Ultrasound-Assisted Lipid Extraction from Chlorella sp.: Taguchi Design and Life Cycle Assessment.

The present study delved into the enhancement of essential oil (EO) extraction process from Chlorella sp. through the implementation of ultrasound-assisted extraction. The Taguchi method was instrumental in determining the ideal parameters for the extraction process, which encompassed ultrasonic amplitude, reaction duration, hexane/ethanol (HE/EtOH) ratio, and processing temperature. The empirical findings indicated that optimal EO yield was realized at an ultrasonic amplitude of 80%, a reaction timeframe of 15 min, a HE/EtOH proportion of 3:1, and a temperature setting of 40 °C. These optimal conditions were further substantiated through additional experimentation, resulting in an EO yield of 18.8 ± 0.2%. A fatty acid profile analysis disclosed that the extracted EO predominantly consisted of long-chain fatty acids (C14-C20), with Palmitic, Heptadecanoic, Oleic, and Linoleic acids featuring as the main components. Nevertheless, a high unsaturation rate of 37.9% in the EO could potentially render it vulnerable to oxidative deterioration during storage, consequently affecting the quality of the ensuing biodiesel. A life cycle assessment of the sonication technique utilized for biodiesel production from Chlorella sp. highlighted that lipid extraction was the principal contributor to global warming and ecotoxicity, as per the CML and TRACI methods. Hence, the ultrasound-assisted extraction of EO from Chlorella sp. appears to be a promising and ecologically viable substitute to conventional techniques employed for biodiesel production.

Removal of total nitrogen from wastewater by a combination of Chlorella sp. and audible sound.

In developing countries, nitrogen in the traditional market wastewater is a critical environmental problem. In this study, the microalga Chlorella sp., which was isolated from wastewater, was used to remove the total nitrogen (TN) from conventional market wastewater in combination with audible sound (Vietnamese classical music). In addition, effects of sound exposure on removal efficiency at different initial cell densities were analyzed. Results revealed that music sound control demonstrates potential to improve the removal efficiency. TN removal efficiencies of 96%, 69.5%, and 4.3% were observed for treatments with Chlorella sp./audible sound, Chlorella sp., and without Chlorella sp., respectively. The significance of probability value (p-value) (<0.05) on the paired sample t-test confirmed the critical role of audible sound and Chlorella sp. density on the TN removal in screening experiments. The predicted optimal conditions for TN removal were as follows: a Chlorella sp. density of 4%, an audible sound of 52.5 dB, and a cultivation time of 4.6 days. Results based on statistical analysis revealed that the quadratic models for TN removal are significant at a low p-value (<0.05) and a high predicted coefficient of determination (R2 = 0.9452) value. The obtained statistical results also indicated that most of the variables are significant for the abatement of TN from market wastewater using Chlorella sp.