Autolysis of Pacific white shrimp (Litopenaeus vannamei) processing by-products: Enzymatic activities, lipid and protein oxidation, and antioxidant activity of hydrolysates

BCP4: A novel antimicrobial peptide with potent efficacy against Bacillus cereus in rice porridge

Bacillus cereus is a common foodborne pathogen that frequently contaminates rice products and produces cereulide toxins, presenting a significant risk to food safety and human health. In contrast, Bacillus subtilis is a promising source of antimicrobial peptides (AMPs). In this research, a novel AMP named BCP4 (KGKTLLQ) was discovered through the fermentation of shrimp waste with B. subtilis, which speculated that BCP4 might be generated through enzymatic hydrolysis catalyzed by endogenous enzymes naturally present in shrimp waste. BCP4 demonstrated potent antibacterial activity against B. cereus with a minimum bactericidal concentration (MBC) of 62.5 μg/mL and bacterial time-kill of 3 h. BCP4 surpassed the bactericidal efficiency of nisin (500 μg/mL), a commonly used AMP of microbial origin. BCP4 operates by causing damage to the bacterial cell wall and membrane, which allows the contents of the cell to flow out. BCP4 also penetrates the cell membrane and binds with DNA, effectively sterilizing the bacteria. Meanwhile, treatment of BCP4 with mammalian red blood cells revealed that it was nonhemolytic. Furthermore, the growth of B. cereus in rice porridge was significantly inhibited by BCP4 at a concentration of 62.5 μg/mL. This study provides a theoretical basis for using BCP4 to control B. cereus contamination.

Enhanced Antioxidant and Digestive Enzyme Inhibitory Activities of Pacific White Shrimp Shell Protein Hydrolysates via Conjugation with Polyphenol: Characterization and Application in Surimi Gel

Pacific white shrimp shell protein hydrolysates (SSPHs) produced using alcalase (UAH) and papain (UPH), and polyphenols (PPNs) conjugates were prepared using variable concentrations (0.5-3% w/v) of different polyphenols (EGCG, catechin, and gallic acid). When 2% (v/v) of a redox pair was used for conjugation, 0.5% (w/v) of PPNs resulted in the highest conjugation efficiency (CE), regardless of the polyphenol types. However, CE decreased further with increasing levels of PPNs (p < 0.05). SSPHs at 2% retained the highest CE when combined with the selected PPN and redox pair concentrations (p < 0.05). FTIR and 1H-NMR analysis confirmed the successful conjugation of PPNs with the SSPHs. Among all the conjugates, EGCG conjugated with UAH (A-E) or UPH (P-E) exhibited the highest DPPH/ABTS radical scavenging, and metal chelating activities, respectively. The highest FRAP activity was noticed for A-E conjugate followed by UAH-catechin (A-C) and UPH-catechin (P-C) conjugates. The A-C sample (6 mg/mL) demonstrated the strongest inhibition efficiency against α-amylase, α-glucosidase, and pancreatic lipase (89.29, 81.23, and 80.69%, respectively) than other conjugates (p < 0.05). When A-C conjugate was added into surimi gels prepared from Indian mackerel (IM) and threadfin bream (TH) mince at various levels (2-6%; w/w), gel strength, and water holding capacity was increased in a dose-dependent manner, regardless of surimi type. However, whiteness decreased with increasing A-C levels. After the in vitro digestion of surimi gels, antioxidant and enzyme inhibitory activities were also increased as compared to the digest prepared from control surimi gels (added without A-C conjugate). Thus, waste from the shrimp industry in conjugation with plant polyphenols could be utilized to produce antioxidant and antidiabetic or anti-obesity agents, which could be explored as a promising additive in functional foods and nutraceuticals.

