Over the last several decades, plants have been developed as a platform for the production of useful recombinant proteins due to a number of advantages, including rapid production and scalability, the ability to produce unique glycoforms, and the intrinsic safety of food crops. The expression methods used to produce target proteins are divided into stable and transient systems depending on applications that use whole plants or minimally processed forms. In the early stages of research, stable expression systems were mostly used; however, in recent years, transient expression systems have been preferred. The production of the plant itself, which produces recombinant proteins, is currently divided into two major approaches, open-field cultivation and closed-indoor systems. The latter encompasses such regimes as greenhouses, vertical farming units, cell bioreactors, and hydroponic systems. Various aspects of each system will be discussed in this review, which focuses mainly on practical examples and commercially feasible approaches.

Both obtaining high-yielding, viable protoplasts and following reliable regeneration protocols are prerequisites for the continuous expansion and development of newly emerging systems involving protoplast utilization. This study determines an efficient process from protoplast isolation to shoot regeneration in vitro. The maximum yield of protoplast extraction, which was 6.36 ± 0.51 × 106 protoplasts/g fresh weight (FW), was approximately 3.7 times higher than that previously reported for potato protoplasts. To obtain data, wounded leaves were used by partially cutting both sides of the midrib, and isolated protoplasts were purified by the sucrose cushion method, with a sucrose concentration of 20%. We confirmed a significant effect on the extraction efficiency by measuring enzymolysis during a 6 h period, with three times more washing buffer than the amount normally used. Protoplasts fixed in alginate lenses with appropriate space were successfully recovered and developed into microcalli 2 weeks after culture. In addition, to induce high efficiency regeneration from protoplasts, calli in which greening occurred for 6 weeks were induced to develop shoots in regeneration medium solidified by Gelrite, and they presented a high regeneration efficiency of 86.24 ± 11.76%.

Fructans are polymers of fructose that are present as storage carbohydrates in various plants. Jerusalem artichoke (Helianthus tuberosus L.) contains a high amount of inulin. Two enzymes are involved in inulin biosynthesis. The sucrose:sucrose 1-fructosyltransferase (1-SST) enzyme mainly catalyzes the synthesis of 1-kestose from sucrose. In the next step, fructan:fructan 1-fructosyltransferase (1-FFT) catalyzes the synthesis of inulin from 1-kestose. In this study, the Ht1-SST and Ht1-FFT genes were isolated from Jerusalem artichoke and expressed in potato (Solanum tuberosum L.), either separately or together, via Agrobacterium-mediated transformation. Transgenic potato tubers overexpressing Ht1-SST accumulated 1-kestose to a high level (up to 3.36 mg/g), while tubers overexpressing both Ht1-SST and Ht1-FFT accumulated up to 3.14 mg/g short-chain inulin-type fructans, with the degree of polymerization (DP) ranging from 3 to 5, excluding high DP inulins. Transgenic potato plants accumulated fructo-oligosaccharides to a high level, following the fructan biosynthetic pathway of Jerusalem artichoke, and therefore present a high potential for the mass production of inulin through established potato breeding and cultivation methods.