# Nutritional and Medicinal Properties of Microbial Oil
## 2 History and Development of Microbial Oil Manufacture  
Microorganisms are a known source of animal feed and human foods. They are no stranger to the history of food, and they are used to ferment food products to improve their nutrition, taste, and texture. In the 20 th century, microbial biomass became a source of nutritional food ingredients. Microbial oil can be an example of a new application of microorganisms [1; 2]. The research on microbial lipids dates back to the 19 th century. In the 1880s, [PERSON] discovered bacteria that can produce fatty acids [7]. According to databases of Scopus and Web of Science, the first recorded papers related to microbial oil were published in the 1940s. The first papers were related to bacterial lipids (Figure 1). The bacterial lipid metabolism had a significant impact on the understanding of the basic lipid metabolic pathways, enzyme mechanisms, and transcriptional regulation. The early work in the _Escherichia coli_ system jump-started the investigation of fatty acid and phospholipid synthesis [8]. Although the study of individual phospholipids and their synthesis began in the 1920s in plants and then mammals, it was not until the early 1960s that [PERSON], using _E. coli_, initiated studies of the bacterial phospholipid metabolism at Harvard Medical School. In the 1970s and 1980s, most of the enzymes responsible for phospholipid biosynthesis were purified and identified, and, in the 1990s, the genes encoding those proteins were sequenced [9]. In 1895, a yeast termed _Torula pulcherrina_ (now _Metschnikowia pulcherrina_) was discovered to produce an oil droplet, and, in 1915, the fungus _Endomyes vernalis_ was demonstrated  
Figure 1: Period distribution of the number of publications on single-cell oil, microbial lipids, and bacterial lipids (Source: Scopus and Web of Science). to produce up to 42% (\(w/w\)) lipid under nitrogen limitation [2; 10]. The records describing the production of lipids from yeast date back to 1878 [11]. The first microbial oil was only marketed in 1985 by the company J & E Sturge (North Yorks, UK) and originated from the mold culture of _Mucor circinelloides_[1]. In the 1960s, yeast and molds became popular microbial lipid factories to be explored, and the study of lipids in cell biology (\"lipidology\") emerged with the first attempts to describe and understand the lipid composition of cells. The number of papers related to microbial oil doubled each decade from the 1960s to the 1990s (Figure 1). The involvement of the yeast _Saccharomyces cerevisiae_, which is a well-established experimental model organism, had proven to be valuable in understanding lipid synthesis and its regulation. Efforts have been made to understand the biochemistry of neutral lipid synthesis and its packaging and assembly into mature lipid droplets (metabolically highly active subcellular organelles present in all eucaryotic cells) [12; 13]. During the 1980s, algae research gained significant importance regarding its potential as a source of oil. Researchers found out that certain types of algae, such as _Chlorella_ and _Spirulina_, contain high levels of fatty acids, including omega-3. This discovery led to the exploration of using algae, as well as bacteria and fungi, to produce microbial oil with a high nutritional value [14]. The rapid development of genetic engineering methods has made it possible to genetically manipulate microorganisms to increase the efficiency of lipid accumulation. For instance, yeast research on omega-3 fatty acids in the 1990s was a significant step for producing microbial oil with a higher nutritional value [15; 16]. It can be seen from Figure 1 that, in the 2000s, the number of papers produced was more than five times higher than that found ten years before, and this number is still increasing now (Figure 1). The commercial production of yeast lipids in 2006 was developed by DuPont (Wilmington, NC, USA).