## 4 Plant Tissue and Organ Cultures in Bioreactors  
Products containing ingredients of plant origin have been indispensable elements of food products, medicines, dietary supplements, or various types of cosmetics for centuries [66; 67; 68; 69; 70]. It is well known that the biologically active compounds contained in plant tissues have beneficial effects on health and beauty. As such, there is growing interest in plant products as sources of extremely attractive ingredients in many products. However, a greater awareness of climate change and the desire to reduce the use of chemical plant protection products or to conserve water resources has forced the search for alternative sources of phytochemicals, such as those from ginseng or aloe. One attractive course of action may be the culture of plants in strictly controlled and optimal in vitro conditions.  
Another important advantage of plant culture is the possibility of increasing the scale of the entire culture process, and a number of new culture systems for plant in vitro cultures have been developed [70; 71; 72; 73; 10; 74]. Combining these culture strategies with the use of special procedures, such as elicitation with biotic or abiotic elicitors, allows for the large-scale production of the target biologically active compound [75]. As such compounds are typically complex molecules, their chemical synthesis is often very complicated and unprofitable. Given this, plant cells are now enjoying growing popularity as miniature factories. Since the times of [PERSON]--who in 1902 initiated the use of plant cell and tissue cultures--describing the process of plant regeneration from callus cultures, there has been a revolution related to the possibilities of their laboratory and industrial application. However, the turning point in bioreactor culture occurred in 1956 when [PERSON] and [PERSON] [76], in cooperation with Pfizer Inc., obtained the first patent for a large-scale in vitro culture of plant cells for secondary metabolites. Subsequently, the techniques of culturing plant cells and organs were improved through the mid-1950s, with a significant achievement being the development of a complete medium for the culture of plant tissues by [PERSON] and [PERSON] [77]. Since then, our understanding of plant cells has changed significantly, and the current technological possibilities allow even the most demanding cells and tissues to be cultivated, thus allowing the efficient production of valuable biologically active compounds. Many technical solutions have been developed to optimize the culture of plant material depending on its origin and specificity. One such example is the bioreactor, most simply defined as a vessel in which a biological reaction or change takes place, and which provides optimal conditions for the culture of cells, tissues, or whole plants [21; 78]. Such bioreactors can be very structurally diverse. Laboratory conditions most often require the use of reactors with a smaller volume and simpler structure, these are often tightly closed vessels with a stirrer, sprinkler, or aeration nozzle, while the industrial ones are complex devices in which most parameters are controlled digitally [79; 80]; they are most often equipped with a microprocessor control unit to monitor the pH, temperature, and density of the cultured cells. The selection of the bioreactor and the process itself depend on the method of production, i.e., secretion into the culture medium or accumulation in biomass. The most common process modes used in such cultures are batch culture, fed batch culture, rapid feed batch culture, two-stage batch culture, and continuous culture. As the optimum conditions for the growth of different types of plant cells or tissues vary considerably, choosing the right bioreactor is not always easy. The most common types of bioreactors are presented below.