Bioenergy productions from microalgae have received wide attention recently and have a high potential to replace fossil fuels. Moreover, due to the high photosynthetic efficiency, microalgae mass cultivation and scale-up are believed to efficiently reduce the impact of greenhouse gas emissions. This review article explores the potential of microalgae as a reliable and sustainable source of bioenergy feedstock. The current review article contains an in-depth discussion of the various methods of producing energy using microalgae, viz. algal fuel cell (AFC), microbial fuel cell (MFC), bioethanol and biodiesel, and various other applications. This article discussed the different aspects of AFC and MFC, such as fuel cell configurations, reaction mechanisms at electrodes, reactor design factors affecting the efficiencies, and strategies to enhance the efficiencies. Moreover, microalgae cultivation, value-added compounds (pigments, polysaccharides, unsaturated fatty acids), liquid fuel production, limitations, the global scenario of microalgae biomass-based energy, and significant advancements in this field. In a nutshell, this review serves as a valuable resource for identifying, developing, and harnessing the potential of microalgae as a promising biofuel source.

The urgent need to address environmental issues associated with the use of conventional fossil fuels has driven the rapid evolution of the global energy landscape. This review explores the background and significance of 3-G biofuel production, emphasizing the shift towards sustainable alternatives amidst escalating greenhouse gas emissions. While various renewable energy sources have gained prominence, biofuels have emerged as a promising solution for the transportation and industrial sectors, particularly from microalgal biomass. The rationale for focusing on microalgal biomass is based on its technical and environmental advantages. Unlike traditional feedstocks, microalgae boast a high lipid content, enhancing biofuel production efficiency. Their rapid growth rates and efficient carbon dioxide sequestration make microalgae frontrunners in scalable and sustainable biofuel production. This review aims to comprehensively analyze recent breakthroughs in 3-G biofuel production from microalgal biomass, filling gaps in the existing literature. The topics covered included species diversity, cultivation techniques, harvesting, pretreatment, lipid extraction methods, and biofuel production pathways. Genetic engineering, downstream processing, energy-efficient practices, and emerging trends, such as artificial intelligence and cross-disciplinary collaboration, will be explored. This study aims to consolidate recent research findings, identify challenges and opportunities, and guide future directions in microalgal biomass-based biofuel production. By synthesizing unpublished research, this review seeks to advance our knowledge and provide insights for researchers to foster sustainable and efficient 3-G biofuel production.

The role of pipecolic acid (Pip) in plant immune responses, particularly against bacterial wilt pathogens, is significant. This research aimed to understand the interaction between plant defense-responsive enzymes and Pip by analyzing methanolic extracts from different treatments of tolerant (GAT5) and susceptible (GT2) tomato cultivars. LC-MS analysis demonstrated that the foliar application of Pip significantly influenced tomato metabolites, especially in bacterial wilt-infected plants, with a more pronounced effect in tolerant varieties. Principal component analysis (PCA) revealed that Pip-treated plants of tolerant varieties exhibited better coordinated metabolome profiles than those of susceptible varieties. Notable variations were observed in the levels of specialized metabolites, such as salicylic acid (SA), N-hydroxy pipecolic acid (NHP), and Pip, which are essential for producing defense compounds. Molecular docking studies further explored Pip’s interactions with key plant enzymes involved in defense mechanisms and showed that Pip acts as an effective organic inducer of systemic acquired resistance (SAR). These findings highlight Pip’s potential as a natural agent for enhancing plant tolerance to pathogens, offering promising implications for agricultural practices and improving crop resilience against diseases. This study enhances our understanding of Pip’s role in plant defense and provides a foundation for developing Pip-based strategies for sustainable agriculture.

Plant growth-promoting rhizobacteria are widely associated with plant drought tolerance, but their intrinsic metabolic responses to reduced-water-availability conditions remain incompletely characterized. This study compared the phytohormonal and culture-associated metabolite profiles of Pseudomonas fluorescens PKR1 and Bacillus subtilis PKR5 in axenic cultures exposed to 30, and 40 w/v % PEG 6000 treatments. Under control conditions, the two strains differed in their production of indole-3-acetic acid, indole-3-butyric acid, and gibberellic acid. Increasing PEG concentration led to strain-specific metabolites and hormone-dependent changes in the phytohormone profile. Multivariate analysis showed significant effects of both strain background (PERMANOVA: F = 3.3409, R² = 0.1727, p = 0.0426) and PEG stress level (F = 8.8334, R² = 0.3557, p = 0.0001) on the qualitative metabolite profiles. PKR1 retained a comparatively similar number of detected features across PEG concentrations, whereas PKR5 showed a broader feature set under 40 w/v % PEG. Several features tentatively assigned as proline derivatives, fatty acids, lipid amides, and phenolic compounds showed strain or treatment-associated distributions. These findings reveal distinct culture-associated metabolite signatures under defined PEG-induced osmotic stress and identify candidate features for targeted analytical validation and subsequent functional investigation.