# Development of an Organic Culture Medium for Autotrophic Production of _Chlorella vulgaris_ Biomass
## 1 Introduction  
Microalgae can be a source of high value compounds, such as polyunsaturated fatty acids, pigments (e.g., chlorophylls and carotenoids), polysaccharides, and proteins, with applications in the food, cosmetic, and pharmaceutical industries, among others [1]. In recent years, the food industry has seen an increased demand for natural, healthy, high quality raw materials, even if the consumer prices of the final product become higher. In scientific terms, \"organic\" usually refers to living organisms and compounds with the presence of carbon, but for consumers this word is often linked to food. Food and Agriculture Organizationof the United Nations (FAO) reported that the term \"organic\" should be viewed as a management claim concerning a process having natural inputs rather than a product claim. Inter-governmentally organizations through partnerships with International Federation of Organic Agriculture Movements (IFAOM) set guidelines in 2002 for organic farming production systems, but in legal terms, labelling and certification is set by different global standards depending on where the food is produced. Food products are an important niche market due to the increasing awareness of customers regarding the nutritional quality and safety of the food they eat. As a result, the worldwide market volume of food products labelled as \"organic\" has quadrupled over the last 15 years [2], a fact that needs to be addressed by the food supply chain. The concept of quality in food has expanded beyond the chemical and organoleptic characteristics of products and embraced the ethical values and the environmental impact of production mode [3]. For consumers, good nutrition is not only the determinant for health maintenance but also for improved quality of life from a cultural, social, and psychological holistic perspective. An ever-growing number of consumers are a conscious and informed elite, who are prepared to pay more for certified organic food products because of the credibility of their origin and their label reliability [4]. Because of this trend, Europe Regulation (EU) 2018/848 has recently been approved, repealing Council Regulation (EC) No 834/2007 on organic production and labelling as organic food products. Euroleaf is the EU logo that identifies packaged organic food products. For consumers, certification is important for two reasons: i) the perception of food safety is enhanced upon purchase by the consumer of the product labelled as \"organic\"; and ii) companies are able to show that the product meets the necessary requirements, providing a competitive advantage as compared to their direct competitors. Certain microalgal species, such as _Chlorella vulgaris_, _Arthrospira platensis_ (often called \"Spirulina\"), and _Tetraselmis chui_, are commonly used in the food sector as novel foods, either as a whole or as food supplements, approved by FDA (Food and Drug Administration), EFSA (European Food Safety Authority), and Regulation (EC) 2017/2470 Directive 2002/46/CE [5]. Functional food, as _C. vulgaris_ biomass, can be directly consumed or incorporated into conventional foods in order to enhance their nutritional content [6]. This freshwater microalga is known to be a rich source of protein, pigments, vitamins, and \(\beta\)-glucans that can help in the regulation of lipid concentration in human blood [6]. One of the most important steps for successful autotrophic microalgal growth is the selection of an adequate culture medium able to supply suitable amounts of nitrogen, phosphorus, iron, and trace minerals that ensure the effective growth of cultures [7]. Similarly, the abiotic growth conditions, including temperature, pH, and light irradiance play a key role in microalgal growth and are known to significantly affect the final biochemical composition of the biomass.