Involvement of Versatile Bacteria Belonging to the Genus Arthrobacter in Milk and Dairy Products.

Milk is naturally a rich source of many essential nutrients; therefore, it is quite a suitable medium for bacterial growth and serves as a reservoir for bacterial contamination. The genus Arthrobacter is a food-related bacterial group commonly present as a contaminant in milk and dairy products as primary and secondary microflora. Arthrobacter bacteria frequently demonstrate the nutritional versatility to degrade different compounds even in extreme environments. As a result of their metabolic diversity, Arthrobacter species have long been of interest to scientists for application in various industry and biotechnology sectors. In the dairy industry, strains from the Arthrobacter genus are part of the microflora of raw milk known as an indicator of hygiene quality. Although they cause spoilage, they are also regarded as important strains responsible for producing fermented milk products, especially cheeses. Several Arthrobacter spp. have reported their significance in the development of cheese color and flavor. Furthermore, based on the data obtained from previous studies about its thermostability, and thermoacidophilic and thermoresistant properties, the genus Arthrobacter promisingly provides advantages for use as a potential producer of ß-galactosidases to fulfill commercial requirements as its enzymes allow dairy products to be treated under mild conditions. In light of these beneficial aspects derived from Arthrobacter spp. including pigmentation, flavor formation, and enzyme production, this bacterial genus is potentially important for the dairy industry.

The Influence of pH, NaCl, and the Deacidifying Yeasts Debaryomyces hansenii and Kluyveromyces marxianus on the Production of Pigments by the Cheese-Ripening Bacteria Arthrobacter arilaitensis.

Arthrobacter arilaitensis is a food-related bacterial species under investigation for its involvement in the coloration of surface-ripened cheeses. Presently, information about this species in association with the development of appropriate cheese coloration is still lacking. This study was performed in order to investigate-with the use of spectrocolorimetry-the influence of pH, NaCl, and deacidifying yeasts on the pigmentation of Arthrobacter arilaitensis biofilms. Three types of cheese-based (curd) solid media were prepared by using different deacidification methods: (i) chemical deacidification by NaOH (CMNaOH); (ii) biological deacidification by the yeast strain Debaryomyces hansenii 304 (CMDh304); and (iii) biological deacidification by the yeast strain Kluyveromyces marxianus 44 (CMKm44). Each medium was prepared with initial pH values of 5.8, 7.0, and 7.5. After pasteurization, agar was incorporated and NaCl was added in varying concentrations (0%, 2%, 4%, and 8% (w/v)). A. arilaitensis Po102 was then inoculated on the so prepared "solid-curd" media, and incubated at 12 °C under light conditions for 28 days. According to the data obtained by spectrocolorimetry in the Compagnie Internationale de l'Eclairage (CIE) L*a*b* color system, all controlled factors appeared to affect the pigments produced by the A. arilaitensis strain. NaCl content in the media showed distinct inhibitory effects on the development of color by this strain when the initial pH was at 5.8. By contrast, when the initial pH of the media was higher (7.0, 7.5), only the highest concentration of NaCl (8%) had this effect, while the coloring capacity of this bacterial species was always higher when D. hansenii 304 was used for deacidification compared to K. marxianus 44.

Production of carotenoids by Arthrobacter arilaitensis strains isolated from smear-ripened cheeses.

Arthrobacter arilaitensis is one of the major microorganisms responsible for the coloration of cheese surface, particularly in smear-ripened cheeses. This study investigated the occurrence of pigment synthesis among A. arilaitensis strains in several aspects covering (1) UV-Vis absorption spectra and HPLC chromatograms of pigment extracts, (2) diversity of pigment production among strains, (3) influence of light on the production of pigment, and (4) kinetic of pigment synthesis. Based on absorption spectra and HPLC analysis, the 14 A. arilaitensis strains studied could be divided into two groups depending on their ability to produce carotenoids, carotenoid-producing, and nonpigmented strains. The methanolic extracts prepared from eight carotenoid-producing strains contained at least four carotenoids represented mainly as polar molecules. The diversity of pigment concentrations among these strains was low, with carotenoids ranging from 0.40 to 0.76 mg L(-1) culture and specific productivities from 0.14 to 0.25 mg pigment per g dry biomass, under light condition. When cultivating these A. arilaitensis strains under darkness condition, carotenoid biosynthesis was lower within a 0.17-0.25 mg L(-1) range. The pigment production time curve of a representative colored A. arilaitensis strain displayed a sigmoid shape which paralleled cell growth, probably indicating a growth-associated pigmentation.

Filamentous fungi are large-scale producers of pigments and colorants for the food industry.

With globalization in the research trends, healthier life styles, and the growing market for the natural food colorants in the economically fast-growing countries all over the world, filamentous fungi are being investigated as readily available sources of chemically diverse colorants. With two selected examples, polyketide-Monascus-like pigments from the new fungal production strains, and the promising and yet unexplored hydroxy-anthraquinoid colorants, the present review highlights exciting recent findings, which may pave the way for alternative and/or additional biotechnological processes for the industrial production of natural food colorants of improved functionality. As an additional aspect, marine fungi are discussed as potential sources of novel pigments of numerous color hues and atypical chemical structures.