Monascus species can produce yellow, orange, and red pigments, depending on the employed cultivation conditions. They are classified as natural pigments and can be applied for coloration of meat, fishes, cheese, beer, and pates, besides their use in inks for printer and dyes for textile, cosmetic, and pharmaceutical industries. These natural pigments also present antimicrobial activity on pathogenic microorganisms and other beneficial effects to the health as antioxidant and anticholesterol activities. Depending on the substrates, the operational conditions (temperature, pH, dissolved oxygen), and fermentation mode (state solid fermentation or submerged fermentation), the production can be directed for one specific color dye. This review has a main objective to present an approach of Monascus pigments as a reality to obtaining and application of natural pigments by microorganisms, as to highlight properties that makes this pigment as promising for worldwide industrial applications.
Pigments can be divided into four categories: natural, nature-identical, synthetic, and inorganic colors. Artificial colorants are the most used in food and pharmaceutical industries because of their advantages related to color range, price, resistance to oxygen degradation, and solubility. However, many natural pigments present health-promoting activities that make them an interesting option for human use and consumption. Natural colorants are derived from sources such as plants, insects, and microorganisms. Carotenoids are natural pigments with important biological activities, such as antioxidant and pro-vitamin A activity, that can be either extracted from plants and algae or synthesized by various microorganisms, including bacteria, yeasts, filamentous fungi, and microalgae. Advantages of microbial production include the ability of microorganisms to use a wide variety of low cost substrates, the better control of cultivation, and the minimized production time. After fermentation, carotenoids are usually recovered by cell disruption, solvent extraction, and concentration. Subsequent purification steps are followed depending on the application. The most prominent industrial applications of carotenoids, considering their health benefits, are in the food, feed, and pharmaceutical industries.
Brewery spent grain represents approximately 85 % of total by-products generated in a brewery. Consisting of carbohydrates, fiber, minerals and low amounts of protein, the use of brewery spent grain is limited to the feeding of ruminants; however, its potential use should be investigated. The reuse of this by-product using microorganisms by solid-state fermentation process as the case of protein enrichment by single-cell protein incorporation is an alternative to ensure sustainability and generate commercially interesting products. In this context, the aim of this study was to grow Rhizopus oligosporus in brewery spent grain under different initial moisture contents and nitrogen sources to increase the protein content of the fermented material. After 7 days of fermentation, increase of 2-4 times in the crude protein and soluble protein content was verified, respectively, compared to unfermented brewery spent grain. The kinetics of protein enrichment demonstrated the possibility of application of this technique, which can be a great alternative for use in diets for animals.
Antimicrobial activity of natural pigments produced by Monascus ruber CCT 3802 in submerged fermentation were studied. The pigments were screened for antimicrobial activity against three foodborne bacteria: Staphylococcus aureus, Escherichia coli and Salmonella enteritidis. The orange pigment presented antimicrobial activity against S. aureus ATCC 25923 and red pigments against S. aureus ATCC 25923 and E. coli ATCC 25922. S. enteritidis ATCC 13076 was not inhibited for orange and red pigments. The minimum inhibitory concentration values, which were sensitive to the pigments produced by M. ruber, were in the range of 10 to 20 mg/mL. These results suggest a possibility of inhibiting the growths of pathogenic microorganisms during processing and storage of food products. In conclusion, in addition to the use as a functional food ingredient, the Monascus pigments may be selected as an inhibitor to preserve food products where a natural preservative is desired.
Practical Applications
The results of this study indicate the possibility of using the pigments as natural colorant and food preservatives, and show the potential these sources have to act as antibacterial ingredients for the food and pharmaceutical industry. The observation of bacteriostatic effects has lead to the consideration that besides the tinctorial properties, the pigments of M. ruber have a preservative value.
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