Optimizing Phycocyanin Extraction from Cyanobacterial Biomass: A Comparative Study of Freeze-Thaw Cycling with Various Solvents.

Cyanobacterial phycocyanin pigment is widely utilized for its properties in various industries, including food, cosmetics, and pharmaceuticals. Despite its potential, challenges exist, such as extraction methods impacting yield, stability, and purity. This study investigates the impact of the number of freeze-thaw (FT) cycles on the extraction of phycocyanin from the wet biomass of four cyanobacteria species (Arthrospira platensis, Chlorogloeopsis fritschii, Phormidium sp., and Synechocystis sp.), along with the impact of five extraction solutions (Tris-HCl buffer, phosphate buffer, CaCl2, deionized water, and tap water) at various pH values. Synechocystis sp. exhibited the highest phycocyanin content among the studied species. For A. platensis, Tris-HCl buffer yielded maximum phycocyanin concentration from the first FT cycle, while phosphate buffer provided satisfactory results from the second cycle. Similarly, Tris-HCl buffer showed promising results for C. fritschii (68.5% of the maximum from the first cycle), with the highest concentration (~12% w/w) achieved during the seventh cycle, using phosphate buffer. Phormidium sp. yielded the maximum pigment concentration from the first cycle using tap water. Among species-specific optimal extraction solutions, Tris-HCl buffer demonstrated sufficient extraction efficacy for all species, from the first cycle. This study represents an initial step toward establishing a universal extraction method for phycocyanin from diverse cyanobacteria species.

Recent advances in sustainable hydrogen production from microalgae: Mechanisms, challenges, and future perspectives.

The depletion of fossil fuel reserves has resulted from their application in the industrial and energy sectors. As a result, substantial efforts have been dedicated to fostering the shift from fossil fuels to renewable energy sources via technological advancements in industrial processes. Microalgae can be used to produce biofuels such as biodiesel, hydrogen, and bioethanol. Microalgae are particularly suitable for hydrogen production due to their rapid growth rate, ability to thrive in diverse habitats, ability to resolve conflicts between fuel and food production, and capacity to capture and utilize atmospheric carbon dioxide. Therefore, microalgae-based biohydrogen production has attracted significant attention as a clean and sustainable fuel to achieve carbon neutrality and sustainability in nature. To this end, the review paper emphasizes recent information related to microalgae-based biohydrogen production, mechanisms of sustainable hydrogen production, factors affecting biohydrogen production by microalgae, bioreactor design and hydrogen production, advanced strategies to improve efficiency of biohydrogen production by microalgae, along with bottlenecks and perspectives to overcome the challenges. This review aims to collate advances and new knowledge emerged in recent years for microalgae-based biohydrogen production and promote the adoption of biohydrogen as an alternative to conventional hydrocarbon biofuels, thereby expediting the carbon neutrality target that is most advantageous to the environment.

Biopolymers production from microalgae and cyanobacteria cultivated in wastewater: Recent advances.

Plastic materials are used to manufacture a broad variety of items with a short useful lifespan, resulting in significant amounts of waste material generation. This form of waste is often observed floating at sea, and different microplastics have been discovered in fish stomachs and women's placentas. Bioplastics are a more biodegradable substitute for fossil-based polymers. Microalgae are capable of producing poly (hydroxy alkanoate) esters (PHAs), aliphatic polyesters that are biodegradable. The most prevalent and well-characterized biopolymer is the poly (3-hydroxy butyrate) ester (PHB), which belongs to the short-chain PHAs. Under aerobic conditions, PHB compounds degrade fully to carbon dioxide and water. They are ecologically neutral, having thermal and mechanical qualities comparable to those of petrochemical polymers. Numerous microalgae species have been reported in the literature to be capable of making bioplastics under certain conditions (N-P restriction, light exposure, etc.), which may be exploited as a source of energy and carbon. To further ameliorate the environmental impact of microalgae culture for bioplastics production, a limited number of published studies have examined the accumulation of bioplastics, from microalgae grown in wastewater, at a concentration of 5.5-65% of dry biomass weight.