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In this work the effects of nutrient availability and light conditions on CO 2 utilization and lipid production in Micractinium pusillum KMC8 is reported. The study investigated the ideal nitrogen concentrations for growth and nitrogen utilization in a 15% CO 2 environment. Logistic and Gompertz models were employed to analyze the kinetics of KMC8 cell growth. Compared to 17.6 mmol L−1 control nitrogen, which generated 1.6 g L−1 growth, doubling and quadrupling nitrogen concentrations boosted biomass growth by 12.5% and 28.78%. At 8.6 mmol L−1 nitrogen, the growth decreased but lipid productivity increased to 18.62 mg L−1 day−1. At 70.6 mmol L−1 nitrogen, elevated nitrogen levels maintained an alkaline pH above 7 and enhanced CO 2 mitigation, achieving 2.27% CO 2 utilization efficiency. Nitrogen shows a positive correlation with higher rates of carbon and nitrogen fixation. The investigation extends to find out the influence of phosphorus and light conditions on microalgae. Increasing light intensity incrementally from 150 to 1200 μmol m−2 s−1 with more phosphorus increased biomass productivity by 85% (255 mg L-1 day−1) and lipid productivity by 2.5-fold (84.76 mg L-1 day−1), with 3.3% CO 2 utilization efficiency compared to directly using 1200 μmol m−2 s−1. This study suggests a water recycling-fed batch cycle with gradual light feeding, which results in high CO 2 fixation (1.1 g L−1 day−1), 7% CO 2 utilization, and significant biomass and lipid productivity (577.23 and 150 mg L−1 day−1). This approach promotes lipid synthesis, maintains carbon fixation, and minimizes biomass loss, thus supporting sustainable bioenergy development in a circular bio-economy framework. [Display omitted] • Investigation of the synergistic effects of nitrogen, phosphorus, and light on microalgae. • Enhanced carbon capture efficiency by combined outputs of biomass and lipids. • The nitrogen and light availability modulate the excretion of organic carbon. • Phosphorus and light crucial for CO 2 fixation and lipid production in nitrogen limitation. • High-density fed-batch maximizes CO 2 utilization, lipid production, and water recycling. [ABSTRACT FROM AUTHOR]

The potential of saponin, a biosurfactant, in the micellar enhanced ultrafiltration (MEUF) process was tested systematically for removal of methyl violet from wastewater. For this, the aqueous extract of reetha ( Sapindus mukorossi ) pericarp which contains saponin was used as the biosurfactant. First, the micellar solubilization of methyl violet in saponin micelles was investigated in terms of molar solubilization power ( SP ) of saponin. It was observed that the adsorption of methyl violet on the agglomerates of saponin micelles was mainly responsible for the enhanced solubilization. The Gibbs free energy of solubilization (calculated as −29.63 kJ mol −1 ) suggested that process was feasible and spontaneous. The MEUF experiments were performed in batch as well as continuous mode using saponin biosurfactant, and the effect of operating parameters on permeate flux and solute retention were evaluated. The removal of methyl violet in MEUF process was >99% achieved with 10 kDa polyethersulfone (PES) membrane for feed dye concentration of 250 mg L −1 at studied conditions. Finally, the saponin in permeate was recovered using n-heptane and n-butanol by solvent extraction process. The solvent n -butanol showed better extraction efficiency as compared to n-heptane for saponin extraction. [ABSTRACT FROM AUTHOR]

