# Malaysian Virgin Soil Extracts as Natural Growth Enhancer for Targeted Green Microalgae Species
###### Abstract
In the 1990s, the commercialized production of docosahexaenoicenoic acid (DHA) and eicosapentaenoic acid (EPA) in particular were heavily commenced for use in aquaculture feed and enrichment of nutritional products [4]. In addition, microalgae can serve as functional feed and as probiotics for aquaculture feeding which could curb the common outbreak of disease-causing enormous economic losses to the aquaculture industry. Although the production of microalgae-based products has been relatively in practice for a long time, the vast applications were directed to industries such as nutraceuticalals and human consumption on a minute scale with an overall worldwide production of fewer than 15,000 tons per year and production costs limited to 10 \(\copyright\) per kg [5]. It can then be concluded that the large-scale commercial production of microalgae is still in its infancy stage and needs substantial improvement. There are a few challenges related to the production of microalgae, namely the necessity for a high volume of water and fertilizers usage even though arable land is not required [6]. In addition, some limitations may discourage the production of microalgae biomass. The cultivation of microalgae requires high energy consumption, incurs high costs when the biomass is converted into valuable end-products, involves technological constraints when the cultivation of microalgae carried out in photobioreactor leads to the upsurge in the formation of biofilms, and limits the light penetration and the occurrence of environmental pollution as a result from the release of the undigested nutrients [7,8]. Among these challenges, the selection of favourable culture conditions and the use of economically feasible and sustainable nutrients for microalgae cultivation should be prioritized for optimization to make commercialization more viable [6]. The formulation of microalgae cultivation medium using organic carbon such as sugar alcohols, sugars, and organic acids in the growth medium of microalgae amplifies the cost of microalgae biomass cultivation [9]. Hence, the research community has devoted immensely to the quest to search for cheaper and sustainable nutritional compositions for enhanced microalgae biomass production. The production of microalgae biomass largely depends on major nutrients, namely nitrogen, phosphorus, and carbon dioxide (CO\({}_{2}\)), whereby for the generation of 100 tons of microalgae biomass, approximately 200 tons of CO\({}_{2}\), 5 tons of nitrogen, and 1 ton of phosphorus are required [5]. Even though sources such as fertilizers and flue gas can be employed to supply these nutrients, ultimately the utilization of these resources is limited due to the consumption of high energy and excessive emissions of carbon dioxide (CO\({}_{2}\)) [5]. Many studies have explored the use of wastewater as an alternative nutrient source which was found successful to enhance microalgae cultivation [1; 5; 9]. Microalgae have been attempted to bioremediate industrial, municipal, food, and animal wastewater whereby the organic compounds and nutrients are simultaneously exploited to support the growth of microalgae [10; 11; 12; 13; 14; 15]. Microalgae are advantageous as biocatalysts for the treatment of wastewater due to their promising ability in removing pollutants such as carbon oxygen demand (COD), heavy metals, and emerging contaminants. Furthermore, microalgae are capable to remove and recover nutrients such as total dissolved nitrogen (TDN) and total dissolved phosphorus (TDP). The treated wastewater by microalgae additionally can be recovered for other purposes and the culture medium can be reused. The summary of the selected wastewater and the production of various microalgae biomass is presented in Table 1. However, it is necessary to explore more sustainable nutrient sources since the microalgae-based industries are blooming.