**1. Introduction**

The recombinant DNA technology, born in early 1970 ties, has nowadays become mature and highly sophisticated. It plays an indispensable role in medicine, industry, and scientific research. Its rapid proliferation into a wide variety of techniques and molecular solutions for genetic engineering is largely owed to its historically first and still dominating recombinant DNA "vehicle" – *E. coli*. These bacteria were used for the construction of the most robust genetic expression systems, such as those based on: T7-*lac* hybrid promoter, bacteriophage lambda *pL* and *pR* promoters or arabinose operon promoter. Other advantages of the systems include fast bacterial growth, cost-effectiveness and deep understanding of the molecular basis of recombinant proteins biosynthesis, as *E. coli* is the most thoroughly studied microorganism. Bioactive molecules, including DNA, RNA, and proteins, designed *de novo*, are being utilized in increasingly diverse scientific, biomedical, industrial and environmental applications. The rapidly developing synthetic biology generates growing demands for synthetic genes of various types, from native to those with a highly modified sequence. The capability of generating DNA molecules of any sequence or size is especially important in biomedical research.

DNA sequences of the designed, synthetic genes may require long repetitive DNA fragments. However, the chemical synthesis of such fragments still poses a great challenge. Thus, there is a current need for the development of new technologies, enabling modular construction of complex synthetic genes.

Vast majority of synthetic recombinant DNA constructs are intended for recombinant protein production. Besides the need for recombinant proteins, the protein fragments, polypeptides, functional domains, protein-derived or natural peptides are being increasingly used, not only for functional studies but also in a wide variety of applied sciences, like material engineering and medicine. The intensive research on peptide-based biomaterials as biologically active tools has resulted in the development of a wide range of peptides and polypeptides with extended functionalities. Both natural and engineered versions of the bioactive peptides have found applications in the construction of biosensors, drug-delivery systems, and medicine [1–4].

To allow detailed investigation and scaled-up production of new macromolecular biomaterials (built from the repetitive DNA, RNA, or protein segments), a reliable method is needed to obtain a high yield of complex recombinant genes and their expression products. Some of the methods enabling construction of such sophisticated recombinant DNA molecules are based on the targeted plasmid vectors, capable of carrying of the multiple, joined (concatemeric) genes. Such concatemerization of the designed DNA, RNA and peptides may improve their stability and boost the biosynthesis level. What is even more interesting, concatemerization can also bring novel and sometimes unexpected features, such as an increase of bioactivity, a formation of bionanoparticles or more precise targeting by means of a gradual release of the bioactive molecule monomers or oligomers at the intended destination.

In order to solve the problems encountered in the techniques existing so far, a new genetic engineering method was developed. The method is dedicated to the formation of DNA concatemers necessary to produce "artificial", repetitive genes, encoding concatemeric RNAs and proteins (of any nucleotide (nt)/amino acid sequence), in a format suitable for a high-level genetic expression [5–7]. The technology is world-wide protected by patents: Polish no. 228341, (2018; first filed in 2015 [8]), United States no US 10,874,735 B2 (2020 [9]), European no EP 3 134 426 B1 (2020 [10]), Japanese no P6692796 (2020 [11]); Israeli – temporary no 248011 (2021 [12]) and patent applications: Chinese no CN 106488983 A (2016 [13]) and Indian no 201647039411 (2020 [14]).
