Modulating cultivation regimes of Messastrum gracile SVMIICT7 for biomass productivity integrated with resource recovery via hydrothermal liquefaction.

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.

Exploring microalgal nutrient-light synergy to enhance CO2 utilization and lipid productivity in sustainable long-term water recycling cultivation.

In this work the effects of nutrient availability and light conditions on CO2 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% CO2 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 CO2 mitigation, achieving 2.27% CO2 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% CO2 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 CO2 fixation (1.1 g L-1 day-1), 7% CO2 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.

Production of a wide spectrum biopesticide from Monoraphidium sp. KMC4 grown in simulated dairy wastewater.

The present work aims on developing an eco-friendly strategy that couples the remediation of dairy wastewater with crop protection strategy using microalgal biomass for sustainable agriculture. In the present study, the microalgal strain Monoraphidium sp. KMC4 was cultivated in dairy wastewater. It was observed that the microalgal strain is able to tolerate up to as high as 2000 mg/L of COD and utilize the organic carbon and other nutrient component of the wastewater for biomass production. The biomass extract demonstrates excellent antimicrobial activity against the two phytopathogens (Xanthomonas oryzae and Pantoea agglomerans). GC-MS analysis of the microalgae extract revealed phytochemicals such as chloroacetic acid and 2, 4- di tert butylphenol that are responsible for the inhibition of the microbial growth. These preliminary results indicates that integration of microalgal cultivation and nutrient recycling from wastewaters for the production of biopesticides is a promising prospect for the replacement of synthetic pesticides.

Valorization of de-oiled microalgal biomass as a carbon-based heterogeneous catalyst for a sustainable biodiesel production.

In this study, a novel carbon-based solid acid catalyst was synthesized by carbonization of de-oiled microalgal biomass followed by sulfonation. The effect of catalyst synthesis conditions such as carbonization temperature, sulfonation time, and H2SO4 concentration on the surface acidity of the catalyst and free fatty acid conversion was determined. The de-oiled microalgal biomass-based solid acid (DMB) catalyst was predominantly composed of carboxylic, phenolic, and sulfonic groups as indicated by the FTIR analysis and supported by the XPS analysis. The catalyst was further characterized by various methods to determine its physiochemical properties. A maximum fatty acid methyl ester (FAME) yield of 94.23% for microalgal oil (AO) and 96.25% for waste cooking oil (WCO) was obtained under optimized transesterification conditions. The catalyst exhibited high catalytic activity (FAME yield >90%) until the fourth cycle. Most of the biodiesel properties were within the permissible limit of EN 14,212 and ASTM D6751 standards.