The cryoprotective effect of Litopenaeus vannamei head-derived peptides and its ice-binding mechanism

Although discarded as waste, shrimp heads are a potential source of antifreeze peptides, which can be used as cryoprotectants in the food industry. Their utilization in frozen foods can help mitigate the negative effects caused by the freezing technique. Litopenaeus vannamei shrimp heads were autolyzed, and the shrimp head autolysate (SHA) was separated via ultra-filtration and ion exchange chromatography. The antifreeze effect of SHA on the biochemical properties of myofibrillar proteins of peeled shrimps during five freeze-thaw cycles was evaluated. Peptide screening was done using the LC-MS/MS technique. A molecular docking (MD) study of the interaction between ice and shrimp head-derived antifreeze peptides was done. Results showed that shrimp-head autolysate has a maximum thermal hysteresis value of 1.84 °C. During the freeze-thaw cycles, the shrimp-head autolysate exhibited an antifreeze effect on frozen peeled shrimps. 1.0 and 3.0%-SHA groups showed significantly lower freeze denaturation than the negative control group. The muscle tissues of SHA-treated groups were not as severely damaged as the negative control group. The molecular docking study revealed that the shrimp head-AFPs bound to ice via hydrogen bonding, and both hydrophilic and hydrophobic amino acid residues were involved in the ice-binding interactions. 6 ice-binding sites were involved in the peptide-ice interaction. Our findings suggest that shrimp head-derived AFPs can be developed into functional additives in frozen foods and add more insights into the existing literature on antifreeze peptides.

Polyphenol oxidase mediates (-)-epigallocatechin gallate to inhibit endogenous cathepsin activity in Apostichopus japonicus

Apostichopus japonicus (A. japonicus) has rich nutritional value and is an important economic crop. Due to its rich endogenous enzyme system, fresh A. japonicus is prone to autolysis during market circulation and storage, resulting in economic losses. In order to alleviate this phenomenon, we investigated the effect of polyphenol oxidase (PPO) mediated (-)-epigallocatechin gallate (EGCG) on the activity and structure of endogenous cathepsin series protein (CEP) from A. japonicus. Research on cathepsin activity showed that PPO mediated EGCG could significantly reduce enzyme activity, resulting in a decrease in enzymatic reaction rate. SDS-PAGE and scanning electron microscopy results showed that PPO mediates EGCG could induce CEP aggregation to form protein aggregates. Various spectral results indicated that EGCG caused changes in the structure of CEP. Meanwhile, the conjugates formed by PPO mediated EGCG had lower thermal stability. In conclusion, PPO mediated EGCG was an effective method to inhibit the endogenous enzyme activity.

Eco-friendly and safe alternatives for the valorization of shrimp farming waste

The seafood industry generates waste, including shells, bones, intestines, and wastewater. The discards are nutrient-rich, containing varying concentrations of carotenoids, proteins, chitin, and other minerals. Thus, it is imperative to subject seafood waste, including shrimp waste (SW), to secondary processing and valorization for demineralization and deproteination to retrieve industrially essential compounds. Although several chemical processes are available for SW processing, most of them are inherently ecotoxic. Bioconversion of SW is cost-effective, ecofriendly, and safe. Microbial fermentation and the action of exogenous enzymes are among the significant SW bioconversion processes that transform seafood waste into valuable products. SW is a potential raw material for agrochemicals, microbial culture media, adsorbents, therapeutics, nutraceuticals, and bio-nanomaterials. This review comprehensively elucidates the valorization approaches of SW, addressing the drawbacks of chemically mediated methods for SW treatments. It is a broad overview of the applications associated with nutrient-rich SW, besides highlighting the role of major shrimp-producing countries in exploring SW to achieve safe, ecofriendly, and efficient bio-products.

