Selenium is a micronutrient that is essential for the proper functioning of all organisms. Studies on the functions of selenium are rapidly developing. This element is a cofactor of many enzymes, for example, glutathione peroxidase or thioredoxin reductase. Insufficient supplementation of this element results in the increased risk of developing many chronic degenerative diseases. Selenium is important for the protection against oxidative stress, demonstrating the highest activity as a free radical scavenger and anti-cancer agent. In food, it is present in organic forms, as exemplified by selenomethionine and selenocysteine. In dietary supplementation, the inorganic forms of selenium (selenite and selenate) are used. Organic compounds are more easily absorbed by human organisms in comparison with inorganic compounds. Currently, selenium is considered an essential trace element of fundamental importance for human health. Extreme selenium deficiencies are widespread among people all over the world. Therefore, it is essential to supplement the deficiency of this micronutrient with selenium-enriched food or yeast cell biomass in the diet.

Over the past several decades, we have observed a very rapid development in the biotechnological use of lactic acid bacteria (LAB) in various branches of the food industry. All such areas of activity of these bacteria are very important and promise enormous economic and industrial successes. LAB are a numerous group of microorganisms that have the ability to ferment sugars into lactic acid and to produce proteolytic enzymes. LAB proteolytic enzymes play an important role in supplying cells with the nitrogen compounds necessary for their growth. Their nutritional requirements in this regard are very high. Lactic acid bacteria require many free amino acids to grow. The available amount of such compounds in the natural environment is usually small, hence the main function of these enzymes is the hydrolysis of proteins to components absorbed by bacterial cells. Enzymes are synthesized inside bacterial cells and are mostly secreted outside the cell. This type of proteinase remains linked to the cell wall structure by covalent bonds. Thanks to advances in enzymology, it is possible to obtain and design new enzymes and their preparations that can be widely used in various biotechnological processes. This article characterizes the proteolytic activity, describes LAB nitrogen metabolism and details the characteristics of the peptide transport system. Potential applications of proteolytic enzymes in many industries are also presented, including the food industry.

Selenium is one of the elements classified within the group of micronutrients which are necessary in trace amounts for the proper functioning of organisms. Selenium participates in the protection of cells against excess H₂O₂, in heavy metal detoxification, and regulation of the immune and reproductive systems as well. It also ensures the proper functioning of the thyroid gland. Selenium induces the occurrence of the selenoprotein synthesis process involved in the antioxidant defense mechanism of the organism. Recent years have brought much success in the studies on selenium. Anticarcinogenic properties of selenium against some cancers have been reported. Supplementation is increasingly becoming a solution to this problem. A large number of different supplementation methods are promoting studies in this area. Slight differences in the selenium content can result in excess or deficiency, therefore supplementation has to be done carefully and cautiously.

The extremely high costs of manufacturing transglutaminase from animal origin (EC 2.3.2.13) have prompted scientists to search for new sources of this enzyme. Interdisciplinary efforts have been aimed at producing enzymes synthesised by microorganisms which may have a wider scope of use. Transglutaminase is an enzyme that catalyses the formation of isopeptide bonds between proteins. Its cross-linking property is widely used in various processes: to manufacture cheese and other dairy products, in meat processing, to produce edible films and to manufacture bakery products. Transglutaminase has considerable potential to improve the firmness, viscosity, elasticity and water-binding capacity of food products. In 1989, microbial transglutaminase was isolated from Streptoverticillium sp. Its characterisation indicated that this isoform could be extremely useful as a biotechnological tool in the food industry. Currently, enzymatic preparations are used in almost all industrial branches because of their wide variety and low costs associated with their biotechnical production processes. This paper presents an overview of the literature addressing the characteristics and applications of transglutaminase.