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Microalgae are the widely employed sources of third generation biofuels, which attracted huge attention by the researchers of the present decade because of their great productivity with lipid content. But to date, the utilization of microalgae for renewable biofuel production is not considered economically viable. The various growth modes employed for microalgal cultivation, such as phototrophic, heterotrophic, mixotrophic, photo-heterotrophic has been compared and conferred in the current investigation. A wide variety of microalgal harvesting techniques that balance energy and economic sustainability is being carried out nowadays. Based on the culture employed, mode and conditions of microalgal cultivation, the choice of bioreactor differs like an open system or closed system bioreactor. This review discusses the basis, key challenges and the future perspective of present-day microalgal cultivation conditions regarding biomass and lipid production. Concurrently the impacts of cultivation mode, bioreactor used for lipid productivity to improve profitable microalgal biodiesel have also been summarized. Department of Science and Technology (DST India) -Promotion of University Research and Scientific Excellence (DST-PURSE) [SR/PURSE Phase 2/38G]; RUSA - Phase 2.0 (Policy (TN Multi-Gen), Department of Education, India) [F.24-51/2014-U]; Scheme for Promotion of Academic and Research Collaboration (SPARC) [SPARC/2018-2019/P485/SL] info:eu-repo/semantics/publishedVersion

Composites are light in weight when compared to woods and metals. It consists of two or more distinct phases such as matrix phase and a dispersed phase. Metal matrix composites are expensive and limitations in achieving stiffness and toughness for materials to overcome these limitations, hybrid metal matrix composites (HMMC’s) are fabricated and designed. In recent years hybrid metal matrix composites (HMMC’s) are plays a vital role especially in material science in the field of aerospace, marine, transportation, military and structural applications. Aluminium (Al) based metal matrix hybrid composites are used extensively in the field of automotive industries due to its low density and high strength-to-weight ratio. In the present study, aluminium A356 alloy with different weight fractions (0, 5, 7.5, 10 and 12.5%) of RHA and Fly ash reinforced hybrid composites are fabricated by using double stir casting technique. Determination the effect of the addition of organic (RHA) and in-organic (Fly Ash) reinforcement with aluminium A356 alloy on the physical and mechanical properties such as hardness, density and porosity were studied. FE-SEM, XRD, and EDS were analysed for A356 alloy/RHA-Fly Ash hybrid composite. The size distribution of the matrix alloy and reinforcement particles was measured using particle size. A significant improvement in the mechanical property was observed when adding the reinforcement with as-cast aluminium matrix alloy.

Over the last century, contamination of polycyclic aromatic hydrocarbons (PAHs) has risen tremendously due to the intensified industrial activities like petrochemical, pharmaceutical, insecticides and fertilizers applications. PAHs are a group of organic pollutants with adverse effects on both humans and the environment. These PAHs are widely distributed in various ecosystems including air, soil, marine water and sediments. Degradation of PAHs generally occurs through processes like photolysis, adsorption, volatilization, chemical degradation and microbial degradation. Microbial degradation of PAHs is done by the utilization of diverse microorganisms like algae, bacteria, fungi which are readily compatible with biodegrading/bio transforming PAHs into H2O, CO2 under aerobic, or CH4 under anaerobic environment. The rate of PAHs degradation using microbes is mainly governed by various cultivation conditions like temperature, pH, nutrients availability, microbial population, chemical nature of PAHs, oxygen and degree of acclimation. Several microbial species including Selenastrum capricornutum, Ralstonia basilensis, Acinetobacter haemolyticus, Pseudomonas migulae, Sphingomonas yanoikuyae and Chlorella sorokiniana are known to degrade PAHs via biosorption and enzyme-mediated degradation. Numerous bacterial mediated PAHs degradation methods are studied globally. Among them, PAHs degradation by bacterial species like Pseudomonas fluorescence, Pseudomonas aeruginosa, Rhodococcus spp., Paenibacillus spp., Mycobacterium spp., and Haemophilus spp., by various degradation modes like biosurfactant, bioaugmentation, biostimulation and biofilms mediated are also investigated. In contrarily, PAHs degradation by fungal species such as Pleurotus ostreatus, Polyporus sulphureus, Fusarium oxysporum occurs using the activity of its ligninolytic enzymes such as lignin peroxidase, laccase, and manganese peroxidase. The present review highlighted on the PAHs degradation activity by the algal, fungal, bacterial species and also focused on their mode of degradation.