Squid meal and shrimp hydrolysate as novel protein sources for dog food

The world's growing pet population is raising sustainability and environmental concerns for the petfood industry. Protein-rich marine by-products might contribute to mitigating negative environmental effects, decreasing waste, and improving economic efficiency. The present study evaluated two marine by-products, squid meal and shrimp hydrolysate, as novel protein sources for dog feeding. Along with the analysis of chemical composition and antioxidant activity, palatability was evaluated by comparing a commercial diet (basal diet) and diets with the inclusion of 150 g kg-1 of squid meal or shrimp hydrolysate using 12 Beagle dogs (2.2 ± 0.03 years). Two in vivo digestibility trials were conducted with six dogs, three experimental periods (10 days each) and three dietary inclusion levels (50, 100 and 150 g kg-1) of squid meal or shrimp hydrolysate in place of the basal diet to evaluate effects of inclusion level on apparent total tract digestibility (ATTD), metabolizable energy content, fecal characteristics, metabolites, and microbiota. Both protein sources presented higher protein and methionine contents than ingredients traditionally used in dog food formulation. Shrimp hydrolysate showed higher antioxidant activity than squid meal. First approach and taste were not affected by the inclusion of protein sources, but animals showed a preference for the basal diet. Effects on nutrient intake reflected the chemical composition of diets, and fecal output and characteristics were not affected by the increasing inclusion levels of both protein sources. The higher ATTD of dry matter, most nutrients and energy of diets with the inclusion of both by-products when compared to the basal diet, suggests their potential to be included in highly digestible diets for dogs. Although not affected by the inclusion level of protein sources, when compared to the basal diet, the inclusion of squid meal decreased butyrate concentration and shrimp hydrolysate increased all volatile fatty acids, except butyrate. Fecal microbiota was not affected by squid meal inclusion, whereas inclusion levels of shrimp hydrolysate significantly affected abundances of Oscillosperaceae (UCG-005), Firmicutes and Lactobacillus. Overall, results suggest that squid meal and shrimp hydrolysate constitute novel and promising protein sources for dog food, but further research is needed to fully evaluate their functional value.

Investigating the migration hypothesis: Effects of trypsin-like protease on the quality of muscle proteins of red shrimp (Solenocera crassicornis) during cold storage

This study aimed to investigate the effect of trypsin-like protease (TLP) on the quality of muscle proteins in red shrimp (Solenocera crassicornis) during cold storage. The results indicated that the activity of TLP decreased significantly in the head of shrimp but increased significantly in the muscle tissues during the cold storage. The myofibril fragmentation index (MFI) value of intact shrimp was significantly higher than that of beheaded shrimp, while the Ca2+-ATPase activity of intact shrimp was significantly lower than that of beheaded shrimp. SDS-PAGE analysis showed that the molecular weight of purified TLP from the shrimp head was about 24 kDa, and the TLP showed high activity at 50 °C and pH 8, indicating that the TLP belongs to the trypsin family. Results from in vitro simulation experiments indicated that the process of TLP incubation significantly reduced the particle size and enlarged the distribution of myofibrillar proteins (MPs) in shrimp muscle tissues. The comparisons were made with respect to the control samples. It can be inferred that TLP migrated from the shrimp head to the muscle tissues during storage and thus promoted the degradation of MPs in red shrimp. The beheading treatment could be an effective mean to maintain better quality and extend the commercialization of shrimp products.

Protein Hydrolysates from Fishery Processing By-Products: Production, Characteristics, Food Applications, and Challenges

Fish processing by-products such as frames, trimmings, and viscera of commercial fish species are rich in proteins. Thus, they could potentially be an economical source of proteins that may be used to obtain bioactive peptides and functional protein hydrolysates for the food and nutraceutical industries. The structure, composition, and biological activities of peptides and hydrolysates depend on the freshness and the actual composition of the material. Peptides isolated from fishery by-products showed antioxidant activity. Changes in hydrolysis parameters changed the sequence and properties of the peptides and determined their physiological functions. The optimization of the value of such peptides and the production costs must be considered for each particular source of marine by-products and for their specific food applications. This review will discuss the functional properties of fishery by-products prepared using hydrolysis and their potential food applications. It also reviews the structure-activity relationships of the antioxidant activity of peptides as well as challenges to the use of fishery by-products for protein hydrolysate production.

