Enzymatic cell disruption followed by application of imposed potential for enhanced lipid extraction from wet algal biomass employing photosynthetic microbial fuel cell

Potential of oleaginous microbes for lipid accumulation and renewable energy generation

Biocomponents (such as lipids) accumulate in oleaginous microorganisms and could be used for renewable energy production. Oleaginous microbes are characterized by their ability to accumulate high levels of lipids, which can be converted into biodiesel. The oleaginous microbes (including microalgae, bacteria, yeast, and fungi) can utilize diverse substrates. Thus, in this study, commercially viable oleaginous microorganisms are comparatively summarized for their growth conditions, substrate utilization, and applications in biotechnological processes. Lipid content is species-dependent, as are culture conditions (such as temperature, pH, nutrients, and culture time) and substrates. Lipid production can be increased by selecting suitable microorganisms and substrates, optimizing environmental conditions, and using genetic engineering techniques. In addition, the emphasis on downstream processes (including harvesting, cell disruption, lipid extraction, and transesterification) highlights their critical role in enhancing cost-effectiveness. Oleaginous microorganisms are potential candidates for lipid biosynthesis and could play a key role in meeting the energy needs of the world in the future.

Application of biomimetically synthesized silver nanoparticles as cathode catalyst, quorum-quencher, and anti-biofouling agent for the performance boosting of microbial fuel cell

A microbial fuel cell (MFC) is a cutting-edge bioelectrochemical technology, which demonstrates power and other valuables recovery while treating wastewater by cultivating electroactive microbes. However, rampant biofilm growth over the cathode surface of air cathode MFC exacerbates the oxidation-reduction reaction rate, triggering a dip in the overall performance of MFC. In this sense, biosynthesized silver nanoparticles (AgNPs) have garnered a plethora of potential applications as cathode catalysts as well as anti-biofouling agent for MFCs without harming nature. The MFC equipped with the mixture of aloe vera and algae (@5 mg/cm2) synthesized AgNPs on cathode generated a maximum power density of 66.5 mW/m2 and chemical oxygen demand removal efficiency of 85.2%, which was ca. 5.6 times and 1.2 times higher compared to control MFC operated without any catalyst on cathode. Thus, this investigation paves the way for using eco-amiable, low-cost bioderived organic compounds to assist MFC in achieving high power output and other valuables with minimal reliance on chemicals.

Roles of microalgae-based biofertilizer in sustainability of green agriculture and food-water-energy security nexus

For years, agrochemical fertilizers have been used in agriculture for crop production. However, intensive utilization of chemical fertilizers is not an ecological and environmental choice since they are destroying soil health and causing an emerging threat to agricultural production on a global scale. Under the circumstances of the increasing utilization of chemical fertilizers, cultivating microalgae to produce biofertilizers would be a wise solution since desired environmental targets will be obtained including (1) replacing chemical fertilizer while improving crop yields and soil health; (2) reducing the harvest of non-renewable elements from limited natural resources for chemical fertilizers production, and (3) mitigating negative influences of climate change through CO₂ capture through microalgae cultivation. Recent improvements in microalgae-derived-biofertilizer-applied agriculture will be summarized in this review article. At last, the recent challenges of applying biofertilizers will be discussed as well as the perspective regarding the concept of circular bio-economy and sustainable development goals (SDGs).

Solid-state fermentation-based enzyme-assisted extraction of eicosapentaenoic acid-rich oil from Nannochloropsis sp

Enzymatic treatment of microalgal biomass is a promising approach for extraction of microalgal lipid, but high cost of commercially sourcing enzyme is a major drawback in industrial implementation. Present study involves extraction of eicosapentaenoic acid-rich oil from Nannochloropsis sp. biomass using low cost cellulolytic enzymes produced from Trichoderma reesei in a solid-state fermentation bioreactor. Maximum total fatty acid recovery of 369.4 ± 4.6 mg/g dry weight (total fatty acid yield of 77%) was achieved in 12 h from the enzymatically treated microalgal cells, of which the eicosapentaenoic acid content was 11%. Sugar release of 1.70 ± 0.05 g/L was obtained post enzymatic treatment at 50 °C. The enzyme was reused thrice for cell wall disruption without compromising on total fatty acid yield. Additionally, high protein content of 47% in the defatted biomass could be explored as a potential aquafeed, thus enhancing the overall economics and sustainability of the process.

Electron-pool promotes interfacial electron transfer efficiency between pyrogenic carbon and anodic microbes

Relying on surface functional groups and graphitized structure, pyrogenic carbon (PC) was reported to facilitate microbial extracellular electron transfer (EET), which plays a crucial role in diverse biogeochemical reactions. However, little is known about the role of electrical capacitance on EET between microbes and PCs. Here, PCs were obtained from fermented steam bread after carbonization at different temperatures from 700 °C to 1100 °C. PC-900 exhibited the lowest charge transfer resistance and highest electrical capacitance, ascribed to combined effects of graphitic structure and hierarchical porous structure. The interfacial EET was further investigated by enriching electroactive biofilms on PC surface. Faster interfacial EET was demonstrated in PC-900. Maximum power density was proportional to electrical capacitance rather than conductivity. PC-900 enriched the most Geobacter sp., which was positively correlated with electrical capacitance according to the distance-based redundancy analysis. Electrical capacitance was suggested to act as electron pool to facilitate interfacial EET efficiency.