Different mass fractions (0, 5%, 10%, and 15%) of the synthesized nano SiC particles reinforced Ti–6Al–4V (Ti64) alloy metal matrix composites (MMCs) were successfully fabricated by the powder metallurgy method. The effects of addition of SiC particle on the mechanical properties of the composites such as hardness and compressive strength were investigated. The optimum density (93.33%) was obtained at the compaction pressure of 6.035 MPa. Scanning electron microscopic (SEM) observations of the microstructures revealed that the wettability and the bonding force were improved in Ti64 alloy/5% nano SiCp composites. The effect of nano SiCp content in Ti64 alloy/SiCp matrix composite on phase formation was investigated by X-ray diffraction. The correlation between mechanical parameter and phase formation was analyzed. The new phase of brittle interfaced reaction formed in the 10% and 15% SiCp composite specimens and resulted in no beneficial effect on the strength and hardness. The compressive strength and hardness of Ti64 alloy/5% nano SiCp MMCs showed higher values. Hence, 5% SiCp can be considered to be the optimal replacement content for the composite.

The most advantageous renewable energy source which is still being explored for the source of renewable energy is biodiesel. But the major hindrance factor in the part of commercialization is the raw material cost under large scale various. Microalgae derived biofuels have drawn compelling interest as a sustainable and potential fossil fuel. The cellular mechanism of microalgae has been found to alter by the effect of some biotic and abiotic factors. Above all, those environmental parameters and production conditions can also act as a critical factor in altering the component quantity and quality of the biodiesel produced by microalgae. The lipids are accumulated inside the oleaginous microbial cells in the form of lipid droplet, and hence the cell disruption is essential for lipid extraction to enhance the yield. Huge varieties of physicochemical and mechanical pretreatment methods are available to facilitate extraction by effective cell membrane degeneration of oleaginous microbes. The present review is to exploit the probable magnitude and advantages of abiotic factors towards microalgal growth and biodiesel production. Additionally, this study tried to evaluate the possible certainties of the microalgal pretreatment processes in lipid accumulation.

Titanium matrix (Ti6Al4V) composites reinforced with TiB2 and TiC were produced through powder metallurgy method. The effect of addition of both TiB2 and TiC with different contents (2.5 wt%, 5.0 wt% and 7.5 wt%) on the density, microstructure and hardness properties of titanium matrix was investigated. The size distributions of the matrix alloy and reinforcement particles were measured by particle size analyzer. Microhardness of the sintered composites was evaluated using Vickers’s hardness tester with a normal load of 3 N and a dwell time of 10 s. Ti6Al4V alloy and Ti6Al4V/TiB2–TiC composites were characterized through X-ray diffraction (XRD) and field emission scanning electron microscope (FESEM) equipped with energy-dispersive spectrometer (EDS). The addition of TiB2 and TiC particles enriches the properties of Ti6Al4V alloy. The sintered Ti6Al4V/TiB2–TiC composite features a dense and pore-free microstructure with varying TiB2 and TiC particle distribution in the metal matrix. The results of this study show that the development of new phases plays a significant role in the properties of these composite materials.

Seaweeds are found abundance in most seashores. They contain relatively high lipid contents and are exhibiting medicinal properties. The present work focused on the use of seaweed species Ulva linza, U. tubulosa, U. fasciata, U. rigida, and U. reticulate to synthesize Mn2ZnO4 composite nanoparticles. The later was utilized for biodiesel production and its antibacterial potential was also assessed. Heterogeneous mixed metal oxides are suitable catalysts for biodiesel production due to ease of separation, reusability and environmental friendliness. The employment of multi-resistant organisms (MROS) is of major importance in modern medicines. Thus there is an extreme need for potential antibacterial alternatives such as metal oxides. Mn2ZnO4 nanoparticles were synthesized by using a co-precipitation method. The crystalline behavior and morphological characterizations were carried out through XRD, FE-SEM, Raman Spectra and FT-IR respectively. The particle size was found to be 42 nm. Fatty Acid Methyl Ester (FAME) produced from Ulva species was analyzed by gas chromatography and physical parameters were also determined. The yields were as follows: U. linza 72.3%, U. tubulosa 72%, U. fasciata 70.6%, U. rigida 70.4%, and U. reticulate 71.5%. The antibacterial potential of synthesized Mn2ZnO4 nanoparticles after transesterification, showed strong antibacterial activity against both gram positive and gram negative bacteria and were found to be comparable to commercially available antibiotics. To assess their antibacterial efficiency, the minimum inhibition concentration was measured. The used catalysts exhibit high efficient catalytic activity on degrading methylene blue under UV irradiation.