The utilization of costly chemical fertilizers and large freshwater requirements make the microalgae cultivation process uneconomical and highly unsustainable. To address this challenge, the present study aimed to integrate cattle wastewater (CW) (alternate for fertilizers) with domestic sewage wastewater (DSW) (substitute for freshwater) to cultivate Chlorella thermophile. To maximize the biomass yield, in-depth nutrient consumption patterns in both batch and fed-batch cultivation conditions were analyzed. Out of the eight (1%–4.5%) different CW feed concentrations tested during the batch cultivation, 2.5% CW set gave the highest biomass yield (2.17 g L−1), which was almost double the yield obtained using Bold Basal Medium (1.24 g L−1) and DSW without any CW addition (1.22 g L−1). However, the biomass yield declined with CW> 2.5%, and the ammonium (NH 4 +) inhibitory effect was observed. To address the (NH 4 +) toxicity challenge and further enhance the biomass yield, fed-batch experiments were designed with an intermittent CW feeding based on nutrient (NH 4 +) consumption pattern. The fed-batch cultivation resulted in twofold increased biomass yield (4.52 g L−1) in comparison to the batch process. The nutrient consumption pattern inferred that the (NH 4 +) concentration greater than 600 mg L−1 during the logarithmic phase was inhibitory for Chlorella thermophila cells. On biomass characterization, a significant improvement in protein content with CW addition was observed. The FAME analysis of the derived lipid stated its competitive biofuel quality with up-gradation of C:16 and C:18 groups. Based on the obtained results, projection analysis for an integrated rural model demonstrated the technology's potential for sustainable water management with valuable resource recovery. [Display omitted] • Eight CW concentrations were tested with DSW for C. thermophile growth. • In batch mode, highest biomass yield (2.17 g L−1) was recorded using 2.5% CW addition. • Fed-batch process resulted in further twofold increase in biomass yield (4.52 g L−1). • Ammonium concentration >600 mg L−1 was found inhibitory to C. thermophila cells. • Circular rural model suggested using developed approach shows technical feasibility. [ABSTRACT FROM AUTHOR]

The present study was designed to assess Messastrum gracile SVMIICT7 potential in treating dairy wastewater (autoclaved (ADWW) and raw (DWW)) with relation to nutrient removal, in-vivo Chl-a-based biomass, and bio-oil synthesis. Chlorophyll a fluorescence kinetics revealed improved photochemical efficiency (0.639, Fv/Fm) in M. gracile when grown with DWW. This may be owing to enhanced electron transport being mediated by an effective water-splitting complex at photosystem (PSII) of thylakoids. The increase in ABS/RC observed in DWW can be attributed to the elevated chlorophyll content and reduced light dissipation, as evident by higher values of ETo/RC and a decrease in non-photochemical quenching (NPQ). M. gracile inoculated in DWW had the highest Chl-a-biomass yield (1.8 g L−1) and biomolecules while maximum nutrient removal efficiency was observed in ADWW (83.7% TN and 60.07% TP). M. gracile exhibited substantial bio-oil yield of 29.6% and high calorific value of 37.19 MJ kg−1, predominantly composed of hydrocarbons along with nitrogen and oxygen cyclic compounds. This research offers a thorough investigation into wastewater treatment, illustrating the conversion of algal biomass into valuable energy sources and chemical intermediates within the framework of a biorefinery. [Display omitted] • Messastrum gracile SVMIICT7 thrived effectivey in both autoclaved and raw dairy wastewater (ADWW and DWW). • Chl-a fluorescence showed a significant correlation with residual TN, TP, and Carbon load resulting improved CO 2 fixation. • Messastrum sp. exhibited bio-oil yield of 29.6% and calorific value of 37.19 MJ kg−1 with diverse metabolite profile. • Self-sustained biorefinery approach for biosynthesis of value-added products with simultaneous treatment. [ABSTRACT FROM AUTHOR]

Pretreatment is an inevitable high energy consuming process en route to biofuel production which alters the recalcitrant structures of lignocellulosic biomass. An attempt has been made to pretreat the areca nut husk fibre using dilute sulphuric acid. The Taguchi robust design method of optimisation (L9 orthogonal array) was applied to this acid catalyzed pretreatment process. Cellulose crystallinity is directly proportional to the degree of enzymatic hydrolysis of any kind of cellulosic substrate; the present study considers it as an index to optimise the process parameters. The study showed that the sulphuric acid concentration plays the major role during the pretreatment of areca nut husk (57% contribution) followed by the duration of operation (24.98% contribution) and solid loading (14.3% contribution). The optimal factors obtained from the design of experiments were further validated using the experimental results. [ABSTRACT FROM AUTHOR]

