The ability of algae to accumulate metals and reduce metal ions make them a superior contender for the biosynthesis of nanoparticles and hence they are called bio-nano factories as both the live and dead dried biomass are used for the synthesis of metallic nanoparticles. Microalgae, forming a substantial part of the planet’s biodiversity, are usually single-celled colony-forming or filamentous photosynthetic microorganisms, including several legal divisions like Chlorophyta, Charophyta, and Bacillariophyta. Whole cells of Plectonema boryanum (filamentous cyanobacteria) proved efficient in promoting the production of Au, Ag, and Pt nanoparticles. The cyanobacterial strains of Anabaena flos-aquae and Calothrix pulvinate were used to implement the biosynthesis of Au, Ag, and Pt nanoparticles. Once synthesized within the cells, the nanoparticles were released into the culture media where they formed stable colloids easing their recovery. Lyngbya majuscule and Chlorella vulgaris have been reported to be used as a cost-effective method for Ag nanoparticle synthesis. Dried edible algae (Spirulina platensis) was reported to be used for the extracellular synthesis of Au, Ag, and Au/Ag bimetallic nanoparticles. Synthesis of extracellular metal bio-nanoparticles using Sargassum wightii and Kappaphycus alvarezi has also been reported. Bioreduction of Au (III)-Au (0) using the biomass of brown alga, Fucus vesiculosus, and biosynthesis of Au nanoparticles using red algal (Chondrus crispus) and green algal (Spyrogira insignis) biomass have also been reported. Algae are relatively convenient to handle, less toxic, and less harmful to the environment; synthesis can be carried out at ambient temperature and pressure and in simple aqueous media at a normal pH value. Therefore, the study of algae-mediated biosynthesis of metallic nanoparticles can be taken toward a new branch, termed phyco-nanotechnology.

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The present study acquaints optimization of ultrasound assisted lime pretreatment to reduce the time of lime pretreatment. The study was conducted on three lignocellulosic biomass materials, Areca nut husk (Areca catechu), bon bogori (Ziziphus rugosa), and moj (Albizia lucida) available in Northeast India, exploiting ultrasound for the pretreatment of lignocellulosic biomass along with lime augments the delignification ratio. The present study reports removal of 68% (bon bogori), 65% (Areca nut husk), and 64% (moj) of the lignin present in the naive lignocellulosic fiber with good recovery of total solid and fermentable sugars, respectively. The simultaneous saccharification and fermentation (SSF) process for the production of bioethanol was also carried out using baker's yeast. The yield of ethanol was found to be in the range from 0.32 to 0.43 for all the ultrasound assisted lime pretreated biomasses.

The computational fluid dynamics (CFD) simulation of the packed bed reactor (PBR) was carried out using ANSYS Fluent software. The various process parameters, such as inlet concentration of 4-chlorophenol (4-CP), flow rate, bed height, and porosity, were optimized to predict maximum biodegradation of 4-CP in immobilized catalyzed PBR. The geometrical mesh of the PBR was constructed using Gambit software, and a mesh size of 236995 was selected from the grid-independent study. A laminar flow model was used to understand the hydrodynamics as well as concentration profile of 4-CP inside the PBR using Fluent software. Through CFD, the effect of the flow rate, inlet concentration, and the bed height and porosity of the immobilized catalyst bed on the static pressure, mass imbalance, velocity, and stress-strain field inside the PBR was visualized. CFD simulation study predicted that maximum biodegradation of 4-CP was found in the presence of 500 mg/L of inlet concentration of 4-CP, 4 mL/min of flow rate, 18 cm of bed height and 0.375 of porosity. An experimental study was conducted for wastewater flow through the <i>B. subtilis MF447840.1</i> immobilized catalyzed PBR to remove the 4-CP in the laminar flow region. It was evident that CFD simulated results agreed well with experimental values.