Assessing the potential of nutrient deficiency for enhancement of biodiesel production in algal resources

Depleting energy sources result in a growing interest in the conversion of microalgal biofuel to improve economic feasibility. Efficient and cost effective biomass conversion to biofuel demands an increase of carbohydrates and lipid accumulation in algal cells. In the present study, it is measured that concomitant nitrogen, phosphorous and, iron deficiency induces significant physiological and biochemical changes in microalgae <i>Oedogonium</i> sp., <i>Ulothrix</i> sp., <i>Cladophora</i> sp. and <i>Spirogyra</i> sp. by using Response surface methodology as the optimization of growth medium tool. In each of the studied algae species, nutrient deficiency reduced the growth rate of algae as well as protein and chlorophyll of individual cells. On other hand, the biochemical compounds such as carbohydrates were increased up to 0.58 mg/g in <i>Oedogonium</i> sp., 0.56 mg/g in <i>Ulothrix</i> sp., 0.61 mg/g in <i>Cladophora</i> sp., and 0.65 mg/g in <i>Spirogyra</i> sp. as compared to controls. The lipid increased by 75% in <i>Oedogonium</i> sp., 83% in <i>Ulothrix</i> sp., 78% in <i>Cladophora</i> sp., and 73% in <i>Spirogyra</i> sp. lipid content and fatty acid fractions of C16:0, C18:1 and C18:0 of algal species improve under nitrogen, phosphorus and iron deficiency that keeps the fuel properties (EN 14214, ASTM 6751 standard) in the acceptable range important to increase biodiesel quality. The results indicate that nutrient deficiency in algal biomass cultivation can enhance oil and carbohydrates and their subsequent biodiesel production on commercial scale.HighlightsImprove lipid yield of algae under nutrient deficiency is studied for first timeOptimization of carbohydrates and lipids of new algal resources was establishedAlgal species could be commercialized for sustainable biodiesel production Improve lipid yield of algae under nutrient deficiency is studied for first time Optimization of carbohydrates and lipids of new algal resources was established Algal species could be commercialized for sustainable biodiesel production

随着能源储量日渐枯竭，人们对微藻生物燃料转化技术的关注度与日俱增，以期提升其经济可行性。实现高效且低成本的生物质向生物燃料转化，需要提升藻类细胞内碳水化合物与脂质的积累量。
本研究以响应面法（Response surface methodology）作为培养基优化工具，探究了氮、磷、铁协同匮乏对鞘藻属（<i>Oedogonium</i> sp.）、丝藻属（<i>Ulothrix</i> sp.）、刚毛藻属（<i>Cladophora</i> sp.）以及水绵属（<i>Spirogyra</i> sp.）四种微藻的生理与生化特性产生的显著影响。在所研究的四种藻类中，营养匮乏均会降低藻类的生长速率，同时减少单个细胞内的蛋白质与叶绿素含量。与之相对的是，相较于对照组，四种藻类的碳水化合物等生化物质含量均得到提升：鞘藻属可达0.58 mg/g，丝藻属可达0.56 mg/g，刚毛藻属可达0.61 mg/g，水绵属可达0.65 mg/g。
四种藻类的脂质含量也分别提升：鞘藻属提升75%，丝藻属提升83%，刚毛藻属提升78%，水绵属提升73%。此外，在氮、磷、铁匮乏条件下，藻类的C16:0、C18:1及C18:0等脂肪酸组分得到优化，使得燃料性能符合EN 14214、ASTM 6751标准的要求，这对提升生物柴油品质至关重要。
研究结果表明，在藻类生物质培养过程中施加营养匮乏条件，可提升藻类油脂与碳水化合物的积累量，进而推动规模化商业生物柴油生产。
研究亮点：
1. 首次探究了营养匮乏条件下藻类脂质产量的提升潜力；
2. 建立了新型藻类资源的碳水化合物与脂质优化方法；
3. 验证了所选用的藻类可商业化用于可持续生物柴油生产。