Effect of haem on the fractionation of bovine haemoglobin peptic hydrolysate by electrodialysis with ultrafiltration membranes

Electrodialysis Processes an Answer to Industrial Sustainability: Toward the Concept of Eco-Circular Economy?-A Review

Wastewater and by-product treatments are substantial issues with consequences for our society, both in terms of environmental impacts and economic losses. With an overall global objective of sustainable development, it is essential to offer eco-efficient and circular solutions. Indeed, one of the major solutions to limit the use of new raw materials and the production of wastes is the transition toward a circular economy. Industries must find ways to close their production loops. Electrodialysis (ED) processes such as conventional ED, selective ED, ED with bipolar membranes, and ED with filtration membranes are processes that have demonstrated, in the past decades and recently, their potential and eco-efficiency. This review presents the most recent valorization opportunities among different industrial sectors (water, food, mining, chemistry, etc.) to manage waste or by-product resources through electrodialysis processes and to improve global industrial sustainability by moving toward circular processes. The limitations of existing studies are raised, especially concerning eco-efficiency. Indeed, electrodialysis processes can be optimized to decrease energy consumption and costs, and to increase efficiency; however, eco-efficiency scores should be determined to compare electrodialysis with conventional processes and support their advantages. The review shows the high potential of the different types of electrodialysis processes to treat wastewaters and liquid by-products in order to add value or to generate new raw materials. It also highlights the strong interest in using eco-efficient processes within a circular economy. The ideal scenario for sustainable development would be to make a transition toward an eco-circular economy.

How Discoloration of Porcine Cruor Hydrolysate Allowed the Identification of New Antifungal Peptides

Porcine blood is an important by-product from slaughterhouses and an abundant source of proteins. Indeed, cruor, the solid part of blood, is mainly composed of hemoglobin. Its enzymatic hydrolysis with pepsin generates a diversity of peptides, particularly antimicrobials. One of the downsides of using these hydrolysates as food bio-preservatives is the color brought by the heme, which can be removed by discoloration. Nonetheless, the effects of this procedure on the antimicrobial peptide population have not been completely investigated. In this study, its impacts were evaluated on the final antibacterial and antifungal activities of a cruor hydrolysate. The results demonstrated that 38 identified and characterized peptides showed a partial or total decrease in the hydrolysate, after discoloration. Antifungal activities were observed for the raw and discolored hydrolysates: MICs vary between 0.1 and 30.0 mg/mL of proteins, and significant differences were detected between both hydrolysates for the strains S. boulardii, C. guilliermondii, K. marxianus, M. racemosus and P. chrysogenum. The raw hydrolysate showed up to 12 times higher antifungal activities. Hence, peptides with the highest relative abundance decrease after discoloration were synthesized and tested individually. In total, eight new antifungal peptides were characterized as active and promising. To our knowledge, this is the first time that effective antifungal peptide sequences have been reported from porcine cruor hydrolysates.

Ultrafiltration Fractionation of Bovine Hemoglobin Hydrolysates: Prediction of Separation Performances for Optimal Enrichment in Antimicrobial Peptide

Hydrolysis of bovine hemoglobin (bHb), the main constituent of bovine cruor by-product, releases a natural antimicrobial peptide (NKT) which could present a major interest for food safety. To enrich this, tangential ultrafiltration can be implemented, but ultrafiltration conditions are mainly empirically established. In this context, the application of a simulation method for predicting the NKT yield and enrichment was investigated. Ultrafiltration performances were studied for decolored bHb hydrolysates at different degrees of hydrolysis (DH; 3%, 5%, 10% and 18%) and colored hydrolysates (3% and 5% DH) with 1 and 3 kg·mol⁻¹ regenerated cellulose membranes. The simulation method helped to identify the most promising hydrolysate (in terms of NKT enrichment, yield and productivity) as the 3% DH colored hydrolysate, and UF conditions (volumetric reduction factor of 5 and 3 with 1 and 3 kg·mol⁻¹ membrane, respectively) for higher antimicrobial recovery. A maximal enrichment factor of about 29 and NKT purity of 70% in permeate were observed. The results showed that the antimicrobial activity was in relation with the process selectivity and NKT purity. Finally, this reliable method, applied for predicting the ultrafiltration performances to enrich peptides of interest, is part of a global approach to rationally valorize protein resources from various by-products.

