A mathematical modeling of microalgae biomass is an essential step to optimize the biomass and lipid production rate and to reduce the cost of microalgal biodiesel production system. In the present study, kinetic studies were carried out to describe the growth and neutral lipid production of two marine microalgae Chlorella salina and Nannochloropsis oculata under the nitrogen-repleted and -depleted conditions using logistic and Luedeking–Piret equations. This research paper provides the information on mathematically efficient procedure to predict suitable environment condition for biomass and lipid production. The predicted results were compared with experimental data, which showed that this model closely agreed with simulated results. From this investigation, it was found that nitrogen was an essential nutrient for algal growth, which increased under nitrogen-rich condition, whereas during nitrogen-limited condition some loss in growth was observed but with increased lipid content. Since metabolic changes occurred under nitrogen- depleted state, the protein and carbohydrate pathways were shifted to lipid biosynthesis.
In this study, enzymatic interesterification is carried out using encapsulated lipase as biocatalyst with methyl acetate as acyl acceptor in a solvent-free system. Lipase, isolated from a marine bacterial isolate, Bacillus sp.S23 (KF220659.1) was immobilized in sodium alginate beads. This investigation elaborated on the effects of various parameters, namely enzyme loading, temperature, water, molar ratio, reaction time and agitation for interesterification. The study resulted in the following optimal conditions: 1.5 g immobilized lipase, 1:12 molar ratio of oil to methyl acetate, 35 °C, 8 % water, 60 h reaction time, 250 rpm of agitation. With the standardized condition, the maximum conversion efficiency was 95.68 %. The immobilized beads, even after ten cycles of repeated usage showed high stability in the presence of methyl acetate and no loss of lipase activity. The microalgal biodiesel composition was analyzed using gas chromatography. The current study was efficient in using immobilized lipase for the interesterification process, since the method was cost-effective and eco-friendly, no solvent was involved and the enzyme was encapsulated in a natural polymer.
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