Vol 61, No 6 (2025)

A highly efficient expression system for recombinant type II L-asparaginase from Escherichia coli (EC 3.5.1.1) was developed using a synthetic gene optimized for the folding energy of mRNA secondary structures in the 5'-region. The engineered E. coli BL21[DE3]/pET28a-AsnSYN strain produced up to 291 ± 9 mg/L of enzymatically active protein (44.5 ± 2.6 mg/(L·OD)) in shake-flask cultures, 50% higher than the control strain with the native gene after 3 hours of induction. Codon optimization increased the mRNA secondary structure stability in the 5'-region from –70 to –47 kcal/mol, potentially improving translation efficiency. The purified asparaginase met pharmacopeial standards, with a total yield ≥25%, specific activity >250 IU/mg, and high purity (no detectable impurities by electrophoresis, <3% multimeric forms by gel filtration). These findings highlight the potential of synthetic gene design with DNA structure optimization for industrial-scale production of therapeutic enzymes.

The bioleaching process of metallurgical slag containing nickel and copper was investigated at temperatures of 40, 45, and 50°C. The experiments involved microbial communities cultivated at 40 and 45°C, which comprised the bacteria Leptospirillum ferriphilum and Sulfobacillus thermosulfidooxidans. The microbial community established at 50°C included representatives of S. thermosulfidooxidans and Acidiplasma sp. The findings indicate that the dissolution of the solid phase and the oxidation of ferrous iron by microorganisms reached their highest levels at 45°C. Under these conditions, the majority of copper (95.5–100%) and nickel (92.3–100%) released into solution within the first day of bioleaching. Kinetic studies of chemical leaching of non-ferrous metals during the initial four hours demonstrated that the presence of 5 g/l Fe³⁺ resulted in the extraction of 93.0% nickel and 94.3% copper, whereas, in the absence of Fe³⁺, 75.0% of nickel and 77.8% of copper were extracted.

The production of the most studied, active and widespread groups of brassinosteroids by salt-tolerant bacteria Priestia megaterium Ср-1, Rhodococcus jostii CA-6 and Pseudomonas koreensis FP2/1 isolated from saline soil samples was studied. It was shown that the studied bacterial strains are capable of producing steroidal phyto-hormones of the brassinolide, 24-epibrassinolide and 28-homobrassinolide groups, as well as brassinosteroid B-ketones, B-lactones and 6-deoxo derivatives. This circumstance may be the reason for the growth-stimulating activity of these bacteria and their effect on plant adaptation to stress factors.

The work is devoted to the experimental study of Arthrospira platensis culture growth in a two-stage luminostat. A new method of flow culture is presented, which allows to increase the efficiency of light energy assimilation, as well as to control the content of photosynthetic pigments in algal biomass. In the first stage, the growth of A. platensis culture in the first stage of luminostat in batch mode was investigated. Due to high surface and spatial irradiance, a prolonged exponential phase is present on the growth curve. The maximum specific growth rate of the culture was 0.96 1/day and the chlorophyll a and C-phycocyanin content was low – 1.37 and 2.3% respectively. The light energy passing through the first stage varied from 2.23 to 33.24% depending on the maintained density of the quasi-continuous culture. The reduction in light flux affected the maximum productivity of A. platensis in the second stage of luminostat, which was 0.08 g/(l·day). In the second experiment, cultivation was carried out in a two-stage luminostat regime, in which the nutrient medium was sequentially flowed through both stages. It was shown that in the second stage, due to a decrease in irradiance, photoadaptation of A. platensis cells occurred, consisting in a slight increase in the proportion of chlorophyll a and a significant increase in C-phycocyanin – 13.6 %. The pigment content was directly influenced by the uniformity of cell irradiation, which for the second stage was only 8 %, which led to a decrease in productivity and an increase in the content of C-phycocyanin. The obtained results allow us to recommend the two-stage luminostat for optimisation problems solving on obtaining microalgae biomass of a given pigment composition.