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Co-Expression of Lipid Transporters Simultaneously Enhances Oil and Starch Accumulation in the Green Microalga Chlamydomonas reinhardtii under Nitrogen Starvation. Metabolites 2023; 13:metabo13010115. [PMID: 36677040 PMCID: PMC9866645 DOI: 10.3390/metabo13010115] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2022] [Revised: 12/31/2022] [Accepted: 01/09/2023] [Indexed: 01/13/2023] Open
Abstract
Lipid transporters synergistically contribute to oil accumulation under normal conditions in microalgae; however, their effects on lipid metabolism under stress conditions are unknown. Here, we examined the effect of the co-expression of lipid transporters, fatty acid transporters, (FAX1 and FAX2) and ABC transporter (ABCA2) on lipid metabolism and physiological changes in the green microalga Chlamydomonas under nitrogen (N) starvation. The results showed that the TAG content in FAX1-FAX2-ABCA2 over-expressor (OE) was 2.4-fold greater than in the parental line. Notably, in FAX1-FAX2-ABCA2-OE, the major membrane lipids and the starch and cellular biomass content also significantly increased compared with the control lines. Moreover, the expression levels of genes directly involved in TAG, fatty acid, and starch biosynthesis were upregulated. FAX1-FAX2-ABCA2-OE showed altered photosynthesis activity and increased ROS levels during nitrogen (N) deprivation. Our results indicated that FAX1-FAX2-ABCA2 overexpression not only enhanced cellular lipids but also improved starch and biomass contents under N starvation through modulation of lipid and starch metabolism and changes in photosynthesis activity. The strategy developed here could also be applied to other microalgae to produce FA-derived energy-rich and value-added compounds.
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Enhanced accumulation of oil through co-expression of fatty acid and ABC transporters in Chlamydomonas under standard growth conditions. BIOTECHNOLOGY FOR BIOFUELS AND BIOPRODUCTS 2022; 15:54. [PMID: 35596223 PMCID: PMC9123788 DOI: 10.1186/s13068-022-02154-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/08/2022] [Accepted: 05/07/2022] [Indexed: 11/10/2022]
Abstract
Abstract
Background
Chloroplast and endoplasmic reticulum (ER)-localized fatty acid (FA) transporters have been reported to play important roles in oil (mainly triacylglycerols, TAG) biosynthesis. However, whether these FA transporters synergistically contribute to lipid accumulation, and their effect on lipid metabolism in microalgae are unknown.
Results
Here, we co-overexpressed two chloroplast-localized FA exporters (FAX1 and FAX2) and one ER-localized FA transporter (ABCA2) in Chlamydomonas. Under standard growth conditions, FAX1/FAX2/ABCA2 over-expression lines (OE) accumulated up to twofold more TAG than the parental strain UVM4, and the total amounts of major polyunsaturated FAs (PUFA) in TAG increased by 4.7-fold. In parallel, the total FA contents and major membrane lipids in FAX1/FAX2/ABCA2-OE also significantly increased compared with those in the control lines. Additionally, the total accumulation contribution ratio of PUFA, to total FA and TAG synthesis in FAX1/FAX2/ABCA2-OE, was 54% and 40% higher than that in UVM4, respectively. Consistently, the expression levels of genes directly involved in TAG synthesis, such as type-II diacylglycerol acyltransferases (DGTT1, DGTT3 and DGTT5), and phospholipid:diacylglycerol acyltransferase 1 (PDAT1), significantly increased, and the expression of PGD1 (MGDG-specific lipase) was upregulated in FAX1/FAX2/ABCA2-OE compared to UVM4.
Conclusion
These results indicate that the increased expression of FAX1/FAX2/ABCA2 has an additive effect on enhancing TAG, total FA and membrane lipid accumulation and accelerates the PUFA remobilization from membrane lipids to TAG by fine-tuning the key genes involved in lipid metabolism under standard growth conditions. Overall, FAX1/FAX2/ABCA2-OE shows better traits for lipid accumulation than the parental line and previously reported individual FA transporter-OE. Our study provides a potential useful strategy to increase the production of FA-derived energy-rich and value-added compounds in microalgae.
