Comparative analysis of microalgae metabolism on BBM and municipal wastewater during salt induced lipid accumulation

Polyhydroxyalkanoates production from microalgae for sustainable bioplastics: A review

Microalgae have emerged as a promising and sustainable source for polyhydroxyalkanoates (PHA), which are increasingly recognized for their potential in bioplastics production. However, the widespread application of microalgae-derived PHA faces challenges related to economic feasibility and scalability. This review provides a comprehensive analysis of recent advancements in the cultivation and optimization of microalgae for PHA production, highlighting the critical role of nutrient limitation, particularly nitrogen and phosphorus, in enhancing PHA accumulation. This review also explores the effectiveness of various cultivation systems, including autotrophic, heterotrophic, and mixotrophic approaches, in maximizing PHA yields. Environmental factors such as light intensity, salinity, and pH are examined for their influence on PHA synthesis pathways. Additionally, it identifies key technical and economic challenges that must be addressed to commercialize microalgae-based bioplastics to fully harness the potential of microalgae in sustainable bioplastic production.

Using PyCaret to model Chlorella vulgaris's growth response to salinity and oil contamination for crude oil bioremediation

Crude oil spills significantly impact aquatic ecosystems, necessitating innovative remediation strategies. Microalgae-based bioremediation, particularly with Chlorella vulgaris, offers a promising solution. This study introduces a novel framework that evaluates the combined effects of selected environmental stressors on microalgal adaptability, advancing beyond traditional isolated factor analyses. By integrating a factorial experimental design with a machine learning approach using PyCaret AutoML and SHAP values, we provide a detailed examination of how crude oil concentration, salinity, and exposure duration affect C. vulgaris growth. The Extra Trees Regressor model emerged as highly accurate in predicting biomass concentration, a crucial adaptability indicator, achieving an MAE of 0.0202, RMSE of 0.029, and an R² of 0.8875. SHAP analysis highlighted salinity and crude oil as significant growth influencers, with exposure duration playing a minor role. Notably, C. vulgaris exhibited more sensitivity to salinity than to crude oil, indicating potential high-salinity challenges but also a strong tolerance to oil pollutants. These findings enhance our understanding of microalgal responses in polluted environments and suggest improved bioremediation approaches for saline waters affected by oil spills, leveraging the synergy of environmental factors and machine learning insights.

A Study on the Effect of Various Media and the Supplementation of Organic Compounds on the Enhanced Production of Astaxanthin from Haematococcus lacustris (Girod-Chantrans) Rostafinski (Chlorophyta)

Natural astaxanthin is in high demand due to its multiple health benefits. The microalga Haematococcus lacustris has been used for the commercial production of astaxanthin. In this study, we investigated the effects of six different media with and without a nitrogen source and supplementation with nine organic compounds on the growth and astaxanthin accumulation of H. lacustris. The highest astaxanthin contents were observed in cultures of H. lacustris in Jaworski's medium (JM), with a level of 9.099 mg/L in JM with a nitrogen source supplemented with leucine (0.65 g/L) and of 20.484 mg/L in JM without a nitrogen source supplemented with sodium glutamate (0.325 g/L). Six of the nine organic compounds examined (leucine, lysine, alanine, sodium glutamate, glutamine, and cellulose) enhanced the production of astaxanthin in H. lacustris, while malic acid, benzoic acid, and maltose showed no beneficial effects.

Salinity-Induced Physiochemical Alterations to Enhance Lipid Content in Oleaginous Microalgae Scenedesmus sp. BHU1 via Two-Stage Cultivation for Biodiesel Feedstock

In the recent past, various microalgae have been considered a renewable energy source for biofuel production, and their amount and extent can be enhanced by applying certain types of stress including salinity. Although microalgae growing under salinity stress result in a higher lipid content, they simultaneously reduce in growth and biomass output. To resolve this issue, the physiochemical changes in microalgae Scenedesmus sp. BHU1 have been assessed through two-stage cultivation. In stage-I, the maximum carbohydrate and lipid contents (39.55 and 34.10%) were found at a 0.4 M NaCl concentration, while in stage-II, the maximum carbohydrate and lipid contents (42.16 and 38.10%) were obtained in the 8-day-old culture. However, under increased salinity, Scenedesmus sp. BHU1 exhibited a decrease in photosynthetic attributes, including Chl-a, Chl-b, Fv/Fm, Y(II), Y(NPQ), NPQ, qP, qL, qN, and ETRmax but increased Y(NO) and carotenoids content. Apart from physiological attributes, osmoprotectants, stress biomarkers, and nonenzymatic antioxidants were also studied to elucidate the role of reactive oxygen species (ROS) facilitated lipid synthesis. Furthermore, elemental and mineral ion analysis of microalgal biomass was performed to evaluate the biomass quality for biofuel and cell homeostasis. Based on fluorometry analysis, we found the maximum neutral lipids in the 8-day-old grown culture at stage-II in Scenedesmus sp. BHU1. Furthermore, the use of Fourier-transform infrared (FT-IR) and nuclear magnetic resonance (NMR) spectroscopy analyses confirmed the presence of higher levels of hydrocarbons and triacylglycerides (TAGs) composed of saturated fatty acids (SFAs) and monounsaturated fatty acids (MUFAs) in the 8-day-old culture. Therefore, Scenedesmus sp. BHU1 can be a promising microalga for potential biodiesel feedstock.

Assessing the prospects of Zygnema heydrichii, a filamentous Chlorophyte, as a biodiesel feedstock

This research aimed to investigate the suitability of the filamentous microalga Zygnema heydrichii as a biodiesel feedstock. Under ambient culture conditions, biomass yield, lipid content, and fatty acid composition were measured. The effects of nutrient deprivation, pH, and salinity on biomass and lipid production were also investigated. Z. heydrichii under nutrient-enriched medium showed specific growth rate (µ) 0.31 day^-1 and lipid content 14.75% DW. The most abundant fatty acids were C16:0, C18:1, C18:2 and C18:3, all of which are considered appropriate for biodiesel production. Nitrogen and phosphorus depletion from the growth medium further increased lipid content to 21.45% and 15.35% DW, respectively. The N depletion of the medium remarkably increased TAG content of the culture. Z. heydrichii possess great ability to grow in salty water (40 Mm NaCl). A low-cost, semi-continuous outdoor culture yielded biomass and lipid productivity of 0.208 g day^-1and 0.038 g L^-1 day^-1, respectively.

Insights into the genetic and metabolic engineering approaches to enhance the competence of microalgae as biofuel resource: A review

Conventional fuel resources are overburden with speedy global energy demand which ensued the urgent need of alternate energy resources. Biofuel generation efficiency of microalgae is notable due to their comparatively rapid biomass production rate and high oil content. But, the employment of microalgae as biofuel resource is in infancy due to low productivity and high production cost. The issues can be addressed by employing engineered microalgal strains that would be able to efficiently generate enhanced levels of biomass with augmented lipid and/or carbohydrate content for proficient biofuel production. Genetic alterations and metabolic engineering of microalgal species might be helpful in developing high stress-tolerant strains with improved properties for biofuel generation. Various omics approaches appeared significant to upgrade the microalgal lipid production. Intervention of genetic and metabolic engineering approaches would facilitate the development of microalgae as a competent biofuel resource and inflate the economic commercialization of biofuels.