D-hydantoinases catalyze an enantioselective opening of 5- and 6-membered cyclic structures and therefore can be used for the production of optically pure precursors for biomedical applications. The thermostable D-hydantoinase from Geobacillus stearothermophilus ATCC 31783 is a manganese-dependent enzyme and exhibits low activity towards bulky hydantoin derivatives. Homology modeling with a known 3D structure (PDB code: 1K1D) allowed us to identify the amino acids to be mutated at the substrate binding site and in its immediate vicinity to modulate the substrate specificity. Both single and double substituted mutants were generated by site-directed mutagenesis at appropriate sites located inside and outside of the stereochemistry gate loops (SGL) involved in the substrate binding. Substrate specificity and kinetic constant data demonstrate that the replacement of Phe159 and Trp287 with alanine leads to an increase in the enzyme activity towards D,L-5-benzyl and D,L-5-indolylmethyl hydantoins. The length of the side chain and the hydrophobicity of substrates are essential parameters to consider when designing the substrate binding pocket for bulky hydantoins. Our data highlight that D-hydantoinase is the authentic dihydropyrimidinase involved in the pyrimidine reductive catabolic pathway in moderate thermophiles.

Background: A pivotal objective in crop production and plant protection lies in developing environmentally friendly insecticidal preparations and biostimulants. Methods: We employed Bacillus thuringiensis strains with varied insecticidal spectra and engineered melanogenic mutants. Results: We demonstrated a significant increase in insecticidal activity in the isolated mutants. Meanwhile, there was no observable impact of the enhanced synthesis of water-soluble melanin on the nature and abundance of spore and crystal formation. This heightened efficacy can be attributed to the photoprotective qualities of the synthesized pigment, shielding spores and crystals against the detrimental effects of UV radiation and insolation. We demonstrated the high biological activity of water-soluble bacterial melanin through in vivo experiments involving multiple plant species. Conclusions: Our findings indicate that bacterial melanin is a potent phytostimulant. This preparation accelerates and amplifies plant growth and development processes, leading to a substantial increase in crop yield by 20–40%. The simultaneous synthesis of two biologically active substance, melanin and insecticidal toxins, ensures an elevated level of effectiveness in utilizing melaninogenic strains.

The synthesis of enantiomeric forms of D-amino acids can be achieved by a two-step “hydantoinase process” based on the sequential catalysis of substrates by specific enzymes, D-carbamoylase and D-hydantoinase. Here, we describe the structural features of D-carbamoylase from Pseudomonas, the encoded gene of which was chemically synthesized and cloned into Escherichia coli. A significant fraction of the overexpressed recombinant protein forms insoluble inclusion bodies, which are partially converted to a soluble state upon treatment with N-lauroylsarcosine or upon incubation of cells at 28 °C. Purified His-tagged protein exhibits the highest activity towards N-carbamoyl-D-alanine and N-carbamoyl-D-tryptophan. Comprehensive virtual analysis of the interactions of bulky carbamylated amino acids with D-carbamoylase provided valuable information. Molecular docking analysis revealed the location of the substrate binding site in the three-dimensional structure of D-carbamoylase. Molecular dynamics simulations showed that the binding pocket of the enzyme in complex with N-carbamoyl-D-tryptophan was stabilized within 100 nanoseconds. The free energy data showed that Arg176 and Asn173 formed hydrogen bonds between the enzyme and substrates. The studies of D-carbamoylases and the properties of our previously obtained D-hydantoinase suggest the possibility of developing a harmonized biotechnological process for the production of new drugs and peptide hormones.

Bacterial cellulose (BC) is a biocompatible, non-toxic, non-cytotoxic, non-allergenic, biodegradable, chemically pure (which allows to significantly reduce environmental pollution), unique biopolymer with high elasticity, flexibility, plasticity, water-absorbing and water-retaining properties. BC is a promising biopolymer for various applications. However, its high cost and low productivity hinder large-scale production of BC. The mutant strain Komagataeibacter xylinus MS2530 obtained by us reduced the fermentation time from 14 to 5-7 days. In order to reduce the cost of the resulting BC, brewing waste without sterilization was used as a nutrient medium (while costs are significantly reduced under production conditions). The use of this medium led to an increase in the BC yield by 2-2.5 times compared to the classic HS medium. Various BC modification methods are used to increase the yield and improve the most important properties of BC. In order to modify the BC obtained by us, the method of co-fermentation with different yeast strains was used. As a result of co-fermentation, the yield of BC increased by 4-5 times. The obtained BC and modified BC were studied using SEM, IR-Fourier, etc. The study showed a change in the microstructure and physical properties of the obtained biofilms, which can contribute to the expansion of their application areas. The results we obtained can become a prerequisite for organizing large-scale production of BC and BC biocomposites.

The synthesis of enantiomeric forms of D-amino acids can be achieved by a two-step "hydantoinase process" based on the sequential catalysis of substrates by specific enzymes, D-carbamoylase and D-hydantoinase. In addition to our previously studied D-hydantoinase, we describe here the structural features of D-carbamoylase from Pseudomonas, the encoded gene of which was chemically synthesized and cloned into Escherichia coli. A significant fraction of the overexpressed recombinant protein forms insoluble inclusion bodies, which are partially converted to a soluble state upon treatment with N-lauroylsarcosine or upon incubation of the cells at low temperatures. Analysis of the substrate specificity of the purified His-tag protein showed that D-carbamoylase exhibits the highest activity toward N-carbamoyl-D-alanine and N-carbamoyl-D-tryptophan. Molecular docking analysis revealed the location of the substrate binding site in the three-dimensional structure of D-carbamoylase. Molecular dynamics simulations showed that the binding pocket of the enzyme in complex with N-carbamoyl-D-tryptophan is stabilized within 100 ns. The free energy of binding indicated a possible role of residues Arg176 and Asn173 in the formation of hydrogen bonds between the enzyme and N-carbamoyl-D-tryptophan. The properties of the studied D-carbamoylase and D-hydantoinase support further development of a combined biotechnological process for the production of new drugs and peptide hormones.