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Carneiro M, Chini Zittelli G, Cicchi B, Touloupakis E, Faraloni C, Maia IB, Pereira H, Santos T, Malcata FX, Otero A, Varela J, Torzillo G. In situ monitoring of chlorophyll a fluorescence in Nannochloropsis oceanica cultures to assess photochemical changes and the onset of lipid accumulation during nitrogen deprivation. Biotechnol Bioeng 2021; 118:4375-4388. [PMID: 34319592 DOI: 10.1002/bit.27906] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2021] [Revised: 07/13/2021] [Accepted: 07/17/2021] [Indexed: 01/28/2023]
Abstract
In situ chlorophyll a fluorescence measurements were applied to monitor changes in the photochemical variables of Nannochloropsis oceanica cultures under nitrogen-deplete and nitrogen-replete (control) conditions. In addition, growth, lipid, fatty acid, and pigment contents were also followed. In the control culture, growth was promoted along with pigment content, electron transport rate (ETR), and polyunsaturated fatty acids, while total lipid content and fatty acid saturation level diminished. Under nitrogen-deplete conditions, the culture showed a higher de-epoxidation state of the xanthophyll cycle pigments. Fast transients revealed a poor processing efficiency for electron transfer beyond QA , which was in line with the low ETR due to nitrogen depletion. Lipid content and the de-epoxidation state were the first biochemical variables triggered by the change in nutrient status, which coincided with a 20% drop in the in situ effective quantum yield of PSII (ΔF'/Fm '), and a raise in the Vj measurements. A good correlation was found between the changes in ΔF'/Fm ' and lipid content (r = -0.96, p < 0.01). The results confirm the reliability and applicability of in situ fluorescence measurements to monitor lipid induction in N. oceanica.
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Affiliation(s)
- Mariana Carneiro
- LEPABE-Laboratory for Process Engineering, Environment, Biotechnology and Energy, Faculty of Engineering of the University of Porto, Porto, Portugal
| | | | - Bernardo Cicchi
- CNR-IBE-Consiglio Nazionale delle Ricerche-Istituto per la BioEconomia, Florence, Italy
| | - Eleftherios Touloupakis
- CNR-IRET - Consiglio Nazionale delle Ricerche-Istituto di Ricerca sugli Ecosistemi Terrestri, Florence, Italy
| | - Cecilia Faraloni
- CNR-IBE-Consiglio Nazionale delle Ricerche-Istituto per la BioEconomia, Florence, Italy
| | - Inês B Maia
- CCMAR-Centre of Marine Sciences, University of Algarve, Faro, Portugal
| | - Hugo Pereira
- Green Colab-Associação Oceano Verde, University of Algarve, Campus de Gambelas, Faro, Portugal
| | - Tamára Santos
- CCMAR-Centre of Marine Sciences, University of Algarve, Faro, Portugal
| | - Francisco X Malcata
- LEPABE-Laboratory for Process Engineering, Environment, Biotechnology and Energy, Faculty of Engineering of the University of Porto, Porto, Portugal
| | - Ana Otero
- USC-Instituto de Acuicultura and Departamento de Microbiología y Parasitología, Universidade de Santiago de Compostela, Santiago de Compostela, Spain
| | - João Varela
- CCMAR-Centre of Marine Sciences, University of Algarve, Faro, Portugal
| | - Giuseppe Torzillo
- CNR-IBE-Consiglio Nazionale delle Ricerche-Istituto per la BioEconomia, Florence, Italy.,CIMAR-Centro de Investigación en Ciencias del Mar y Limnología, Universidad de Costa Rica, San José, Costa Rica
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Xi Y, Kong F, Chi Z. ROS Induce β-Carotene Biosynthesis Caused by Changes of Photosynthesis Efficiency and Energy Metabolism in Dunaliella salina Under Stress Conditions. Front Bioeng Biotechnol 2021; 8:613768. [PMID: 33520962 PMCID: PMC7844308 DOI: 10.3389/fbioe.2020.613768] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2020] [Accepted: 11/25/2020] [Indexed: 11/13/2022] Open
Abstract
