The rapid increase in the antibiotic resistance of microorganisms, capable of causing diseases in humans as destroying cultural heritage sites, is a great challenge for modern science. In this regard, it is necessary to develop fundamentally novel and highly active compounds. In this study, a series of N⁴-alkylcytidines, including 5- and 6-methylcytidine derivatives, with extended alkyl substituents, were obtained in order to develop a new generation of antibacterial and antifungal biocides based on nucleoside derivatives. It has been shown that N⁴-alkyl 5- or 6-methylcytidines effectively inhibit the growth of molds, isolated from the paintings in the halls of the Ancient Russian Paintings of the State Tretyakov Gallery, Russia, Moscow. The novel compounds showed activity similar to antiseptics commonly used to protect works of art, such as benzalkonium chloride, to which a number of microorganisms have acquired resistance. It was also shown that the activity of N⁴-alkylcytidines is comparable to that of some antibiotics used in medicine to fight Gram-positive bacteria, including resistant strains of Staphylococcus aureus and Mycobacterium smegmatis. N⁴-dodecyl-5- and 6-methylcytidines turned out to be the best. This compound seems promising for expanding the palette of antiseptics used in painting, since quite often the destruction of painting materials is caused by joint fungi and bacteria infection.

The Maillard reaction is a network of interconnected interactions yielding in formation a number of toxic derivatives in processed foods. Acrylamide, a potential carcinogen and a product of the Maillard reaction, is formed under food processing, predominantly from asparagine and reducing sugars at temperatures over 120 °C. In this study, we investigated the potency of recombinant hyperthermophilic L-asparaginase from Thermococcus sibiricus TsAI to mitigate dietary acrylamide by hydrolyzing substrate for its synthesis under various operation conditions. Using a simplified food system for self-cooking, high acrylamide levels were found in baked samples regardless of whether L- or D-enantiomer of asparagine was added. TsAI effectively reduced acrylamide content under various pretreatment conditions, such as temperature, concentration, and time of incubation. The lowest acrylamide level of 1.0–1.1% of the control values or 3.52–3.76 µg/kg was observed in samples pretreated with TsAI 20 U/mL at 90 °C for 20–25 min. Due to the exceptionally high D-asparaginase activity of hyperthermophilic TsAI, the dietary acrylamide content formed from D-asparagine was reduced by 54.8% compared to the control. Comparison of the wild-type TsAI and its mutant reveal that an enzyme displaying enhanced stability is more functional for food-processing application. The native TsAI decreased acrylamide level by 98.9%, while the highly active mutant, with increased structural flexibility, decreased it by only 26.8%. TsAI treatment effectively blocked acrylamide synthesis, but not melanoidin formation via the Maillard reaction, thus not affecting sample characteristics such as color (browning) and aroma, which are important for consumer perception.

Secondary metabolites, some of which have antimicrobial activity, are a key tool that helps filamentous fungi to occupy a wide variety of ecological niches. In particular, some of these microorganisms are capable of growing on painting materials, which leads to their deterioration. However, this natural reservoir has not been screened for antimicrobial compounds. In the current work, we studied the activity of fungi-destructors of tempera painting isolated in the State Tretyakov Gallery from: the Orthodox icon “Prophet Solomon” of the 18th century—Penicillium chrysogenum STG-117; the Old Russian icon of Sergiev Posadsky school dating to the 15th century—Penicillium rubens STG-305, Penicillium sp. STG-333, P. chrysogenum STG-344, Aspergillus fumigatus STG-345, Penicillium sp. STG-348; and from the Old Believer icon “Descent into Hell” of the 16th century—Syncephalastrum sp. STG-160, Cladosporium sphaerospermum STG-161. The strain Simplicillium lamellicola STG-96 was isolated in Hall 61 of the State Tretyakov Gallery. Optimization of cultivation conditions was carried out for the three strains, STG-96, STG-117 and STG-344, that demonstrated promising antimicrobial activity against panel of representative test cultures on two nutrient media—Czapek-Dox and #2 Gause, with different pH values, in the range of 5.0–10.0. The highest antimicrobial activity was observed at the second and third week of culturing. The antimicrobial activity was also tested for novel isolates: STG-160, STG-161, STG-305, STG-333, STG-345 and STG-348. Strains from the Aspergillaceae family showed high activity against such representative test cultures as methicillin-resistant Staphylococcus aureus (MRSA), Pseudomonas aeruginosa and Mycobacterium smegmatis. Our work demonstrates that fungi-destructors of tempera painting are promising producers of antimicrobial compounds.

Extremophilic microorganisms produce valuable enzymes for various practical applications. Here, we report for the first time that L-asparaginases from hyperthermophilic archaea Thermococcus sibiricus (TsA) and thermophilic bacteria Melioribacter roseus (MrA) are promising biocatalysts for producing safe low-acrylamide containing foods processed at high temperatures. The ability of enzymes to reduce acrylamide level was assessed using multicomponent food mixtures baked at 190°C. The results of the study revealed that L-asparaginases TsA and MrA drastically reduce acrylamide content by up to 80% in samples pretreated at 40, 70 and 90°C compared to control. The results confirmed high efficiency of both enzymes in this system. However, the lowest level of residual acrylamide was observed at 90°C for hyperthermophilic L-asparaginase from Thermococcus sibiricus—1.1% compared to 3.7% for MrA. High activity and stability of extremozymes TsA and MrA at elevated temperatures in multicomponent food mixtures makes them good candidates for use in the food industry.