Guamara and Cocuixtle: Source of Proteases for the Transformation of Shrimp By-Products into Hydrolysates with Potential Application

Since the fruits of Bromelia pinguin and Bromelia karatas are rich in proteases, the aim of this research was to optimize the hydrolysis process of cooked white shrimp by-products due to the effect of these proteases. A robust Taguchi L_16' design was used to optimize the hydrolysis process. Similarly, the amino acid profile by GC-MS and antioxidant capacity (ABTS and FRAP) were determined. The optimal conditions for hydrolysis of cooked shrimp by-products were pH 8.0, 30 °C, 0.5 h, 1 g of substrate and 100 µg/mL of B. karatas, pH 7.5, 40 °C, 0.5 h, 0.5 g substrate and 100 µg/mL enzyme extract from B. pinguin and pH 7.0, 37 °C, 1 h, 1.5 g substrate and 100 µg/mL enzyme bromelain. The optimized hydrolyzates of B. karatas B. pinguin and bromelain had 8 essential amino acids in their composition. The evaluation of the antioxidant capacity of the hydrolyzates under optimal conditions showed more than 80% inhibition of in ABTS radical, B. karatas hydrolyzates had better higher ferric ion reduction capacity with 10.09 ± 0.02 mM TE/mL. Finally, the use of proteolytic extracts from B. pinguin and B. karatas to optimize hydrolysis process allowed obtaining hydrolyzates of cooked shrimp by-products with potential antioxidant capacity.

A review on the processing of functional proteins or peptides derived from fish by-products and their industrial applications

To understand the production and characteristics of protein hydrolysates pertaining to individual fish species, we selected and analyzed the most important commercial fish species according to the market value based on the Statistics on International Exports of Fishery Commodities by Food and Agriculture Organization. Accordingly, salmon, shrimp, cod, tuna, squid, and herring are marine species with high global value. Peptides obtained from their by-products were predominant in hydrophobic amino acids such as alanine, phenylalanine, methionine, proline, valine, tyrosine, tryptophan, leucine, and isoleucine. Bioactive peptides are short with a length of 2-20 amino acids. They remain inactive when they are within their parent proteins. Low molecular weight (0.3-8 kDa) peptides from hydrolyzed protein are easily digestible, readily absorbed by the body and are water-soluble. The hydrophobic nature contributes to their bioactivity, which facilitates their interactions with the membrane lipid bilayers. Incomplete hydrolysis results in low yields of hydrophobic amino acids. The glycosylation type of the resulting peptide fragment determines the different applications of the hydrolysate. The degree of conservation of the glycosidic residues and the size of the peptides are influenced by the method used to generate these hydrolysates. Therefore, it is crucial to explore inexpensive novel methodologies to generate bioactive peptides. According to the current studies, a unified approach (in silico estimation coupled with peptidomics) can be used for the identification of novel peptides with diverse physiological and technological functions. From an industrial perspective, the reusability of immobilized enzymes and membrane separation techniques (e.g., ultrafiltration) on marine by-products can offer low operating costs and higher yield for large-scale production of bioactive peptides. This review summarizes the production processes and essential characteristics of protein hydrolysates from fish by-products and presents the advances in their application.

Formation of Oxidative Compounds during Enzymatic Hydrolysis of Byproducts of the Seafood Industry