The unicellular alga Dunaliella salina is regarded as a promising cell factory for the commercial production of β-carotene due to its high yield of carotenoids. However, the underlying mechanism of β-carotene accumulation is still unclear. In this study, the regulatory mechanism of β-carotene accumulation in D. salina under stress conditions was investigated. Our results indicated that there is a significant positive correlation between the cellular ROS level and β-carotene content, and the maximum quantum efficiency (Fv/Fm) of PSII is negatively correlated with β-carotene content under stress conditions. The increase of ROS was found to be coupled with the inhibition of Fv/Fm of PSII in D. salina under stress conditions. Furthermore, transcriptomic analysis of the cells cultivated with H2O2 supplementation showed that the major differentially expressed genes involved in β-carotene metabolism were upregulated, whereas the genes involved in photosynthesis were downregulated. These results indicated that ROS induce β-carotene accumulation in D. salina through fine-tuning genes which were involved in photosynthesis and β-carotene biosynthesis. Our study provided a better understanding of the regulatory mechanism involved in β-carotene accumulation in D. salina, which might be useful for overaccumulation of carotenoids and other valuable compounds in other microalgae.
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Affiliation(s)
- Yimei Xi
- School of Bioengineering, Dalian University of Technology, Dalian, China
| | - Fantao Kong
- School of Bioengineering, Dalian University of Technology, Dalian, China
| | - Zhanyou Chi
- School of Bioengineering, Dalian University of Technology, Dalian, China
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Ran W, Wang H, Liu Y, Qi M, Xiang Q, Yao C, Zhang Y, Lan X. Storage of starch and lipids in microalgae: Biosynthesis and manipulation by nutrients. BIORESOURCE TECHNOLOGY 2019; 291:121894. [PMID: 31387839 DOI: 10.1016/j.biortech.2019.121894] [Citation(s) in RCA: 66] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2019] [Revised: 07/22/2019] [Accepted: 07/23/2019] [Indexed: 05/28/2023]
Abstract
Microalgae accumulate starch and lipid as storage metabolites under nutrient depletion, which can be used as sustainable feedstock for biorefinery. Omics analysis coupled with enzymatic and genetic verifications uncovered a partial picture of pathways and important enzymes or regulators related to starch and lipid biosynthesis as well as the carbon partitioning between them under nutrient depletion conditions. Depletion of macronutrients (N, P, and S) resulted in considerable enhancement of starch and/or lipid content in microalgae, but the accompanying declined photosynthesis hampered the achievements of high concentrations. This review summarized the current knowledge on the pathways and the committed steps as well as their carbon allocation involved in starch and lipid biosynthesis, and focused on the manipulation of different nutrients and the alleviation of oxidative stress for enhanced storage metabolites production. The biological and engineering approaches to cope with the conflict between biomass production and storage metabolites accumulation are proposed.
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Affiliation(s)
- Wenyi Ran
- Department of Pharmaceutical & Biological Engineering, School of Chemical Engineering, Sichuan University, Chengdu, Sichuan 610065, China
| | - Haitao Wang
- National Engineering Research Center of Seafood, School of Food Science and Technology, Dalian Polytechnic University, Dalian, Liaoning 116034, China
| | - Yinghui Liu
- Information Management Center of Sichuan University, Chengdu, Sichuan 610065, China
| | - Man Qi
- Department of Pharmaceutical & Biological Engineering, School of Chemical Engineering, Sichuan University, Chengdu, Sichuan 610065, China
| | - Qi Xiang
- Department of Pharmaceutical & Biological Engineering, School of Chemical Engineering, Sichuan University, Chengdu, Sichuan 610065, China
| | - Changhong Yao
- Department of Pharmaceutical & Biological Engineering, School of Chemical Engineering, Sichuan University, Chengdu, Sichuan 610065, China.
