Biological activity of peptides isolated from feather keratin waste through microbial and enzymatic hydrolysis

Peptide recovery from chicken feather keratin and their anti-biofilm properties against methicillin-resistant Staphylococcus aureus (MRSA)

Bacteria have the potential to adhere to abiotic surfaces, which has an undesirable effect in the food industry because they can survive for sustained periods through biofilm formation. In this study, an antibacterial peptide (ABP), with a molecular mass of 3861 Da, was purified from hydrolyzed chicken feathers using a locally isolated keratinolytic bacterium, namely Rhodococcus erythropolis, and its antibacterial and antibiofilm potential were investigated against planktonic and biofilm cells of Methicillin-Resistant Staphylococcus Aureus (MRSA). The results demonstrated that purified ABP showed the growth inhibition of MRSA cells with the minimum inhibitory concentration (MIC) of 45 µg/ml and disrupted MRSA biofilm formation at a concentration of 200 ug/ml, which results were confirmed by scanning electron micrograph (SEM). Moreover, the secondary structures of the peptide were assessed as part of the FTIR analysis to evaluate its mode of action. ExPASy tools were used to predict the ABP sequence, EPCVQUQDSRVVIQPSPVVVVTLPGPILSSFPQNTA, from a chicken feather keratin sequence database following in silico digestion by trypsin. Also, ABP had 54.29% hydrophobic amino acids, potentially contributing to its antimicrobial activity. The findings of toxicity prediction of the peptide by the ToxinPred tool revealed that ABP had non-toxic effects. Thus, these results support the potential of this peptide to be used as an antimicrobial agent for the treatment or prevention of MRSA biofilm formation in feed, food, or pharmaceutical applications.

Bioactive Peptides and Protein Hydrolysates as Lipoxygenase Inhibitors

Lipoxygenases are non-heme iron-containing enzymes that catalyze the oxidation of polyunsaturated fatty acids, resulting in the production of lipid hydroperoxides, which are precursors of inflammatory lipid mediators. These enzymes are widely distributed in humans, other eukaryotes, and cyanobacteria. Lipoxygenases hold promise as therapeutic targets for several human diseases, including cancer and inflammation-related disorders. Inhibitors of lipoxygenase have potential applications in pharmaceuticals, cosmetics, and food. Bioactive peptides are short amino acid sequences embedded within parent proteins, which can be released by enzymatic hydrolysis, microbial fermentation, and gastrointestinal digestion. A wide variety of bioactivities have been documented for protein hydrolysates and peptides derived from different biological sources. Recent findings indicate that protein hydrolysates and peptides derived from both edible and non-edible bioresources can act as lipoxygenase inhibitors. This review aims to provide an overview of the current knowledge regarding the production of anti-lipoxygenase protein hydrolysates and peptides from millet grains, chia seeds, insects, milk proteins, fish feed, velvet antler blood, fish scales, and feather keratins. The anti-lipoxygenase activities and modes of action of these protein hydrolysates and peptides are discussed. The strengths and shortcomings of previous research in this area are emphasized. Additionally, potential research directions and areas for improvement are suggested to accelerate the discovery of anti-lipoxygenase peptides in the near future.

Bioactivity and nutritional quality of nutgall (Rhus semialata Murray), an underutilized fruit of Manipur

Introduction

Underutilized fruits plays a significant role in socio economic, cultural, nutritional and ethnomedicinal status of tribal people. However, scientific studies on the nutritional and other pharmaceuticals/biological activities of these fruits are meagre. Hence, the present study dealt with the quantification of nutritional quality and deciphering the bioactivity of nutgall (Rhus semialata Murray syn. Rhus chinensis Mill.), an underutilized fruit crop mainly found in foothill tracks of Eastern Himalaya, India, China, Japan, Korea and other South East Asian countries.

Methods

The Rhus semialata Murray fruits were collected from five different locations in Purul sub-division, Senapati district, Manipur, India. The nutritional composition of the fruit pulp was analysed. Further the fruit pulp was extracted in methanol and water. The methanol and water extracts were studied for bioactivity properties such as antioxidant, antihyperglycemic, antihypertensive, antihyperuricemia, anti-tyrosinase, and antimicrobial activity.

Results and discussion

The fruit was rich in essential fatty acids. The presence of linoleic and oleic acids, along with traces of docosahexaenoic acid and eicosapantaenoic acid, revealed the potential food value of the fruit. 59.18% of the total amino acid composition of the protein present was constituted by essential amino acids. The IC₅₀ value of methanolic extract (MExt) and Water extract (WExt) of the fruit were recorded as 4.05 ± 0.22 and 4.45 ± 0.16 μg/mL, respectively, in the DPPH assay and 5.43 ± 0.37 and 11.36 ± 2.9 μg/mL, respectively, in the ABTS assay as compared to Ascorbic acid (3 and 5.4 μg/mL in DPPH and ABTS assay, respectively). The CUPRAC assay also showed a high antioxidant potential of MExt and WExt (1143.84 ± 88.34 and 456.53 ± 30.02 mg Ascorbic Acid Equivalent/g, respectively). MExt and WExt of the fruit were more active against α-glucosidase (IC₅₀ of 1.61 ± 0.34 and 7.74 ± 0.54 μg/ mL, respectively) than α-amylase enzyme (IC₅₀ 14.15 ± 0.57 and 123.33 ± 14.7 μg/mL, respectively). In addition, the methanolic fruit extract showed low to moderate pharmacological potential in terms of antihypertensive (Angiotensin converting enzyme-I inhibition), antihyperuricemia (xanthine oxidase inhibition), anti-tyrosinase, and antimicrobial activity. The IC₅₀ values of angiotensin-converting enzyme I inhibition, xanthine oxidase inhibition and tyrosinase inhibition were recorded as 13.35 ± 1.21 mg/mL, 93.16 ± 4.65 mg/mL, and 862.7 ± 12.62 μg/mL, respectively. The study evidently indicates that nutgall fruit is a potential source of phytonutrients, bestowed with commercially exploitable, multifaceted health benefits.

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.

Preparation Methods and Functional Characteristics of Regenerated Keratin-Based Biofilms

The recycling, development, and application of keratin-containing waste (e.g., hair, wool, feather, and so on) provide an important means to address related environmental pollution and energy shortage issues. The extraction of keratin and the development of keratin-based functional materials are key to solving keratin-containing waste pollution. Keratin-based biofilms are gaining substantial interest due to their excellent characteristics, such as good biocompatibility, high biodegradability, appropriate adsorption, and rich renewable sources, among others. At present, keratin-based biofilms are a good option for various applications, and the development of keratin-based biofilms from keratin-containing waste is considered crucial for sustainable development. In this paper, in order to achieve clean production while maintaining the functional characteristics of natural keratin as much as possible, four important keratin extraction methods—thermal hydrolysis, ultrasonic technology, eco-friendly solvent system, and microbial decomposition—are described, and the characteristics of these four extraction methods are analysed. Next, methods for the preparation of keratin-based biofilms are introduced, including solvent casting, electrospinning, template self-assembly, freeze-drying, and soft lithography methods. Then, the functional properties and application prospects of keratin-based biofilms are discussed. Finally, future research directions related to keratin-based biofilms are proposed. Overall, it can be concluded that the high-value conversion of keratin-containing waste into regenerated keratin-based biofilms has great importance for sustainable development and is highly suggested due to their great potential for use in biomedical materials, optoelectronic devices, and metal ion detection applications. It is hoped that this paper can provide some basic information for the development and application of keratin-based biofilms.