Many species of microalgae produce greatly enhanced amounts of triacylglycerides (TAGs), the key product for biodiesel production, in response to specific environmental stresses. Improvement of TAG production by microalgae through optimization of growth regimes is of great interest. This relies on understanding microalgal lipid metabolism in relation to stress response in particular the deprivation of nutrients that can induce enhanced TAG synthesis. In this study, a detailed investigation of changes in lipid composition in Chlorella sp. and Nannochloropsis sp. in response to nitrogen deprivation (N-deprivation) was performed to provide novel mechanistic insights into the lipidome during stress. As expected, an increase in TAGs and an overall decrease in polar lipids were observed. However, while most membrane lipid classes (phosphoglycerolipids and glycolipids) were found to decrease, the non-nitrogen containing phosphatidylglycerol levels increased considerably in both algae from initially low levels. Of particular significance, it was observed that the acyl composition of TAGs in Nannochloropsis sp. remain relatively constant, whereas Chlorella sp. showed greater variability following N-deprivation. In both algae the overall fatty acid profiles of the polar lipid classes were largely unaffected by N-deprivation, suggesting a specific FA profile for each compartment is maintained to enable continued function despite considerable reductions in the amount of these lipids. The changes observed in the overall fatty acid profile were due primarily to the decrease in proportion of polar lipids to TAGs. This study provides the most detailed lipidomic information on two different microalgae with utility in biodiesel production and nutraceutical industries and proposes the mechanisms for this rearrangement. This research also highlights the usefulness of the latest MS-based approaches for microalgae lipid research.

Lipidome

Nannochloropsis

10.1371/journal.pone.0103389

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Citations (133)

Laccase mediated transformation of fluoroquinolone antibiotics: Analyzing degradation pathways and assessing algal toxicity

Environmental Pollution (2024)

Purvi Mathur Mandira Kochar Xavier A. Conlan Frederick M. Pfeffer Mukul Dubey

Improper waste disposal or inadequate wastewater treatment can result in pharmaceuticals reaching water bodies, posing environmental hazards. In this study, crude extracts containing the laccase enzyme from Pleurotus florida, Pleurotus eryngii, and Pleurotus sajor caju were used to degrade the fluoroquinolone antibiotics (FQs) levofloxacin (LEV), norfloxacin (NOR), ciprofloxacin (CIP), ofloxacin (OFL), and enrofloxacin (ENR) in aqueous solutions. The results for the fungi derived laccase extracts were compared with those obtained using commercially sourced laccase. Proteomics analysis of the crude extracts confirmed the presence of laccase enzyme across all three tested species, with proteins matching those found in Trametes versicolor and Pleurotus ostreatus. In vivo studies were conducted using species pure lines of fungal whole cells. The highest degradation efficiency observed was 77.7% for LEV in the presence of P. sajor caju after 25 days of treatment. Degradation efficiencies ranged from approximately 60-72% for P. florida, 45–76% for P. eryngii, and 47–78% for P. sajor caju. A series of in vitro experiments were also conducted using crude extracts from the three species and outcomes compared with those obtained when commercial laccase was used confirmed laccase as the enzyme responsible for antibiotic removal. The degradation efficiencies in vitro surpassed those measured in vivo, ranging from approximately 91-98% for commercial laccase, 77–92% for P. florida, 76–92% for P. eryngii, and 78–88% for P. sajor caju. Liquid chromatography–high-resolution mass spectrometry (LC-MS/MS) identified the degradation products, indicating a consistent enzymatic degradation pathway targeting the piperazine moiety common to all tested FQs, irrespective of the initial antibiotic structure. Phytoplankton toxicity studies with Dunaliella tertiolecta were performed to aid in understanding the impact of emerging contaminants on ecosystems, and by-products were analysed for ecotoxicity to assess treatment efficacy. Laccase-mediated enzymatic oxidation shows promising results in reducing algal toxicity, notably with Pleurotus eryngii extract achieving a 97.7% decrease for CIP and a 90% decrease for LEV. These findings suggest the potential of these naturally sourced extracts in mitigating antibiotic contamination in aquatic ecosystems.

Pleurotus

Trametes versicolor

Pleurotus eryngii

10.1016/j.envpol.2024.124700

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Citations (1)

The assimilation of glycerol into lipid acyl chains and associated carbon backbones of Nannochloropsis salina varies under nitrogen replete and deplete conditions

Biotechnology and Bioengineering (2020)

Nature Poddar Sheik Nadeem Elahee Doomun Damien L. Callahan Greg M. Kowalski Gregory J.O. Martin

Mixotrophic cultivation can increase microalgae productivity, yet the associated lipid metabolism remains mostly unknown. Stable isotope labeling was used to track assimilation of glycerol into the triacylglyceride (TAG) and membrane lipids of Nannochloropsis salina. In N-replete media, glycerol uptake and 13 C incorporation into acyl chains were, respectively, 6-fold and 12-fold higher than in N-deplete conditions. In N-replete cultures, 42% of the carbon in the consumed glycerol was assimilated into lipid acyl chains, mostly in membrane lipids rather than TAG. In N-deplete cultures, only 11% of the limited amount of consumed glycerol was fixed into lipid acyl chains. Labeled lipid-associated glycerol backbones were predominantly 13 C3 labeled, suggesting that intact glycerol molecules were directly esterified with fatty acids/polar head groups. However, the presence of singly and doubly labeled lipid-bound glycerol species suggested that some glycerol also went through the central carbon metabolism before forming glycerol-3-phosphate destined for lipid esterification. 13 C incorporation was higher in the saturated and monounsaturated than the polyunsaturated acyl chains of TAG, indicating the flux of carbon from glycerol went first to de novo fatty acid synthesis before acyl editing reactions. The results demonstrate that nitrogen availability influences both glycerol consumption and utilization for lipid synthesis in Nannochloropsis, providing novel insights for developing mixotrophic cultivation strategies.

Nannochloropsis

Mixotroph

Assimilation (phonology)

Fatty acid synthesis

10.1002/bit.27498

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Citations (3)

Nano/micro plastics – Challenges on quantification and remediation: A review

Journal of Water Process Engineering (2021)

Marie Enfrin Cyril Hachemi Peter Hodgson Veeriah Jegatheesan Johannes S. Vrouwenvelder

Nanometre

10.1016/j.jwpe.2021.102128