| | - Yongkui Zhang
- Department of Pharmaceutical & Biological Engineering, School of Chemical Engineering, Sichuan University, Chengdu, Sichuan 610065, China
| | - Xianqiu Lan
- Department of Pharmaceutical & Biological Engineering, School of Chemical Engineering, Sichuan University, Chengdu, Sichuan 610065, China
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Oh SH, Chang YK, Lee JH. Identification of significant proxy variable for the physiological status affecting salt stress-induced lipid accumulation in Chlorella sorokiniana HS1. BIOTECHNOLOGY FOR BIOFUELS 2019; 12:242. [PMID: 31632454 PMCID: PMC6790037 DOI: 10.1186/s13068-019-1582-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/06/2019] [Accepted: 10/01/2019] [Indexed: 06/10/2023]
Abstract
BACKGROUND Current efforts on the optimization of the two-stage cultivation using stress-induced lipid accumulation have mostly focused only on the lipid induction stage. Although recent studies have shown that stress-induced lipid accumulation is affected by the physiological status of the cells harvested at the preceding cultivation stage, this issue has hardly been examined hitherto. Such a study needs to be carried out in a systematic way in order to induce lipid accumulation in a consistent and predictable manner with regard for variances seen at the cultivation stage. RESULTS After a photoautotrophic cultivation of Chlorella sorokiniana HS1 in a modified BG11, harvested cells were re-suspended in the fresh medium, and then NaCl was added as the sole stress inducer with light illumination to induce additional accumulation of lipid. Effects of culture temperature on the lipid accumulation were analyzed by the Kruskal-Wallis test. From the microscopic observation, we had observed a definite increase in lipid body induced by the stress since the cell entered a stationary phase. A multiple linear regression model was developed so as to identify significant parameters to be included for the estimation of lipid induction. As a result, several key parameters at the end of cultivation, such as cell weight, total lipid content, chlorophyll a in a cell, and Fv/Fm, were identified as the important proxy variables for the cell's physiological status, and the modeling accuracy was achieved by 87.6%. In particular, the variables related to Fv/Fm were shown to have the largest influence, accounting for 65.7% of the total variance, and the Fv/Fm had an optimal point of maximum induction at below its average. Clustering analysis using the K-means algorithm indicated that the algae which are 0.15 pg cell-1 or less in chlorophyll concentration, regardless of other conditions, had achieved high induction results. CONCLUSION Experimental results showed that it usually achieves high lipid induction after the cells naturally end their division and begin to synthesize lipid. The amount of lipid induction could be estimated by the selected proxy variables, and the estimation method can be adapted according to practical situations such as those with limited measurements.
