Microalgae has been identified as a potential feedstock for biodiesel production since its cultivation requires less cropland compared to conventional oil crops and the high growth rate of microalgae. Research on microalgae oils often are focused on microalgae oil extraction and biomass harvesting techniques. However, energy intensive and costly lipid extraction methods are the major obstacles hampering microalgae biodiesel commercialisation. Direct biodiesel synthesis avoids such problems as it combines lipid extraction techniques and transesterification into a single step. In this review, the potential of direct biodiesel synthesis from microalgae biomass was comprehensively analysed. The various species of microalgae commonly used as biodiesel feedstock was critically assessed, particularly on high lipid content species. The production of microalgae biodiesel via direct conversion from biomass was systematically discussed, covering major enhancements such as heterogeneous catalysts, the use of ultrasonic and microwave- techniques and supercritical alcohols that focus on the overall improvement of biodiesel production. In addition, this review illustrates the cultivation conditions for biomass growth and lipid productivity improvement, the available harvesting and lipid extraction technologies, as well as the key challenges and future prospect of microalgae biodiesel production. This review serves as a basis for future research on direct biodiesel synthesis from modified microalgae biomass to improve profitability of microalgae biodiesel.

Sustainability of direct biodiesel synthesis from microalgae biomass: a critical review.

Biofabrication and characterization of silver nanoparticles using aqueous extract of seaweed Enteromorpha compressa and its biomedical properties.

Progress in utilisation of waste cooking oil for sustainable biodiesel and biojet fuel production

The growing application of nanotechnology causes the release of engineered nanoparticles (NPs) into aquatic environments. With increasing concerns over the potential effect of NPs on aquatic organisms, investigations on NP toxicity to algae are rising. To date, the overall algal response to cope with NP toxicity is still uncertain. In this review, a meta-analysis was conducted to quantitatively assess the toxicity mechanisms dominated by oxidative stress. The reactive oxygen species elevated by 90% caused retarded algal growth by reduction (38%) in cell density, and NP toxicity was strongly dependent on the NP type and dose. Specifically, the mechanisms of NP toxicity were discussed in different “omics” levels. Further, we summarized the current knowledge and mechanisms of defense strategies, including formation of a protective bio-barrier and adjustment in intracellular processes (internalization, transformation and compartmentation) to decrease cellular NP concentrations. Based on the response patterns of algae to NPs, we addressed the possibility of NP application for algal bloom control. A systematic understanding of algal response mechanisms to NPs will help develop safe and sustainable nanotechnology in aquatic ecosystems.

Algae response to engineered nanoparticles: current understanding, mechanisms and implications

Biosynthesis of the silver nanoparticle (AgNPs) is gaining significant importance since it is eco-friendly and can withstand variable environmental conditions. In this present study, AgNPs have been synthesized by using a freshwater green alga, Chlorella vulgaris. For the improved production, experiments on the standardization of AgNPs synthesis were investigated at different parameters. The results affirmed that the synthesize of AgNPs was at 8:2 v/v in extract ratio, pH 12 in the solution of AgNO3, 3 mM in molarity of AgNO3, shaking process in the incubation of reactants and 24 h time in synthesis period. Further, synthesized AgNPs were characterized by using spectroscopic and microscopic techniques. The synthesized AgNPs showed the Surface Plasmon Resonance (SPR) peak between the 410–450 nm. Fourier Transform Infrared Spectroscopy (FTIR) revealed that the algal extract has stabilized with the nanoparticles by capping. The Field Emission Scanning Electron Microscopy (FESEM) analysis confirms the spherical shape of the AgNPs with an average size of 55.06 ± 9.67 nm. The X-ray diffraction (XRD) analysis showed a crystalline nature of the particle with an average size of 61.89 ± 12.13 nm. The photocatalytic decolorization of the methylene blue by using synthesized AgNPs was evaluated under the sunlight irradiation method. The synthesized AgNPs have shown 96.51% of photocatalytic decolorization activity by using methylene blue dye (100 ppm) within 3 h incubation time.

A green approach for the synthesis of silver nanoparticles by Chlorella vulgaris and its application in photocatalytic dye degradation activity

Biosynthesis of silver nanoparticle and its application in cell wall disruption to release carbohydrate and lipid from C. vulgaris for biofuel production.

Surendhiran Duraiarasan

Papers

Biosynthesis of silver nanoparticle and its application in cell wall disruption to release carbohydrate and lipid from C. vulgaris for biofuel production.