Developing an efficient photobioreactor (PBR) and reducing freshwater dependence are among the significant challenges for generating 3rd generation biomass feedstock. Addressing these, the present study focused on developing a modified airlift (MoAL) PBR. Its performance was further evaluated and compared with the traditional airlift PBR by cultivating microalgae in dark fermentation spent wash. Lower mixing time and higher interfacial mass transfer coefficient was observed in the MoAL PBR having a perforated draft tube. Experimentally, the MoAL exhibited the maximum biomass concentration of 3.18 g L−1, which was 30% higher than that of the conventional airlift PBR. The semi-continuous operation of the MoAL (with water recycling) achieved the maximum biomass productivity of 0.83 g L−1 d−1, two folds superior to that of batch culture. The comprehensive biomass characterization (proximate, ultimate, and thermochemical) further confirmed its potential for bioenergy application. Considering that, hydrothermal liquefaction of the biomass resulted in a maximum biocrude yield of 31% w/w with a higher heating value (HHV) of 36.6 MJ kg−1. In addition, the biocrude comprised 66.6% w/w lighter fraction (<343 °C), including 21.5% w/w of heavy naphtha, 20.5% w/w of kerosene, and 24.6% w/w of diesel. The results can help develop sustainable technology for simultaneous wastewater remediation and biocrude production. [Display omitted] • Modified airlift (MoAL) photobioreactor was designed for enhanced biomass yield. • Dark fermentation spent wash (DFSW) was found suitable for mixotrophic algal growth. • Biomass concentration was 30% higher in the MoAL than that of the conventional PBR. • Semi-continuous operation of MoAL PBR with water recycling was successfully studied. [ABSTRACT FROM AUTHOR]

Pyrolysis kinetics and thermodynamic parameters of two non-edible seeds, Pongamia pinnata (PP) and Sapindus emarginatus (SE), and their blend in the ratio of 1:1 (PS) were studied using the thermogravimetric analyzer. Kinetic triplets were determined using both model-free [Starink (STR), Friedman (FRM), Iterative Kissinger-Akahira-Sunose (IT-KAS), Iterative Ozawa-Flynn-Wall (IT-OFW), Vyazovkin (VYZ), and Master plot (MP)] and model fitting Coats-Redfern (CR) methods at three different heating rates 10, 30 and 50 °C/min. Activation energies were 192.66, 179.44, and 163.25 kJ/mol for PP, SE, and PS, respectively. It was found that the blend of the two-biomass (PS) showed promising results with lower activation energy compared to the individual biomass. Thermodynamic parameters (ΔG, ΔS, and ΔH) were obtained using the model-free isoconversional method. The three hidden layers of complex neuron topology are well fitted to the experimental DTG curves by artificial neural network (ANN). The study confirmed that the heating rate had a significant impact on the kinetics and thermodynamic parameters. The reaction mechanism was also in consonance with the experimental data. The study suggests that the PP and SE seeds can be an appropriate feed for pyrolysis, and their blend (PS) can be a viable alternative in optimizing the entire process. [Display omitted] • Both model-free and model-fitting methods are scrutinized. • Kinetics suggested that the binary mixture was suitable for pyrolysis. • The thermodynamics feasibility of the binary mixture is also determined. • Three-layer ANN topology is well fitted with DTG experimental data. [ABSTRACT FROM AUTHOR]

The viability of the FO process for concentration of sugarcane juice by using a commercially available aquaporin embedded hollow fibre membrane module (HFFO) (active area, 2.3 m2) is presented. NaCl is used as a draw solution (DS), and the selection of suitable DS concentration, flow conditions and flow configuration are observed to be vital aspects to minimize the reverse solute flux (RSF) and energy consumption. Further, the one dimensional mathematical model for the batch and continuous FO process using HF module is developed and validated with experimental data within the error limit of 5% for water flux and RSF. Based on the flowsheet modelling, the method for establishing the optimized FO process is presented. The optimized FO flowsheet presented in this study can concentrate the sugarcane juice from 150 g L−1 to 531 g L−1 with energy consumption of 92.14 WL-1 of permeate and specific RSF = 1.57 g L−1. Further, to commercialize FO process for sugarcane juice concentration application, the selection of suitable food-grade draw solute that can provide high osmotic pressure and low RSF is a very important aspect. • Laboratory-scale FO process was evaluated for concentration of sugarcane juice. • A model for tank mass balance and concentration polarisation has been developed. • Counter-current and co-current were studied with associated parameters evaluation. • Specific energy consumption was 74% higher in batch mode than continuous mode. [ABSTRACT FROM AUTHOR]