Functionally and physiologically active peptides are produced from several food proteins during gastrointestinal digestion and fermentation of food materials with lactic acid bacteria. Once bioactive peptides (BPs) are liberated, they exhibit a wide variety of physiological functions in the human body such as gastrointestinal, cardiovascular, immune, endocrine, and nervous systems. These functionalities of the peptides in human health and physiology include antihypertensive, antimicrobial, antioxidative, antithrombotic, opioid, anti-appetizing, immunomodulatory and mineral-binding activities. Most of the bioactivities of milk proteins are latent, being absent or incomplete in the original native protein, but full activities are manifested upon proteolytic digestion to release and activate encrypted bioactive peptides from the original protein. Bioactive peptides have been identified within the amino acid sequences of native milk proteins. Due to their physiological and physico-chemical versatility, milk peptides are regarded as greatly important components for health promoting foods or pharmaceutical applications. Milk and colostrum of bovine and other dairy species are considered as the most important source of natural bioactive components. Over the past a few decades, major advances and developments have been achieved on the science, technology and commercial applications of bioactive components which are present naturally in the milk. Although the majority of published works are associated with the search of bioactive peptides in bovine milk samples, some of them are involved in the investigation of ovine or caprine milk. The advent of functional foods has been facilitated by increasing scientific knowledge about the metabolic and genomic effects of diet and specific dietary components on human health.

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Studies on the discovery and function of antioxidants are consistently being performed because oxidative stress can cause various diseases. Many compounds and natural products have antioxidant activity in vitro; however, it is often difficult to reproduce their effects in vivo. Additionally, methods to measure antioxidant activities in cells are also scarce. Here, we investigated the antioxidant activity of milk proteins by observing the formation of arsenite‐induced stress granules as a tool to evaluate antioxidant activity in cells. Milk proteins not only decreased the formation of stress granules in several cell types but also scavenged 2,2'‐azino‐bis(3‐ethylbenzothiazoline‐6‐sulfonic acid) (ABTS) radical cations in vitro. In addition, milk proteins inhibited cellular senescence based on an SA‐β‐galactosidase assay, and increased differentiation to myotubes from myoblasts isolated from the skeletal muscles of mouse pups. Taken together, our results demonstrate that milk proteins have an antiaging effect, especially prevention of skeletal muscle loss, through their antioxidant activities. Practical Application Our results provide that antioxidant effects of milk proteins containing α‐caseins, β‐caseins, and β‐lactoglobulin can mitigate aging‐related damage induced by oxidative stress through showing inhibition of cellular senescence and increase of differentiation and maturation of myoblast. Therefore, we suggest that milk proteins could be potent health supplements to prevent aging‐associated diseases, especially sarcopenia.

The alkaline protease was successfully purified and characterized from the bacterium Serratia marcescens S3-R1, which has potential for industrial application, including milk protein hydrolysates.

This study was conducted to isolate and characterize Paenibacillus sp. MBT213 possessing β-glucosidase activity from raw milk, and examine the enzymatic capacity on the hydrolysis of a major ginsenoside (Rb1). Strain MBT213 was found to have a high hydrolytic ability on ginsenoside Rb1 by Esculin Iron Agar test. 16S rDNA analysis revealed that MBT213 was Paenibacillu sp. Crude enzyme of MBT213 strain exhibited high conversion capacity on ginsenoside Rb1 into ginsenoside Rd proven by TLC and HPLC analyses. The API ZYM kit confirmed that Paenibacillu sp. MBT213 exerted higher β-glucosidase and β-galactosidase activity than other strains. Optimum pH and temperature for crude enzyme were found at 7.0 and 35°C in hydrolysis of ginsenoside Rb1. After 10 d of optimal reaction conditions for the crude enzyme, ginsenoside Rb1 fully converted to ginsenoside Rd. Ginseng roots (20%) were fermented for 14 d, and analyzed by HPLC showed that amount of ginsenoside Rb1 significantly decreased, while that of ginsenoside Rd was significantly increased. The study confirmed that the β-glucosidase produced by Paenibacillus sp. MBT213 can hydrolyze the major ginsenoside Rb1 and convert to Rd during fermentation of the ginseng. The β-glucosidase activity of this novel Paenibacillus sp. MBT213 strain may be utilized in development of variety of health foods, dairy foods and pharmaceutical products.

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