Production and optimization of biofuels from locally isolated algal biomass: Strategies for circular economy integration

In the present study, we investigated the potential of locally isolated algal strains as alternative energy sources for sustainable biofuel production. The focus of this study was to identify algal strains that are capable of accumulating oils rich in essential fatty acids. Algal samples were collected from different areas and 14 isolates were obtained. Among the various pretreatment methods tested, hydrothermal pretreatment using sulfuric acid at 95 °C yielded the best results, with sample IIB-14 containing more than 2% reducing sugars. These sugars were then used for fermentation with the S. cerevisiae strain, resulting in an ethanol concentration of 3.52% ± 0.2%. This holistic approach contributes to the development of low-cost and environmentally friendly alternatives to traditional energy sources. While algal biofuels offer a promising substitute for fossil fuels, further advancements are needed before they can be widely adopted in the fuel market. Among these, isolates IIB-8 and IIB-9 showed the highest oil yields of 22.84% and 24.69% (w/w), respectively. The specific environmental settings for optimal growth of these strains were determined, and the physicochemical parameters of the oils, including iodine value, viscosity, density, acid value, saponification value, unsaponifiable mass, and peroxide value, were analyzed. The transesterification of oils into fatty acid methyl esters (FAMEs) revealed the presence of significant amounts of fatty acids, including EPA, DHA, and linoleic acid. Moreover, the study also explored the potential of algal biomass for bioethanol production, addressing the sustainability concerns of renewable energy supplies. Hydrothermal pretreatment using sulfuric acid at 95 °C yielded the highest concentration of reducing sugars (>2%) in IIB-14. Sugar extracted from algal biomass was used for fermentation. The Saccharomyces cerevisiae strain used for the fermentation process yielded an ethanol concentration of 3.52% ± 0.2%. This holistic approach contributes to the development of low-cost and environment-friendly alternatives to renewable energy sources. Algal biofuels may offer a practical substitute for fossil fuels, but there is still a long way to go before they can enter the fuel market and are widely used.