An effort in contributing to the reduction of fossil resource dependence along with utilization of lignocellulosic wastes, will be a beneficial approach in biofuel production. These approaches will aid in sustainable waste management and will contribute to economic feasibility. This study probed the exploitation of abundant, non-edible lignocellulosic wastes such as sugarcane bagasse and rice husk as a low-cost carbon source for the cultivation of oleaginous yeast isolates and lipid accumulation, respectively. The hydrolysis of the lignocellulose was explored by steam explosion alone to reduce the inflation of toxic compounds like hydroxy methyl furfural (HMF), furfural, and acetic acid. This optimization study investigated the effects of carbon sources (sugarcane bagasse hydrolysate, rice husk hydrolysate, and commercial glucose), nitrogen sources, and pH on biodiesel production using central composite design (CCD), and achieved a full factorial design. All the three variables were found to have a positive influence on biodiesel production. Greater biomass production was achieved by SY2 (Pichia kudriavzevii) with a value of −8.37 ± 0.067 g/L when sugarcane bagasse hydrolysate was used. Maximum lipid content of 37.99 ± 0.003% was attained by the strain G5 (Meyerozyma guilliermondii) upon using sugarcane bagasse hydrolysate in the production medium and higher lipid accumulation of 2.39 ± 0.003 g/L was attained by SY2 (Pichia kudriavzevii) upon using rice husk hydrolysate. Analysis of the kinematic properties of FAME (Fatty Acid Methyl Esters) was obtained using Biodiesel analyzer V1.1. software, and affirmed the values similar to the biodiesel standard values (EN 14214, ASTM, IS 15607). The kinematic studies used to figure out the quality of the biodiesel, revealed that FAME produced by SY2 (Pichia kudriavzevii) strain showed greater oxidation stability (37.17 h) and better kinematic viscosity (1.3084). These properties ensured that SY2 (Pichia kudriavzevii) strain was appropriate in producing exceptional quality biodiesel. Hence, the present investigation tried to prove the competency of the yeast isolates in sustainable biodiesel production by engaging agronomic wastes.

Microalgal isolates (Chlorella sp. and Spirulina sp.) and yeast isolates (Candida albicans and Saccharomyces sp.) were employed as the resources of biodiesel production and silver nanoparticle synthesis. The prominent peaks of the FTIR spectrum accustomed the efficient lipid property. The developed profile containing fatty acid methyl ester (FAME) displayed the elevated amount of both saturated (C15:0, C17:0, C21:0) and unsaturated (C17:1, C18:2, C20:4) fatty acids. The physicochemical properties analyzed by using Biodiesel analyzer V1.1.software, confirmed the competency of the isolates for sustainable biodiesel production. Biosynthesis of silvernanoparticles (AgNPs) were accomplished extracellularly by using supernatant of microalgal and yeast culture. The maximum absorbance at 420 and 421 nm under UV–visible spectra showed the presence of nanoparticles. The purity of the synthesized AgNPs were analyzed by XRD analysis. The elemental silver presence was affirmed by EDAX, SEM and AFM, the results revealed spherical crystalline shaped nanoparticles of size ranging from 2.0 to 7.3 nm. The antimicrobial efficacy of the silver nanoparticles (AgNPs) against various clinical pathogens which includes Bacillus sp., E. coli, Klebsiella sp., Proteus sp. and Staphylococcus aureus were observed. However, enhanced antimicrobial activity was displayed by the AgNPs, produced by Candida albicans (12 mm) against Bacillus sp., and E.coli, the nanoparticle produced by Chlorella sp. showed the least antagonistic activity (07 mm).