# Malaysian Virgin Soil Extracts as Natural Growth Enhancer for Targeted Green Microalgae Species
###### Abstract  
The microalgae-based industries are trending upwards, particularly as the feed ingredient for aquaculture. Therefore, a sustainable and reasonably priced source of nutrients to support the mass cultivation of microalgae is in great demand. The present study explored the feasibility of using extracts from virgin soil as natural growth-promoting nutrients for the cultivation of _Nannochloropsis ocantica_, _Nannochloropsis ocantica_, and _Chlorella sorokiniana_. The extracts were obtained from Bera Lake Forest using five different treatment methods. The greatest retrieval of dissolved organic carbon, total dissolved nitrogen, and total dissolved phosphorus were observed with the autoclave treatment method at 121 \({}^{\circ}\)C twice, yielding a respective concentration of 336.56 mg/L, 13.40 mg/L, and 0.14 mg/L, respectively. The highest growth was recorded with _Nannochloropsis ocantica_ resulting in an optical density of 0.488 \(\pm\) 0.009 (\(\times 10^{3}\) cell mL\({}^{-1}\)), exhibiting 43% and 44% enhanced growth in comparison to _Nannochloropsis ocanica_ and _Chlorella sorokiniana_, respectively. The specific growth rate (0.114 \({}^{\pm}\) 0.007 d\({}^{-1}\)) was the highest for _Nannochloropsis ocantica_ when the 24 h-extraction method was used, whereas the utilization of the autoclave 121 \({}^{\circ}\)C twice treatment method contributed to the highest specific growth of _Nannochloropsis ocanica_ (0.069 \({}^{\pm}\) 0.003 d\({}^{-1}\)) and _Chlorella sorokiniana_ (0.080 \({}^{\pm}\) 0.001 d\({}^{-1}\)). Collectively, these findings suggested that the addition of soil extracts which is sustainable and inexpensive promoted the growth of microalgae compared to the control system. A further study investigating the optimum culture conditions for enhanced microalgae growth will be carried out for the mass production of microalgae biomass. Chlorella sorokiniana; microalgae growth  
production models must be developed to minimize waste and use the waste from other processes as raw material. In this context, the cultivation of microalgae for the benefit of many industrial applications supports this agenda well [1]. Microalgae can be classified as photosynthetic microorganisms which can generate biologically active compounds, namely pigments, lipids, polyunsaturated fatty acids, carbohydrates, proteins, and vitamins, through the conversion of carbon dioxide (CO\({}_{2}\)) [2]. These bioactive compounds are applied in many industries particularly in food as feedstock and human nutrition, as pigments in cosmetics products and as antimicrobial, antiviral, antibacterial, and anticancer drugs in pharmaceuticals [3]. Moreover, due to microalgae's high content of proteins, high-quality essential amino acids, vitamins, carotenoids, antioxidants, and other substances beneficial to animal health, these photosynthetic microorganisms contribute significantly to animal nutrition and the aquaculture industry [1]. In addition, when compared to higher plants, microalgae exhibit certain favourable characteristics such as the requirement for low water feeding, high carbon dioxide (CO\({}_{2}\)) fixation and oxygen generation, rapid growth, and simple harvest [2]. Taking into account all the exceptional characteristics of microalgae that led to their commercial importance, the strategies for mass production of microalgae at a reasonable cost must be endeavoured. Microalgae cultivation, both prokaryotic and eukaryotic, has been studied for over 70 years and is still a hot topic of research and development. Commercialised microalgae, namely _Chlorella_ and _Spirulina_, are mostly produced for human food and nutrition (nutraceuticalals) [3]. In addition, _Dunaliella salina_ and _Haematococcus pluvialis_ were mass-produced popularly in the 1980s for microalgal pigments which were marketed mostly for human nutrition as food additives since these microalgae contain high-value carotenoids, beta-carotene, and astaxanthin, respectively [3].