Enhancing lipid accumulation in Tetraselmis sp.: integrating nitrogen deprivation and glucose supplementation for biofuel production

Abstract

Fossil fuel combustion is a major contributor to the greenhouse effect, which drives global environmental challenges such as climate change. The rapid depletion of fossil fuel reserves necessitates the urgent management of greenhouse gas emissions and the development of sustainable alternatives. Green algae are a promising resource for biofuel production because of their high lipid content (up to 70% dry weight), which can be converted into biofuel. This study investigated the lipid production potential of Tetraselmis sp. under different nutrient media conditions to determine the glucose concentration that maximizes lipid accumulation to advance biofuel research. To determine the effect of glucose concentration on lipid accumulation, Tetraselmis sp. was cultured in three different nutrient media: standard microalgal culture medium (F/2), seawater, and nitrogen-deficient medium (NDM) supplemented with different glucose concentrations. The glucose concentration that maximized lipid accumulation was incorporated into NDM (NDM+G) and effect of the medium was compared with the effects of other media over 9 days. Additionally, reactive oxygen species (ROS) levels and apoptosis rates were measured to assess the cellular effects of glucose supplementation and nitrogen deprivation. NDM+G, with 2 mg/mL glucose, was the most effective medium for lipid accumulation in Tetraselmis sp., with lipid levels peaking significantly (p < 0.05) at 79.8% on day 6 post-glucose supplementation. This suggests that maximum lipid yield can be achieved by harvesting Tetraselmis sp. cultured in glucose-supplemented NDM on day 6. However, ROS levels were elevated significantly (p < 0.05) by day 4, and apoptosis rate reached 31% by day 9, indicating potential cellular stress under the conditions. The use of seawater and cost-effective nutrient formulations improves the industrial feasibility of the approach, while the high lipid yield within a short cultivation period supports its potential application in sustainable large-scale biofuel production. Further research is required to optimize culture conditions using low-cost nitrogen and carbon sources. Such optimization should aim to reduce costs and cellular damage while maximizing lipid production, ultimately enabling more sustainable biofuel solutions.