Bioethanol Production from Green Alga Chlorococcum minutum through Reduced Graphene Oxide-Supported Platinum-Ruthenium (Pt-Ru/RGO) Nanoparticles

Due to the continuous depletion of non-renewable fossil fuels, there is a focus on renewable energy sources such as bioethanol, biobutanol, biohydrogen and biodiesel. Microalgae have been used to yield high sugar content via alteration of the photosynthetic pathway, thereby enhancing ethanol production. Moreover, certain nanostructured composites in the medium supports biomass enhancement through modification of the photosynthetic pathway. In the present study, reduced graphene oxide-supported platinum-ruthenium (Pt-Ru/RGO) nanoparticles were synthesised, characterised and assessed the role in tris–acetate phosphate (TAP) medium for the improvement of green alga Chlorococcum minutum (C. minutum) biomass under in vitro conditions. Chemically, Pt-Ru/RGO nanoparticles play a useful role as a catalyst in the improvement of chemical reactions and influence the electron supply/transport system. Total chlorophyll and wet biomass contents were 8.26 mg/L and 14.0 g/L in TAP with 1.0 mg/L of nano-Pt-Ru/RGO (CM2) medium when compared with untreated cultures, but total lipid content was more (24.5 g/100 g) in TAP with 0.5 mg/L of nano-Pt-Ru/RGO (CM1) medium. Later, these nano Pt-Ru/RGO-assisted algal feedstocks were used to convert sugars into ethanol by Saccharomyces cerevisiae (yeast) dark fermentation. The current standardised TAP media in the presence of 0.5 or 1.0 mg/L of Pt-Ru/RGO nanoparticles (CM1 or CM2 medium) improved the ethanol production (32.6 and 31.2 g/L at 72 h respectively) from feedstocks of C. minutum. In conclusion, Pt-Ru/RGO nanoparticles can enhance the chemical reactions in photosynthesis likely at the electron transport system and increased the biomass in turn ethanol production.