There is a significant potential to increase the sustainability of the fishing and aquaculture industries through the maximization of the processing of byproducts. Enzymatic hydrolysis provides an opportunity to valorize downstream fish industry byproducts for the production of protein hydrolysates (FPH) as a source of bioactive peptides (BAP) with health benefits. Deteriorative oxidative reactions may occur during the enzymatic hydrolysis of byproducts, influencing the safety or bioactivities of the end product. Lipid oxidation, autolysis mediated by endogenous enzymes in viscera, protein degradation, and formation of low-molecular-weight metabolites are the main reactions that are expected to occur during hydrolysis and need to be controlled. These depend on the freshness, proper handling, and the type of byproducts used. Viscera, frames, trimmings, and heads are the byproducts most available for enzymatic hydrolysis. They differ in their composition, and, thus, require standardization of both the hydrolysis procedures and the testing methods for each source. Hydrolysis conditions (e.g., enzyme type and concentration, temperature, and time) also have a significant role in producing FPH with specific structures, stability, and bioactivity. Protein hydrolysates with good safety and quality should have many applications in foods, nutraceuticals, and pharmaceuticals. This review discusses the oxidative reactions during the enzymatic hydrolysis of byproducts from different fish industry sectors and possible ways to reduce oxidation.

A comprehensive review of the control and utilization of aquatic animal products by autolysis-based processes: Mechanism, process, factors, and application

Animal aquatic products have high water content, abundant enzyme system and their own diverse microbial flora. These products are severely susceptible to autolysis and degradation after death, resulting in many adverse effects on storage, processing, and transportation. Among them, the endogenous enzyme are the key factor that caused the autolysis and degradation. Autolytic hydrolysis provides an effective way to maximize the use of aquatic by-products and achieve increased protein resources and reduce environmental pollution from by-products. To better acquaintance the autolysis phenomenon and regulation of the autolysis phenomenon. This paper reviews the autolytic mechanism, biochemical changes, influencing factors, and potential applications of animal aquatic products and their by-products to explore autolysis and its effective utilization and regulation. In addition, this study also emphasizes the importance of making full use of aquatic by-products. Furthermore, the research trends and future challenges of autolysis are also discussed. Autolysis can effectively transform aquatic products and by-products into bioactive hydrolysates. The hydrolysates produced by the autolysis of aquatic products and their by-products have attracted attention because of their wide applications in food, healthcare, and animal feed industries. However, the mechanism and regulation (promotion or inhibition) of autolysis should be further studied, and autolysate at the industrial level should be produced to provide high-value-added products for by-product processing and realize the sustainable utilization of resources.

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.

Ameliorating Effects of Bioactive Peptides Extracted from Litopenaeus vannamei Wastes on Oxidative Stress, Glucose Regulation, and Autophagy Gene Expression in Nonalcoholic Fatty Liver-Induced Rats

This study aimed to investigate the effect of bioactive peptides from Litopenaeus vannamei on oxidative stress, glucose regulation, and autophagy gene expression in the induced nonalcoholic fatty liver rats. Bioactive peptides used in the current study were extracted in a progressive rise in temperature (40–60°C) (GP). For this purpose, twenty-four healthy male rats (initial weight, 230.1 ± 22 g) were divided in four experimental groups including control (standard diet), HFD (high-fat diet), HFD + GP20, and 300 (high-fat diet + 20, 300 mg peptides/kg body weight). After 70 days, the results indicated that experimental treatments did not affect the body and liver weight (P > 0.05), although the higher liver weight was seen in HFD treatment. Based on these results, the use of GP peptides improved antioxidant enzymes and decreased MDA concentration, and a significant difference was observed between peptide treatments and HFD (P < 0.05). In comparison to the HFD group, significantly lower liver enzymes (ALT and AST) were seen in peptide treatments (P < 0.05). Also, the results indicated that the lowest amylase, alkaline phosphatase, glucose, insulin, HOMA-IR, and inflammation cytokines (TNF-ɑ and IL-6) were seen in peptide groups. The autophagy gene expression was measured in the liver cells, and the results showed that, unlike HFD treatment, the use of GP peptides decreased Beclin 1, Atg7, and P62 expression in male rat's livers. Overall, the results of the current study demonstrated that the use of GP peptides at low concentration shows significant hypoglycemia and antioxidant properties in nonalcoholic fatty liver-induced rats.

