TABLE 2.
Comparison of the mainly parameters and technologies for biodiesel production.
| Main parameters | Factors | Microalgae type | Lipid content | Biomass growth/Productivity | ||
| Microalgae cultivation | Light | Chlorella sp. | 2700 lx, | 19.44% | 1.05/d | Monika et al., 2015 |
| Chlorella vulgaris | 520 mmol/m2 s | 22.2% | 0.36/d | Maria et al., 2019 | ||
| Temperature | Chlorella vulgaris | 25 °C | 14.7% | 0.14/d | Attilio et al., 2009 | |
| Chaetoceros sp. | 25 °C | 16.8% | 0.87/d | Susan et al., 2002 | ||
| pH | Chlorella sp. | 8 | 23% | 0.1995 g/L | Monika et al., 2015 | |
| Chlorella pyrenoidosa | 7 | 30.9% | 1.41 g/L | Peng et al., 2020 | ||
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| Main parameters | Factors | Microalgae type | Wastewater type | Lipid content | Biomass Growth/Productivity | |
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| Microalgae cultivation systems | Agricultural wastewater | Chlorella sorokiniana | BBM | – | 0.25/d | Khalid et al., 2019 |
| Chlorella sorokiniana | POME | – | 0.23/d | |||
| Scenedesmus sp. | Diluted swine w | 17.19% | 0.40 g/L | Zhao et al., 2022 | ||
| Industrial wastewater | Chlorella vulgaris | Tofu wastewater | 23.25% | 0.8 g/L | Dianursanti et al., 2014 | |
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| Lipid induction technologies | Factors | Microalgae type | Optimum conditions | Lipid intensity/Productivity | Effects of variation on lipid productivity/content | |
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| Nutrient starvation stress | Chloroidium i | 2.9 mM Nitrates | Lipid productivity 3.31 ± 0.16 mg/L/d | Lipid productivity 4.73 ± 0.12 mg/L/d, 40.37 ± 1.01% increase in lipid yield L/day | Prasanthkumar et al., 2020 | |
| Chloroidium saccharophillum | 0.5 mM Phosphate | Lipid productivity 2.31 ± 0.62 mg/L/d | Lipid productivity 3.96 ± 1.04 mg/L/d, 33.57 ± 3.72% increase in lipid yield L/day | |||
| Salinity stress | Chloroidium saccharophillum | 10 mM NaCl | Lipid productivity 1.78 ± 0.32 Mg/L/d | Lipid productivity 4.70 ± 0.24 mg/L/d, 40.18 ± 1.97% increase in lipid yield L/day | Prasanthkumar et al., 2020 | |
| Chromochloris zofingiensis | 0.25 M NaCl | Lipid content 13 mg/g DW | Lipid content 195 mg/g DW, 15-fold increase in TAG content | Yaping et al., 2020 | ||
| Light stress | Chromochloris zofingiensis | 400 μE/m⋅s | Lipid content 13 mg/g DW | Lipid content 195 mg/g DW, 15-fold increase in TAG content | Yaping et al., 2020 | |
| Chlorella sp. | 40 μmol/m⋅s | – | Higher lipid content of 17.2% achieved | Moreno-Garcia et al., 2019 | ||
| Temperature stress | Gracilariopsis lemaneiformis | High temperature 33 °C | Lipid intensity 5 × E10 | Lipid intensity 7 × E10, Increase in C20:5 fatty acid by 88%, PUFA improved | Zhang X. et al., 2020 | |
| Porosira glacialis | 2 °C | Lipid content 19.5% | Lipid content peaked at 33.4 ± 4.0% | Jon et al., 2019 | ||
| Carbon dioxide supplementation | Nannochloropsis sp. | 5% CO2 concentration | Lipid production 112.91 ± 17.34 | Maximum lipid production of 782.7 ± 24.49 mg⋅L− 1 attained | Peng et al., 2020 | |
| Arthrospira ZJU9000 | 171.2 mM HCO3–1 Concentration | Lipid content 9.5 (Wt%) | 3.8-fold higher expression of gene encoding ATP-synthase. | Hongxiang et al., 2019 | ||
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| Microalgae harvesting | Technique | Microalgae type | Operating conditions | Recovery efficiency | ||
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| Chemical flocculation (Self-flocculation) | Chlorella vulgaris | pH adjustment, NaOH; V = 30 L, pH = 10.8, HM = batch, CD = 9 mg/g | 98% | Dries et al., 2011 | ||
| pH adjustment, Ca(OH)2, | 98% | |||||
| Ca(OH)2, V = 30 L; pH = 10.8; HM = batch, CD = 18 mg/g | ||||||
| pH adjustment, Mg(OH)2, V = 30 L; pH = 9.7; HM = batch, CD = 27 mg/g | 98% | |||||
| Chlorella sp. | P: Polyacrylamide; C: High; S: 1000; FD: 34; T: 60 | 98% | Arivalagan et al., 2019 | |||
| Chlorella vulgaris | P: Polyacrylamide; MW: High; C: High; D: 0.26; S: 3000; FD: 5; T: 30 | 100% | ||||
| Bio-flocculation | Chlorella sp. | pH = 8, chitosan concentration: 100 mg/500 mL, cationic inducer concentration: 50 mg/L, stirring speed: 240 rpm | 96.12% | Hadiyanto et al., 2022 | ||
| Chlorella pyrenoidosa | Citrobacter W4; bacterial-algal ratio: 4:1, G value: 26.30 s–1, harvesting time: 6 h | 87.37 ± 2.96% | He et al., 2022 | |||
| Flotation | Asterionella formosa | Aluminum sulfate: 0.0314 ng Al/cell, pH = 7, Flotation time: 10 min | 98.9% | Henderson et al., 2008a | ||
| Scenedesmus quadricauda | CTAB: 40 mg/L, pH = 8, Flotation time: 20 min | 90% | Chen et al., 1998 | |||
| Chlorella vulgaris | CTAB: 0.005 mequiv/L, pH = 7, Flotation time: 10 min | 54% | Henderson et al., 2008b | |||
| Chlorella | Ferric sulfate: 3.5 mg Fe/L, pH = 5.5, Flotation time: 10 min | 94% | Jarvis et al., 2009 | |||
| Filtration | M. aeruginosa | CPAM-assisted filtration with a 100-μm sieve | 90% | Cai et al., 2022 | ||
| Chlorella vulgaris | CF: 78 L/m2 h, F: 3 HZ | 68.8% | Zhao et al., 2020 | |||
| Centrifugation | Chlorella sp. | Disk-stack centrifuge: 15 min | 93% | Abhishek et al., 2016 | ||
| Chlorella vulgaris | Decanter centrifuges, Energy consumption: 8 kWh/m3, Final slurry Concentration: 22.2% | 92% | Wiley and Campbell, 2011 | |||