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Affiliation(s)
- Seung Hwan Oh
- Department of Chemical and Biomolecular Engineering, KAIST, 291 Daehak-ro, Yuseong-gu, Daejeon, 305-701 Republic of Korea
| | - Yong Keun Chang
- Department of Chemical and Biomolecular Engineering, KAIST, 291 Daehak-ro, Yuseong-gu, Daejeon, 305-701 Republic of Korea
- Advanced Biomass R&D Center, KAIST, 291 Daehak-ro, Yuseong-gu, Daejeon, 305-701 Republic of Korea
| | - Jay Hyung Lee
- Department of Chemical and Biomolecular Engineering, KAIST, 291 Daehak-ro, Yuseong-gu, Daejeon, 305-701 Republic of Korea
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He Y, Wang X, Wei H, Zhang J, Chen B, Chen F. Direct enzymatic ethanolysis of potential Nannochloropsis biomass for co-production of sustainable biodiesel and nutraceutical eicosapentaenoic acid. BIOTECHNOLOGY FOR BIOFUELS 2019; 12:78. [PMID: 30992715 PMCID: PMC6449970 DOI: 10.1186/s13068-019-1418-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2018] [Accepted: 03/27/2019] [Indexed: 05/24/2023]
Abstract
BACKGROUND Marine microalga Nannochloropsis is a promising source for the production of renewable and sustainable biodiesel in replacement of depleting petroleum. Other than biodiesel, Nannochloropsis is a green and potential resource for the commercial production of nutraceutical eicosapentaenoic acid (EPA, C20:5). In recent studies, low-value biodiesel can be achieved by transesterification of Nannochloropsis biomass. However, it is undoubtedly wasteful to produce microalgal biodiesel containing EPA from nutritional and economical aspects. A new strategy was addressed and exploited to produce low-value bulky biodiesel along with EPA enrichment via enzymatic ethanolysis of Nannochloropsis biomass with a specific lipase. RESULTS Cellulase pretreatment on Nannochloropsis sp. biomass significantly improved the biodiesel conversion by direct ethanolysis with five enzymes from Candida antarctica (CALA and CALB), Thermomyces lanuginosus (TL), Rhizomucor miehei (RM), and Aspergillus oryzae (PLA). Among these five biocatalysts, CALA was the best suitable enzyme to yield high biodiesel conversion and effectively enrich EPA. After optimization, the maximum biodiesel conversion (46.53-48.57%) was attained by CALA at 8:1 ethanol/biomass ratio (v/w) in 10-15% water content with 10% lipase weight at 35 °C for 72 h. Meanwhile, EPA (60.81%) was highly enriched in microalgae NPLs (neutral lipids and polar lipids), increasing original EPA levels by 1.51-fold. Moreover, this process was re-evaluated with two Nannochloropsis species (IMET1 and Salina 537). Under the optimized conditions, the biodiesel conversions of IMET1 and Salina 537 by CALA were 63.41% and 54.33%, respectively. EPA contents of microalgal NPLs were 50.06% for IMET1 and 53.73% for Salina 537. CONCLUSION CALA was the potential biocatalyst to discriminate against EPA in the ethanolysis of Nannochloropsis biomass. The biodiesel conversion and EPA enrich efficiency of CALA were greatly dependent on lipidic class and fatty acid compositions of Nannochloropsis biomass. CALA-catalyzed ethanolysis with Nannochloropsis biomass was a promising approach for co-production of low-value biodiesel and high-value microalgae products rich in EPA.
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Affiliation(s)
- Yongjin He
- BIC-ESAT, College of Engineering, Peking University, Beijing, 100871 China
- Institute for Food & Bioresource Engineering, College of Engineering, Peking University, Beijing, 100871 China
- Key Laboratory of Feed Biotechnology, The Ministry of Agriculture of the People’s Republic of China, Beijing, 100081 China
- College of Life Science, Fujian Normal University, Fuzhou, 350117 China
| | - Xiaofei Wang
- BIC-ESAT, College of Engineering, Peking University, Beijing, 100871 China
- Institute for Food & Bioresource Engineering, College of Engineering, Peking University, Beijing, 100871 China
| | - Hehong Wei
- BIC-ESAT, College of Engineering, Peking University, Beijing, 100871 China
- Institute for Food & Bioresource Engineering, College of Engineering, Peking University, Beijing, 100871 China
| | - Jianzhi Zhang
- BIC-ESAT, College of Engineering, Peking University, Beijing, 100871 China
- Institute for Food & Bioresource Engineering, College of Engineering, Peking University, Beijing, 100871 China
| | - Bilian Chen
- College of Life Science, Fujian Normal University, Fuzhou, 350117 China
| | - Feng Chen
- BIC-ESAT, College of Engineering, Peking University, Beijing, 100871 China
- Institute for Food & Bioresource Engineering, College of Engineering, Peking University, Beijing, 100871 China
- Institute for Advanced Study, Shenzhen University, Shenzhen, 518000 China
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