result, production and application of marine byproduct autolysates is increasing in the global protein hydrolysates market. Nevertheless, several restrictions occur with autolysis, including lipid and protein oxidation mediated by the heterogeneous composition of byproducts. The generally poor storage and handling of byproducts may increase the formation of undesirable metabolites during autolysis, which can be harmful. The formation of nitrogenous compounds (i.e., biogenic amines), loss of freshness, and process of autolysis in the byproducts could increase the rate of quality and safety loss and lead to more significant concern about the use of autolysates for human food applications. The current review focuses on the autolysis process, which is applied for the hydrolysis of aquaculture and marine discards to obtain peptides as functional or nutritive ingredients. It further addresses the latest findings on the mechanisms and factors contributing the deterioration of byproducts and possible ways to control oxidation and other food quality and safety issues in raw materials and protein hydrolysates.