Identification of antifreeze peptides in shrimp byproducts autolysate using peptidomics and bioinformatics

In the present study, a novel method based on peptidomics and bioinformatic was applied to identification and characterization of antifreeze peptides (AFPs) from shrimp byproducts autolysate (SBPA). According to the results of in silico prediction and high peptide structural inflexibility, DEYEESGPGIVH and EQICINFCNEK were picked as potential AFP-1 and AFP-2, respectively. The outcomes of DSC determination indicated that TH of synthesized AFP-1 and AFP-2 (10 mg/mL) were 1.37 °C and 1.57 °C, respectively. Besides, 0.1 %-3 % AFPs showed significant cryoprotection in shrimp muscle after 3 and 6 freeze-thaw cycles, evidenced by higher SSP content, Ca²⁺-ATPase activity, sulfhydryl content and lower surface hydrophobicity than control; while the higher concentration resulted in better protection against freeze induced denaturation. Both AFP-1&2 showed favorable hydrogen bonding affinity which facilitated ice binding and ice crystal growth inhibition. This work could provide new ideals for identification and characterization of AFPs.

Comparison of the Proximate Composition and Nutritional Profile of Byproducts and Edible Parts of Five Species of Shrimp

The nutritional components of different parts (meat, head, shell and tail) of Litopenaeus vannamei (L.v), Macrobrachium rosenbergii (M.r), Penaeus monodon (P.m), Fenneropenaeus chinensis (F.c), and Penaeus japonicus (P.j) were analyzed and their nutritional values were evaluated. For the five species of shrimp, the meat yield was 37.47–55.94%, and the byproduct yield was 44.06–62.53%. The meat yields of L.v and F.c were the highest (55.94 and 55.92%, respectively), and the meat yield of M.r was the lowest (37.47%). The shrimp contain high amounts of crude protein, and the values of the amino acid score (AAS), chemical score (CS), and essential amino index (EAAI) were greater than or close to 1.00, indicating that shrimp protein had higher nutritional value. The shrimp head was rich in polyunsaturated fatty acids and the ratio of n-6 to n-3 PUFAs was from 0.37 to 1.68, indicating that the shrimp head is rich in n-3 PUFAs and is a good source of n-3 PUFAs. The five species of shrimp were rich in macro- and micro-minerals, especially in shrimp byproducts. The shrimp byproducts were also rich in other bioactive ingredients (astaxanthin), which are also very valuable for developing biological resources. Therefore, shrimp have many nutritional benefits, and their byproducts can also be used to develop natural nutraceuticals, which are considered to be one of the healthiest foods.

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

Antioxidant activity of Klunzinger's mullet (Liza klunzingeri) muscle hydrolysates obtained using Bacillus licheniformis fermentation and enzymatic hydrolysis was determined. Hydrolysates obtained after 6 days of fermentation with B. licheniformis showed the highest free radical scavenging activity, metal chelating ability and ferric reducing antioxidant power (FRAP) (P ≤ 0.05). Microbial fermentation led to a higher percentage of small peptides and higher solubility compared with Alcalase hydrolysis (P ≤ 0.05). Hydrolysates showing the highest antioxidant properties attenuated serum, liver, and kidney oxidative stress biomarkers in male Wister rats stressed by carbon tetrachloride (P ≤ 0.05). At 300 mg/kg oral administration, hydrolysates increased serum, renal, and hepatic total antioxidant capacity (TAC) (P ≤ 0.05) and reduced their elevated levels of malondialdehyde (MDA), nitric oxide (NO^•), and serum liver enzymes (AST, ALP, and ALT) (P ≤ 0.05). The hydrolysates were able to ameliorate hepatic damage by reducing necrosis, fatty changes, and inflammation. Results showed the antioxidant and hepato-toxic protective activities of Klunzinger's mullet muscle hydrolysates obtained using microbial fermentation, which may, therefore, potentially be considered as a functional food ingredient.