## 1 Introduction
is found in soil, marshes, freshwater, brackish water, and seawater with commercial availability in large quantities [32; 33]. It has a lipid content of 6.4-8% by the weight of the dry biomass in usual growth conditions [34]. [PERSON] et al. [30] studied lipid extraction from _Chlorella_ sp. using the Bligh and Dyer method [35]. Dry biomass was first ultrasonicated for 30 min in 2:1 (_v/v_) chloroform/methanol. Then, water and additional chloroform were added, and the mixture was centrifuged at 4500 rpm for 10 min. Finally, the solvent was collected and dried in a rotary evaporator at 60 \({}^{\circ}\)C. [PERSON] et al. [36] studied lipid extraction and biodiesel production from _Chlorella vulgaris_. Lipid was extracted using chloroform:methanol (2:1). They examined the effects of different reaction conditions, including catalysts, molar ratio, temperature etc., under microwave irradiation on biodiesel outputs and compared them with findings under conventional heating. [PERSON] et al. [37] studied a flux balance approach to optimize the specific growth rate and the lipid production rate of _Chlorella vulgaris_ AG10032. They found that the microalgal cells could produce maximal lipid yield under N-starvation conditions. [PERSON] et al. [38] studied the lipid production process of _Spirulina_ sp. The dried microalgae (2 g) was placed in a conical flask with 40 mL of chloroform:methanol (2:1 _v/v_) added, and stirred for 1 h in a shaker. Thus, maximization of the output from these low lipid content feedstocks has not been studied extensively and needs to be addressed. The conventional biodiesel production process is alcoholysis of lipids using catalysts, either homogeneous or heterogeneous, as the reaction promoter, or supercritical reactions with or without the presence of a catalyst [39; 40; 41]. Both homogeneous catalyst and heterogeneous catalyst have been studied exhaustively in the literature. On the other hand, enzymatic catalysts are gaining attention as catalysts in transesterification or alcoholysis, especially from microalgae. Immobilized lipases are extensively used in enzymatic alcoholysis of triglycerides into fatty acid methyl esters (FAMEs) [42]. Recently, [PERSON] [43] reported the optimization of methanolysis of _Manilkan zapota_ (L.) using lipases, such as Novozyme 435 (_C. antarctica_ lipase-B immobilized on acrylic resin) and CLEA (crosslinked enzyme aggregate) of _C. antarctica_ lipase-B as biocatalyst. The author found that under similar operating conditions, 93% biodiesel was obtained after 12 h of reaction using Novozyme 435, whereas CLEA produced 84% biodiesel. [PERSON] et al. [44] studied biodiesel production from _Chlorella vulgaris_ ESP-31 microalgae by enzymatic transesterification using an immobilized lipase originating from _Burkholderia_ sp. C20. A high conversion efficiency of 97.25 wt.% oil occured when static lipase was utilized. This worked in a high water (>71.39% wt.%) level and high molar ratio settings (>67.93% wt.%). This work aimed to compare the efficacies of three lipid extraction methods viz. solvent extraction, Soxhlet extraction, and ultrasonication, to obtain microalgal crude oil from _Chlorella_ sp. and _Spirulina_ sp. The maximization of lipids using Soxhlet and ultrasonic methods was attempted by varying the operating parameters to achieve maximum lipid output. Lipids were then converted to biodiesel using the enzymatic transesterification process. The immobilized lipase was used as a catalyst under constant operating conditions. Finally, the biodiesel was characterized using Fourier transform infrared spectroscopy (FTIR) and gas chromatography (GC).