Electroseparation of Slaughterhouse By-Product: Antimicrobial Peptide Enrichment by pH Modification

The fractionation of bioactive peptides from hydrolysate is a main challenge to produce efficient alternative for synthetic additives. In this work, electrodialysis with ultrafiltration membrane (EDUF) was proposed to increase the purity of one antimicrobial peptide from slaughterhouse by-product hydrolysate. This targeted-peptide, α137–141 (653 Da, TSKYR), inhibits a large spectrum of microbial growths and delays meat rancidity; therefore, if concentrated, it could be used as food antimicrobial. In this context, three pH values were investigated during EDUF treatment to increase the α137–141 purity: 4.7, 6.5, and 9. pH 9 showed the highest purity increase—75-fold compared to the initial hydrolysate. Although the whole hydrolysate contains more than 100 peptides, only six peptides were recovered at a significant concentration. In this fraction, the α137–141 peptide represented more than 50% of the recovered total peptide concentration. The EDUF α137–141-enriched fraction obtained in this optimized condition would be a promising natural preservative to substitute synthetic additives used to protect food.

Harnessing slaughterhouse by-products: From wastes to high-added value natural food preservative

Blood, from slaughterhouses, is an inevitable part of meat production, causing environmental problems due to the large volumes recovered and its low valorization. However, the α137-141 peptide, a natural antimicrobial peptide, can be obtained after hydrolysis of hemoglobin, the main constituent of blood red part. To recover it at a sufficient concentration for antimicrobial applications, a new sustainable technology, called electrodialysis with ultrafiltration membrane (EDUF), was investigated. The α137-141 concentration was increased about 4-fold at a feed peptide concentration of 8% with an enrichment factor above 24-fold. This feed peptide concentration also needed the lowest relative energy consumption. Moreover, this peptide fraction protected meat against microbial growth, as well as rancidity, during 14 days under refrigeration. This peptide fraction was validated as a natural preservative and substitute for synthetic additives against food spoilage. Finally, producing antimicrobial/antioxidant peptide from wastes by EDUF fits perfectly with the concept of circular economy.

Alkaline hydrolysis of porcine blood haemoglobin: applications for peptide and amino acid production

Alkaline hydrolysis of proteins recovered from slaughterhouse blood is a method to obtain profitable peptides and free amino acids for animal feed, besides decreasing the waste produced by this industry. The current trend to use enzymatic hydrolysis may need reconsidering due to its high cost in materials and the need for control processes that are both complex and expensive. The use of caustic soda (NaOH), which is a low-cost product, to obtain useful peptides from porcine haemoglobin is studied in this paper. Concentrations of 6 M NaOH at 50°C for 24 h afforded an 80% peptide recovery yield with an average peptide size of 13 kDa. Product obtained at 24 h was composed of soluble haemoglobin (7%), peptides larger than 10 kDa (63%), peptides between 6 and 10 kDa (16%), peptides between 1 and 6 kDa (1%), free amino acids (4%) and non-soluble compounds (8%). A kinetic model was subsequently developed. It is proposed that neutralising the alkaline product using acid products allows the processing of a higher amount of protein while employing the same amounts of reagents, although this topic requires further research.

Use of an electrodialytic reactor for the simultaneous β-lactoglobulin enzymatic hydrolysis and fractionation of generated bioactive peptides

The enzymatic hydrolysis of β-lactoglobulin and the fractionation of peptides were performed in one step in an electrodialysis cell with ultrafiltration membranes stacked. After 240 min of treatment, 15 anionic and 4 cationic peptides were detected in the anionic and cationic peptide recovery compartments. Amongst these 15 anionic peptides, 2 hypocholesterolemic, 3 antihypertensive and 1 antibacterial peptides were recovered and concentrated with migration rates ranging from 5.5% and 81.7%. Amongst the 4 cationic peptides, the peptide sequence ALPMHIR, identified as lactokinin and known to exert an important antihypertensive effect, was recovered with an estimated 66% migration rate. To our knowledge, it was the first attempt to perform hydrolysis under an electric field and to simultaneously separate anionic and cationic peptides produced.

The yield of peptides and amino acids following acid hydrolysis of haemoglobin from porcine blood

Animal blood is the most important waste product from the meat industry due to the huge volumes produced and its pollutant power. Different methods are currently employed to process this by-product, such as drying, incineration or enzymatic hydrolysis. All these techniques are expensive, do not result in revalorisation or are not applicable at an industrial scale. In this paper, chemical hydrolysis is presented as an alternative to recover and increase the value of purified haemoglobin, the most abundant protein in blood. Non-enzymatic hydrolysis of haemoglobin is a good method for obtaining peptides due to its low cost, ease of control and the large amount of peptides produced, as well as being suitable for industrial applications. This paper presents a study of the use of two acids (sulfuric and hydrochloric) for this purpose under different experimental conditions. From the analysis of the kinetics of the hydrolysis process, four fractions can be defined: unbroken haemoglobin, soluble peptides, non-soluble peptides and free amino acids. A kinetic model was developed to simulate the hydrolysis mechanisms, providing a good fit to the experimental results. Both sulfuric and hydrochloric acid at concentrations of 6 M can hydrolyse the haemoglobin completely, but the average peptide size is lower for sulfuric than for hydrochloric acid.